[PATCH 0/6] Implement proper MST fallback retraining in i915

[PATCH 0/6] Implement proper MST fallback retraining in i915

[Lyude Paul]

This is the first version of my patch series to implement MST fallback
retraining in i915, along with improving the stability of i915's mst
retraining in general. Additionally, it also introduces helpers into DRM
to help with correctly handling MST fallback retraining so that other
drivers may also implement it. If your driver has a homegrown
implementation of this, you should convert it to these helpers to ensure
that the behavior of atomic commits and connector's link status
properties in the event of requiring retraining on an MST topology
remains consistent between DRM drivers.

Additionally, this lets me use the DisplayPort on my dock so I can
finally free up the thunderbolt 3 connector on it for more useful
things. At long last :).

Cc: Manasi Navare <manasi.d.navare@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>

Lyude Paul (6):
  drm/i915: Remove unused DP_LINK_CHECK_TIMEOUT
  drm/i915: Move DP modeset retry work into intel_dp
  drm/i915: Only use one link bw config for MST topologies
  drm/dp_mst: Add drm_dp_mst_topology_mgr_lower_link_rate()
  drm/dp_mst: Add drm_atomic_dp_mst_retrain_topology()
  drm/i915: Implement proper fallback training for MST

 drivers/gpu/drm/drm_dp_mst_topology.c         | 296 ++++++++++++++++++++-
 drivers/gpu/drm/i915/intel_display.c          |  23 +-
 drivers/gpu/drm/i915/intel_dp.c               | 360 +++++++++++++++++++-------
 drivers/gpu/drm/i915/intel_dp_link_training.c |   2 +-
 drivers/gpu/drm/i915/intel_dp_mst.c           |  64 +++--
 drivers/gpu/drm/i915/intel_drv.h              |  23 +-
 include/drm/drm_dp_mst_helper.h               |   5 +
 7 files changed, 662 insertions(+), 111 deletions(-)

-- 
2.14.3

[PATCH 1/6] drm/i915: Remove unused DP_LINK_CHECK_TIMEOUT

[Lyude Paul]

Signed-off-by: Lyude Paul <lyude@redhat.com>
Cc: Manasi Navare <manasi.d.navare@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
---
 drivers/gpu/drm/i915/intel_dp.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 9a4a51e79fa1..4dd1b2287dd6 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -43,7 +43,6 @@
 #include <drm/i915_drm.h>
 #include "i915_drv.h"
 
-#define DP_LINK_CHECK_TIMEOUT	(10 * 1000)
 #define DP_DPRX_ESI_LEN 14
 
 /* Compliance test status bits  */
-- 
2.14.3

Re: [PATCH 1/6] drm/i915: Remove unused DP_LINK_CHECK_TIMEOUT

[Manasi Navare]

On Thu, Mar 08, 2018 at 06:24:15PM -0500, Lyude Paul wrote:
> Signed-off-by: Lyude Paul <lyude@redhat.com>
> Cc: Manasi Navare <manasi.d.navare@intel.com>
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>

Reviewed-by: Manasi Navare <manasi.d.navare@intel.com>

> ---
>  drivers/gpu/drm/i915/intel_dp.c | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 9a4a51e79fa1..4dd1b2287dd6 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -43,7 +43,6 @@
>  #include <drm/i915_drm.h>
>  #include "i915_drv.h"
>  
> -#define DP_LINK_CHECK_TIMEOUT	(10 * 1000)
>  #define DP_DPRX_ESI_LEN 14
>  
>  /* Compliance test status bits  */
> -- 
> 2.14.3
> 
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel

[PATCH 2/6] drm/i915: Move DP modeset retry work into intel_dp

[Lyude Paul]

While having the modeset_retry_work in intel_connector makes sense with
SST, this paradigm doesn't make a whole ton of sense when it comes to
MST since we have to deal with multiple connectors. In most cases, it's
more useful to just use the intel_dp struct since it indicates whether
or not we're dealing with an MST device, along with being able to easily
trace the intel_dp struct back to it's respective connector (if there is
any). So, move the modeset_retry_work function out of the
intel_connector struct and into intel_dp.

Signed-off-by: Lyude Paul <lyude@redhat.com>
Cc: Manasi Navare <manasi.d.navare@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
---
 drivers/gpu/drm/i915/intel_display.c          | 23 +++++++++++++++++++++--
 drivers/gpu/drm/i915/intel_dp.c               | 10 ++++------
 drivers/gpu/drm/i915/intel_dp_link_training.c |  2 +-
 drivers/gpu/drm/i915/intel_drv.h              |  9 ++++++---
 4 files changed, 32 insertions(+), 12 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index f424fff477f6..85d5af4e4f5b 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -15394,16 +15394,35 @@ static void intel_hpd_poll_fini(struct drm_device *dev)
 {
 	struct intel_connector *connector;
 	struct drm_connector_list_iter conn_iter;
+	struct work_struct *work;
 
 	/* Kill all the work that may have been queued by hpd. */
 	drm_connector_list_iter_begin(dev, &conn_iter);
 	for_each_intel_connector_iter(connector, &conn_iter) {
-		if (connector->modeset_retry_work.func)
-			cancel_work_sync(&connector->modeset_retry_work);
 		if (connector->hdcp_shim) {
 			cancel_delayed_work_sync(&connector->hdcp_check_work);
 			cancel_work_sync(&connector->hdcp_prop_work);
 		}
+
+		if (connector->base.connector_type !=
+		    DRM_MODE_CONNECTOR_DisplayPort)
+			continue;
+
+		if (connector->mst_port) {
+			work = &connector->mst_port->modeset_retry_work;
+		} else {
+			struct intel_encoder *intel_encoder =
+				connector->encoder;
+			struct intel_dp *intel_dp;
+
+			if (!intel_encoder)
+				continue;
+
+			intel_dp = enc_to_intel_dp(&intel_encoder->base);
+			work = &intel_dp->modeset_retry_work;
+		}
+
+		cancel_work_sync(work);
 	}
 	drm_connector_list_iter_end(&conn_iter);
 }
diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 4dd1b2287dd6..5abf0c95725a 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -6261,12 +6261,10 @@ static bool intel_edp_init_connector(struct intel_dp *intel_dp,
 
 static void intel_dp_modeset_retry_work_fn(struct work_struct *work)
 {
-	struct intel_connector *intel_connector;
-	struct drm_connector *connector;
+	struct intel_dp *intel_dp = container_of(work, typeof(*intel_dp),
+						 modeset_retry_work);
+	struct drm_connector *connector = &intel_dp->attached_connector->base;
 
-	intel_connector = container_of(work, typeof(*intel_connector),
-				       modeset_retry_work);
-	connector = &intel_connector->base;
 	DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n", connector->base.id,
 		      connector->name);
 
@@ -6295,7 +6293,7 @@ intel_dp_init_connector(struct intel_digital_port *intel_dig_port,
 	int type;
 
 	/* Initialize the work for modeset in case of link train failure */
-	INIT_WORK(&intel_connector->modeset_retry_work,
+	INIT_WORK(&intel_dp->modeset_retry_work,
 		  intel_dp_modeset_retry_work_fn);
 
 	if (WARN(intel_dig_port->max_lanes < 1,
diff --git a/drivers/gpu/drm/i915/intel_dp_link_training.c b/drivers/gpu/drm/i915/intel_dp_link_training.c
index f59b59bb0a21..2cfa58ce1f95 100644
--- a/drivers/gpu/drm/i915/intel_dp_link_training.c
+++ b/drivers/gpu/drm/i915/intel_dp_link_training.c
@@ -340,7 +340,7 @@ intel_dp_start_link_train(struct intel_dp *intel_dp)
 							     intel_dp->link_rate,
 							     intel_dp->lane_count))
 			/* Schedule a Hotplug Uevent to userspace to start modeset */
-			schedule_work(&intel_connector->modeset_retry_work);
+			schedule_work(&intel_dp->modeset_retry_work);
 	} else {
 		DRM_ERROR("[CONNECTOR:%d:%s] Link Training failed at link rate = %d, lane count = %d",
 			  intel_connector->base.base.id,
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index 83e5ca889d9c..3700fcfddb1f 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -406,14 +406,14 @@ struct intel_connector {
 
 	struct intel_dp *mst_port;
 
-	/* Work struct to schedule a uevent on link train failure */
-	struct work_struct modeset_retry_work;
-
 	const struct intel_hdcp_shim *hdcp_shim;
 	struct mutex hdcp_mutex;
 	uint64_t hdcp_value; /* protected by hdcp_mutex */
 	struct delayed_work hdcp_check_work;
 	struct work_struct hdcp_prop_work;
+
+	/* Work struct to schedule a uevent on link train failure */
+	struct work_struct modeset_retry_work;
 };
 
 struct intel_digital_connector_state {
@@ -1135,6 +1135,9 @@ struct intel_dp {
 
 	/* Displayport compliance testing */
 	struct intel_dp_compliance compliance;
+
+	/* Work struct to schedule a uevent on link train failure */
+	struct work_struct modeset_retry_work;
 };
 
 struct intel_lspcon {
-- 
2.14.3

[PATCH v2 2/6] drm/i915: Move DP modeset retry work into intel_dp

[Lyude Paul]

While having the modeset_retry_work in intel_connector makes sense with
SST, this paradigm doesn't make a whole ton of sense when it comes to
MST since we have to deal with multiple connectors. In most cases, it's
more useful to just use the intel_dp struct since it indicates whether
or not we're dealing with an MST device, along with being able to easily
trace the intel_dp struct back to it's respective connector (if there is
any). So, move the modeset_retry_work function out of the
intel_connector struct and into intel_dp.

V2:
 - Remove accidental duplicate modeset_retry_work in intel_connector

Signed-off-by: Lyude Paul <lyude@redhat.com>
Cc: Manasi Navare <manasi.d.navare@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
---
 drivers/gpu/drm/i915/intel_display.c          | 23 +++++++++++++++++++++--
 drivers/gpu/drm/i915/intel_dp.c               | 10 ++++------
 drivers/gpu/drm/i915/intel_dp_link_training.c |  2 +-
 drivers/gpu/drm/i915/intel_drv.h              |  6 +++---
 4 files changed, 29 insertions(+), 12 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index f424fff477f6..85d5af4e4f5b 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -15394,16 +15394,35 @@ static void intel_hpd_poll_fini(struct drm_device *dev)
 {
 	struct intel_connector *connector;
 	struct drm_connector_list_iter conn_iter;
+	struct work_struct *work;
 
 	/* Kill all the work that may have been queued by hpd. */
 	drm_connector_list_iter_begin(dev, &conn_iter);
 	for_each_intel_connector_iter(connector, &conn_iter) {
-		if (connector->modeset_retry_work.func)
-			cancel_work_sync(&connector->modeset_retry_work);
 		if (connector->hdcp_shim) {
 			cancel_delayed_work_sync(&connector->hdcp_check_work);
 			cancel_work_sync(&connector->hdcp_prop_work);
 		}
+
+		if (connector->base.connector_type !=
+		    DRM_MODE_CONNECTOR_DisplayPort)
+			continue;
+
+		if (connector->mst_port) {
+			work = &connector->mst_port->modeset_retry_work;
+		} else {
+			struct intel_encoder *intel_encoder =
+				connector->encoder;
+			struct intel_dp *intel_dp;
+
+			if (!intel_encoder)
+				continue;
+
+			intel_dp = enc_to_intel_dp(&intel_encoder->base);
+			work = &intel_dp->modeset_retry_work;
+		}
+
+		cancel_work_sync(work);
 	}
 	drm_connector_list_iter_end(&conn_iter);
 }
diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 4dd1b2287dd6..5abf0c95725a 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -6261,12 +6261,10 @@ static bool intel_edp_init_connector(struct intel_dp *intel_dp,
 
 static void intel_dp_modeset_retry_work_fn(struct work_struct *work)
 {
-	struct intel_connector *intel_connector;
-	struct drm_connector *connector;
+	struct intel_dp *intel_dp = container_of(work, typeof(*intel_dp),
+						 modeset_retry_work);
+	struct drm_connector *connector = &intel_dp->attached_connector->base;
 
-	intel_connector = container_of(work, typeof(*intel_connector),
-				       modeset_retry_work);
-	connector = &intel_connector->base;
 	DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n", connector->base.id,
 		      connector->name);
 
@@ -6295,7 +6293,7 @@ intel_dp_init_connector(struct intel_digital_port *intel_dig_port,
 	int type;
 
 	/* Initialize the work for modeset in case of link train failure */
-	INIT_WORK(&intel_connector->modeset_retry_work,
+	INIT_WORK(&intel_dp->modeset_retry_work,
 		  intel_dp_modeset_retry_work_fn);
 
 	if (WARN(intel_dig_port->max_lanes < 1,
diff --git a/drivers/gpu/drm/i915/intel_dp_link_training.c b/drivers/gpu/drm/i915/intel_dp_link_training.c
index f59b59bb0a21..2cfa58ce1f95 100644
--- a/drivers/gpu/drm/i915/intel_dp_link_training.c
+++ b/drivers/gpu/drm/i915/intel_dp_link_training.c
@@ -340,7 +340,7 @@ intel_dp_start_link_train(struct intel_dp *intel_dp)
 							     intel_dp->link_rate,
 							     intel_dp->lane_count))
 			/* Schedule a Hotplug Uevent to userspace to start modeset */
-			schedule_work(&intel_connector->modeset_retry_work);
+			schedule_work(&intel_dp->modeset_retry_work);
 	} else {
 		DRM_ERROR("[CONNECTOR:%d:%s] Link Training failed at link rate = %d, lane count = %d",
 			  intel_connector->base.base.id,
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index 83e5ca889d9c..3f19dc80997f 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -406,9 +406,6 @@ struct intel_connector {
 
 	struct intel_dp *mst_port;
 
-	/* Work struct to schedule a uevent on link train failure */
-	struct work_struct modeset_retry_work;
-
 	const struct intel_hdcp_shim *hdcp_shim;
 	struct mutex hdcp_mutex;
 	uint64_t hdcp_value; /* protected by hdcp_mutex */
@@ -1135,6 +1132,9 @@ struct intel_dp {
 
 	/* Displayport compliance testing */
 	struct intel_dp_compliance compliance;
+
+	/* Work struct to schedule a uevent on link train failure */
+	struct work_struct modeset_retry_work;
 };
 
 struct intel_lspcon {
-- 
2.14.3

Re: [PATCH v2 2/6] drm/i915: Move DP modeset retry work into intel_dp

[Manasi Navare]

On Thu, Mar 08, 2018 at 06:41:22PM -0500, Lyude Paul wrote:
> While having the modeset_retry_work in intel_connector makes sense with
> SST, this paradigm doesn't make a whole ton of sense when it comes to
> MST since we have to deal with multiple connectors. In most cases, it's
> more useful to just use the intel_dp struct since it indicates whether
> or not we're dealing with an MST device, along with being able to easily
> trace the intel_dp struct back to it's respective connector (if there is
> any). So, move the modeset_retry_work function out of the
> intel_connector struct and into intel_dp.
> 
> V2:
>  - Remove accidental duplicate modeset_retry_work in intel_connector
> 
> Signed-off-by: Lyude Paul <lyude@redhat.com>
> Cc: Manasi Navare <manasi.d.navare@intel.com>
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
>  drivers/gpu/drm/i915/intel_display.c          | 23 +++++++++++++++++++++--
>  drivers/gpu/drm/i915/intel_dp.c               | 10 ++++------
>  drivers/gpu/drm/i915/intel_dp_link_training.c |  2 +-
>  drivers/gpu/drm/i915/intel_drv.h              |  6 +++---
>  4 files changed, 29 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index f424fff477f6..85d5af4e4f5b 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -15394,16 +15394,35 @@ static void intel_hpd_poll_fini(struct drm_device *dev)
>  {
>  	struct intel_connector *connector;
>  	struct drm_connector_list_iter conn_iter;
> +	struct work_struct *work;
>  
>  	/* Kill all the work that may have been queued by hpd. */
>  	drm_connector_list_iter_begin(dev, &conn_iter);
>  	for_each_intel_connector_iter(connector, &conn_iter) {
> -		if (connector->modeset_retry_work.func)
> -			cancel_work_sync(&connector->modeset_retry_work);
>  		if (connector->hdcp_shim) {
>  			cancel_delayed_work_sync(&connector->hdcp_check_work);
>  			cancel_work_sync(&connector->hdcp_prop_work);
>  		}
> +
> +		if (connector->base.connector_type !=
> +		    DRM_MODE_CONNECTOR_DisplayPort)

I know we dont fallback on eDP now but since link training is a common code between
eDP and DP, this modeset retry can also be called from eDP. So we should check against
DRM_MODE_CONNECTOR_eDP type as well.

Other than that, I agree that it is better for this work function to be part of intel_dp struct
as opposed to intel_connector. 

So after this change,

Reviewed-by: Manasi Navare <manasi.d.navare@intel.com>

Manasi

> +			continue;
> +
> +		if (connector->mst_port) {
> +			work = &connector->mst_port->modeset_retry_work;
> +		} else {
> +			struct intel_encoder *intel_encoder =
> +				connector->encoder;
> +			struct intel_dp *intel_dp;
> +
> +			if (!intel_encoder)
> +				continue;
> +
> +			intel_dp = enc_to_intel_dp(&intel_encoder->base);
> +			work = &intel_dp->modeset_retry_work;
> +		}
> +
> +		cancel_work_sync(work);
>  	}
>  	drm_connector_list_iter_end(&conn_iter);
>  }
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 4dd1b2287dd6..5abf0c95725a 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -6261,12 +6261,10 @@ static bool intel_edp_init_connector(struct intel_dp *intel_dp,
>  
>  static void intel_dp_modeset_retry_work_fn(struct work_struct *work)
>  {
> -	struct intel_connector *intel_connector;
> -	struct drm_connector *connector;
> +	struct intel_dp *intel_dp = container_of(work, typeof(*intel_dp),
> +						 modeset_retry_work);
> +	struct drm_connector *connector = &intel_dp->attached_connector->base;
>  
> -	intel_connector = container_of(work, typeof(*intel_connector),
> -				       modeset_retry_work);
> -	connector = &intel_connector->base;
>  	DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n", connector->base.id,
>  		      connector->name);
>  
> @@ -6295,7 +6293,7 @@ intel_dp_init_connector(struct intel_digital_port *intel_dig_port,
>  	int type;
>  
>  	/* Initialize the work for modeset in case of link train failure */
> -	INIT_WORK(&intel_connector->modeset_retry_work,
> +	INIT_WORK(&intel_dp->modeset_retry_work,
>  		  intel_dp_modeset_retry_work_fn);
>  
>  	if (WARN(intel_dig_port->max_lanes < 1,
> diff --git a/drivers/gpu/drm/i915/intel_dp_link_training.c b/drivers/gpu/drm/i915/intel_dp_link_training.c
> index f59b59bb0a21..2cfa58ce1f95 100644
> --- a/drivers/gpu/drm/i915/intel_dp_link_training.c
> +++ b/drivers/gpu/drm/i915/intel_dp_link_training.c
> @@ -340,7 +340,7 @@ intel_dp_start_link_train(struct intel_dp *intel_dp)
>  							     intel_dp->link_rate,
>  							     intel_dp->lane_count))
>  			/* Schedule a Hotplug Uevent to userspace to start modeset */
> -			schedule_work(&intel_connector->modeset_retry_work);
> +			schedule_work(&intel_dp->modeset_retry_work);
>  	} else {
>  		DRM_ERROR("[CONNECTOR:%d:%s] Link Training failed at link rate = %d, lane count = %d",
>  			  intel_connector->base.base.id,
> diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> index 83e5ca889d9c..3f19dc80997f 100644
> --- a/drivers/gpu/drm/i915/intel_drv.h
> +++ b/drivers/gpu/drm/i915/intel_drv.h
> @@ -406,9 +406,6 @@ struct intel_connector {
>  
>  	struct intel_dp *mst_port;
>  
> -	/* Work struct to schedule a uevent on link train failure */
> -	struct work_struct modeset_retry_work;
> -
>  	const struct intel_hdcp_shim *hdcp_shim;
>  	struct mutex hdcp_mutex;
>  	uint64_t hdcp_value; /* protected by hdcp_mutex */
> @@ -1135,6 +1132,9 @@ struct intel_dp {
>  
>  	/* Displayport compliance testing */
>  	struct intel_dp_compliance compliance;
> +
> +	/* Work struct to schedule a uevent on link train failure */
> +	struct work_struct modeset_retry_work;
>  };
>  
>  struct intel_lspcon {
> -- 
> 2.14.3
> 

[PATCH 3/6] drm/i915: Only use one link bw config for MST topologies

[Lyude Paul]

When a DP MST link needs retraining, sometimes the hub will detect that
the current link bw config is impossible and will update it's RX caps in
the DPCD to reflect the new maximum link rate. Currently, we make the
assumption that the RX caps in the dpcd will never change like this.
This means if the sink changes it's RX caps after we've already set up
an MST link and we attempt to add or remove another sink from the
topology, we could put ourselves into an invalid state where we've tried
to configure different sinks on the same MST topology with different
link rates. We could also run into this situation if a sink reports a
higher link rate after suspend, usually from us having trained it with a
fallback bw configuration before suspending.

So: "lock" the bw config by only using the max DP link rate/lane count
on the first modeset for an MST topology. For every modeset following,
we instead use the last configured link bw for this topology. We only
unlock the bw config when we've detected a new MST sink.

Signed-off-by: Lyude Paul <lyude@redhat.com>
Cc: Manasi Navare <manasi.d.navare@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
---
 drivers/gpu/drm/i915/intel_dp.c     | 11 +++++++++--
 drivers/gpu/drm/i915/intel_dp_mst.c | 22 +++++++++++++++-------
 drivers/gpu/drm/i915/intel_drv.h    |  6 ++++++
 3 files changed, 30 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 5abf0c95725a..5645a194de92 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -3871,18 +3871,25 @@ intel_dp_can_mst(struct intel_dp *intel_dp)
 static void
 intel_dp_configure_mst(struct intel_dp *intel_dp)
 {
+	bool was_mst;
+
 	if (!i915_modparams.enable_dp_mst)
 		return;
 
 	if (!intel_dp->can_mst)
 		return;
 
+	was_mst = intel_dp->is_mst;
 	intel_dp->is_mst = intel_dp_can_mst(intel_dp);
 
-	if (intel_dp->is_mst)
+	if (intel_dp->is_mst) {
 		DRM_DEBUG_KMS("Sink is MST capable\n");
-	else
+
+		if (!was_mst)
+			intel_dp->mst_bw_locked = false;
+	} else {
 		DRM_DEBUG_KMS("Sink is not MST capable\n");
+	}
 
 	drm_dp_mst_topology_mgr_set_mst(&intel_dp->mst_mgr,
 					intel_dp->is_mst);
diff --git a/drivers/gpu/drm/i915/intel_dp_mst.c b/drivers/gpu/drm/i915/intel_dp_mst.c
index c3de0918ee13..c0553456b18e 100644
--- a/drivers/gpu/drm/i915/intel_dp_mst.c
+++ b/drivers/gpu/drm/i915/intel_dp_mst.c
@@ -42,7 +42,7 @@ static bool intel_dp_mst_compute_config(struct intel_encoder *encoder,
 		to_intel_connector(conn_state->connector);
 	struct drm_atomic_state *state = pipe_config->base.state;
 	int bpp;
-	int lane_count, slots;
+	int lane_count, link_rate, slots;
 	const struct drm_display_mode *adjusted_mode = &pipe_config->base.adjusted_mode;
 	int mst_pbn;
 	bool reduce_m_n = drm_dp_has_quirk(&intel_dp->desc,
@@ -56,16 +56,22 @@ static bool intel_dp_mst_compute_config(struct intel_encoder *encoder,
 			      bpp);
 	}
 	/*
-	 * for MST we always configure max link bw - the spec doesn't
-	 * seem to suggest we should do otherwise.
+	 * for MST we always configure max link bw if we don't know better -
+	 * the spec doesn't seem to suggest we should do otherwise. But,
+	 * ensure it always stays consistent with the rest of this hub's
+	 * state.
 	 */
-	lane_count = intel_dp_max_lane_count(intel_dp);
+	if (intel_dp->mst_bw_locked) {
+		lane_count = intel_dp->lane_count;
+		link_rate = intel_dp->link_rate;
+	} else {
+		lane_count = intel_dp_max_lane_count(intel_dp);
+		link_rate = intel_dp_max_link_rate(intel_dp);
+	}
 
 	pipe_config->lane_count = lane_count;
-
 	pipe_config->pipe_bpp = bpp;
-
-	pipe_config->port_clock = intel_dp_max_link_rate(intel_dp);
+	pipe_config->port_clock = link_rate;
 
 	if (drm_dp_mst_port_has_audio(&intel_dp->mst_mgr, connector->port))
 		pipe_config->has_audio = true;
@@ -221,6 +227,8 @@ static void intel_mst_pre_enable_dp(struct intel_encoder *encoder,
 	connector->encoder = encoder;
 	intel_mst->connector = connector;
 
+	intel_dp->mst_bw_locked = true;
+
 	DRM_DEBUG_KMS("active links %d\n", intel_dp->active_mst_links);
 
 	drm_dp_send_power_updown_phy(&intel_dp->mst_mgr, connector->port, true);
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index 3700fcfddb1f..e5d3ef6754a5 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -1110,6 +1110,12 @@ struct intel_dp {
 	bool can_mst; /* this port supports mst */
 	bool is_mst;
 	int active_mst_links;
+	/* Set when we've already decided on a link bw for mst, to prevent us
+	 * from setting different link bandwiths if the hub tries to confuse
+	 * us by changing it later
+	 */
+	bool mst_bw_locked;
+
 	/* connector directly attached - won't be use for modeset in mst world */
 	struct intel_connector *attached_connector;
 
-- 
2.14.3

[PATCH 4/6] drm/dp_mst: Add drm_dp_mst_topology_mgr_lower_link_rate()

[Lyude Paul]

Unlike SST, MST can have far more then a single display hooked up on a
single port. What this also means however, is that if the DisplayPort
link to the top-level MST branch device becomes unstable then every
single branch device also has an unstable link. Additionally, MST has a
few more steps that must be taken in order to properly retrain the
entire topology under a lower link rate. Since the VCID allocations for
each mstb is determined based off the link rate for the top of the
topology, we also have to recalculate all of the VCID allocations for
the downstream ports as well to ensure that we still have enough link
bandwidth to drive each mstb.

Additionally, since we have multiple downstream connectors per port,
setting the link status of the parent mstb's port to bad isn't enough:
all of the downstream mstb ports have to have their link status set to
bad.

This basically follows the same paradigm that our DP link status logic
in DRM does, in that we simply tell userspace that all of the mstb ports
need retraining and additionally applying the new lower bandwidth
constraints to all of the atomic commits on the topology that follow.

Since the work of figuring out which connectors live downstream on an
MST topology and updating their link status is something that any driver
supporting MST is going to need to do in order to retrain MST links
properly, we add the drm_dp_mst_topology_mgr_lower_link_rate() helper
which simply recalculates the pbn_div for a given mst topology, then
marks the link status of all connectors living in that topology as bad.
We'll make use of it in i915 later in this series.

Signed-off-by: Lyude Paul <lyude@redhat.com>
Cc: Manasi Navare <manasi.d.navare@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
---
 drivers/gpu/drm/drm_dp_mst_topology.c | 73 ++++++++++++++++++++++++++++++++++-
 include/drm/drm_dp_mst_helper.h       |  3 ++
 2 files changed, 75 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index 6fac4129e6a2..0d6604500b29 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -2076,7 +2076,7 @@ static bool drm_dp_get_vc_payload_bw(int dp_link_bw,
 {
 	switch (dp_link_bw) {
 	default:
-		DRM_DEBUG_KMS("invalid link bandwidth in DPCD: %x (link count: %d)\n",
+		DRM_DEBUG_KMS("invalid link bandwidth: %x (link count: %d)\n",
 			      dp_link_bw, dp_link_count);
 		return false;
 
@@ -2096,6 +2096,77 @@ static bool drm_dp_get_vc_payload_bw(int dp_link_bw,
 	return true;
 }
 
+static void drm_dp_set_mstb_link_status(struct drm_dp_mst_branch *mstb,
+					enum drm_link_status status)
+{
+	struct drm_dp_mst_branch *rmstb;
+	struct drm_dp_mst_port *port;
+
+	list_for_each_entry(port, &mstb->ports, next) {
+		rmstb = drm_dp_get_validated_mstb_ref(mstb->mgr, port->mstb);
+		if (rmstb) {
+			drm_dp_set_mstb_link_status(rmstb, status);
+			drm_dp_put_mst_branch_device(rmstb);
+		}
+
+		if (port->connector)
+			port->connector->state->link_status = status;
+	}
+}
+
+/**
+ * drm_dp_mst_topology_mgr_lower_link_rate() - Override the DP link bw/count
+ * for all connectors in a given MST topology
+ * @mgr: manager to set state for
+ * @dp_link_bw: The new DP link bandwidth
+ * @dp_link_count: The new DP link count
+ *
+ * This is called by the driver when it detects that the current DP link for
+ * the given topology manager is unstable, and needs to be retrained at a
+ * lower link rate.
+ *
+ * This takes care of updating the link status on all downstream connectors
+ * along with recalculating the VC payloads. The driver should send a hotplug
+ * event after calling this function to notify userspace of the link status
+ * change.
+ *
+ * RETURNS:
+ *
+ * True for success, or negative error code on failure.
+ */
+int drm_dp_mst_topology_mgr_lower_link_rate(struct drm_dp_mst_topology_mgr *mgr,
+					    int dp_link_bw, int dp_link_count)
+{
+	struct drm_device *dev = mgr->dev;
+	struct drm_dp_mst_branch *mst_primary;
+	int new_pbn_div;
+	int ret = 0;
+
+	drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
+
+	if (!drm_dp_get_vc_payload_bw(drm_dp_link_rate_to_bw_code(dp_link_bw),
+				      dp_link_count, &new_pbn_div)) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	mst_primary = drm_dp_get_validated_mstb_ref(mgr, mgr->mst_primary);
+	if (!mst_primary)
+		goto out;
+
+	DRM_DEBUG_KMS("MST link failed to retrain, lowering pbn_div to %d\n",
+		      new_pbn_div);
+	mgr->pbn_div = new_pbn_div;
+
+	drm_dp_set_mstb_link_status(mst_primary, DRM_MODE_LINK_STATUS_BAD);
+
+	drm_dp_put_mst_branch_device(mst_primary);
+out:
+	drm_modeset_unlock(&dev->mode_config.connection_mutex);
+	return ret;
+}
+EXPORT_SYMBOL(drm_dp_mst_topology_mgr_lower_link_rate);
+
 /**
  * drm_dp_mst_topology_mgr_set_mst() - Set the MST state for a topology manager
  * @mgr: manager to set state for
diff --git a/include/drm/drm_dp_mst_helper.h b/include/drm/drm_dp_mst_helper.h
index 7f78d26a0766..6261ec43a2c0 100644
--- a/include/drm/drm_dp_mst_helper.h
+++ b/include/drm/drm_dp_mst_helper.h
@@ -634,4 +634,7 @@ int drm_dp_atomic_release_vcpi_slots(struct drm_atomic_state *state,
 int drm_dp_send_power_updown_phy(struct drm_dp_mst_topology_mgr *mgr,
 				 struct drm_dp_mst_port *port, bool power_up);
 
+int drm_dp_mst_topology_mgr_lower_link_rate(struct drm_dp_mst_topology_mgr *mgr,
+					    int dp_link_bw, int dp_link_count);
+
 #endif
-- 
2.14.3

[PATCH 5/6] drm/dp_mst: Add drm_atomic_dp_mst_retrain_topology()

[Lyude Paul]

Retraining MST is rather difficult. In order to do it properly while
guaranteeing that we'll never run into a spot where we commit a
physically impossible configuration, we have to do a lot of checks on
atomic commits which affect MST topologies. All of this work is going to
need to be repeated for every driver at some point, so let's save
ourselves some trouble and just implement these atomic checks as
a single helper.

Signed-off-by: Lyude Paul <lyude@redhat.com>
Cc: Manasi Navare <manasi.d.navare@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
---
 drivers/gpu/drm/drm_dp_mst_topology.c | 223 ++++++++++++++++++++++++++++++++++
 include/drm/drm_dp_mst_helper.h       |   2 +
 2 files changed, 225 insertions(+)

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index 0d6604500b29..c4a91b1ba61b 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -2167,6 +2167,229 @@ int drm_dp_mst_topology_mgr_lower_link_rate(struct drm_dp_mst_topology_mgr *mgr,
 }
 EXPORT_SYMBOL(drm_dp_mst_topology_mgr_lower_link_rate);
 
+static bool drm_atomic_dp_mst_state_only_disables_mstbs(struct drm_atomic_state *state,
+							struct drm_dp_mst_topology_mgr *mgr,
+							struct drm_dp_mst_branch *mstb)
+{
+	struct drm_dp_mst_branch *rmstb;
+	struct drm_dp_mst_port *port;
+	struct drm_connector *connector;
+	struct drm_connector_state *conn_state;
+	struct drm_crtc *crtc;
+	struct drm_crtc_state *crtc_state;
+	int ret;
+
+	list_for_each_entry(port, &mstb->ports, next) {
+		rmstb = drm_dp_get_validated_mstb_ref(mstb->mgr, port->mstb);
+		if (rmstb) {
+			ret = drm_atomic_dp_mst_state_only_disables_mstbs(
+			    state, mgr, rmstb);
+			drm_dp_put_mst_branch_device(rmstb);
+			if (!ret)
+				return false;
+		}
+
+		connector = port->connector;
+		if (!connector)
+			continue;
+
+		conn_state = drm_atomic_get_new_connector_state(
+		    state, connector);
+		if (!conn_state)
+			continue;
+
+		crtc = conn_state->crtc;
+		if (!crtc)
+			continue;
+
+		crtc_state = drm_atomic_get_new_crtc_state(state, crtc);
+		if (!crtc_state)
+			continue;
+
+		if (drm_atomic_crtc_needs_modeset(crtc_state))
+			return false;
+	}
+
+	return true;
+}
+
+static int drm_atomic_dp_mst_all_mstbs_disabled(struct drm_atomic_state *state,
+						struct drm_dp_mst_topology_mgr *mgr,
+						struct drm_dp_mst_branch *mstb)
+{
+	struct drm_dp_mst_branch *rmstb;
+	struct drm_dp_mst_port *port;
+	struct drm_connector *connector;
+	struct drm_connector_state *conn_state;
+	int ret;
+
+	list_for_each_entry(port, &mstb->ports, next) {
+		rmstb = drm_dp_get_validated_mstb_ref(mstb->mgr, port->mstb);
+		if (rmstb) {
+			ret = drm_atomic_dp_mst_all_mstbs_disabled(
+			    state, mgr, rmstb);
+			drm_dp_put_mst_branch_device(rmstb);
+			if (ret <= 0)
+				return ret;
+		}
+
+		connector = port->connector;
+		if (!connector)
+			continue;
+
+		conn_state = drm_atomic_get_connector_state(
+		    state, connector);
+		if (IS_ERR(conn_state))
+			return PTR_ERR(conn_state);
+
+		if (conn_state->crtc)
+			return false;
+	}
+
+	/* No enabled CRTCs found */
+	return true;
+}
+
+static int drm_atomic_dp_mst_retrain_mstb(struct drm_atomic_state *state,
+					  struct drm_dp_mst_topology_mgr *mgr,
+					  struct drm_dp_mst_branch *mstb,
+					  bool full_modeset)
+{
+	struct drm_dp_mst_branch *rmstb;
+	struct drm_dp_mst_port *port;
+	struct drm_connector *connector;
+	struct drm_connector_state *conn_state;
+	struct drm_crtc *crtc;
+	struct drm_crtc_state *crtc_state;
+	int ret;
+
+	list_for_each_entry(port, &mstb->ports, next) {
+		rmstb = drm_dp_get_validated_mstb_ref(mstb->mgr, port->mstb);
+		if (rmstb) {
+			ret = drm_atomic_dp_mst_retrain_mstb(
+			    state, mgr, rmstb, full_modeset);
+			drm_dp_put_mst_branch_device(rmstb);
+			if (ret)
+				return ret;
+		}
+
+		connector = port->connector;
+		if (!connector)
+			continue;
+
+		conn_state = drm_atomic_get_connector_state(state, connector);
+		if (IS_ERR(conn_state))
+			return PTR_ERR(conn_state);
+
+		if (conn_state->link_status != DRM_MODE_LINK_STATUS_GOOD) {
+			DRM_DEBUG_ATOMIC("[CONNECTOR:%d:%s] link status bad -> good\n",
+					 connector->base.id, connector->name);
+			conn_state->link_status = DRM_MODE_LINK_STATUS_GOOD;
+		}
+
+		if (!full_modeset)
+			continue;
+
+		crtc = conn_state->crtc;
+		if (!crtc)
+			continue;
+
+		crtc_state = drm_atomic_get_crtc_state(state, crtc);
+		if (IS_ERR(crtc_state))
+			return PTR_ERR(crtc_state);
+
+		if (!crtc_state->mode_changed) {
+			DRM_DEBUG_ATOMIC("[CRTC:%d:%s] needs full modeset\n",
+					 crtc->base.id, crtc->name);
+			crtc_state->mode_changed = true;
+		}
+	}
+
+	return 0;
+}
+
+/**
+ * drm_atomic_dp_mst_retrain_topology() - prepare a modeset that will retrain
+ * an MST topology
+ * @state: The new state that would retrain the topology link
+ * @mgr: The topology manager to use
+ *
+ * After userspace has been signaled that connectors are in need of
+ * retraining, it's expected that a modeset will be performed for any CRTCs on
+ * said connectors. Since all of the branch devices in an MST topology share a
+ * single link, they also share the same link status, lane count, and link
+ * rate.
+ *
+ * Since all of these characteristics are shared, there's only two valid
+ * solutions when fallback link training parameters need to be applied. The
+ * first is simply unassigning each mstb connector's CRTC. Since this action
+ * can only free slots on the VCPI table and not allocate them, this can be
+ * done without pulling in additional CRTCs on the MST topology. Additionally
+ * if this action would result in there no longer being any CRTCs assigned to
+ * mstb connectors, this would be enough to bring the topology back into a
+ * trained state since there would be nothing left requiring VCPI
+ * reallocations.
+ *
+ * The second solution is to commit new modes to all of the connectors on the
+ * topology. Since this action would result in VCPI reallocations with a new
+ * link rate and lane count, a modeset must also be performed on every other
+ * CRTC driving a branch device on the given topology at the same time. This
+ * is to ensure that all VCPI allocations are properly recalculated in
+ * response to the new link rate and lane count, that the new modes will fit
+ * into the recalculated VCPI table, and that the new atomic state could never
+ * result in an otherwise physically impossible configuration (e.g. different
+ * mstbs with CRTCs trained to different link rates/lane counts).
+ *
+ * Finally, any atomic commit which would result in going from an
+ * unrecoverable link state to a properly trained link state must also take
+ * care of appropriately updating the link status properties of all connectors
+ * on the topology from bad to good. This function takes care of all of these
+ * checks in @state for the topology manager @mgr including possibly pulling
+ * in additional CRTCs into the modeset, and possibly updating the link status
+ * of each mstb's DRM connector.
+ *
+ * This function should be called within the driver's atomic check callbacks
+ * whenever a modeset happens on an MST connector with it's link status set to
+ * DRM_MODE_LINK_STATUS_BAD.
+ *
+ * RETURNS:
+ *
+ * Returns 0 for success, or negative error code for failure.
+ */
+int drm_atomic_dp_mst_retrain_topology(struct drm_atomic_state *state,
+				       struct drm_dp_mst_topology_mgr *mgr)
+{
+	struct drm_dp_mst_branch *mstb =
+		drm_dp_get_validated_mstb_ref(mgr, mgr->mst_primary);
+	int ret = 0;
+	bool need_modeset = false;
+
+	if (!mstb)
+		return 0;
+
+	if (drm_atomic_dp_mst_state_only_disables_mstbs(state, mgr, mstb)) {
+		ret = drm_atomic_dp_mst_all_mstbs_disabled(state, mgr, mstb);
+		if (ret < 0)
+			goto out;
+
+		if (ret)
+			DRM_DEBUG_ATOMIC("state %p disables all CRTCs on mst mgr %p\n",
+					 state, mgr);
+		else
+			goto out; /* valid, but doesn't retrain link */
+	} else {
+		DRM_DEBUG_ATOMIC("state %p requires full modeset for CRTCs on mst mgr %p\n",
+				 state, mgr);
+		need_modeset = true;
+	}
+
+	ret = drm_atomic_dp_mst_retrain_mstb(state, mgr, mstb, need_modeset);
+out:
+	drm_dp_put_mst_branch_device(mgr->mst_primary);
+	return ret;
+}
+EXPORT_SYMBOL(drm_atomic_dp_mst_retrain_topology);
+
 /**
  * drm_dp_mst_topology_mgr_set_mst() - Set the MST state for a topology manager
  * @mgr: manager to set state for
diff --git a/include/drm/drm_dp_mst_helper.h b/include/drm/drm_dp_mst_helper.h
index 6261ec43a2c0..24075eb2dd1b 100644
--- a/include/drm/drm_dp_mst_helper.h
+++ b/include/drm/drm_dp_mst_helper.h
@@ -636,5 +636,7 @@ int drm_dp_send_power_updown_phy(struct drm_dp_mst_topology_mgr *mgr,
 
 int drm_dp_mst_topology_mgr_lower_link_rate(struct drm_dp_mst_topology_mgr *mgr,
 					    int dp_link_bw, int dp_link_count);
+int drm_atomic_dp_mst_retrain_topology(struct drm_atomic_state *state,
+				       struct drm_dp_mst_topology_mgr *mgr);
 
 #endif
-- 
2.14.3

[PATCH 6/6] drm/i915: Implement proper fallback training for MST

[Lyude Paul]

For a while we actually haven't had any way of retraining MST links with
fallback link parameters like we do with SST. While uncommon, certain
setups such as my Caldigit TS3 + EVGA MST hub require this since
otherwise, they end up getting stuck in an infinite MST retraining loop.

MST retraining is somewhat different then SST retraining. While it's
possible during the normal link retraining sequence for a hub to indicate
bad link status, it's also possible for a hub to only indicate this
status through ESI messages and it's possible for this to happen after
the initial link training succeeds. This can lead to a pattern that
looks like this:

- Train MST link
- Training completes successfully
- MST hub sets Channel EQ failed bit in ESI
- Retraining starts
- Retraining completes successfully
- MST hub sets Channel EQ failed bit in ESI again
- Rinse and repeat

In these situations, we need to be able to actually trigger fallback
link training from the ESI handler as well, along with using the ESI
handler during retraining to figure out whether or not our retraining
actually succeeded.

This gets a bit more complicated since we have to ensure that we don't
block the ESI handler at all while doing retraining. If we do, due to
DisplayPort's general issues with being sensitive to IRQ latency most
MST hubs will just stop responding to us if their interrupts aren't
handled in a timely manner.

So: move retraining into it's own seperate handler. Running in a
seperate handler allows us to avoid stalling the ESI during link
retraining, and we can have the ESI signal that the channel EQ bit was
cleared through a simple completion struct. Additionally, we take care
to stick as much of this into the SST retraining path as possible since
sharing is caring.

Signed-off-by: Lyude Paul <lyude@redhat.com>
Cc: Manasi Navare <manasi.d.navare@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
---
 drivers/gpu/drm/i915/intel_dp.c     | 342 +++++++++++++++++++++++++++---------
 drivers/gpu/drm/i915/intel_dp_mst.c |  42 ++++-
 drivers/gpu/drm/i915/intel_drv.h    |   8 +
 3 files changed, 302 insertions(+), 90 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 5645a194de92..7626652732b6 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -45,6 +45,8 @@
 
 #define DP_DPRX_ESI_LEN 14
 
+#define DP_MST_RETRAIN_TIMEOUT (msecs_to_jiffies(100))
+
 /* Compliance test status bits  */
 #define INTEL_DP_RESOLUTION_SHIFT_MASK	0
 #define INTEL_DP_RESOLUTION_PREFERRED	(1 << INTEL_DP_RESOLUTION_SHIFT_MASK)
@@ -4224,6 +4226,118 @@ static void intel_dp_handle_test_request(struct intel_dp *intel_dp)
 		DRM_DEBUG_KMS("Could not write test response to sink\n");
 }
 
+/* Get a mask of the CRTCs that are running on the given intel_dp struct. For
+ * MST, this returns a crtc mask containing all of the CRTCs driving
+ * downstream sinks, for SST it just returns a mask of the attached
+ * connector's CRTC.
+ */
+int
+intel_dp_get_crtc_mask(struct intel_dp *intel_dp)
+{
+	struct drm_device *dev = dp_to_dig_port(intel_dp)->base.base.dev;
+	struct drm_connector *connector;
+	struct drm_connector_state *conn_state;
+	struct intel_connector *intel_connector;
+	struct drm_crtc *crtc;
+	int crtc_mask = 0;
+
+	WARN_ON(!drm_modeset_is_locked(&dev->mode_config.connection_mutex));
+
+	if (intel_dp->is_mst) {
+		struct drm_connector_list_iter conn_iter;
+
+		drm_connector_list_iter_begin(dev, &conn_iter);
+		for_each_intel_connector_iter(intel_connector, &conn_iter) {
+			if (intel_connector->mst_port != intel_dp)
+				continue;
+
+			conn_state = intel_connector->base.state;
+			if (!conn_state->crtc)
+				continue;
+
+			crtc_mask |= drm_crtc_mask(conn_state->crtc);
+		}
+		drm_connector_list_iter_end(&conn_iter);
+	} else {
+		connector = &intel_dp->attached_connector->base;
+		crtc = connector->state->crtc;
+
+		if (crtc)
+			crtc_mask |= drm_crtc_mask(crtc);
+	}
+
+	return crtc_mask;
+}
+
+static bool
+intel_dp_needs_link_retrain(struct intel_dp *intel_dp,
+			    const u8 esi[DP_DPRX_ESI_LEN])
+{
+	u8 buf[max(DP_LINK_STATUS_SIZE, DP_DPRX_ESI_LEN)];
+	const u8 *link_status = NULL;
+
+	if (intel_dp->is_mst) {
+		if (!intel_dp->active_mst_links)
+			return false;
+		if (intel_dp->mst_link_is_bad)
+			return false;
+
+		if (esi) {
+			link_status = &esi[10];
+		} else {
+			/* We're not running from the ESI handler, so wait a
+			 * little bit to see if the ESI handler lets us know
+			 * that the link status is OK
+			 */
+			if (wait_for_completion_timeout(
+				&intel_dp->mst_retrain_completion,
+				DP_MST_RETRAIN_TIMEOUT))
+				return false;
+		}
+	} else {
+		if (intel_dp->link_trained)
+			return false;
+		if (!intel_dp_get_link_status(intel_dp, buf))
+			return false;
+
+		link_status = buf;
+	}
+
+	/*
+	 * Validate the cached values of intel_dp->link_rate and
+	 * intel_dp->lane_count before attempting to retrain.
+	 */
+	if (!intel_dp_link_params_valid(intel_dp, intel_dp->link_rate,
+					intel_dp->lane_count))
+		return false;
+
+	if (link_status) {
+		return !drm_dp_channel_eq_ok(link_status,
+					     intel_dp->lane_count);
+	} else {
+		return true;
+	}
+}
+
+static inline void
+intel_dp_mst_check_link_status(struct intel_dp *intel_dp,
+			       const u8 esi[DP_DPRX_ESI_LEN])
+{
+	if (intel_dp_needs_link_retrain(intel_dp, esi)) {
+		DRM_DEBUG_KMS("Channel EQ failing\n");
+
+		if (!work_busy(&intel_dp->mst_retrain_work)) {
+			reinit_completion(&intel_dp->mst_retrain_completion);
+			schedule_work(&intel_dp->mst_retrain_work);
+			DRM_DEBUG_KMS("Retraining started\n");
+		}
+	} else if (work_busy(&intel_dp->mst_retrain_work) &&
+		   !completion_done(&intel_dp->mst_retrain_completion)) {
+		DRM_DEBUG_KMS("Channel EQ stable\n");
+		complete_all(&intel_dp->mst_retrain_completion);
+	}
+}
+
 static int
 intel_dp_check_mst_status(struct intel_dp *intel_dp)
 {
@@ -4237,14 +4351,7 @@ intel_dp_check_mst_status(struct intel_dp *intel_dp)
 		bret = intel_dp_get_sink_irq_esi(intel_dp, esi);
 go_again:
 		if (bret == true) {
-
-			/* check link status - esi[10] = 0x200c */
-			if (intel_dp->active_mst_links &&
-			    !drm_dp_channel_eq_ok(&esi[10], intel_dp->lane_count)) {
-				DRM_DEBUG_KMS("channel EQ not ok, retraining\n");
-				intel_dp_start_link_train(intel_dp);
-				intel_dp_stop_link_train(intel_dp);
-			}
+			intel_dp_mst_check_link_status(intel_dp, esi);
 
 			DRM_DEBUG_KMS("got esi %3ph\n", esi);
 			ret = drm_dp_mst_hpd_irq(&intel_dp->mst_mgr, esi, &handled);
@@ -4281,29 +4388,6 @@ intel_dp_check_mst_status(struct intel_dp *intel_dp)
 	return -EINVAL;
 }
 
-static bool
-intel_dp_needs_link_retrain(struct intel_dp *intel_dp)
-{
-	u8 link_status[DP_LINK_STATUS_SIZE];
-
-	if (!intel_dp->link_trained)
-		return false;
-
-	if (!intel_dp_get_link_status(intel_dp, link_status))
-		return false;
-
-	/*
-	 * Validate the cached values of intel_dp->link_rate and
-	 * intel_dp->lane_count before attempting to retrain.
-	 */
-	if (!intel_dp_link_params_valid(intel_dp, intel_dp->link_rate,
-					intel_dp->lane_count))
-		return false;
-
-	/* Retrain if Channel EQ or CR not ok */
-	return !drm_dp_channel_eq_ok(link_status, intel_dp->lane_count);
-}
-
 /*
  * If display is now connected check links status,
  * there has been known issues of link loss triggering
@@ -4319,64 +4403,78 @@ intel_dp_needs_link_retrain(struct intel_dp *intel_dp)
 int intel_dp_retrain_link(struct intel_encoder *encoder,
 			  struct drm_modeset_acquire_ctx *ctx)
 {
-	struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
+	struct drm_device *dev = encoder->base.dev;
+	struct drm_i915_private *dev_priv = to_i915(dev);
 	struct intel_dp *intel_dp = enc_to_intel_dp(&encoder->base);
-	struct intel_connector *connector = intel_dp->attached_connector;
-	struct drm_connector_state *conn_state;
-	struct intel_crtc_state *crtc_state;
-	struct intel_crtc *crtc;
+	struct drm_crtc *crtc;
+	struct intel_crtc *intel_crtc;
+	int crtc_mask, retry_count = 0;
 	int ret;
 
-	/* FIXME handle the MST connectors as well */
-
-	if (!connector || connector->base.status != connector_status_connected)
-		return 0;
-
 	ret = drm_modeset_lock(&dev_priv->drm.mode_config.connection_mutex,
 			       ctx);
 	if (ret)
 		return ret;
 
-	conn_state = connector->base.state;
-
-	crtc = to_intel_crtc(conn_state->crtc);
-	if (!crtc)
-		return 0;
+	crtc_mask = intel_dp_get_crtc_mask(intel_dp);
+	for_each_intel_crtc_mask(dev, intel_crtc, crtc_mask) {
+		struct drm_crtc_state *crtc_state;
+		struct intel_crtc_state *intel_crtc_state;
 
-	ret = drm_modeset_lock(&crtc->base.mutex, ctx);
-	if (ret)
-		return ret;
+		crtc = &intel_crtc->base;
+		ret = drm_modeset_lock(&crtc->mutex, ctx);
+		if (ret)
+			return ret;
 
-	crtc_state = to_intel_crtc_state(crtc->base.state);
+		crtc_state = crtc->state;
+		intel_crtc_state = to_intel_crtc_state(crtc_state);
+		WARN_ON(!intel_crtc_has_dp_encoder(intel_crtc_state));
 
-	WARN_ON(!intel_crtc_has_dp_encoder(crtc_state));
+		if (crtc_state->commit &&
+		    !try_wait_for_completion(&crtc_state->commit->hw_done))
+			return 0;
+	}
 
-	if (!crtc_state->base.active)
+	if (!intel_dp_needs_link_retrain(intel_dp, NULL))
 		return 0;
 
-	if (conn_state->commit &&
-	    !try_wait_for_completion(&conn_state->commit->hw_done))
-		return 0;
+	for_each_intel_crtc_mask(dev, intel_crtc, crtc_mask) {
+		intel_set_cpu_fifo_underrun_reporting(
+		    dev_priv, intel_crtc->pipe, false);
 
-	if (!intel_dp_needs_link_retrain(intel_dp))
-		return 0;
+		if (intel_crtc->config->has_pch_encoder) {
+			intel_set_pch_fifo_underrun_reporting(
+			    dev_priv, intel_crtc_pch_transcoder(intel_crtc),
+			    false);
+		}
+	}
 
-	/* Suppress underruns caused by re-training */
-	intel_set_cpu_fifo_underrun_reporting(dev_priv, crtc->pipe, false);
-	if (crtc->config->has_pch_encoder)
-		intel_set_pch_fifo_underrun_reporting(dev_priv,
-						      intel_crtc_pch_transcoder(crtc), false);
+	do {
+		if (++retry_count > 5) {
+			DRM_DEBUG_KMS("Too many retries, can't retrain\n");
+			return -EINVAL;
+		}
 
-	intel_dp_start_link_train(intel_dp);
-	intel_dp_stop_link_train(intel_dp);
+		intel_dp_start_link_train(intel_dp);
+		intel_dp_stop_link_train(intel_dp);
+	} while (intel_dp_needs_link_retrain(intel_dp, NULL));
+
+	/* Wait for things to become stable */
+	for_each_intel_crtc_mask(dev, intel_crtc, crtc_mask)
+		intel_wait_for_vblank(dev_priv, intel_crtc->pipe);
 
-	/* Keep underrun reporting disabled until things are stable */
-	intel_wait_for_vblank(dev_priv, crtc->pipe);
+	/* Now that we know everything is OK, finally re-enable underrun
+	 * reporting */
+	for_each_intel_crtc_mask(dev, intel_crtc, crtc_mask) {
+		intel_set_cpu_fifo_underrun_reporting(
+		    dev_priv, intel_crtc->pipe, true);
 
-	intel_set_cpu_fifo_underrun_reporting(dev_priv, crtc->pipe, true);
-	if (crtc->config->has_pch_encoder)
-		intel_set_pch_fifo_underrun_reporting(dev_priv,
-						      intel_crtc_pch_transcoder(crtc), true);
+		if (intel_crtc->config->has_pch_encoder) {
+			intel_set_pch_fifo_underrun_reporting(
+			    dev_priv, intel_crtc_pch_transcoder(intel_crtc),
+			    true);
+		}
+	}
 
 	return 0;
 }
@@ -4402,6 +4500,10 @@ static bool intel_dp_hotplug(struct intel_encoder *encoder,
 
 	changed = intel_encoder_hotplug(encoder, connector);
 
+	/* We don't want to end up trying to retrain MST links! */
+	if (encoder && enc_to_intel_dp(&encoder->base)->is_mst)
+		return changed;
+
 	drm_modeset_acquire_init(&ctx, 0);
 
 	for (;;) {
@@ -4478,7 +4580,7 @@ intel_dp_short_pulse(struct intel_dp *intel_dp)
 	}
 
 	/* defer to the hotplug work for link retraining if needed */
-	if (intel_dp_needs_link_retrain(intel_dp))
+	if (intel_dp_needs_link_retrain(intel_dp, NULL))
 		return false;
 
 	if (intel_dp->compliance.test_type == DP_TEST_LINK_TRAINING) {
@@ -6266,25 +6368,98 @@ static bool intel_edp_init_connector(struct intel_dp *intel_dp,
 	return false;
 }
 
+static void intel_dp_mst_retrain_link_work(struct work_struct *work)
+{
+	struct drm_modeset_acquire_ctx ctx;
+	struct intel_dp *intel_dp = container_of(work, typeof(*intel_dp),
+						 mst_retrain_work);
+	struct intel_encoder *intel_encoder = &dp_to_dig_port(intel_dp)->base;
+	struct drm_device *dev = intel_encoder->base.dev;
+	int ret;
+	bool had_error = false;
+
+	drm_modeset_acquire_init(&ctx, 0);
+
+	for (;;) {
+		ret = intel_dp_retrain_link(intel_encoder, &ctx);
+		if (ret == -EDEADLK) {
+			drm_modeset_backoff(&ctx);
+			continue;
+		}
+
+		break;
+	}
+	if (!ret) {
+		DRM_DEBUG_KMS("Retrain complete\n");
+		goto out;
+	} else if (ret == -EIO) {
+		DRM_ERROR("IO error with sink during retrain? Aborting\n");
+		had_error = true;
+		goto out;
+	}
+
+	DRM_DEBUG_KMS("Retraining failed with %d, marking link status as bad\n",
+		      ret);
+
+	/* We ran out of retries, if the sink hasn't changed the link rate in
+	 * it's dpcd yet force us to fallback to a lower link rate/count */
+	if (ret == -EINVAL) {
+		ret = intel_dp_get_dpcd(intel_dp);
+		if (!ret) {
+			DRM_ERROR("IO error while reading dpcd from sink\n");
+			had_error = true;
+			goto out;
+		}
+
+		if (intel_dp->link_rate == intel_dp_max_link_rate(intel_dp) &&
+		    intel_dp->lane_count == intel_dp_max_lane_count(intel_dp)) {
+			intel_dp_get_link_train_fallback_values(
+			    intel_dp, intel_dp_max_link_rate(intel_dp),
+			    intel_dp_max_lane_count(intel_dp));
+		}
+	}
+
+	intel_dp->mst_link_is_bad = true;
+	intel_dp->mst_bw_locked = false;
+	schedule_work(&intel_dp->modeset_retry_work);
+out:
+	drm_modeset_drop_locks(&ctx);
+	drm_modeset_acquire_fini(&ctx);
+	if (had_error)
+		drm_kms_helper_hotplug_event(dev);
+}
+
 static void intel_dp_modeset_retry_work_fn(struct work_struct *work)
 {
 	struct intel_dp *intel_dp = container_of(work, typeof(*intel_dp),
 						 modeset_retry_work);
-	struct drm_connector *connector = &intel_dp->attached_connector->base;
+	struct intel_digital_port *intel_dig_port = dp_to_dig_port(intel_dp);
+	struct drm_device *dev = intel_dig_port->base.base.dev;
+	struct drm_connector *connector;
 
-	DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n", connector->base.id,
-		      connector->name);
+	mutex_lock(&dev->mode_config.mutex);
 
-	/* Grab the locks before changing connector property*/
-	mutex_lock(&connector->dev->mode_config.mutex);
-	/* Set connector link status to BAD and send a Uevent to notify
-	 * userspace to do a modeset.
+	/* Set the connector link status of all (possibly downstream) ports to
+	 * BAD and send a Uevent to notify userspace to do a modeset.
 	 */
-	drm_mode_connector_set_link_status_property(connector,
-						    DRM_MODE_LINK_STATUS_BAD);
-	mutex_unlock(&connector->dev->mode_config.mutex);
+	if (intel_dp->is_mst) {
+		drm_dp_mst_topology_mgr_lower_link_rate(
+		    &intel_dp->mst_mgr,
+		    intel_dp_max_link_rate(intel_dp),
+		    intel_dp_max_lane_count(intel_dp));
+	} else {
+		connector = &intel_dp->attached_connector->base;
+
+		DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n",
+			      connector->base.id, connector->name);
+		drm_mode_connector_set_link_status_property(
+		    connector, DRM_MODE_LINK_STATUS_BAD);
+	}
+
+	mutex_unlock(&dev->mode_config.mutex);
+
 	/* Send Hotplug uevent so userspace can reprobe */
-	drm_kms_helper_hotplug_event(connector->dev);
+	drm_kms_helper_hotplug_event(dev);
 }
 
 bool
@@ -6302,6 +6477,9 @@ intel_dp_init_connector(struct intel_digital_port *intel_dig_port,
 	/* Initialize the work for modeset in case of link train failure */
 	INIT_WORK(&intel_dp->modeset_retry_work,
 		  intel_dp_modeset_retry_work_fn);
+	INIT_WORK(&intel_dp->mst_retrain_work,
+		  intel_dp_mst_retrain_link_work);
+	init_completion(&intel_dp->mst_retrain_completion);
 
 	if (WARN(intel_dig_port->max_lanes < 1,
 		 "Not enough lanes (%d) for DP on port %c\n",
diff --git a/drivers/gpu/drm/i915/intel_dp_mst.c b/drivers/gpu/drm/i915/intel_dp_mst.c
index c0553456b18e..31202f838e89 100644
--- a/drivers/gpu/drm/i915/intel_dp_mst.c
+++ b/drivers/gpu/drm/i915/intel_dp_mst.c
@@ -110,21 +110,32 @@ static int intel_dp_mst_atomic_check(struct drm_connector *connector,
 	struct drm_connector_state *old_conn_state;
 	struct drm_crtc *old_crtc;
 	struct drm_crtc_state *crtc_state;
+	struct drm_dp_mst_topology_mgr *mgr;
+	struct drm_encoder *encoder;
 	int slots, ret = 0;
+	bool could_retrain = false;
+
+	if (new_conn_state->crtc) {
+		crtc_state = drm_atomic_get_new_crtc_state(
+		    state, new_conn_state->crtc);
+		if (crtc_state && drm_atomic_crtc_needs_modeset(crtc_state))
+			could_retrain = true;
+	}
 
 	old_conn_state = drm_atomic_get_old_connector_state(state, connector);
 	old_crtc = old_conn_state->crtc;
 	if (!old_crtc)
-		return ret;
+		goto out;
 
 	crtc_state = drm_atomic_get_new_crtc_state(state, old_crtc);
-	slots = to_intel_crtc_state(crtc_state)->dp_m_n.tu;
-	if (drm_atomic_crtc_needs_modeset(crtc_state) && slots > 0) {
-		struct drm_dp_mst_topology_mgr *mgr;
-		struct drm_encoder *old_encoder;
+	if (!drm_atomic_crtc_needs_modeset(crtc_state))
+		goto out;
+	could_retrain = true;
 
-		old_encoder = old_conn_state->best_encoder;
-		mgr = &enc_to_mst(old_encoder)->primary->dp.mst_mgr;
+	slots = to_intel_crtc_state(crtc_state)->dp_m_n.tu;
+	if (slots > 0) {
+		encoder = old_conn_state->best_encoder;
+		mgr = &enc_to_mst(encoder)->primary->dp.mst_mgr;
 
 		ret = drm_dp_atomic_release_vcpi_slots(state, mgr, slots);
 		if (ret)
@@ -132,6 +143,18 @@ static int intel_dp_mst_atomic_check(struct drm_connector *connector,
 		else
 			to_intel_crtc_state(crtc_state)->dp_m_n.tu = 0;
 	}
+
+out:
+	if (could_retrain &&
+	    old_conn_state->link_status == DRM_MODE_LINK_STATUS_BAD) {
+		if (new_conn_state->best_encoder)
+			encoder = new_conn_state->best_encoder;
+		else
+			encoder = old_conn_state->best_encoder;
+
+		mgr = &enc_to_mst(encoder)->primary->dp.mst_mgr;
+		ret = drm_atomic_dp_mst_retrain_topology(state, mgr);
+	}
 	return ret;
 }
 
@@ -186,9 +209,12 @@ static void intel_mst_post_disable_dp(struct intel_encoder *encoder,
 	intel_dp->active_mst_links--;
 
 	intel_mst->connector = NULL;
-	if (intel_dp->active_mst_links == 0)
+	if (intel_dp->active_mst_links == 0) {
+		intel_dp->mst_link_is_bad = false;
+
 		intel_dig_port->base.post_disable(&intel_dig_port->base,
 						  old_crtc_state, NULL);
+	}
 
 	DRM_DEBUG_KMS("active links %d\n", intel_dp->active_mst_links);
 }
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index e5d3ef6754a5..c63c65923c3e 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -1122,6 +1122,13 @@ struct intel_dp {
 	/* mst connector list */
 	struct intel_dp_mst_encoder *mst_encoders[I915_MAX_PIPES];
 	struct drm_dp_mst_topology_mgr mst_mgr;
+	/* We can't handle retraining from the dig workqueue, so... */
+	struct work_struct mst_retrain_work;
+	struct completion mst_retrain_completion;
+	/* Set when retraining the link at the current parameters is
+	 * impossible for an MST connection
+	 */
+	bool mst_link_is_bad;
 
 	uint32_t (*get_aux_clock_divider)(struct intel_dp *dp, int index);
 	/*
@@ -1689,6 +1696,7 @@ void intel_dp_compute_rate(struct intel_dp *intel_dp, int port_clock,
 bool intel_dp_source_supports_hbr2(struct intel_dp *intel_dp);
 bool
 intel_dp_get_link_status(struct intel_dp *intel_dp, uint8_t link_status[DP_LINK_STATUS_SIZE]);
+int intel_dp_get_crtc_mask(struct intel_dp *intel_dp);
 
 static inline unsigned int intel_dp_unused_lane_mask(int lane_count)
 {
-- 
2.14.3

[PATCH v3 1/5] drm/i915: Move DP modeset retry work into intel_dp

[Lyude Paul]

While having the modeset_retry_work in intel_connector makes sense with
SST, this paradigm doesn't make a whole ton of sense when it comes to
MST since we have to deal with multiple connectors. In most cases, it's
more useful to just use the intel_dp struct since it indicates whether
or not we're dealing with an MST device, along with being able to easily
trace the intel_dp struct back to it's respective connector (if there is
any). So, move the modeset_retry_work function out of the
intel_connector struct and into intel_dp.

Signed-off-by: Lyude Paul <lyude@redhat.com>
Reviewed-by: Manasi Navare <manasi.d.navare@intel.com>
Cc: Manasi Navare <manasi.d.navare@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>

V2:
 - Remove accidental duplicate modeset_retry_work in intel_connector
V3:
 - Also check against eDP in intel_hpd_poll_fini() - mdnavare
Signed-off-by: Lyude Paul <lyude@redhat.com>
---
 drivers/gpu/drm/i915/intel_display.c          | 25 +++++++++++++++++++++++--
 drivers/gpu/drm/i915/intel_dp.c               | 10 ++++------
 drivers/gpu/drm/i915/intel_dp_link_training.c |  2 +-
 drivers/gpu/drm/i915/intel_drv.h              |  6 +++---
 4 files changed, 31 insertions(+), 12 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index f424fff477f6..3b7fa430a84a 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -15394,16 +15394,37 @@ static void intel_hpd_poll_fini(struct drm_device *dev)
 {
 	struct intel_connector *connector;
 	struct drm_connector_list_iter conn_iter;
+	struct work_struct *work;
+	int conn_type;
 
 	/* Kill all the work that may have been queued by hpd. */
 	drm_connector_list_iter_begin(dev, &conn_iter);
 	for_each_intel_connector_iter(connector, &conn_iter) {
-		if (connector->modeset_retry_work.func)
-			cancel_work_sync(&connector->modeset_retry_work);
 		if (connector->hdcp_shim) {
 			cancel_delayed_work_sync(&connector->hdcp_check_work);
 			cancel_work_sync(&connector->hdcp_prop_work);
 		}
+
+		conn_type = connector->base.connector_type;
+		if (conn_type != DRM_MODE_CONNECTOR_eDP &&
+		    conn_type != DRM_MODE_CONNECTOR_DisplayPort)
+			continue;
+
+		if (connector->mst_port) {
+			work = &connector->mst_port->modeset_retry_work;
+		} else {
+			struct intel_encoder *intel_encoder =
+				connector->encoder;
+			struct intel_dp *intel_dp;
+
+			if (!intel_encoder)
+				continue;
+
+			intel_dp = enc_to_intel_dp(&intel_encoder->base);
+			work = &intel_dp->modeset_retry_work;
+		}
+
+		cancel_work_sync(work);
 	}
 	drm_connector_list_iter_end(&conn_iter);
 }
diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 4dd1b2287dd6..5abf0c95725a 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -6261,12 +6261,10 @@ static bool intel_edp_init_connector(struct intel_dp *intel_dp,
 
 static void intel_dp_modeset_retry_work_fn(struct work_struct *work)
 {
-	struct intel_connector *intel_connector;
-	struct drm_connector *connector;
+	struct intel_dp *intel_dp = container_of(work, typeof(*intel_dp),
+						 modeset_retry_work);
+	struct drm_connector *connector = &intel_dp->attached_connector->base;
 
-	intel_connector = container_of(work, typeof(*intel_connector),
-				       modeset_retry_work);
-	connector = &intel_connector->base;
 	DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n", connector->base.id,
 		      connector->name);
 
@@ -6295,7 +6293,7 @@ intel_dp_init_connector(struct intel_digital_port *intel_dig_port,
 	int type;
 
 	/* Initialize the work for modeset in case of link train failure */
-	INIT_WORK(&intel_connector->modeset_retry_work,
+	INIT_WORK(&intel_dp->modeset_retry_work,
 		  intel_dp_modeset_retry_work_fn);
 
 	if (WARN(intel_dig_port->max_lanes < 1,
diff --git a/drivers/gpu/drm/i915/intel_dp_link_training.c b/drivers/gpu/drm/i915/intel_dp_link_training.c
index f59b59bb0a21..2cfa58ce1f95 100644
--- a/drivers/gpu/drm/i915/intel_dp_link_training.c
+++ b/drivers/gpu/drm/i915/intel_dp_link_training.c
@@ -340,7 +340,7 @@ intel_dp_start_link_train(struct intel_dp *intel_dp)
 							     intel_dp->link_rate,
 							     intel_dp->lane_count))
 			/* Schedule a Hotplug Uevent to userspace to start modeset */
-			schedule_work(&intel_connector->modeset_retry_work);
+			schedule_work(&intel_dp->modeset_retry_work);
 	} else {
 		DRM_ERROR("[CONNECTOR:%d:%s] Link Training failed at link rate = %d, lane count = %d",
 			  intel_connector->base.base.id,
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index 83e5ca889d9c..3f19dc80997f 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -406,9 +406,6 @@ struct intel_connector {
 
 	struct intel_dp *mst_port;
 
-	/* Work struct to schedule a uevent on link train failure */
-	struct work_struct modeset_retry_work;
-
 	const struct intel_hdcp_shim *hdcp_shim;
 	struct mutex hdcp_mutex;
 	uint64_t hdcp_value; /* protected by hdcp_mutex */
@@ -1135,6 +1132,9 @@ struct intel_dp {
 
 	/* Displayport compliance testing */
 	struct intel_dp_compliance compliance;
+
+	/* Work struct to schedule a uevent on link train failure */
+	struct work_struct modeset_retry_work;
 };
 
 struct intel_lspcon {
-- 
2.14.3

[PATCH v3 2/5] drm/i915: Only use one link bw config for MST topologies

[Lyude Paul]

When a DP MST link needs retraining, sometimes the hub will detect that
the current link bw config is impossible and will update it's RX caps in
the DPCD to reflect the new maximum link rate. Currently, we make the
assumption that the RX caps in the dpcd will never change like this.
This means if the sink changes it's RX caps after we've already set up
an MST link and we attempt to add or remove another sink from the
topology, we could put ourselves into an invalid state where we've tried
to configure different sinks on the same MST topology with different
link rates. We could also run into this situation if a sink reports a
higher link rate after suspend, usually from us having trained it with a
fallback bw configuration before suspending.

So: "lock" the bw config by only using the max DP link rate/lane count
on the first modeset for an MST topology. For every modeset following,
we instead use the last configured link bw for this topology. We only
unlock the bw config when we've detected a new MST sink.

Signed-off-by: Lyude Paul <lyude@redhat.com>
Cc: Manasi Navare <manasi.d.navare@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
---
 drivers/gpu/drm/i915/intel_dp.c     | 11 +++++++++--
 drivers/gpu/drm/i915/intel_dp_mst.c | 22 +++++++++++++++-------
 drivers/gpu/drm/i915/intel_drv.h    |  6 ++++++
 3 files changed, 30 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 5abf0c95725a..5645a194de92 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -3871,18 +3871,25 @@ intel_dp_can_mst(struct intel_dp *intel_dp)
 static void
 intel_dp_configure_mst(struct intel_dp *intel_dp)
 {
+	bool was_mst;
+
 	if (!i915_modparams.enable_dp_mst)
 		return;
 
 	if (!intel_dp->can_mst)
 		return;
 
+	was_mst = intel_dp->is_mst;
 	intel_dp->is_mst = intel_dp_can_mst(intel_dp);
 
-	if (intel_dp->is_mst)
+	if (intel_dp->is_mst) {
 		DRM_DEBUG_KMS("Sink is MST capable\n");
-	else
+
+		if (!was_mst)
+			intel_dp->mst_bw_locked = false;
+	} else {
 		DRM_DEBUG_KMS("Sink is not MST capable\n");
+	}
 
 	drm_dp_mst_topology_mgr_set_mst(&intel_dp->mst_mgr,
 					intel_dp->is_mst);
diff --git a/drivers/gpu/drm/i915/intel_dp_mst.c b/drivers/gpu/drm/i915/intel_dp_mst.c
index c3de0918ee13..c0553456b18e 100644
--- a/drivers/gpu/drm/i915/intel_dp_mst.c
+++ b/drivers/gpu/drm/i915/intel_dp_mst.c
@@ -42,7 +42,7 @@ static bool intel_dp_mst_compute_config(struct intel_encoder *encoder,
 		to_intel_connector(conn_state->connector);
 	struct drm_atomic_state *state = pipe_config->base.state;
 	int bpp;
-	int lane_count, slots;
+	int lane_count, link_rate, slots;
 	const struct drm_display_mode *adjusted_mode = &pipe_config->base.adjusted_mode;
 	int mst_pbn;
 	bool reduce_m_n = drm_dp_has_quirk(&intel_dp->desc,
@@ -56,16 +56,22 @@ static bool intel_dp_mst_compute_config(struct intel_encoder *encoder,
 			      bpp);
 	}
 	/*
-	 * for MST we always configure max link bw - the spec doesn't
-	 * seem to suggest we should do otherwise.
+	 * for MST we always configure max link bw if we don't know better -
+	 * the spec doesn't seem to suggest we should do otherwise. But,
+	 * ensure it always stays consistent with the rest of this hub's
+	 * state.
 	 */
-	lane_count = intel_dp_max_lane_count(intel_dp);
+	if (intel_dp->mst_bw_locked) {
+		lane_count = intel_dp->lane_count;
+		link_rate = intel_dp->link_rate;
+	} else {
+		lane_count = intel_dp_max_lane_count(intel_dp);
+		link_rate = intel_dp_max_link_rate(intel_dp);
+	}
 
 	pipe_config->lane_count = lane_count;
-
 	pipe_config->pipe_bpp = bpp;
-
-	pipe_config->port_clock = intel_dp_max_link_rate(intel_dp);
+	pipe_config->port_clock = link_rate;
 
 	if (drm_dp_mst_port_has_audio(&intel_dp->mst_mgr, connector->port))
 		pipe_config->has_audio = true;
@@ -221,6 +227,8 @@ static void intel_mst_pre_enable_dp(struct intel_encoder *encoder,
 	connector->encoder = encoder;
 	intel_mst->connector = connector;
 
+	intel_dp->mst_bw_locked = true;
+
 	DRM_DEBUG_KMS("active links %d\n", intel_dp->active_mst_links);
 
 	drm_dp_send_power_updown_phy(&intel_dp->mst_mgr, connector->port, true);
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index 3f19dc80997f..fc338529e918 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -1107,6 +1107,12 @@ struct intel_dp {
 	bool can_mst; /* this port supports mst */
 	bool is_mst;
 	int active_mst_links;
+	/* Set when we've already decided on a link bw for mst, to prevent us
+	 * from setting different link bandwiths if the hub tries to confuse
+	 * us by changing it later
+	 */
+	bool mst_bw_locked;
+
 	/* connector directly attached - won't be use for modeset in mst world */
 	struct intel_connector *attached_connector;
 
-- 
2.14.3

Re: [PATCH v3 2/5] drm/i915: Only use one link bw config for MST topologies

[Manasi Navare]

On Fri, Mar 09, 2018 at 04:32:28PM -0500, Lyude Paul wrote:
> When a DP MST link needs retraining, sometimes the hub will detect that
> the current link bw config is impossible and will update it's RX caps in
> the DPCD to reflect the new maximum link rate. Currently, we make the
> assumption that the RX caps in the dpcd will never change like this.
> This means if the sink changes it's RX caps after we've already set up
> an MST link and we attempt to add or remove another sink from the
> topology, we could put ourselves into an invalid state where we've tried
> to configure different sinks on the same MST topology with different
> link rates. We could also run into this situation if a sink reports a
> higher link rate after suspend, usually from us having trained it with a
> fallback bw configuration before suspending.
> 
> So: "lock" the bw config by only using the max DP link rate/lane count
> on the first modeset for an MST topology. For every modeset following,
> we instead use the last configured link bw for this topology. We only
> unlock the bw config when we've detected a new MST sink.
>

Just a nit here on commit message about where we unlock the link bw. So we also unlock it
meaning set the mst_link_bw_locked to false when we read the dpcd again
and obtain the fallback values since at that time the RX cap could have
changed and so we do unlock the link_bw so that during retraining it reads
the new max link rate and lane count during the mst compute config.
Isnt that the case or am I missing something here?

Manasi

> Signed-off-by: Lyude Paul <lyude@redhat.com>
> Cc: Manasi Navare <manasi.d.navare@intel.com>
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
>  drivers/gpu/drm/i915/intel_dp.c     | 11 +++++++++--
>  drivers/gpu/drm/i915/intel_dp_mst.c | 22 +++++++++++++++-------
>  drivers/gpu/drm/i915/intel_drv.h    |  6 ++++++
>  3 files changed, 30 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 5abf0c95725a..5645a194de92 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -3871,18 +3871,25 @@ intel_dp_can_mst(struct intel_dp *intel_dp)
>  static void
>  intel_dp_configure_mst(struct intel_dp *intel_dp)
>  {
> +	bool was_mst;
> +
>  	if (!i915_modparams.enable_dp_mst)
>  		return;
>  
>  	if (!intel_dp->can_mst)
>  		return;
>  
> +	was_mst = intel_dp->is_mst;
>  	intel_dp->is_mst = intel_dp_can_mst(intel_dp);
>  
> -	if (intel_dp->is_mst)
> +	if (intel_dp->is_mst) {
>  		DRM_DEBUG_KMS("Sink is MST capable\n");
> -	else
> +
> +		if (!was_mst)
> +			intel_dp->mst_bw_locked = false;
> +	} else {
>  		DRM_DEBUG_KMS("Sink is not MST capable\n");
> +	}
>  
>  	drm_dp_mst_topology_mgr_set_mst(&intel_dp->mst_mgr,
>  					intel_dp->is_mst);
> diff --git a/drivers/gpu/drm/i915/intel_dp_mst.c b/drivers/gpu/drm/i915/intel_dp_mst.c
> index c3de0918ee13..c0553456b18e 100644
> --- a/drivers/gpu/drm/i915/intel_dp_mst.c
> +++ b/drivers/gpu/drm/i915/intel_dp_mst.c
> @@ -42,7 +42,7 @@ static bool intel_dp_mst_compute_config(struct intel_encoder *encoder,
>  		to_intel_connector(conn_state->connector);
>  	struct drm_atomic_state *state = pipe_config->base.state;
>  	int bpp;
> -	int lane_count, slots;
> +	int lane_count, link_rate, slots;
>  	const struct drm_display_mode *adjusted_mode = &pipe_config->base.adjusted_mode;
>  	int mst_pbn;
>  	bool reduce_m_n = drm_dp_has_quirk(&intel_dp->desc,
> @@ -56,16 +56,22 @@ static bool intel_dp_mst_compute_config(struct intel_encoder *encoder,
>  			      bpp);
>  	}
>  	/*
> -	 * for MST we always configure max link bw - the spec doesn't
> -	 * seem to suggest we should do otherwise.
> +	 * for MST we always configure max link bw if we don't know better -
> +	 * the spec doesn't seem to suggest we should do otherwise. But,
> +	 * ensure it always stays consistent with the rest of this hub's
> +	 * state.
>  	 */
> -	lane_count = intel_dp_max_lane_count(intel_dp);
> +	if (intel_dp->mst_bw_locked) {
> +		lane_count = intel_dp->lane_count;
> +		link_rate = intel_dp->link_rate;
> +	} else {
> +		lane_count = intel_dp_max_lane_count(intel_dp);
> +		link_rate = intel_dp_max_link_rate(intel_dp);
> +	}
>  
>  	pipe_config->lane_count = lane_count;
> -
>  	pipe_config->pipe_bpp = bpp;
> -
> -	pipe_config->port_clock = intel_dp_max_link_rate(intel_dp);
> +	pipe_config->port_clock = link_rate;
>  
>  	if (drm_dp_mst_port_has_audio(&intel_dp->mst_mgr, connector->port))
>  		pipe_config->has_audio = true;
> @@ -221,6 +227,8 @@ static void intel_mst_pre_enable_dp(struct intel_encoder *encoder,
>  	connector->encoder = encoder;
>  	intel_mst->connector = connector;
>  
> +	intel_dp->mst_bw_locked = true;
> +
>  	DRM_DEBUG_KMS("active links %d\n", intel_dp->active_mst_links);
>  
>  	drm_dp_send_power_updown_phy(&intel_dp->mst_mgr, connector->port, true);
> diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> index 3f19dc80997f..fc338529e918 100644
> --- a/drivers/gpu/drm/i915/intel_drv.h
> +++ b/drivers/gpu/drm/i915/intel_drv.h
> @@ -1107,6 +1107,12 @@ struct intel_dp {
>  	bool can_mst; /* this port supports mst */
>  	bool is_mst;
>  	int active_mst_links;
> +	/* Set when we've already decided on a link bw for mst, to prevent us
> +	 * from setting different link bandwiths if the hub tries to confuse
> +	 * us by changing it later
> +	 */
> +	bool mst_bw_locked;
> +
>  	/* connector directly attached - won't be use for modeset in mst world */
>  	struct intel_connector *attached_connector;
>  
> -- 
> 2.14.3
> 

Re: [PATCH v3 2/5] drm/i915: Only use one link bw config for MST topologies

[Lyude Paul]

On Mon, 2018-03-12 at 13:45 -0700, Manasi Navare wrote:
> On Fri, Mar 09, 2018 at 04:32:28PM -0500, Lyude Paul wrote:
> > When a DP MST link needs retraining, sometimes the hub will detect that
> > the current link bw config is impossible and will update it's RX caps in
> > the DPCD to reflect the new maximum link rate. Currently, we make the
> > assumption that the RX caps in the dpcd will never change like this.
> > This means if the sink changes it's RX caps after we've already set up
> > an MST link and we attempt to add or remove another sink from the
> > topology, we could put ourselves into an invalid state where we've tried
> > to configure different sinks on the same MST topology with different
> > link rates. We could also run into this situation if a sink reports a
> > higher link rate after suspend, usually from us having trained it with a
> > fallback bw configuration before suspending.
> > 
> > So: "lock" the bw config by only using the max DP link rate/lane count
> > on the first modeset for an MST topology. For every modeset following,
> > we instead use the last configured link bw for this topology. We only
> > unlock the bw config when we've detected a new MST sink.
> > 
> 
> Just a nit here on commit message about where we unlock the link bw. So we
> also unlock it
> meaning set the mst_link_bw_locked to false when we read the dpcd again
> and obtain the fallback values since at that time the RX cap could have
> changed and so we do unlock the link_bw so that during retraining it reads
> the new max link rate and lane count during the mst compute config.
> Isnt that the case or am I missing something here?
I'm not sure I understand what you mean, are you talking about how we unlock the
link bw when retraining fails and we decide to fallback? If so, that's probably
something we should just mention in the patch that implements the actual
retraining as opposed to this patch.
> 
> Manasi
> 
> > Signed-off-by: Lyude Paul <lyude@redhat.com>
> > Cc: Manasi Navare <manasi.d.navare@intel.com>
> > Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > ---
> >  drivers/gpu/drm/i915/intel_dp.c     | 11 +++++++++--
> >  drivers/gpu/drm/i915/intel_dp_mst.c | 22 +++++++++++++++-------
> >  drivers/gpu/drm/i915/intel_drv.h    |  6 ++++++
> >  3 files changed, 30 insertions(+), 9 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/intel_dp.c
> > b/drivers/gpu/drm/i915/intel_dp.c
> > index 5abf0c95725a..5645a194de92 100644
> > --- a/drivers/gpu/drm/i915/intel_dp.c
> > +++ b/drivers/gpu/drm/i915/intel_dp.c
> > @@ -3871,18 +3871,25 @@ intel_dp_can_mst(struct intel_dp *intel_dp)
> >  static void
> >  intel_dp_configure_mst(struct intel_dp *intel_dp)
> >  {
> > +	bool was_mst;
> > +
> >  	if (!i915_modparams.enable_dp_mst)
> >  		return;
> >  
> >  	if (!intel_dp->can_mst)
> >  		return;
> >  
> > +	was_mst = intel_dp->is_mst;
> >  	intel_dp->is_mst = intel_dp_can_mst(intel_dp);
> >  
> > -	if (intel_dp->is_mst)
> > +	if (intel_dp->is_mst) {
> >  		DRM_DEBUG_KMS("Sink is MST capable\n");
> > -	else
> > +
> > +		if (!was_mst)
> > +			intel_dp->mst_bw_locked = false;
> > +	} else {
> >  		DRM_DEBUG_KMS("Sink is not MST capable\n");
> > +	}
> >  
> >  	drm_dp_mst_topology_mgr_set_mst(&intel_dp->mst_mgr,
> >  					intel_dp->is_mst);
> > diff --git a/drivers/gpu/drm/i915/intel_dp_mst.c
> > b/drivers/gpu/drm/i915/intel_dp_mst.c
> > index c3de0918ee13..c0553456b18e 100644
> > --- a/drivers/gpu/drm/i915/intel_dp_mst.c
> > +++ b/drivers/gpu/drm/i915/intel_dp_mst.c
> > @@ -42,7 +42,7 @@ static bool intel_dp_mst_compute_config(struct
> > intel_encoder *encoder,
> >  		to_intel_connector(conn_state->connector);
> >  	struct drm_atomic_state *state = pipe_config->base.state;
> >  	int bpp;
> > -	int lane_count, slots;
> > +	int lane_count, link_rate, slots;
> >  	const struct drm_display_mode *adjusted_mode = &pipe_config-
> > >base.adjusted_mode;
> >  	int mst_pbn;
> >  	bool reduce_m_n = drm_dp_has_quirk(&intel_dp->desc,
> > @@ -56,16 +56,22 @@ static bool intel_dp_mst_compute_config(struct
> > intel_encoder *encoder,
> >  			      bpp);
> >  	}
> >  	/*
> > -	 * for MST we always configure max link bw - the spec doesn't
> > -	 * seem to suggest we should do otherwise.
> > +	 * for MST we always configure max link bw if we don't know better
> > -
> > +	 * the spec doesn't seem to suggest we should do otherwise. But,
> > +	 * ensure it always stays consistent with the rest of this hub's
> > +	 * state.
> >  	 */
> > -	lane_count = intel_dp_max_lane_count(intel_dp);
> > +	if (intel_dp->mst_bw_locked) {
> > +		lane_count = intel_dp->lane_count;
> > +		link_rate = intel_dp->link_rate;
> > +	} else {
> > +		lane_count = intel_dp_max_lane_count(intel_dp);
> > +		link_rate = intel_dp_max_link_rate(intel_dp);
> > +	}
> >  
> >  	pipe_config->lane_count = lane_count;
> > -
> >  	pipe_config->pipe_bpp = bpp;
> > -
> > -	pipe_config->port_clock = intel_dp_max_link_rate(intel_dp);
> > +	pipe_config->port_clock = link_rate;
> >  
> >  	if (drm_dp_mst_port_has_audio(&intel_dp->mst_mgr, connector->port))
> >  		pipe_config->has_audio = true;
> > @@ -221,6 +227,8 @@ static void intel_mst_pre_enable_dp(struct intel_encoder
> > *encoder,
> >  	connector->encoder = encoder;
> >  	intel_mst->connector = connector;
> >  
> > +	intel_dp->mst_bw_locked = true;
> > +
> >  	DRM_DEBUG_KMS("active links %d\n", intel_dp->active_mst_links);
> >  
> >  	drm_dp_send_power_updown_phy(&intel_dp->mst_mgr, connector->port,
> > true);
> > diff --git a/drivers/gpu/drm/i915/intel_drv.h
> > b/drivers/gpu/drm/i915/intel_drv.h
> > index 3f19dc80997f..fc338529e918 100644
> > --- a/drivers/gpu/drm/i915/intel_drv.h
> > +++ b/drivers/gpu/drm/i915/intel_drv.h
> > @@ -1107,6 +1107,12 @@ struct intel_dp {
> >  	bool can_mst; /* this port supports mst */
> >  	bool is_mst;
> >  	int active_mst_links;
> > +	/* Set when we've already decided on a link bw for mst, to prevent
> > us
> > +	 * from setting different link bandwiths if the hub tries to
> > confuse
> > +	 * us by changing it later
> > +	 */
> > +	bool mst_bw_locked;
> > +
> >  	/* connector directly attached - won't be use for modeset in mst
> > world */
> >  	struct intel_connector *attached_connector;
> >  
> > -- 
> > 2.14.3
> > 

Re: [PATCH v3 2/5] drm/i915: Only use one link bw config for MST topologies

[Ville Syrjälä]

On Fri, Mar 09, 2018 at 04:32:28PM -0500, Lyude Paul wrote:
> When a DP MST link needs retraining, sometimes the hub will detect that
> the current link bw config is impossible and will update it's RX caps in
> the DPCD to reflect the new maximum link rate. Currently, we make the
> assumption that the RX caps in the dpcd will never change like this.
> This means if the sink changes it's RX caps after we've already set up
> an MST link and we attempt to add or remove another sink from the
> topology, we could put ourselves into an invalid state where we've tried
> to configure different sinks on the same MST topology with different
> link rates. We could also run into this situation if a sink reports a
> higher link rate after suspend, usually from us having trained it with a
> fallback bw configuration before suspending.
> 
> So: "lock" the bw config by only using the max DP link rate/lane count
> on the first modeset for an MST topology. For every modeset following,
> we instead use the last configured link bw for this topology. We only
> unlock the bw config when we've detected a new MST sink.
> 
> Signed-off-by: Lyude Paul <lyude@redhat.com>
> Cc: Manasi Navare <manasi.d.navare@intel.com>
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
>  drivers/gpu/drm/i915/intel_dp.c     | 11 +++++++++--
>  drivers/gpu/drm/i915/intel_dp_mst.c | 22 +++++++++++++++-------
>  drivers/gpu/drm/i915/intel_drv.h    |  6 ++++++
>  3 files changed, 30 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 5abf0c95725a..5645a194de92 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -3871,18 +3871,25 @@ intel_dp_can_mst(struct intel_dp *intel_dp)
>  static void
>  intel_dp_configure_mst(struct intel_dp *intel_dp)
>  {
> +	bool was_mst;
> +
>  	if (!i915_modparams.enable_dp_mst)
>  		return;
>  
>  	if (!intel_dp->can_mst)
>  		return;
>  
> +	was_mst = intel_dp->is_mst;
>  	intel_dp->is_mst = intel_dp_can_mst(intel_dp);
>  
> -	if (intel_dp->is_mst)
> +	if (intel_dp->is_mst) {
>  		DRM_DEBUG_KMS("Sink is MST capable\n");
> -	else
> +
> +		if (!was_mst)
> +			intel_dp->mst_bw_locked = false;
> +	} else {
>  		DRM_DEBUG_KMS("Sink is not MST capable\n");
> +	}
>  
>  	drm_dp_mst_topology_mgr_set_mst(&intel_dp->mst_mgr,
>  					intel_dp->is_mst);
> diff --git a/drivers/gpu/drm/i915/intel_dp_mst.c b/drivers/gpu/drm/i915/intel_dp_mst.c
> index c3de0918ee13..c0553456b18e 100644
> --- a/drivers/gpu/drm/i915/intel_dp_mst.c
> +++ b/drivers/gpu/drm/i915/intel_dp_mst.c
> @@ -42,7 +42,7 @@ static bool intel_dp_mst_compute_config(struct intel_encoder *encoder,
>  		to_intel_connector(conn_state->connector);
>  	struct drm_atomic_state *state = pipe_config->base.state;
>  	int bpp;
> -	int lane_count, slots;
> +	int lane_count, link_rate, slots;
>  	const struct drm_display_mode *adjusted_mode = &pipe_config->base.adjusted_mode;
>  	int mst_pbn;
>  	bool reduce_m_n = drm_dp_has_quirk(&intel_dp->desc,
> @@ -56,16 +56,22 @@ static bool intel_dp_mst_compute_config(struct intel_encoder *encoder,
>  			      bpp);
>  	}
>  	/*
> -	 * for MST we always configure max link bw - the spec doesn't
> -	 * seem to suggest we should do otherwise.
> +	 * for MST we always configure max link bw if we don't know better -
> +	 * the spec doesn't seem to suggest we should do otherwise. But,
> +	 * ensure it always stays consistent with the rest of this hub's
> +	 * state.
>  	 */
> -	lane_count = intel_dp_max_lane_count(intel_dp);
> +	if (intel_dp->mst_bw_locked) {
> +		lane_count = intel_dp->lane_count;
> +		link_rate = intel_dp->link_rate;

This feels like something we should be tracking in the MST state.

> +	} else {
> +		lane_count = intel_dp_max_lane_count(intel_dp);
> +		link_rate = intel_dp_max_link_rate(intel_dp);
> +	}
>  
>  	pipe_config->lane_count = lane_count;
> -
>  	pipe_config->pipe_bpp = bpp;
> -
> -	pipe_config->port_clock = intel_dp_max_link_rate(intel_dp);
> +	pipe_config->port_clock = link_rate;
>  
>  	if (drm_dp_mst_port_has_audio(&intel_dp->mst_mgr, connector->port))
>  		pipe_config->has_audio = true;
> @@ -221,6 +227,8 @@ static void intel_mst_pre_enable_dp(struct intel_encoder *encoder,
>  	connector->encoder = encoder;
>  	intel_mst->connector = connector;
>  
> +	intel_dp->mst_bw_locked = true;
> +
>  	DRM_DEBUG_KMS("active links %d\n", intel_dp->active_mst_links);
>  
>  	drm_dp_send_power_updown_phy(&intel_dp->mst_mgr, connector->port, true);
> diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> index 3f19dc80997f..fc338529e918 100644
> --- a/drivers/gpu/drm/i915/intel_drv.h
> +++ b/drivers/gpu/drm/i915/intel_drv.h
> @@ -1107,6 +1107,12 @@ struct intel_dp {
>  	bool can_mst; /* this port supports mst */
>  	bool is_mst;
>  	int active_mst_links;
> +	/* Set when we've already decided on a link bw for mst, to prevent us
> +	 * from setting different link bandwiths if the hub tries to confuse
> +	 * us by changing it later
> +	 */
> +	bool mst_bw_locked;
> +
>  	/* connector directly attached - won't be use for modeset in mst world */
>  	struct intel_connector *attached_connector;
>  
> -- 
> 2.14.3

-- 
Ville Syrjälä
Intel OTC

[PATCH v3 3/5] drm/dp_mst: Add drm_dp_mst_topology_mgr_lower_link_rate()

[Lyude Paul]

Unlike SST, MST can have far more then a single display hooked up on a
single port. What this also means however, is that if the DisplayPort
link to the top-level MST branch device becomes unstable then every
single branch device also has an unstable link. Additionally, MST has a
few more steps that must be taken in order to properly retrain the
entire topology under a lower link rate. Since the VCID allocations for
each mstb is determined based off the link rate for the top of the
topology, we also have to recalculate all of the VCID allocations for
the downstream ports as well to ensure that we still have enough link
bandwidth to drive each mstb.

Additionally, since we have multiple downstream connectors per port,
setting the link status of the parent mstb's port to bad isn't enough:
all of the downstream mstb ports have to have their link status set to
bad.

This basically follows the same paradigm that our DP link status logic
in DRM does, in that we simply tell userspace that all of the mstb ports
need retraining and additionally applying the new lower bandwidth
constraints to all of the atomic commits on the topology that follow.

Since the work of figuring out which connectors live downstream on an
MST topology and updating their link status is something that any driver
supporting MST is going to need to do in order to retrain MST links
properly, we add the drm_dp_mst_topology_mgr_lower_link_rate() helper
which simply recalculates the pbn_div for a given mst topology, then
marks the link status of all connectors living in that topology as bad.
We'll make use of it in i915 later in this series.

Signed-off-by: Lyude Paul <lyude@redhat.com>
Cc: Manasi Navare <manasi.d.navare@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
---
 drivers/gpu/drm/drm_dp_mst_topology.c | 73 ++++++++++++++++++++++++++++++++++-
 include/drm/drm_dp_mst_helper.h       |  3 ++
 2 files changed, 75 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index 6fac4129e6a2..0d6604500b29 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -2076,7 +2076,7 @@ static bool drm_dp_get_vc_payload_bw(int dp_link_bw,
 {
 	switch (dp_link_bw) {
 	default:
-		DRM_DEBUG_KMS("invalid link bandwidth in DPCD: %x (link count: %d)\n",
+		DRM_DEBUG_KMS("invalid link bandwidth: %x (link count: %d)\n",
 			      dp_link_bw, dp_link_count);
 		return false;
 
@@ -2096,6 +2096,77 @@ static bool drm_dp_get_vc_payload_bw(int dp_link_bw,
 	return true;
 }
 
+static void drm_dp_set_mstb_link_status(struct drm_dp_mst_branch *mstb,
+					enum drm_link_status status)
+{
+	struct drm_dp_mst_branch *rmstb;
+	struct drm_dp_mst_port *port;
+
+	list_for_each_entry(port, &mstb->ports, next) {
+		rmstb = drm_dp_get_validated_mstb_ref(mstb->mgr, port->mstb);
+		if (rmstb) {
+			drm_dp_set_mstb_link_status(rmstb, status);
+			drm_dp_put_mst_branch_device(rmstb);
+		}
+
+		if (port->connector)
+			port->connector->state->link_status = status;
+	}
+}
+
+/**
+ * drm_dp_mst_topology_mgr_lower_link_rate() - Override the DP link bw/count
+ * for all connectors in a given MST topology
+ * @mgr: manager to set state for
+ * @dp_link_bw: The new DP link bandwidth
+ * @dp_link_count: The new DP link count
+ *
+ * This is called by the driver when it detects that the current DP link for
+ * the given topology manager is unstable, and needs to be retrained at a
+ * lower link rate.
+ *
+ * This takes care of updating the link status on all downstream connectors
+ * along with recalculating the VC payloads. The driver should send a hotplug
+ * event after calling this function to notify userspace of the link status
+ * change.
+ *
+ * RETURNS:
+ *
+ * True for success, or negative error code on failure.
+ */
+int drm_dp_mst_topology_mgr_lower_link_rate(struct drm_dp_mst_topology_mgr *mgr,
+					    int dp_link_bw, int dp_link_count)
+{
+	struct drm_device *dev = mgr->dev;
+	struct drm_dp_mst_branch *mst_primary;
+	int new_pbn_div;
+	int ret = 0;
+
+	drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
+
+	if (!drm_dp_get_vc_payload_bw(drm_dp_link_rate_to_bw_code(dp_link_bw),
+				      dp_link_count, &new_pbn_div)) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	mst_primary = drm_dp_get_validated_mstb_ref(mgr, mgr->mst_primary);
+	if (!mst_primary)
+		goto out;
+
+	DRM_DEBUG_KMS("MST link failed to retrain, lowering pbn_div to %d\n",
+		      new_pbn_div);
+	mgr->pbn_div = new_pbn_div;
+
+	drm_dp_set_mstb_link_status(mst_primary, DRM_MODE_LINK_STATUS_BAD);
+
+	drm_dp_put_mst_branch_device(mst_primary);
+out:
+	drm_modeset_unlock(&dev->mode_config.connection_mutex);
+	return ret;
+}
+EXPORT_SYMBOL(drm_dp_mst_topology_mgr_lower_link_rate);
+
 /**
  * drm_dp_mst_topology_mgr_set_mst() - Set the MST state for a topology manager
  * @mgr: manager to set state for
diff --git a/include/drm/drm_dp_mst_helper.h b/include/drm/drm_dp_mst_helper.h
index 7f78d26a0766..6261ec43a2c0 100644
--- a/include/drm/drm_dp_mst_helper.h
+++ b/include/drm/drm_dp_mst_helper.h
@@ -634,4 +634,7 @@ int drm_dp_atomic_release_vcpi_slots(struct drm_atomic_state *state,
 int drm_dp_send_power_updown_phy(struct drm_dp_mst_topology_mgr *mgr,
 				 struct drm_dp_mst_port *port, bool power_up);
 
+int drm_dp_mst_topology_mgr_lower_link_rate(struct drm_dp_mst_topology_mgr *mgr,
+					    int dp_link_bw, int dp_link_count);
+
 #endif
-- 
2.14.3

Re: [PATCH v3 3/5] drm/dp_mst: Add drm_dp_mst_topology_mgr_lower_link_rate()

[Manasi Navare]

On Fri, Mar 09, 2018 at 04:32:29PM -0500, Lyude Paul wrote:
> Unlike SST, MST can have far more then a single display hooked up on a
> single port. What this also means however, is that if the DisplayPort
> link to the top-level MST branch device becomes unstable then every
> single branch device also has an unstable link. Additionally, MST has a
> few more steps that must be taken in order to properly retrain the
> entire topology under a lower link rate. Since the VCID allocations for
> each mstb is determined based off the link rate for the top of the
> topology, we also have to recalculate all of the VCID allocations for
> the downstream ports as well to ensure that we still have enough link
> bandwidth to drive each mstb.
> 
> Additionally, since we have multiple downstream connectors per port,
> setting the link status of the parent mstb's port to bad isn't enough:
> all of the downstream mstb ports have to have their link status set to
> bad.
> 
> This basically follows the same paradigm that our DP link status logic
> in DRM does, in that we simply tell userspace that all of the mstb ports
> need retraining and additionally applying the new lower bandwidth
> constraints to all of the atomic commits on the topology that follow.
> 
> Since the work of figuring out which connectors live downstream on an
> MST topology and updating their link status is something that any driver
> supporting MST is going to need to do in order to retrain MST links
> properly, we add the drm_dp_mst_topology_mgr_lower_link_rate() helper
> which simply recalculates the pbn_div for a given mst topology, then
> marks the link status of all connectors living in that topology as bad.
> We'll make use of it in i915 later in this series.
> 
> Signed-off-by: Lyude Paul <lyude@redhat.com>
> Cc: Manasi Navare <manasi.d.navare@intel.com>
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
>  drivers/gpu/drm/drm_dp_mst_topology.c | 73 ++++++++++++++++++++++++++++++++++-
>  include/drm/drm_dp_mst_helper.h       |  3 ++
>  2 files changed, 75 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
> index 6fac4129e6a2..0d6604500b29 100644
> --- a/drivers/gpu/drm/drm_dp_mst_topology.c
> +++ b/drivers/gpu/drm/drm_dp_mst_topology.c
> @@ -2076,7 +2076,7 @@ static bool drm_dp_get_vc_payload_bw(int dp_link_bw,
>  {
>  	switch (dp_link_bw) {
>  	default:
> -		DRM_DEBUG_KMS("invalid link bandwidth in DPCD: %x (link count: %d)\n",
> +		DRM_DEBUG_KMS("invalid link bandwidth: %x (link count: %d)\n",
>  			      dp_link_bw, dp_link_count);
>  		return false;
>  
> @@ -2096,6 +2096,77 @@ static bool drm_dp_get_vc_payload_bw(int dp_link_bw,
>  	return true;
>  }
>  
> +static void drm_dp_set_mstb_link_status(struct drm_dp_mst_branch *mstb,
> +					enum drm_link_status status)
> +{
> +	struct drm_dp_mst_branch *rmstb;
> +	struct drm_dp_mst_port *port;
> +
> +	list_for_each_entry(port, &mstb->ports, next) {
> +		rmstb = drm_dp_get_validated_mstb_ref(mstb->mgr, port->mstb);
> +		if (rmstb) {
> +			drm_dp_set_mstb_link_status(rmstb, status);
> +			drm_dp_put_mst_branch_device(rmstb);
> +		}
> +
> +		if (port->connector)
> +			port->connector->state->link_status = status;
> +	}
> +}
> +
> +/**
> + * drm_dp_mst_topology_mgr_lower_link_rate() - Override the DP link bw/count
> + * for all connectors in a given MST topology
> + * @mgr: manager to set state for
> + * @dp_link_bw: The new DP link bandwidth

I would rather call this argument as dp_link_rate since thats what we are passing
and not dp_link_bw.

> + * @dp_link_count: The new DP link count
> + *
> + * This is called by the driver when it detects that the current DP link for
> + * the given topology manager is unstable, and needs to be retrained at a
> + * lower link rate.
> + *
> + * This takes care of updating the link status on all downstream connectors
> + * along with recalculating the VC payloads. The driver should send a hotplug
> + * event after calling this function to notify userspace of the link status
> + * change.
> + *
> + * RETURNS:
> + *
> + * True for success, or negative error code on failure.
> + */
> +int drm_dp_mst_topology_mgr_lower_link_rate(struct drm_dp_mst_topology_mgr *mgr,
> +					    int dp_link_bw, int dp_link_count)
> +{
> +	struct drm_device *dev = mgr->dev;
> +	struct drm_dp_mst_branch *mst_primary;
> +	int new_pbn_div;
> +	int ret = 0;
> +
> +	drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
> +
> +	if (!drm_dp_get_vc_payload_bw(drm_dp_link_rate_to_bw_code(dp_link_bw),

This explains my comment above, we convert link rate to link_bw here so better
call that link_rate to begin with

> +				      dp_link_count, &new_pbn_div)) {
> +		ret = -EINVAL;
> +		goto out;
> +	}
> +
> +	mst_primary = drm_dp_get_validated_mstb_ref(mgr, mgr->mst_primary);
> +	if (!mst_primary)
> +		goto out;
> +
> +	DRM_DEBUG_KMS("MST link failed to retrain, lowering pbn_div to %d\n",
> +		      new_pbn_div);

This debug message seems a little misleading since we are saying that it failed
to train link or retrain at the same params and now we are retraining with fallback
values. Clarify this a bit more in this message like "MST link training failed
or retrain at same params failed"..?

Manasi

> +	mgr->pbn_div = new_pbn_div;
> +
> +	drm_dp_set_mstb_link_status(mst_primary, DRM_MODE_LINK_STATUS_BAD);
> +
> +	drm_dp_put_mst_branch_device(mst_primary);
> +out:
> +	drm_modeset_unlock(&dev->mode_config.connection_mutex);
> +	return ret;
> +}
> +EXPORT_SYMBOL(drm_dp_mst_topology_mgr_lower_link_rate);
> +
>  /**
>   * drm_dp_mst_topology_mgr_set_mst() - Set the MST state for a topology manager
>   * @mgr: manager to set state for
> diff --git a/include/drm/drm_dp_mst_helper.h b/include/drm/drm_dp_mst_helper.h
> index 7f78d26a0766..6261ec43a2c0 100644
> --- a/include/drm/drm_dp_mst_helper.h
> +++ b/include/drm/drm_dp_mst_helper.h
> @@ -634,4 +634,7 @@ int drm_dp_atomic_release_vcpi_slots(struct drm_atomic_state *state,
>  int drm_dp_send_power_updown_phy(struct drm_dp_mst_topology_mgr *mgr,
>  				 struct drm_dp_mst_port *port, bool power_up);
>  
> +int drm_dp_mst_topology_mgr_lower_link_rate(struct drm_dp_mst_topology_mgr *mgr,
> +					    int dp_link_bw, int dp_link_count);
> +
>  #endif
> -- 
> 2.14.3
> 

[PATCH v3 4/5] drm/dp_mst: Add drm_atomic_dp_mst_retrain_topology()

[Lyude Paul]

Retraining MST is rather difficult. In order to do it properly while
guaranteeing that we'll never run into a spot where we commit a
physically impossible configuration, we have to do a lot of checks on
atomic commits which affect MST topologies. All of this work is going to
need to be repeated for every driver at some point, so let's save
ourselves some trouble and just implement these atomic checks as
a single helper.

Signed-off-by: Lyude Paul <lyude@redhat.com>
Cc: Manasi Navare <manasi.d.navare@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
---
 drivers/gpu/drm/drm_dp_mst_topology.c | 223 ++++++++++++++++++++++++++++++++++
 include/drm/drm_dp_mst_helper.h       |   2 +
 2 files changed, 225 insertions(+)

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index 0d6604500b29..c4a91b1ba61b 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -2167,6 +2167,229 @@ int drm_dp_mst_topology_mgr_lower_link_rate(struct drm_dp_mst_topology_mgr *mgr,
 }
 EXPORT_SYMBOL(drm_dp_mst_topology_mgr_lower_link_rate);
 
+static bool drm_atomic_dp_mst_state_only_disables_mstbs(struct drm_atomic_state *state,
+							struct drm_dp_mst_topology_mgr *mgr,
+							struct drm_dp_mst_branch *mstb)
+{
+	struct drm_dp_mst_branch *rmstb;
+	struct drm_dp_mst_port *port;
+	struct drm_connector *connector;
+	struct drm_connector_state *conn_state;
+	struct drm_crtc *crtc;
+	struct drm_crtc_state *crtc_state;
+	int ret;
+
+	list_for_each_entry(port, &mstb->ports, next) {
+		rmstb = drm_dp_get_validated_mstb_ref(mstb->mgr, port->mstb);
+		if (rmstb) {
+			ret = drm_atomic_dp_mst_state_only_disables_mstbs(
+			    state, mgr, rmstb);
+			drm_dp_put_mst_branch_device(rmstb);
+			if (!ret)
+				return false;
+		}
+
+		connector = port->connector;
+		if (!connector)
+			continue;
+
+		conn_state = drm_atomic_get_new_connector_state(
+		    state, connector);
+		if (!conn_state)
+			continue;
+
+		crtc = conn_state->crtc;
+		if (!crtc)
+			continue;
+
+		crtc_state = drm_atomic_get_new_crtc_state(state, crtc);
+		if (!crtc_state)
+			continue;
+
+		if (drm_atomic_crtc_needs_modeset(crtc_state))
+			return false;
+	}
+
+	return true;
+}
+
+static int drm_atomic_dp_mst_all_mstbs_disabled(struct drm_atomic_state *state,
+						struct drm_dp_mst_topology_mgr *mgr,
+						struct drm_dp_mst_branch *mstb)
+{
+	struct drm_dp_mst_branch *rmstb;
+	struct drm_dp_mst_port *port;
+	struct drm_connector *connector;
+	struct drm_connector_state *conn_state;
+	int ret;
+
+	list_for_each_entry(port, &mstb->ports, next) {
+		rmstb = drm_dp_get_validated_mstb_ref(mstb->mgr, port->mstb);
+		if (rmstb) {
+			ret = drm_atomic_dp_mst_all_mstbs_disabled(
+			    state, mgr, rmstb);
+			drm_dp_put_mst_branch_device(rmstb);
+			if (ret <= 0)
+				return ret;
+		}
+
+		connector = port->connector;
+		if (!connector)
+			continue;
+
+		conn_state = drm_atomic_get_connector_state(
+		    state, connector);
+		if (IS_ERR(conn_state))
+			return PTR_ERR(conn_state);
+
+		if (conn_state->crtc)
+			return false;
+	}
+
+	/* No enabled CRTCs found */
+	return true;
+}
+
+static int drm_atomic_dp_mst_retrain_mstb(struct drm_atomic_state *state,
+					  struct drm_dp_mst_topology_mgr *mgr,
+					  struct drm_dp_mst_branch *mstb,
+					  bool full_modeset)
+{
+	struct drm_dp_mst_branch *rmstb;
+	struct drm_dp_mst_port *port;
+	struct drm_connector *connector;
+	struct drm_connector_state *conn_state;
+	struct drm_crtc *crtc;
+	struct drm_crtc_state *crtc_state;
+	int ret;
+
+	list_for_each_entry(port, &mstb->ports, next) {
+		rmstb = drm_dp_get_validated_mstb_ref(mstb->mgr, port->mstb);
+		if (rmstb) {
+			ret = drm_atomic_dp_mst_retrain_mstb(
+			    state, mgr, rmstb, full_modeset);
+			drm_dp_put_mst_branch_device(rmstb);
+			if (ret)
+				return ret;
+		}
+
+		connector = port->connector;
+		if (!connector)
+			continue;
+
+		conn_state = drm_atomic_get_connector_state(state, connector);
+		if (IS_ERR(conn_state))
+			return PTR_ERR(conn_state);
+
+		if (conn_state->link_status != DRM_MODE_LINK_STATUS_GOOD) {
+			DRM_DEBUG_ATOMIC("[CONNECTOR:%d:%s] link status bad -> good\n",
+					 connector->base.id, connector->name);
+			conn_state->link_status = DRM_MODE_LINK_STATUS_GOOD;
+		}
+
+		if (!full_modeset)
+			continue;
+
+		crtc = conn_state->crtc;
+		if (!crtc)
+			continue;
+
+		crtc_state = drm_atomic_get_crtc_state(state, crtc);
+		if (IS_ERR(crtc_state))
+			return PTR_ERR(crtc_state);
+
+		if (!crtc_state->mode_changed) {
+			DRM_DEBUG_ATOMIC("[CRTC:%d:%s] needs full modeset\n",
+					 crtc->base.id, crtc->name);
+			crtc_state->mode_changed = true;
+		}
+	}
+
+	return 0;
+}
+
+/**
+ * drm_atomic_dp_mst_retrain_topology() - prepare a modeset that will retrain
+ * an MST topology
+ * @state: The new state that would retrain the topology link
+ * @mgr: The topology manager to use
+ *
+ * After userspace has been signaled that connectors are in need of
+ * retraining, it's expected that a modeset will be performed for any CRTCs on
+ * said connectors. Since all of the branch devices in an MST topology share a
+ * single link, they also share the same link status, lane count, and link
+ * rate.
+ *
+ * Since all of these characteristics are shared, there's only two valid
+ * solutions when fallback link training parameters need to be applied. The
+ * first is simply unassigning each mstb connector's CRTC. Since this action
+ * can only free slots on the VCPI table and not allocate them, this can be
+ * done without pulling in additional CRTCs on the MST topology. Additionally
+ * if this action would result in there no longer being any CRTCs assigned to
+ * mstb connectors, this would be enough to bring the topology back into a
+ * trained state since there would be nothing left requiring VCPI
+ * reallocations.
+ *
+ * The second solution is to commit new modes to all of the connectors on the
+ * topology. Since this action would result in VCPI reallocations with a new
+ * link rate and lane count, a modeset must also be performed on every other
+ * CRTC driving a branch device on the given topology at the same time. This
+ * is to ensure that all VCPI allocations are properly recalculated in
+ * response to the new link rate and lane count, that the new modes will fit
+ * into the recalculated VCPI table, and that the new atomic state could never
+ * result in an otherwise physically impossible configuration (e.g. different
+ * mstbs with CRTCs trained to different link rates/lane counts).
+ *
+ * Finally, any atomic commit which would result in going from an
+ * unrecoverable link state to a properly trained link state must also take
+ * care of appropriately updating the link status properties of all connectors
+ * on the topology from bad to good. This function takes care of all of these
+ * checks in @state for the topology manager @mgr including possibly pulling
+ * in additional CRTCs into the modeset, and possibly updating the link status
+ * of each mstb's DRM connector.
+ *
+ * This function should be called within the driver's atomic check callbacks
+ * whenever a modeset happens on an MST connector with it's link status set to
+ * DRM_MODE_LINK_STATUS_BAD.
+ *
+ * RETURNS:
+ *
+ * Returns 0 for success, or negative error code for failure.
+ */
+int drm_atomic_dp_mst_retrain_topology(struct drm_atomic_state *state,
+				       struct drm_dp_mst_topology_mgr *mgr)
+{
+	struct drm_dp_mst_branch *mstb =
+		drm_dp_get_validated_mstb_ref(mgr, mgr->mst_primary);
+	int ret = 0;
+	bool need_modeset = false;
+
+	if (!mstb)
+		return 0;
+
+	if (drm_atomic_dp_mst_state_only_disables_mstbs(state, mgr, mstb)) {
+		ret = drm_atomic_dp_mst_all_mstbs_disabled(state, mgr, mstb);
+		if (ret < 0)
+			goto out;
+
+		if (ret)
+			DRM_DEBUG_ATOMIC("state %p disables all CRTCs on mst mgr %p\n",
+					 state, mgr);
+		else
+			goto out; /* valid, but doesn't retrain link */
+	} else {
+		DRM_DEBUG_ATOMIC("state %p requires full modeset for CRTCs on mst mgr %p\n",
+				 state, mgr);
+		need_modeset = true;
+	}
+
+	ret = drm_atomic_dp_mst_retrain_mstb(state, mgr, mstb, need_modeset);
+out:
+	drm_dp_put_mst_branch_device(mgr->mst_primary);
+	return ret;
+}
+EXPORT_SYMBOL(drm_atomic_dp_mst_retrain_topology);
+
 /**
  * drm_dp_mst_topology_mgr_set_mst() - Set the MST state for a topology manager
  * @mgr: manager to set state for
diff --git a/include/drm/drm_dp_mst_helper.h b/include/drm/drm_dp_mst_helper.h
index 6261ec43a2c0..24075eb2dd1b 100644
--- a/include/drm/drm_dp_mst_helper.h
+++ b/include/drm/drm_dp_mst_helper.h
@@ -636,5 +636,7 @@ int drm_dp_send_power_updown_phy(struct drm_dp_mst_topology_mgr *mgr,
 
 int drm_dp_mst_topology_mgr_lower_link_rate(struct drm_dp_mst_topology_mgr *mgr,
 					    int dp_link_bw, int dp_link_count);
+int drm_atomic_dp_mst_retrain_topology(struct drm_atomic_state *state,
+				       struct drm_dp_mst_topology_mgr *mgr);
 
 #endif
-- 
2.14.3

[PATCH v3 5/5] drm/i915: Implement proper fallback training for MST

[Lyude Paul]

For a while we actually haven't had any way of retraining MST links with
fallback link parameters like we do with SST. While uncommon, certain
setups such as my Caldigit TS3 + EVGA MST hub require this since
otherwise, they end up getting stuck in an infinite MST retraining loop.

MST retraining is somewhat different then SST retraining. While it's
possible during the normal link retraining sequence for a hub to indicate
bad link status, it's also possible for a hub to only indicate this
status through ESI messages and it's possible for this to happen after
the initial link training succeeds. This can lead to a pattern that
looks like this:

- Train MST link
- Training completes successfully
- MST hub sets Channel EQ failed bit in ESI
- Retraining starts
- Retraining completes successfully
- MST hub sets Channel EQ failed bit in ESI again
- Rinse and repeat

In these situations, we need to be able to actually trigger fallback
link training from the ESI handler as well, along with using the ESI
handler during retraining to figure out whether or not our retraining
actually succeeded.

This gets a bit more complicated since we have to ensure that we don't
block the ESI handler at all while doing retraining. If we do, due to
DisplayPort's general issues with being sensitive to IRQ latency most
MST hubs will just stop responding to us if their interrupts aren't
handled in a timely manner.

So: move retraining into it's own seperate handler. Running in a
seperate handler allows us to avoid stalling the ESI during link
retraining, and we can have the ESI signal that the channel EQ bit was
cleared through a simple completion struct. Additionally, we take care
to stick as much of this into the SST retraining path as possible since
sharing is caring.

Signed-off-by: Lyude Paul <lyude@redhat.com>
Cc: Manasi Navare <manasi.d.navare@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
---
 drivers/gpu/drm/i915/intel_dp.c     | 342 +++++++++++++++++++++++++++---------
 drivers/gpu/drm/i915/intel_dp_mst.c |  42 ++++-
 drivers/gpu/drm/i915/intel_drv.h    |   8 +
 3 files changed, 302 insertions(+), 90 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 5645a194de92..7626652732b6 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -45,6 +45,8 @@
 
 #define DP_DPRX_ESI_LEN 14
 
+#define DP_MST_RETRAIN_TIMEOUT (msecs_to_jiffies(100))
+
 /* Compliance test status bits  */
 #define INTEL_DP_RESOLUTION_SHIFT_MASK	0
 #define INTEL_DP_RESOLUTION_PREFERRED	(1 << INTEL_DP_RESOLUTION_SHIFT_MASK)
@@ -4224,6 +4226,118 @@ static void intel_dp_handle_test_request(struct intel_dp *intel_dp)
 		DRM_DEBUG_KMS("Could not write test response to sink\n");
 }
 
+/* Get a mask of the CRTCs that are running on the given intel_dp struct. For
+ * MST, this returns a crtc mask containing all of the CRTCs driving
+ * downstream sinks, for SST it just returns a mask of the attached
+ * connector's CRTC.
+ */
+int
+intel_dp_get_crtc_mask(struct intel_dp *intel_dp)
+{
+	struct drm_device *dev = dp_to_dig_port(intel_dp)->base.base.dev;
+	struct drm_connector *connector;
+	struct drm_connector_state *conn_state;
+	struct intel_connector *intel_connector;
+	struct drm_crtc *crtc;
+	int crtc_mask = 0;
+
+	WARN_ON(!drm_modeset_is_locked(&dev->mode_config.connection_mutex));
+
+	if (intel_dp->is_mst) {
+		struct drm_connector_list_iter conn_iter;
+
+		drm_connector_list_iter_begin(dev, &conn_iter);
+		for_each_intel_connector_iter(intel_connector, &conn_iter) {
+			if (intel_connector->mst_port != intel_dp)
+				continue;
+
+			conn_state = intel_connector->base.state;
+			if (!conn_state->crtc)
+				continue;
+
+			crtc_mask |= drm_crtc_mask(conn_state->crtc);
+		}
+		drm_connector_list_iter_end(&conn_iter);
+	} else {
+		connector = &intel_dp->attached_connector->base;
+		crtc = connector->state->crtc;
+
+		if (crtc)
+			crtc_mask |= drm_crtc_mask(crtc);
+	}
+
+	return crtc_mask;
+}
+
+static bool
+intel_dp_needs_link_retrain(struct intel_dp *intel_dp,
+			    const u8 esi[DP_DPRX_ESI_LEN])
+{
+	u8 buf[max(DP_LINK_STATUS_SIZE, DP_DPRX_ESI_LEN)];
+	const u8 *link_status = NULL;
+
+	if (intel_dp->is_mst) {
+		if (!intel_dp->active_mst_links)
+			return false;
+		if (intel_dp->mst_link_is_bad)
+			return false;
+
+		if (esi) {
+			link_status = &esi[10];
+		} else {
+			/* We're not running from the ESI handler, so wait a
+			 * little bit to see if the ESI handler lets us know
+			 * that the link status is OK
+			 */
+			if (wait_for_completion_timeout(
+				&intel_dp->mst_retrain_completion,
+				DP_MST_RETRAIN_TIMEOUT))
+				return false;
+		}
+	} else {
+		if (intel_dp->link_trained)
+			return false;
+		if (!intel_dp_get_link_status(intel_dp, buf))
+			return false;
+
+		link_status = buf;
+	}
+
+	/*
+	 * Validate the cached values of intel_dp->link_rate and
+	 * intel_dp->lane_count before attempting to retrain.
+	 */
+	if (!intel_dp_link_params_valid(intel_dp, intel_dp->link_rate,
+					intel_dp->lane_count))
+		return false;
+
+	if (link_status) {
+		return !drm_dp_channel_eq_ok(link_status,
+					     intel_dp->lane_count);
+	} else {
+		return true;
+	}
+}
+
+static inline void
+intel_dp_mst_check_link_status(struct intel_dp *intel_dp,
+			       const u8 esi[DP_DPRX_ESI_LEN])
+{
+	if (intel_dp_needs_link_retrain(intel_dp, esi)) {
+		DRM_DEBUG_KMS("Channel EQ failing\n");
+
+		if (!work_busy(&intel_dp->mst_retrain_work)) {
+			reinit_completion(&intel_dp->mst_retrain_completion);
+			schedule_work(&intel_dp->mst_retrain_work);
+			DRM_DEBUG_KMS("Retraining started\n");
+		}
+	} else if (work_busy(&intel_dp->mst_retrain_work) &&
+		   !completion_done(&intel_dp->mst_retrain_completion)) {
+		DRM_DEBUG_KMS("Channel EQ stable\n");
+		complete_all(&intel_dp->mst_retrain_completion);
+	}
+}
+
 static int
 intel_dp_check_mst_status(struct intel_dp *intel_dp)
 {
@@ -4237,14 +4351,7 @@ intel_dp_check_mst_status(struct intel_dp *intel_dp)
 		bret = intel_dp_get_sink_irq_esi(intel_dp, esi);
 go_again:
 		if (bret == true) {
-
-			/* check link status - esi[10] = 0x200c */
-			if (intel_dp->active_mst_links &&
-			    !drm_dp_channel_eq_ok(&esi[10], intel_dp->lane_count)) {
-				DRM_DEBUG_KMS("channel EQ not ok, retraining\n");
-				intel_dp_start_link_train(intel_dp);
-				intel_dp_stop_link_train(intel_dp);
-			}
+			intel_dp_mst_check_link_status(intel_dp, esi);
 
 			DRM_DEBUG_KMS("got esi %3ph\n", esi);
 			ret = drm_dp_mst_hpd_irq(&intel_dp->mst_mgr, esi, &handled);
@@ -4281,29 +4388,6 @@ intel_dp_check_mst_status(struct intel_dp *intel_dp)
 	return -EINVAL;
 }
 
-static bool
-intel_dp_needs_link_retrain(struct intel_dp *intel_dp)
-{
-	u8 link_status[DP_LINK_STATUS_SIZE];
-
-	if (!intel_dp->link_trained)
-		return false;
-
-	if (!intel_dp_get_link_status(intel_dp, link_status))
-		return false;
-
-	/*
-	 * Validate the cached values of intel_dp->link_rate and
-	 * intel_dp->lane_count before attempting to retrain.
-	 */
-	if (!intel_dp_link_params_valid(intel_dp, intel_dp->link_rate,
-					intel_dp->lane_count))
-		return false;
-
-	/* Retrain if Channel EQ or CR not ok */
-	return !drm_dp_channel_eq_ok(link_status, intel_dp->lane_count);
-}
-
 /*
  * If display is now connected check links status,
  * there has been known issues of link loss triggering
@@ -4319,64 +4403,78 @@ intel_dp_needs_link_retrain(struct intel_dp *intel_dp)
 int intel_dp_retrain_link(struct intel_encoder *encoder,
 			  struct drm_modeset_acquire_ctx *ctx)
 {
-	struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
+	struct drm_device *dev = encoder->base.dev;
+	struct drm_i915_private *dev_priv = to_i915(dev);
 	struct intel_dp *intel_dp = enc_to_intel_dp(&encoder->base);
-	struct intel_connector *connector = intel_dp->attached_connector;
-	struct drm_connector_state *conn_state;
-	struct intel_crtc_state *crtc_state;
-	struct intel_crtc *crtc;
+	struct drm_crtc *crtc;
+	struct intel_crtc *intel_crtc;
+	int crtc_mask, retry_count = 0;
 	int ret;
 
-	/* FIXME handle the MST connectors as well */
-
-	if (!connector || connector->base.status != connector_status_connected)
-		return 0;
-
 	ret = drm_modeset_lock(&dev_priv->drm.mode_config.connection_mutex,
 			       ctx);
 	if (ret)
 		return ret;
 
-	conn_state = connector->base.state;
-
-	crtc = to_intel_crtc(conn_state->crtc);
-	if (!crtc)
-		return 0;
+	crtc_mask = intel_dp_get_crtc_mask(intel_dp);
+	for_each_intel_crtc_mask(dev, intel_crtc, crtc_mask) {
+		struct drm_crtc_state *crtc_state;
+		struct intel_crtc_state *intel_crtc_state;
 
-	ret = drm_modeset_lock(&crtc->base.mutex, ctx);
-	if (ret)
-		return ret;
+		crtc = &intel_crtc->base;
+		ret = drm_modeset_lock(&crtc->mutex, ctx);
+		if (ret)
+			return ret;
 
-	crtc_state = to_intel_crtc_state(crtc->base.state);
+		crtc_state = crtc->state;
+		intel_crtc_state = to_intel_crtc_state(crtc_state);
+		WARN_ON(!intel_crtc_has_dp_encoder(intel_crtc_state));
 
-	WARN_ON(!intel_crtc_has_dp_encoder(crtc_state));
+		if (crtc_state->commit &&
+		    !try_wait_for_completion(&crtc_state->commit->hw_done))
+			return 0;
+	}
 
-	if (!crtc_state->base.active)
+	if (!intel_dp_needs_link_retrain(intel_dp, NULL))
 		return 0;
 
-	if (conn_state->commit &&
-	    !try_wait_for_completion(&conn_state->commit->hw_done))
-		return 0;
+	for_each_intel_crtc_mask(dev, intel_crtc, crtc_mask) {
+		intel_set_cpu_fifo_underrun_reporting(
+		    dev_priv, intel_crtc->pipe, false);
 
-	if (!intel_dp_needs_link_retrain(intel_dp))
-		return 0;
+		if (intel_crtc->config->has_pch_encoder) {
+			intel_set_pch_fifo_underrun_reporting(
+			    dev_priv, intel_crtc_pch_transcoder(intel_crtc),
+			    false);
+		}
+	}
 
-	/* Suppress underruns caused by re-training */
-	intel_set_cpu_fifo_underrun_reporting(dev_priv, crtc->pipe, false);
-	if (crtc->config->has_pch_encoder)
-		intel_set_pch_fifo_underrun_reporting(dev_priv,
-						      intel_crtc_pch_transcoder(crtc), false);
+	do {
+		if (++retry_count > 5) {
+			DRM_DEBUG_KMS("Too many retries, can't retrain\n");
+			return -EINVAL;
+		}
 
-	intel_dp_start_link_train(intel_dp);
-	intel_dp_stop_link_train(intel_dp);
+		intel_dp_start_link_train(intel_dp);
+		intel_dp_stop_link_train(intel_dp);
+	} while (intel_dp_needs_link_retrain(intel_dp, NULL));
+
+	/* Wait for things to become stable */
+	for_each_intel_crtc_mask(dev, intel_crtc, crtc_mask)
+		intel_wait_for_vblank(dev_priv, intel_crtc->pipe);
 
-	/* Keep underrun reporting disabled until things are stable */
-	intel_wait_for_vblank(dev_priv, crtc->pipe);
+	/* Now that we know everything is OK, finally re-enable underrun
+	 * reporting */
+	for_each_intel_crtc_mask(dev, intel_crtc, crtc_mask) {
+		intel_set_cpu_fifo_underrun_reporting(
+		    dev_priv, intel_crtc->pipe, true);
 
-	intel_set_cpu_fifo_underrun_reporting(dev_priv, crtc->pipe, true);
-	if (crtc->config->has_pch_encoder)
-		intel_set_pch_fifo_underrun_reporting(dev_priv,
-						      intel_crtc_pch_transcoder(crtc), true);
+		if (intel_crtc->config->has_pch_encoder) {
+			intel_set_pch_fifo_underrun_reporting(
+			    dev_priv, intel_crtc_pch_transcoder(intel_crtc),
+			    true);
+		}
+	}
 
 	return 0;
 }
@@ -4402,6 +4500,10 @@ static bool intel_dp_hotplug(struct intel_encoder *encoder,
 
 	changed = intel_encoder_hotplug(encoder, connector);
 
+	/* We don't want to end up trying to retrain MST links! */
+	if (encoder && enc_to_intel_dp(&encoder->base)->is_mst)
+		return changed;
+
 	drm_modeset_acquire_init(&ctx, 0);
 
 	for (;;) {
@@ -4478,7 +4580,7 @@ intel_dp_short_pulse(struct intel_dp *intel_dp)
 	}
 
 	/* defer to the hotplug work for link retraining if needed */
-	if (intel_dp_needs_link_retrain(intel_dp))
+	if (intel_dp_needs_link_retrain(intel_dp, NULL))
 		return false;
 
 	if (intel_dp->compliance.test_type == DP_TEST_LINK_TRAINING) {
@@ -6266,25 +6368,98 @@ static bool intel_edp_init_connector(struct intel_dp *intel_dp,
 	return false;
 }
 
+static void intel_dp_mst_retrain_link_work(struct work_struct *work)
+{
+	struct drm_modeset_acquire_ctx ctx;
+	struct intel_dp *intel_dp = container_of(work, typeof(*intel_dp),
+						 mst_retrain_work);
+	struct intel_encoder *intel_encoder = &dp_to_dig_port(intel_dp)->base;
+	struct drm_device *dev = intel_encoder->base.dev;
+	int ret;
+	bool had_error = false;
+
+	drm_modeset_acquire_init(&ctx, 0);
+
+	for (;;) {
+		ret = intel_dp_retrain_link(intel_encoder, &ctx);
+		if (ret == -EDEADLK) {
+			drm_modeset_backoff(&ctx);
+			continue;
+		}
+
+		break;
+	}
+	if (!ret) {
+		DRM_DEBUG_KMS("Retrain complete\n");
+		goto out;
+	} else if (ret == -EIO) {
+		DRM_ERROR("IO error with sink during retrain? Aborting\n");
+		had_error = true;
+		goto out;
+	}
+
+	DRM_DEBUG_KMS("Retraining failed with %d, marking link status as bad\n",
+		      ret);
+
+	/* We ran out of retries, if the sink hasn't changed the link rate in
+	 * it's dpcd yet force us to fallback to a lower link rate/count */
+	if (ret == -EINVAL) {
+		ret = intel_dp_get_dpcd(intel_dp);
+		if (!ret) {
+			DRM_ERROR("IO error while reading dpcd from sink\n");
+			had_error = true;
+			goto out;
+		}
+
+		if (intel_dp->link_rate == intel_dp_max_link_rate(intel_dp) &&
+		    intel_dp->lane_count == intel_dp_max_lane_count(intel_dp)) {
+			intel_dp_get_link_train_fallback_values(
+			    intel_dp, intel_dp_max_link_rate(intel_dp),
+			    intel_dp_max_lane_count(intel_dp));
+		}
+	}
+
+	intel_dp->mst_link_is_bad = true;
+	intel_dp->mst_bw_locked = false;
+	schedule_work(&intel_dp->modeset_retry_work);
+out:
+	drm_modeset_drop_locks(&ctx);
+	drm_modeset_acquire_fini(&ctx);
+	if (had_error)
+		drm_kms_helper_hotplug_event(dev);
+}
+
 static void intel_dp_modeset_retry_work_fn(struct work_struct *work)
 {
 	struct intel_dp *intel_dp = container_of(work, typeof(*intel_dp),
 						 modeset_retry_work);
-	struct drm_connector *connector = &intel_dp->attached_connector->base;
+	struct intel_digital_port *intel_dig_port = dp_to_dig_port(intel_dp);
+	struct drm_device *dev = intel_dig_port->base.base.dev;
+	struct drm_connector *connector;
 
-	DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n", connector->base.id,
-		      connector->name);
+	mutex_lock(&dev->mode_config.mutex);
 
-	/* Grab the locks before changing connector property*/
-	mutex_lock(&connector->dev->mode_config.mutex);
-	/* Set connector link status to BAD and send a Uevent to notify
-	 * userspace to do a modeset.
+	/* Set the connector link status of all (possibly downstream) ports to
+	 * BAD and send a Uevent to notify userspace to do a modeset.
 	 */
-	drm_mode_connector_set_link_status_property(connector,
-						    DRM_MODE_LINK_STATUS_BAD);
-	mutex_unlock(&connector->dev->mode_config.mutex);
+	if (intel_dp->is_mst) {
+		drm_dp_mst_topology_mgr_lower_link_rate(
+		    &intel_dp->mst_mgr,
+		    intel_dp_max_link_rate(intel_dp),
+		    intel_dp_max_lane_count(intel_dp));
+	} else {
+		connector = &intel_dp->attached_connector->base;
+
+		DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n",
+			      connector->base.id, connector->name);
+		drm_mode_connector_set_link_status_property(
+		    connector, DRM_MODE_LINK_STATUS_BAD);
+	}
+
+	mutex_unlock(&dev->mode_config.mutex);
+
 	/* Send Hotplug uevent so userspace can reprobe */
-	drm_kms_helper_hotplug_event(connector->dev);
+	drm_kms_helper_hotplug_event(dev);
 }
 
 bool
@@ -6302,6 +6477,9 @@ intel_dp_init_connector(struct intel_digital_port *intel_dig_port,
 	/* Initialize the work for modeset in case of link train failure */
 	INIT_WORK(&intel_dp->modeset_retry_work,
 		  intel_dp_modeset_retry_work_fn);
+	INIT_WORK(&intel_dp->mst_retrain_work,
+		  intel_dp_mst_retrain_link_work);
+	init_completion(&intel_dp->mst_retrain_completion);
 
 	if (WARN(intel_dig_port->max_lanes < 1,
 		 "Not enough lanes (%d) for DP on port %c\n",
diff --git a/drivers/gpu/drm/i915/intel_dp_mst.c b/drivers/gpu/drm/i915/intel_dp_mst.c
index c0553456b18e..31202f838e89 100644
--- a/drivers/gpu/drm/i915/intel_dp_mst.c
+++ b/drivers/gpu/drm/i915/intel_dp_mst.c
@@ -110,21 +110,32 @@ static int intel_dp_mst_atomic_check(struct drm_connector *connector,
 	struct drm_connector_state *old_conn_state;
 	struct drm_crtc *old_crtc;
 	struct drm_crtc_state *crtc_state;
+	struct drm_dp_mst_topology_mgr *mgr;
+	struct drm_encoder *encoder;
 	int slots, ret = 0;
+	bool could_retrain = false;
+
+	if (new_conn_state->crtc) {
+		crtc_state = drm_atomic_get_new_crtc_state(
+		    state, new_conn_state->crtc);
+		if (crtc_state && drm_atomic_crtc_needs_modeset(crtc_state))
+			could_retrain = true;
+	}
 
 	old_conn_state = drm_atomic_get_old_connector_state(state, connector);
 	old_crtc = old_conn_state->crtc;
 	if (!old_crtc)
-		return ret;
+		goto out;
 
 	crtc_state = drm_atomic_get_new_crtc_state(state, old_crtc);
-	slots = to_intel_crtc_state(crtc_state)->dp_m_n.tu;
-	if (drm_atomic_crtc_needs_modeset(crtc_state) && slots > 0) {
-		struct drm_dp_mst_topology_mgr *mgr;
-		struct drm_encoder *old_encoder;
+	if (!drm_atomic_crtc_needs_modeset(crtc_state))
+		goto out;
+	could_retrain = true;
 
-		old_encoder = old_conn_state->best_encoder;
-		mgr = &enc_to_mst(old_encoder)->primary->dp.mst_mgr;
+	slots = to_intel_crtc_state(crtc_state)->dp_m_n.tu;
+	if (slots > 0) {
+		encoder = old_conn_state->best_encoder;
+		mgr = &enc_to_mst(encoder)->primary->dp.mst_mgr;
 
 		ret = drm_dp_atomic_release_vcpi_slots(state, mgr, slots);
 		if (ret)
@@ -132,6 +143,18 @@ static int intel_dp_mst_atomic_check(struct drm_connector *connector,
 		else
 			to_intel_crtc_state(crtc_state)->dp_m_n.tu = 0;
 	}
+
+out:
+	if (could_retrain &&
+	    old_conn_state->link_status == DRM_MODE_LINK_STATUS_BAD) {
+		if (new_conn_state->best_encoder)
+			encoder = new_conn_state->best_encoder;
+		else
+			encoder = old_conn_state->best_encoder;
+
+		mgr = &enc_to_mst(encoder)->primary->dp.mst_mgr;
+		ret = drm_atomic_dp_mst_retrain_topology(state, mgr);
+	}
 	return ret;
 }
 
@@ -186,9 +209,12 @@ static void intel_mst_post_disable_dp(struct intel_encoder *encoder,
 	intel_dp->active_mst_links--;
 
 	intel_mst->connector = NULL;
-	if (intel_dp->active_mst_links == 0)
+	if (intel_dp->active_mst_links == 0) {
+		intel_dp->mst_link_is_bad = false;
+
 		intel_dig_port->base.post_disable(&intel_dig_port->base,
 						  old_crtc_state, NULL);
+	}
 
 	DRM_DEBUG_KMS("active links %d\n", intel_dp->active_mst_links);
 }
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index fc338529e918..f4a5861e4dff 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -1119,6 +1119,13 @@ struct intel_dp {
 	/* mst connector list */
 	struct intel_dp_mst_encoder *mst_encoders[I915_MAX_PIPES];
 	struct drm_dp_mst_topology_mgr mst_mgr;
+	/* We can't handle retraining from the dig workqueue, so... */
+	struct work_struct mst_retrain_work;
+	struct completion mst_retrain_completion;
+	/* Set when retraining the link at the current parameters is
+	 * impossible for an MST connection
+	 */
+	bool mst_link_is_bad;
 
 	uint32_t (*get_aux_clock_divider)(struct intel_dp *dp, int index);
 	/*
@@ -1686,6 +1693,7 @@ void intel_dp_compute_rate(struct intel_dp *intel_dp, int port_clock,
 bool intel_dp_source_supports_hbr2(struct intel_dp *intel_dp);
 bool
 intel_dp_get_link_status(struct intel_dp *intel_dp, uint8_t link_status[DP_LINK_STATUS_SIZE]);
+int intel_dp_get_crtc_mask(struct intel_dp *intel_dp);
 
 static inline unsigned int intel_dp_unused_lane_mask(int lane_count)
 {
-- 
2.14.3

Re: [PATCH v3 5/5] drm/i915: Implement proper fallback training for MST

[Ville Syrjälä]

On Fri, Mar 09, 2018 at 04:32:31PM -0500, Lyude Paul wrote:
> @@ -6266,25 +6368,98 @@ static bool intel_edp_init_connector(struct intel_dp *intel_dp,
>  	return false;
>  }
>  
> +static void intel_dp_mst_retrain_link_work(struct work_struct *work)
> +{

Why do we need another work for this? Can't we just retrain from the
hotplug work always?

> +	struct drm_modeset_acquire_ctx ctx;
> +	struct intel_dp *intel_dp = container_of(work, typeof(*intel_dp),
> +						 mst_retrain_work);
> +	struct intel_encoder *intel_encoder = &dp_to_dig_port(intel_dp)->base;
> +	struct drm_device *dev = intel_encoder->base.dev;
> +	int ret;
> +	bool had_error = false;
> +
> +	drm_modeset_acquire_init(&ctx, 0);
> +
> +	for (;;) {
> +		ret = intel_dp_retrain_link(intel_encoder, &ctx);
> +		if (ret == -EDEADLK) {
> +			drm_modeset_backoff(&ctx);
> +			continue;
> +		}
> +
> +		break;
> +	}
> +	if (!ret) {
> +		DRM_DEBUG_KMS("Retrain complete\n");
> +		goto out;
> +	} else if (ret == -EIO) {
> +		DRM_ERROR("IO error with sink during retrain? Aborting\n");
> +		had_error = true;
> +		goto out;
> +	}
> +
> +	DRM_DEBUG_KMS("Retraining failed with %d, marking link status as bad\n",
> +		      ret);
> +
> +	/* We ran out of retries, if the sink hasn't changed the link rate in
> +	 * it's dpcd yet force us to fallback to a lower link rate/count */
> +	if (ret == -EINVAL) {
> +		ret = intel_dp_get_dpcd(intel_dp);
> +		if (!ret) {
> +			DRM_ERROR("IO error while reading dpcd from sink\n");
> +			had_error = true;
> +			goto out;
> +		}
> +
> +		if (intel_dp->link_rate == intel_dp_max_link_rate(intel_dp) &&
> +		    intel_dp->lane_count == intel_dp_max_lane_count(intel_dp)) {
> +			intel_dp_get_link_train_fallback_values(
> +			    intel_dp, intel_dp_max_link_rate(intel_dp),
> +			    intel_dp_max_lane_count(intel_dp));
> +		}
> +	}
> +
> +	intel_dp->mst_link_is_bad = true;
> +	intel_dp->mst_bw_locked = false;
> +	schedule_work(&intel_dp->modeset_retry_work);
> +out:
> +	drm_modeset_drop_locks(&ctx);
> +	drm_modeset_acquire_fini(&ctx);
> +	if (had_error)
> +		drm_kms_helper_hotplug_event(dev);
> +}
> +

-- 
Ville Syrjälä
Intel OTC

Re: [PATCH v3 5/5] drm/i915: Implement proper fallback training for MST

[Manasi Navare]

On Fri, Mar 09, 2018 at 04:32:31PM -0500, Lyude Paul wrote:
> For a while we actually haven't had any way of retraining MST links with
> fallback link parameters like we do with SST. While uncommon, certain
> setups such as my Caldigit TS3 + EVGA MST hub require this since
> otherwise, they end up getting stuck in an infinite MST retraining loop.
> 
> MST retraining is somewhat different then SST retraining. While it's
> possible during the normal link retraining sequence for a hub to indicate
> bad link status, it's also possible for a hub to only indicate this
> status through ESI messages and it's possible for this to happen after
> the initial link training succeeds. This can lead to a pattern that
> looks like this:
> 
> - Train MST link
> - Training completes successfully
> - MST hub sets Channel EQ failed bit in ESI
> - Retraining starts
> - Retraining completes successfully
> - MST hub sets Channel EQ failed bit in ESI again
> - Rinse and repeat
> 
> In these situations, we need to be able to actually trigger fallback
> link training from the ESI handler as well, along with using the ESI
> handler during retraining to figure out whether or not our retraining
> actually succeeded.
> 
> This gets a bit more complicated since we have to ensure that we don't
> block the ESI handler at all while doing retraining. If we do, due to
> DisplayPort's general issues with being sensitive to IRQ latency most
> MST hubs will just stop responding to us if their interrupts aren't
> handled in a timely manner.
> 
> So: move retraining into it's own seperate handler. Running in a
> seperate handler allows us to avoid stalling the ESI during link
> retraining, and we can have the ESI signal that the channel EQ bit was
> cleared through a simple completion struct. Additionally, we take care
> to stick as much of this into the SST retraining path as possible since
> sharing is caring.
>

Thanks for the patch for MST retraining. So just to confirm my understanding of the
cases where MS retraining is handled:
1. On link the first link training failure during the modeset, this would just
use SST modeset retry function and set the link status to BAD through drm_dp_mst_topology_mgr_lower_link_rate()

2. In case that it suceeds here but then loses synchronization in between, that time it will send IRQ_HPD and
indicate this through ESI and the way its handled is through intel_dp_mst_check_link_status() and then through
the separate mst_retrain_link work. And this time we first try to retrain at the current values for 5 times and
then fallback and retry by sending hotplug uevent.

Is this correct?

Manasi

> Signed-off-by: Lyude Paul <lyude@redhat.com>
> Cc: Manasi Navare <manasi.d.navare@intel.com>
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
>  drivers/gpu/drm/i915/intel_dp.c     | 342 +++++++++++++++++++++++++++---------
>  drivers/gpu/drm/i915/intel_dp_mst.c |  42 ++++-
>  drivers/gpu/drm/i915/intel_drv.h    |   8 +
>  3 files changed, 302 insertions(+), 90 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 5645a194de92..7626652732b6 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -45,6 +45,8 @@
>  
>  #define DP_DPRX_ESI_LEN 14
>  
> +#define DP_MST_RETRAIN_TIMEOUT (msecs_to_jiffies(100))
> +
>  /* Compliance test status bits  */
>  #define INTEL_DP_RESOLUTION_SHIFT_MASK	0
>  #define INTEL_DP_RESOLUTION_PREFERRED	(1 << INTEL_DP_RESOLUTION_SHIFT_MASK)
> @@ -4224,6 +4226,118 @@ static void intel_dp_handle_test_request(struct intel_dp *intel_dp)
>  		DRM_DEBUG_KMS("Could not write test response to sink\n");
>  }
>  
> +/* Get a mask of the CRTCs that are running on the given intel_dp struct. For
> + * MST, this returns a crtc mask containing all of the CRTCs driving
> + * downstream sinks, for SST it just returns a mask of the attached
> + * connector's CRTC.
> + */
> +int
> +intel_dp_get_crtc_mask(struct intel_dp *intel_dp)
> +{
> +	struct drm_device *dev = dp_to_dig_port(intel_dp)->base.base.dev;
> +	struct drm_connector *connector;
> +	struct drm_connector_state *conn_state;
> +	struct intel_connector *intel_connector;
> +	struct drm_crtc *crtc;
> +	int crtc_mask = 0;
> +
> +	WARN_ON(!drm_modeset_is_locked(&dev->mode_config.connection_mutex));
> +
> +	if (intel_dp->is_mst) {
> +		struct drm_connector_list_iter conn_iter;
> +
> +		drm_connector_list_iter_begin(dev, &conn_iter);
> +		for_each_intel_connector_iter(intel_connector, &conn_iter) {
> +			if (intel_connector->mst_port != intel_dp)
> +				continue;
> +
> +			conn_state = intel_connector->base.state;
> +			if (!conn_state->crtc)
> +				continue;
> +
> +			crtc_mask |= drm_crtc_mask(conn_state->crtc);
> +		}
> +		drm_connector_list_iter_end(&conn_iter);
> +	} else {
> +		connector = &intel_dp->attached_connector->base;
> +		crtc = connector->state->crtc;
> +
> +		if (crtc)
> +			crtc_mask |= drm_crtc_mask(crtc);
> +	}
> +
> +	return crtc_mask;
> +}
> +
> +static bool
> +intel_dp_needs_link_retrain(struct intel_dp *intel_dp,
> +			    const u8 esi[DP_DPRX_ESI_LEN])
> +{
> +	u8 buf[max(DP_LINK_STATUS_SIZE, DP_DPRX_ESI_LEN)];
> +	const u8 *link_status = NULL;
> +
> +	if (intel_dp->is_mst) {
> +		if (!intel_dp->active_mst_links)
> +			return false;
> +		if (intel_dp->mst_link_is_bad)
> +			return false;
> +
> +		if (esi) {
> +			link_status = &esi[10];
> +		} else {
> +			/* We're not running from the ESI handler, so wait a
> +			 * little bit to see if the ESI handler lets us know
> +			 * that the link status is OK
> +			 */
> +			if (wait_for_completion_timeout(
> +				&intel_dp->mst_retrain_completion,
> +				DP_MST_RETRAIN_TIMEOUT))
> +				return false;
> +		}
> +	} else {
> +		if (intel_dp->link_trained)
> +			return false;
> +		if (!intel_dp_get_link_status(intel_dp, buf))
> +			return false;
> +
> +		link_status = buf;
> +	}
> +
> +	/*
> +	 * Validate the cached values of intel_dp->link_rate and
> +	 * intel_dp->lane_count before attempting to retrain.
> +	 */
> +	if (!intel_dp_link_params_valid(intel_dp, intel_dp->link_rate,
> +					intel_dp->lane_count))
> +		return false;
> +
> +	if (link_status) {
> +		return !drm_dp_channel_eq_ok(link_status,
> +					     intel_dp->lane_count);
> +	} else {
> +		return true;
> +	}
> +}
> +
> +static inline void
> +intel_dp_mst_check_link_status(struct intel_dp *intel_dp,
> +			       const u8 esi[DP_DPRX_ESI_LEN])
> +{
> +	if (intel_dp_needs_link_retrain(intel_dp, esi)) {
> +		DRM_DEBUG_KMS("Channel EQ failing\n");
> +
> +		if (!work_busy(&intel_dp->mst_retrain_work)) {
> +			reinit_completion(&intel_dp->mst_retrain_completion);
> +			schedule_work(&intel_dp->mst_retrain_work);
> +			DRM_DEBUG_KMS("Retraining started\n");
> +		}
> +	} else if (work_busy(&intel_dp->mst_retrain_work) &&
> +		   !completion_done(&intel_dp->mst_retrain_completion)) {
> +		DRM_DEBUG_KMS("Channel EQ stable\n");
> +		complete_all(&intel_dp->mst_retrain_completion);
> +	}
> +}
> +
>  static int
>  intel_dp_check_mst_status(struct intel_dp *intel_dp)
>  {
> @@ -4237,14 +4351,7 @@ intel_dp_check_mst_status(struct intel_dp *intel_dp)
>  		bret = intel_dp_get_sink_irq_esi(intel_dp, esi);
>  go_again:
>  		if (bret == true) {
> -
> -			/* check link status - esi[10] = 0x200c */
> -			if (intel_dp->active_mst_links &&
> -			    !drm_dp_channel_eq_ok(&esi[10], intel_dp->lane_count)) {
> -				DRM_DEBUG_KMS("channel EQ not ok, retraining\n");
> -				intel_dp_start_link_train(intel_dp);
> -				intel_dp_stop_link_train(intel_dp);
> -			}
> +			intel_dp_mst_check_link_status(intel_dp, esi);
>  
>  			DRM_DEBUG_KMS("got esi %3ph\n", esi);
>  			ret = drm_dp_mst_hpd_irq(&intel_dp->mst_mgr, esi, &handled);
> @@ -4281,29 +4388,6 @@ intel_dp_check_mst_status(struct intel_dp *intel_dp)
>  	return -EINVAL;
>  }
>  
> -static bool
> -intel_dp_needs_link_retrain(struct intel_dp *intel_dp)
> -{
> -	u8 link_status[DP_LINK_STATUS_SIZE];
> -
> -	if (!intel_dp->link_trained)
> -		return false;
> -
> -	if (!intel_dp_get_link_status(intel_dp, link_status))
> -		return false;
> -
> -	/*
> -	 * Validate the cached values of intel_dp->link_rate and
> -	 * intel_dp->lane_count before attempting to retrain.
> -	 */
> -	if (!intel_dp_link_params_valid(intel_dp, intel_dp->link_rate,
> -					intel_dp->lane_count))
> -		return false;
> -
> -	/* Retrain if Channel EQ or CR not ok */
> -	return !drm_dp_channel_eq_ok(link_status, intel_dp->lane_count);
> -}
> -
>  /*
>   * If display is now connected check links status,
>   * there has been known issues of link loss triggering
> @@ -4319,64 +4403,78 @@ intel_dp_needs_link_retrain(struct intel_dp *intel_dp)
>  int intel_dp_retrain_link(struct intel_encoder *encoder,
>  			  struct drm_modeset_acquire_ctx *ctx)
>  {
> -	struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
> +	struct drm_device *dev = encoder->base.dev;
> +	struct drm_i915_private *dev_priv = to_i915(dev);
>  	struct intel_dp *intel_dp = enc_to_intel_dp(&encoder->base);
> -	struct intel_connector *connector = intel_dp->attached_connector;
> -	struct drm_connector_state *conn_state;
> -	struct intel_crtc_state *crtc_state;
> -	struct intel_crtc *crtc;
> +	struct drm_crtc *crtc;
> +	struct intel_crtc *intel_crtc;
> +	int crtc_mask, retry_count = 0;
>  	int ret;
>  
> -	/* FIXME handle the MST connectors as well */
> -
> -	if (!connector || connector->base.status != connector_status_connected)
> -		return 0;
> -
>  	ret = drm_modeset_lock(&dev_priv->drm.mode_config.connection_mutex,
>  			       ctx);
>  	if (ret)
>  		return ret;
>  
> -	conn_state = connector->base.state;
> -
> -	crtc = to_intel_crtc(conn_state->crtc);
> -	if (!crtc)
> -		return 0;
> +	crtc_mask = intel_dp_get_crtc_mask(intel_dp);
> +	for_each_intel_crtc_mask(dev, intel_crtc, crtc_mask) {
> +		struct drm_crtc_state *crtc_state;
> +		struct intel_crtc_state *intel_crtc_state;
>  
> -	ret = drm_modeset_lock(&crtc->base.mutex, ctx);
> -	if (ret)
> -		return ret;
> +		crtc = &intel_crtc->base;
> +		ret = drm_modeset_lock(&crtc->mutex, ctx);
> +		if (ret)
> +			return ret;
>  
> -	crtc_state = to_intel_crtc_state(crtc->base.state);
> +		crtc_state = crtc->state;
> +		intel_crtc_state = to_intel_crtc_state(crtc_state);
> +		WARN_ON(!intel_crtc_has_dp_encoder(intel_crtc_state));
>  
> -	WARN_ON(!intel_crtc_has_dp_encoder(crtc_state));
> +		if (crtc_state->commit &&
> +		    !try_wait_for_completion(&crtc_state->commit->hw_done))
> +			return 0;
> +	}
>  
> -	if (!crtc_state->base.active)
> +	if (!intel_dp_needs_link_retrain(intel_dp, NULL))
>  		return 0;
>  
> -	if (conn_state->commit &&
> -	    !try_wait_for_completion(&conn_state->commit->hw_done))
> -		return 0;
> +	for_each_intel_crtc_mask(dev, intel_crtc, crtc_mask) {
> +		intel_set_cpu_fifo_underrun_reporting(
> +		    dev_priv, intel_crtc->pipe, false);
>  
> -	if (!intel_dp_needs_link_retrain(intel_dp))
> -		return 0;
> +		if (intel_crtc->config->has_pch_encoder) {
> +			intel_set_pch_fifo_underrun_reporting(
> +			    dev_priv, intel_crtc_pch_transcoder(intel_crtc),
> +			    false);
> +		}
> +	}
>  
> -	/* Suppress underruns caused by re-training */
> -	intel_set_cpu_fifo_underrun_reporting(dev_priv, crtc->pipe, false);
> -	if (crtc->config->has_pch_encoder)
> -		intel_set_pch_fifo_underrun_reporting(dev_priv,
> -						      intel_crtc_pch_transcoder(crtc), false);
> +	do {
> +		if (++retry_count > 5) {
> +			DRM_DEBUG_KMS("Too many retries, can't retrain\n");
> +			return -EINVAL;
> +		}
>  
> -	intel_dp_start_link_train(intel_dp);
> -	intel_dp_stop_link_train(intel_dp);
> +		intel_dp_start_link_train(intel_dp);
> +		intel_dp_stop_link_train(intel_dp);
> +	} while (intel_dp_needs_link_retrain(intel_dp, NULL));
> +
> +	/* Wait for things to become stable */
> +	for_each_intel_crtc_mask(dev, intel_crtc, crtc_mask)
> +		intel_wait_for_vblank(dev_priv, intel_crtc->pipe);
>  
> -	/* Keep underrun reporting disabled until things are stable */
> -	intel_wait_for_vblank(dev_priv, crtc->pipe);
> +	/* Now that we know everything is OK, finally re-enable underrun
> +	 * reporting */
> +	for_each_intel_crtc_mask(dev, intel_crtc, crtc_mask) {
> +		intel_set_cpu_fifo_underrun_reporting(
> +		    dev_priv, intel_crtc->pipe, true);
>  
> -	intel_set_cpu_fifo_underrun_reporting(dev_priv, crtc->pipe, true);
> -	if (crtc->config->has_pch_encoder)
> -		intel_set_pch_fifo_underrun_reporting(dev_priv,
> -						      intel_crtc_pch_transcoder(crtc), true);
> +		if (intel_crtc->config->has_pch_encoder) {
> +			intel_set_pch_fifo_underrun_reporting(
> +			    dev_priv, intel_crtc_pch_transcoder(intel_crtc),
> +			    true);
> +		}
> +	}
>  
>  	return 0;
>  }
> @@ -4402,6 +4500,10 @@ static bool intel_dp_hotplug(struct intel_encoder *encoder,
>  
>  	changed = intel_encoder_hotplug(encoder, connector);
>  
> +	/* We don't want to end up trying to retrain MST links! */
> +	if (encoder && enc_to_intel_dp(&encoder->base)->is_mst)
> +		return changed;
> +
>  	drm_modeset_acquire_init(&ctx, 0);
>  
>  	for (;;) {
> @@ -4478,7 +4580,7 @@ intel_dp_short_pulse(struct intel_dp *intel_dp)
>  	}
>  
>  	/* defer to the hotplug work for link retraining if needed */
> -	if (intel_dp_needs_link_retrain(intel_dp))
> +	if (intel_dp_needs_link_retrain(intel_dp, NULL))
>  		return false;
>  
>  	if (intel_dp->compliance.test_type == DP_TEST_LINK_TRAINING) {
> @@ -6266,25 +6368,98 @@ static bool intel_edp_init_connector(struct intel_dp *intel_dp,
>  	return false;
>  }
>  
> +static void intel_dp_mst_retrain_link_work(struct work_struct *work)
> +{
> +	struct drm_modeset_acquire_ctx ctx;
> +	struct intel_dp *intel_dp = container_of(work, typeof(*intel_dp),
> +						 mst_retrain_work);
> +	struct intel_encoder *intel_encoder = &dp_to_dig_port(intel_dp)->base;
> +	struct drm_device *dev = intel_encoder->base.dev;
> +	int ret;
> +	bool had_error = false;
> +
> +	drm_modeset_acquire_init(&ctx, 0);
> +
> +	for (;;) {
> +		ret = intel_dp_retrain_link(intel_encoder, &ctx);
> +		if (ret == -EDEADLK) {
> +			drm_modeset_backoff(&ctx);
> +			continue;
> +		}
> +
> +		break;
> +	}
> +	if (!ret) {
> +		DRM_DEBUG_KMS("Retrain complete\n");
> +		goto out;
> +	} else if (ret == -EIO) {
> +		DRM_ERROR("IO error with sink during retrain? Aborting\n");
> +		had_error = true;
> +		goto out;
> +	}
> +
> +	DRM_DEBUG_KMS("Retraining failed with %d, marking link status as bad\n",
> +		      ret);
> +
> +	/* We ran out of retries, if the sink hasn't changed the link rate in
> +	 * it's dpcd yet force us to fallback to a lower link rate/count */
> +	if (ret == -EINVAL) {
> +		ret = intel_dp_get_dpcd(intel_dp);
> +		if (!ret) {
> +			DRM_ERROR("IO error while reading dpcd from sink\n");
> +			had_error = true;
> +			goto out;
> +		}
> +
> +		if (intel_dp->link_rate == intel_dp_max_link_rate(intel_dp) &&
> +		    intel_dp->lane_count == intel_dp_max_lane_count(intel_dp)) {
> +			intel_dp_get_link_train_fallback_values(
> +			    intel_dp, intel_dp_max_link_rate(intel_dp),
> +			    intel_dp_max_lane_count(intel_dp));
> +		}
> +	}
> +
> +	intel_dp->mst_link_is_bad = true;
> +	intel_dp->mst_bw_locked = false;
> +	schedule_work(&intel_dp->modeset_retry_work);
> +out:
> +	drm_modeset_drop_locks(&ctx);
> +	drm_modeset_acquire_fini(&ctx);
> +	if (had_error)
> +		drm_kms_helper_hotplug_event(dev);
> +}
> +
>  static void intel_dp_modeset_retry_work_fn(struct work_struct *work)
>  {
>  	struct intel_dp *intel_dp = container_of(work, typeof(*intel_dp),
>  						 modeset_retry_work);
> -	struct drm_connector *connector = &intel_dp->attached_connector->base;
> +	struct intel_digital_port *intel_dig_port = dp_to_dig_port(intel_dp);
> +	struct drm_device *dev = intel_dig_port->base.base.dev;
> +	struct drm_connector *connector;
>  
> -	DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n", connector->base.id,
> -		      connector->name);
> +	mutex_lock(&dev->mode_config.mutex);
>  
> -	/* Grab the locks before changing connector property*/
> -	mutex_lock(&connector->dev->mode_config.mutex);
> -	/* Set connector link status to BAD and send a Uevent to notify
> -	 * userspace to do a modeset.
> +	/* Set the connector link status of all (possibly downstream) ports to
> +	 * BAD and send a Uevent to notify userspace to do a modeset.
>  	 */
> -	drm_mode_connector_set_link_status_property(connector,
> -						    DRM_MODE_LINK_STATUS_BAD);
> -	mutex_unlock(&connector->dev->mode_config.mutex);
> +	if (intel_dp->is_mst) {
> +		drm_dp_mst_topology_mgr_lower_link_rate(
> +		    &intel_dp->mst_mgr,
> +		    intel_dp_max_link_rate(intel_dp),
> +		    intel_dp_max_lane_count(intel_dp));
> +	} else {
> +		connector = &intel_dp->attached_connector->base;
> +
> +		DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n",
> +			      connector->base.id, connector->name);
> +		drm_mode_connector_set_link_status_property(
> +		    connector, DRM_MODE_LINK_STATUS_BAD);
> +	}
> +
> +	mutex_unlock(&dev->mode_config.mutex);
> +
>  	/* Send Hotplug uevent so userspace can reprobe */
> -	drm_kms_helper_hotplug_event(connector->dev);
> +	drm_kms_helper_hotplug_event(dev);
>  }
>  
>  bool
> @@ -6302,6 +6477,9 @@ intel_dp_init_connector(struct intel_digital_port *intel_dig_port,
>  	/* Initialize the work for modeset in case of link train failure */
>  	INIT_WORK(&intel_dp->modeset_retry_work,
>  		  intel_dp_modeset_retry_work_fn);
> +	INIT_WORK(&intel_dp->mst_retrain_work,
> +		  intel_dp_mst_retrain_link_work);
> +	init_completion(&intel_dp->mst_retrain_completion);
>  
>  	if (WARN(intel_dig_port->max_lanes < 1,
>  		 "Not enough lanes (%d) for DP on port %c\n",
> diff --git a/drivers/gpu/drm/i915/intel_dp_mst.c b/drivers/gpu/drm/i915/intel_dp_mst.c
> index c0553456b18e..31202f838e89 100644
> --- a/drivers/gpu/drm/i915/intel_dp_mst.c
> +++ b/drivers/gpu/drm/i915/intel_dp_mst.c
> @@ -110,21 +110,32 @@ static int intel_dp_mst_atomic_check(struct drm_connector *connector,
>  	struct drm_connector_state *old_conn_state;
>  	struct drm_crtc *old_crtc;
>  	struct drm_crtc_state *crtc_state;
> +	struct drm_dp_mst_topology_mgr *mgr;
> +	struct drm_encoder *encoder;
>  	int slots, ret = 0;
> +	bool could_retrain = false;
> +
> +	if (new_conn_state->crtc) {
> +		crtc_state = drm_atomic_get_new_crtc_state(
> +		    state, new_conn_state->crtc);
> +		if (crtc_state && drm_atomic_crtc_needs_modeset(crtc_state))
> +			could_retrain = true;
> +	}
>  
>  	old_conn_state = drm_atomic_get_old_connector_state(state, connector);
>  	old_crtc = old_conn_state->crtc;
>  	if (!old_crtc)
> -		return ret;
> +		goto out;
>  
>  	crtc_state = drm_atomic_get_new_crtc_state(state, old_crtc);
> -	slots = to_intel_crtc_state(crtc_state)->dp_m_n.tu;
> -	if (drm_atomic_crtc_needs_modeset(crtc_state) && slots > 0) {
> -		struct drm_dp_mst_topology_mgr *mgr;
> -		struct drm_encoder *old_encoder;
> +	if (!drm_atomic_crtc_needs_modeset(crtc_state))
> +		goto out;
> +	could_retrain = true;
>  
> -		old_encoder = old_conn_state->best_encoder;
> -		mgr = &enc_to_mst(old_encoder)->primary->dp.mst_mgr;
> +	slots = to_intel_crtc_state(crtc_state)->dp_m_n.tu;
> +	if (slots > 0) {
> +		encoder = old_conn_state->best_encoder;
> +		mgr = &enc_to_mst(encoder)->primary->dp.mst_mgr;
>  
>  		ret = drm_dp_atomic_release_vcpi_slots(state, mgr, slots);
>  		if (ret)
> @@ -132,6 +143,18 @@ static int intel_dp_mst_atomic_check(struct drm_connector *connector,
>  		else
>  			to_intel_crtc_state(crtc_state)->dp_m_n.tu = 0;
>  	}
> +
> +out:
> +	if (could_retrain &&
> +	    old_conn_state->link_status == DRM_MODE_LINK_STATUS_BAD) {
> +		if (new_conn_state->best_encoder)
> +			encoder = new_conn_state->best_encoder;
> +		else
> +			encoder = old_conn_state->best_encoder;
> +
> +		mgr = &enc_to_mst(encoder)->primary->dp.mst_mgr;
> +		ret = drm_atomic_dp_mst_retrain_topology(state, mgr);
> +	}
>  	return ret;
>  }
>  
> @@ -186,9 +209,12 @@ static void intel_mst_post_disable_dp(struct intel_encoder *encoder,
>  	intel_dp->active_mst_links--;
>  
>  	intel_mst->connector = NULL;
> -	if (intel_dp->active_mst_links == 0)
> +	if (intel_dp->active_mst_links == 0) {
> +		intel_dp->mst_link_is_bad = false;
> +
>  		intel_dig_port->base.post_disable(&intel_dig_port->base,
>  						  old_crtc_state, NULL);
> +	}
>  
>  	DRM_DEBUG_KMS("active links %d\n", intel_dp->active_mst_links);
>  }
> diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> index fc338529e918..f4a5861e4dff 100644
> --- a/drivers/gpu/drm/i915/intel_drv.h
> +++ b/drivers/gpu/drm/i915/intel_drv.h
> @@ -1119,6 +1119,13 @@ struct intel_dp {
>  	/* mst connector list */
>  	struct intel_dp_mst_encoder *mst_encoders[I915_MAX_PIPES];
>  	struct drm_dp_mst_topology_mgr mst_mgr;
> +	/* We can't handle retraining from the dig workqueue, so... */
> +	struct work_struct mst_retrain_work;
> +	struct completion mst_retrain_completion;
> +	/* Set when retraining the link at the current parameters is
> +	 * impossible for an MST connection
> +	 */
> +	bool mst_link_is_bad;
>  
>  	uint32_t (*get_aux_clock_divider)(struct intel_dp *dp, int index);
>  	/*
> @@ -1686,6 +1693,7 @@ void intel_dp_compute_rate(struct intel_dp *intel_dp, int port_clock,
>  bool intel_dp_source_supports_hbr2(struct intel_dp *intel_dp);
>  bool
>  intel_dp_get_link_status(struct intel_dp *intel_dp, uint8_t link_status[DP_LINK_STATUS_SIZE]);
> +int intel_dp_get_crtc_mask(struct intel_dp *intel_dp);
>  
>  static inline unsigned int intel_dp_unused_lane_mask(int lane_count)
>  {
> -- 
> 2.14.3
> 
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel

Re: [PATCH v3 5/5] drm/i915: Implement proper fallback training for MST

[Lyude Paul]

On Mon, 2018-03-12 at 15:05 -0700, Manasi Navare wrote:
> On Fri, Mar 09, 2018 at 04:32:31PM -0500, Lyude Paul wrote:
> > For a while we actually haven't had any way of retraining MST links with
> > fallback link parameters like we do with SST. While uncommon, certain
> > setups such as my Caldigit TS3 + EVGA MST hub require this since
> > otherwise, they end up getting stuck in an infinite MST retraining loop.
> > 
> > MST retraining is somewhat different then SST retraining. While it's
> > possible during the normal link retraining sequence for a hub to indicate
> > bad link status, it's also possible for a hub to only indicate this
> > status through ESI messages and it's possible for this to happen after
> > the initial link training succeeds. This can lead to a pattern that
> > looks like this:
> > 
> > - Train MST link
> > - Training completes successfully
> > - MST hub sets Channel EQ failed bit in ESI
> > - Retraining starts
> > - Retraining completes successfully
> > - MST hub sets Channel EQ failed bit in ESI again
> > - Rinse and repeat
> > 
> > In these situations, we need to be able to actually trigger fallback
> > link training from the ESI handler as well, along with using the ESI
> > handler during retraining to figure out whether or not our retraining
> > actually succeeded.
> > 
> > This gets a bit more complicated since we have to ensure that we don't
> > block the ESI handler at all while doing retraining. If we do, due to
> > DisplayPort's general issues with being sensitive to IRQ latency most
> > MST hubs will just stop responding to us if their interrupts aren't
> > handled in a timely manner.
> > 
> > So: move retraining into it's own seperate handler. Running in a
> > seperate handler allows us to avoid stalling the ESI during link
> > retraining, and we can have the ESI signal that the channel EQ bit was
> > cleared through a simple completion struct. Additionally, we take care
> > to stick as much of this into the SST retraining path as possible since
> > sharing is caring.
> > 
> 
> Thanks for the patch for MST retraining. So just to confirm my understanding
> of the
> cases where MS retraining is handled:
> 1. On link the first link training failure during the modeset, this would
> just
> use SST modeset retry function and set the link status to BAD through
> drm_dp_mst_topology_mgr_lower_link_rate()
This shoyuld be the  the case for hubs that are a bit less awkward then mine.
I haven't actually seen the link training fail during the initial modeset once
on my setup here, only the channel EQ bit in the ESI handler ever seems to get
set.
> 
> 2. In case that it suceeds here but then loses synchronization in between,
> that time it will send IRQ_HPD and
> indicate this through ESI and the way its handled is through
> intel_dp_mst_check_link_status() and then through
> the separate mst_retrain_link work. And this time we first try to retrain at
> the current values for 5 times and
> then fallback and retry by sending hotplug uevent.
Yes. As well, there's two ways we could run into a situation that would count
as a failure:

 * (Note, this doesn't happen because I forgot to include it in this patch
   series, but it'll be fixed in the next revision) If the hub does everything
   it's supposed to and actually reports the link training status as failing
   through the registers that intel_dp_start_link_train() relies on, then
   intel_dp_start_link_train() will try five times; fail; and then we'll skip
   any additional attempts in intel_dp_retrain_link() and start the modeset
   retry work.
 * If the hub doesn't do everything that it's supposed to like mine does and
   only reports channel EQ failures through the ESI handler, we'll end up
   successfully link training; time out waiting for the ESI handler to signal
   through mst_retrain_completion that the channel EQ bit has been cleared,
   and repeat five times until we give up and fall back to a lower link rate
   with the modeset retry work.

> 
> Is this correct?
> 
> Manasi
> 
> > Signed-off-by: Lyude Paul <lyude@redhat.com>
> > Cc: Manasi Navare <manasi.d.navare@intel.com>
> > Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > ---
> >  drivers/gpu/drm/i915/intel_dp.c     | 342 +++++++++++++++++++++++++++--
> > -------
> >  drivers/gpu/drm/i915/intel_dp_mst.c |  42 ++++-
> >  drivers/gpu/drm/i915/intel_drv.h    |   8 +
> >  3 files changed, 302 insertions(+), 90 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/intel_dp.c
> > b/drivers/gpu/drm/i915/intel_dp.c
> > index 5645a194de92..7626652732b6 100644
> > --- a/drivers/gpu/drm/i915/intel_dp.c
> > +++ b/drivers/gpu/drm/i915/intel_dp.c
> > @@ -45,6 +45,8 @@
> >  
> >  #define DP_DPRX_ESI_LEN 14
> >  
> > +#define DP_MST_RETRAIN_TIMEOUT (msecs_to_jiffies(100))
> > +
> >  /* Compliance test status bits  */
> >  #define INTEL_DP_RESOLUTION_SHIFT_MASK	0
> >  #define INTEL_DP_RESOLUTION_PREFERRED	(1 <<
> > INTEL_DP_RESOLUTION_SHIFT_MASK)
> > @@ -4224,6 +4226,118 @@ static void intel_dp_handle_test_request(struct
> > intel_dp *intel_dp)
> >  		DRM_DEBUG_KMS("Could not write test response to sink\n");
> >  }
> >  
> > +/* Get a mask of the CRTCs that are running on the given intel_dp struct.
> > For
> > + * MST, this returns a crtc mask containing all of the CRTCs driving
> > + * downstream sinks, for SST it just returns a mask of the attached
> > + * connector's CRTC.
> > + */
> > +int
> > +intel_dp_get_crtc_mask(struct intel_dp *intel_dp)
> > +{
> > +	struct drm_device *dev = dp_to_dig_port(intel_dp)->base.base.dev;
> > +	struct drm_connector *connector;
> > +	struct drm_connector_state *conn_state;
> > +	struct intel_connector *intel_connector;
> > +	struct drm_crtc *crtc;
> > +	int crtc_mask = 0;
> > +
> > +	WARN_ON(!drm_modeset_is_locked(&dev-
> > >mode_config.connection_mutex));
> > +
> > +	if (intel_dp->is_mst) {
> > +		struct drm_connector_list_iter conn_iter;
> > +
> > +		drm_connector_list_iter_begin(dev, &conn_iter);
> > +		for_each_intel_connector_iter(intel_connector,
> > &conn_iter) {
> > +			if (intel_connector->mst_port != intel_dp)
> > +				continue;
> > +
> > +			conn_state = intel_connector->base.state;
> > +			if (!conn_state->crtc)
> > +				continue;
> > +
> > +			crtc_mask |= drm_crtc_mask(conn_state->crtc);
> > +		}
> > +		drm_connector_list_iter_end(&conn_iter);
> > +	} else {
> > +		connector = &intel_dp->attached_connector->base;
> > +		crtc = connector->state->crtc;
> > +
> > +		if (crtc)
> > +			crtc_mask |= drm_crtc_mask(crtc);
> > +	}
> > +
> > +	return crtc_mask;
> > +}
> > +
> > +static bool
> > +intel_dp_needs_link_retrain(struct intel_dp *intel_dp,
> > +			    const u8 esi[DP_DPRX_ESI_LEN])
> > +{
> > +	u8 buf[max(DP_LINK_STATUS_SIZE, DP_DPRX_ESI_LEN)];
> > +	const u8 *link_status = NULL;
> > +
> > +	if (intel_dp->is_mst) {
> > +		if (!intel_dp->active_mst_links)
> > +			return false;
> > +		if (intel_dp->mst_link_is_bad)
> > +			return false;
> > +
> > +		if (esi) {
> > +			link_status = &esi[10];
> > +		} else {
> > +			/* We're not running from the ESI handler, so
> > wait a
> > +			 * little bit to see if the ESI handler lets us
> > know
> > +			 * that the link status is OK
> > +			 */
> > +			if (wait_for_completion_timeout(
> > +				&intel_dp->mst_retrain_completion,
> > +				DP_MST_RETRAIN_TIMEOUT))
> > +				return false;
> > +		}
> > +	} else {
> > +		if (intel_dp->link_trained)
> > +			return false;
> > +		if (!intel_dp_get_link_status(intel_dp, buf))
> > +			return false;
> > +
> > +		link_status = buf;
> > +	}
> > +
> > +	/*
> > +	 * Validate the cached values of intel_dp->link_rate and
> > +	 * intel_dp->lane_count before attempting to retrain.
> > +	 */
> > +	if (!intel_dp_link_params_valid(intel_dp, intel_dp->link_rate,
> > +					intel_dp->lane_count))
> > +		return false;
> > +
> > +	if (link_status) {
> > +		return !drm_dp_channel_eq_ok(link_status,
> > +					     intel_dp->lane_count);
> > +	} else {
> > +		return true;
> > +	}
> > +}
> > +
> > +static inline void
> > +intel_dp_mst_check_link_status(struct intel_dp *intel_dp,
> > +			       const u8 esi[DP_DPRX_ESI_LEN])
> > +{
> > +	if (intel_dp_needs_link_retrain(intel_dp, esi)) {
> > +		DRM_DEBUG_KMS("Channel EQ failing\n");
> > +
> > +		if (!work_busy(&intel_dp->mst_retrain_work)) {
> > +			reinit_completion(&intel_dp-
> > >mst_retrain_completion);
> > +			schedule_work(&intel_dp->mst_retrain_work);
> > +			DRM_DEBUG_KMS("Retraining started\n");
> > +		}
> > +	} else if (work_busy(&intel_dp->mst_retrain_work) &&
> > +		   !completion_done(&intel_dp->mst_retrain_completion)) {
> > +		DRM_DEBUG_KMS("Channel EQ stable\n");
> > +		complete_all(&intel_dp->mst_retrain_completion);
> > +	}
> > +}
> > +
> >  static int
> >  intel_dp_check_mst_status(struct intel_dp *intel_dp)
> >  {
> > @@ -4237,14 +4351,7 @@ intel_dp_check_mst_status(struct intel_dp
> > *intel_dp)
> >  		bret = intel_dp_get_sink_irq_esi(intel_dp, esi);
> >  go_again:
> >  		if (bret == true) {
> > -
> > -			/* check link status - esi[10] = 0x200c */
> > -			if (intel_dp->active_mst_links &&
> > -			    !drm_dp_channel_eq_ok(&esi[10], intel_dp-
> > >lane_count)) {
> > -				DRM_DEBUG_KMS("channel EQ not ok,
> > retraining\n");
> > -				intel_dp_start_link_train(intel_dp);
> > -				intel_dp_stop_link_train(intel_dp);
> > -			}
> > +			intel_dp_mst_check_link_status(intel_dp, esi);
> >  
> >  			DRM_DEBUG_KMS("got esi %3ph\n", esi);
> >  			ret = drm_dp_mst_hpd_irq(&intel_dp->mst_mgr, esi,
> > &handled);
> > @@ -4281,29 +4388,6 @@ intel_dp_check_mst_status(struct intel_dp
> > *intel_dp)
> >  	return -EINVAL;
> >  }
> >  
> > -static bool
> > -intel_dp_needs_link_retrain(struct intel_dp *intel_dp)
> > -{
> > -	u8 link_status[DP_LINK_STATUS_SIZE];
> > -
> > -	if (!intel_dp->link_trained)
> > -		return false;
> > -
> > -	if (!intel_dp_get_link_status(intel_dp, link_status))
> > -		return false;
> > -
> > -	/*
> > -	 * Validate the cached values of intel_dp->link_rate and
> > -	 * intel_dp->lane_count before attempting to retrain.
> > -	 */
> > -	if (!intel_dp_link_params_valid(intel_dp, intel_dp->link_rate,
> > -					intel_dp->lane_count))
> > -		return false;
> > -
> > -	/* Retrain if Channel EQ or CR not ok */
> > -	return !drm_dp_channel_eq_ok(link_status, intel_dp->lane_count);
> > -}
> > -
> >  /*
> >   * If display is now connected check links status,
> >   * there has been known issues of link loss triggering
> > @@ -4319,64 +4403,78 @@ intel_dp_needs_link_retrain(struct intel_dp
> > *intel_dp)
> >  int intel_dp_retrain_link(struct intel_encoder *encoder,
> >  			  struct drm_modeset_acquire_ctx *ctx)
> >  {
> > -	struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
> > +	struct drm_device *dev = encoder->base.dev;
> > +	struct drm_i915_private *dev_priv = to_i915(dev);
> >  	struct intel_dp *intel_dp = enc_to_intel_dp(&encoder->base);
> > -	struct intel_connector *connector = intel_dp->attached_connector;
> > -	struct drm_connector_state *conn_state;
> > -	struct intel_crtc_state *crtc_state;
> > -	struct intel_crtc *crtc;
> > +	struct drm_crtc *crtc;
> > +	struct intel_crtc *intel_crtc;
> > +	int crtc_mask, retry_count = 0;
> >  	int ret;
> >  
> > -	/* FIXME handle the MST connectors as well */
> > -
> > -	if (!connector || connector->base.status !=
> > connector_status_connected)
> > -		return 0;
> > -
> >  	ret = drm_modeset_lock(&dev_priv-
> > >drm.mode_config.connection_mutex,
> >  			       ctx);
> >  	if (ret)
> >  		return ret;
> >  
> > -	conn_state = connector->base.state;
> > -
> > -	crtc = to_intel_crtc(conn_state->crtc);
> > -	if (!crtc)
> > -		return 0;
> > +	crtc_mask = intel_dp_get_crtc_mask(intel_dp);
> > +	for_each_intel_crtc_mask(dev, intel_crtc, crtc_mask) {
> > +		struct drm_crtc_state *crtc_state;
> > +		struct intel_crtc_state *intel_crtc_state;
> >  
> > -	ret = drm_modeset_lock(&crtc->base.mutex, ctx);
> > -	if (ret)
> > -		return ret;
> > +		crtc = &intel_crtc->base;
> > +		ret = drm_modeset_lock(&crtc->mutex, ctx);
> > +		if (ret)
> > +			return ret;
> >  
> > -	crtc_state = to_intel_crtc_state(crtc->base.state);
> > +		crtc_state = crtc->state;
> > +		intel_crtc_state = to_intel_crtc_state(crtc_state);
> > +		WARN_ON(!intel_crtc_has_dp_encoder(intel_crtc_state));
> >  
> > -	WARN_ON(!intel_crtc_has_dp_encoder(crtc_state));
> > +		if (crtc_state->commit &&
> > +		    !try_wait_for_completion(&crtc_state->commit-
> > >hw_done))
> > +			return 0;
> > +	}
> >  
> > -	if (!crtc_state->base.active)
> > +	if (!intel_dp_needs_link_retrain(intel_dp, NULL))
> >  		return 0;
> >  
> > -	if (conn_state->commit &&
> > -	    !try_wait_for_completion(&conn_state->commit->hw_done))
> > -		return 0;
> > +	for_each_intel_crtc_mask(dev, intel_crtc, crtc_mask) {
> > +		intel_set_cpu_fifo_underrun_reporting(
> > +		    dev_priv, intel_crtc->pipe, false);
> >  
> > -	if (!intel_dp_needs_link_retrain(intel_dp))
> > -		return 0;
> > +		if (intel_crtc->config->has_pch_encoder) {
> > +			intel_set_pch_fifo_underrun_reporting(
> > +			    dev_priv,
> > intel_crtc_pch_transcoder(intel_crtc),
> > +			    false);
> > +		}
> > +	}
> >  
> > -	/* Suppress underruns caused by re-training */
> > -	intel_set_cpu_fifo_underrun_reporting(dev_priv, crtc->pipe,
> > false);
> > -	if (crtc->config->has_pch_encoder)
> > -		intel_set_pch_fifo_underrun_reporting(dev_priv,
> > -						      intel_crtc_pch_tran
> > scoder(crtc), false);
> > +	do {
> > +		if (++retry_count > 5) {
> > +			DRM_DEBUG_KMS("Too many retries, can't
> > retrain\n");
> > +			return -EINVAL;
> > +		}
> >  
> > -	intel_dp_start_link_train(intel_dp);
> > -	intel_dp_stop_link_train(intel_dp);
> > +		intel_dp_start_link_train(intel_dp);
> > +		intel_dp_stop_link_train(intel_dp);
> > +	} while (intel_dp_needs_link_retrain(intel_dp, NULL));
> > +
> > +	/* Wait for things to become stable */
> > +	for_each_intel_crtc_mask(dev, intel_crtc, crtc_mask)
> > +		intel_wait_for_vblank(dev_priv, intel_crtc->pipe);
> >  
> > -	/* Keep underrun reporting disabled until things are stable */
> > -	intel_wait_for_vblank(dev_priv, crtc->pipe);
> > +	/* Now that we know everything is OK, finally re-enable underrun
> > +	 * reporting */
> > +	for_each_intel_crtc_mask(dev, intel_crtc, crtc_mask) {
> > +		intel_set_cpu_fifo_underrun_reporting(
> > +		    dev_priv, intel_crtc->pipe, true);
> >  
> > -	intel_set_cpu_fifo_underrun_reporting(dev_priv, crtc->pipe,
> > true);
> > -	if (crtc->config->has_pch_encoder)
> > -		intel_set_pch_fifo_underrun_reporting(dev_priv,
> > -						      intel_crtc_pch_tran
> > scoder(crtc), true);
> > +		if (intel_crtc->config->has_pch_encoder) {
> > +			intel_set_pch_fifo_underrun_reporting(
> > +			    dev_priv,
> > intel_crtc_pch_transcoder(intel_crtc),
> > +			    true);
> > +		}
> > +	}
> >  
> >  	return 0;
> >  }
> > @@ -4402,6 +4500,10 @@ static bool intel_dp_hotplug(struct intel_encoder
> > *encoder,
> >  
> >  	changed = intel_encoder_hotplug(encoder, connector);
> >  
> > +	/* We don't want to end up trying to retrain MST links! */
> > +	if (encoder && enc_to_intel_dp(&encoder->base)->is_mst)
> > +		return changed;
> > +
> >  	drm_modeset_acquire_init(&ctx, 0);
> >  
> >  	for (;;) {
> > @@ -4478,7 +4580,7 @@ intel_dp_short_pulse(struct intel_dp *intel_dp)
> >  	}
> >  
> >  	/* defer to the hotplug work for link retraining if needed */
> > -	if (intel_dp_needs_link_retrain(intel_dp))
> > +	if (intel_dp_needs_link_retrain(intel_dp, NULL))
> >  		return false;
> >  
> >  	if (intel_dp->compliance.test_type == DP_TEST_LINK_TRAINING) {
> > @@ -6266,25 +6368,98 @@ static bool intel_edp_init_connector(struct
> > intel_dp *intel_dp,
> >  	return false;
> >  }
> >  
> > +static void intel_dp_mst_retrain_link_work(struct work_struct *work)
> > +{
> > +	struct drm_modeset_acquire_ctx ctx;
> > +	struct intel_dp *intel_dp = container_of(work, typeof(*intel_dp),
> > +						 mst_retrain_work);
> > +	struct intel_encoder *intel_encoder = &dp_to_dig_port(intel_dp)-
> > >base;
> > +	struct drm_device *dev = intel_encoder->base.dev;
> > +	int ret;
> > +	bool had_error = false;
> > +
> > +	drm_modeset_acquire_init(&ctx, 0);
> > +
> > +	for (;;) {
> > +		ret = intel_dp_retrain_link(intel_encoder, &ctx);
> > +		if (ret == -EDEADLK) {
> > +			drm_modeset_backoff(&ctx);
> > +			continue;
> > +		}
> > +
> > +		break;
> > +	}
> > +	if (!ret) {
> > +		DRM_DEBUG_KMS("Retrain complete\n");
> > +		goto out;
> > +	} else if (ret == -EIO) {
> > +		DRM_ERROR("IO error with sink during retrain?
> > Aborting\n");
> > +		had_error = true;
> > +		goto out;
> > +	}
> > +
> > +	DRM_DEBUG_KMS("Retraining failed with %d, marking link status as
> > bad\n",
> > +		      ret);
> > +
> > +	/* We ran out of retries, if the sink hasn't changed the link
> > rate in
> > +	 * it's dpcd yet force us to fallback to a lower link rate/count
> > */
> > +	if (ret == -EINVAL) {
> > +		ret = intel_dp_get_dpcd(intel_dp);
> > +		if (!ret) {
> > +			DRM_ERROR("IO error while reading dpcd from
> > sink\n");
> > +			had_error = true;
> > +			goto out;
> > +		}
> > +
> > +		if (intel_dp->link_rate ==
> > intel_dp_max_link_rate(intel_dp) &&
> > +		    intel_dp->lane_count ==
> > intel_dp_max_lane_count(intel_dp)) {
> > +			intel_dp_get_link_train_fallback_values(
> > +			    intel_dp, intel_dp_max_link_rate(intel_dp),
> > +			    intel_dp_max_lane_count(intel_dp));
> > +		}
> > +	}
> > +
> > +	intel_dp->mst_link_is_bad = true;
> > +	intel_dp->mst_bw_locked = false;
> > +	schedule_work(&intel_dp->modeset_retry_work);
> > +out:
> > +	drm_modeset_drop_locks(&ctx);
> > +	drm_modeset_acquire_fini(&ctx);
> > +	if (had_error)
> > +		drm_kms_helper_hotplug_event(dev);
> > +}
> > +
> >  static void intel_dp_modeset_retry_work_fn(struct work_struct *work)
> >  {
> >  	struct intel_dp *intel_dp = container_of(work, typeof(*intel_dp),
> >  						 modeset_retry_work);
> > -	struct drm_connector *connector = &intel_dp->attached_connector-
> > >base;
> > +	struct intel_digital_port *intel_dig_port =
> > dp_to_dig_port(intel_dp);
> > +	struct drm_device *dev = intel_dig_port->base.base.dev;
> > +	struct drm_connector *connector;
> >  
> > -	DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n", connector->base.id,
> > -		      connector->name);
> > +	mutex_lock(&dev->mode_config.mutex);
> >  
> > -	/* Grab the locks before changing connector property*/
> > -	mutex_lock(&connector->dev->mode_config.mutex);
> > -	/* Set connector link status to BAD and send a Uevent to notify
> > -	 * userspace to do a modeset.
> > +	/* Set the connector link status of all (possibly downstream)
> > ports to
> > +	 * BAD and send a Uevent to notify userspace to do a modeset.
> >  	 */
> > -	drm_mode_connector_set_link_status_property(connector,
> > -						    DRM_MODE_LINK_STATUS_
> > BAD);
> > -	mutex_unlock(&connector->dev->mode_config.mutex);
> > +	if (intel_dp->is_mst) {
> > +		drm_dp_mst_topology_mgr_lower_link_rate(
> > +		    &intel_dp->mst_mgr,
> > +		    intel_dp_max_link_rate(intel_dp),
> > +		    intel_dp_max_lane_count(intel_dp));
> > +	} else {
> > +		connector = &intel_dp->attached_connector->base;
> > +
> > +		DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n",
> > +			      connector->base.id, connector->name);
> > +		drm_mode_connector_set_link_status_property(
> > +		    connector, DRM_MODE_LINK_STATUS_BAD);
> > +	}
> > +
> > +	mutex_unlock(&dev->mode_config.mutex);
> > +
> >  	/* Send Hotplug uevent so userspace can reprobe */
> > -	drm_kms_helper_hotplug_event(connector->dev);
> > +	drm_kms_helper_hotplug_event(dev);
> >  }
> >  
> >  bool
> > @@ -6302,6 +6477,9 @@ intel_dp_init_connector(struct intel_digital_port
> > *intel_dig_port,
> >  	/* Initialize the work for modeset in case of link train failure
> > */
> >  	INIT_WORK(&intel_dp->modeset_retry_work,
> >  		  intel_dp_modeset_retry_work_fn);
> > +	INIT_WORK(&intel_dp->mst_retrain_work,
> > +		  intel_dp_mst_retrain_link_work);
> > +	init_completion(&intel_dp->mst_retrain_completion);
> >  
> >  	if (WARN(intel_dig_port->max_lanes < 1,
> >  		 "Not enough lanes (%d) for DP on port %c\n",
> > diff --git a/drivers/gpu/drm/i915/intel_dp_mst.c
> > b/drivers/gpu/drm/i915/intel_dp_mst.c
> > index c0553456b18e..31202f838e89 100644
> > --- a/drivers/gpu/drm/i915/intel_dp_mst.c
> > +++ b/drivers/gpu/drm/i915/intel_dp_mst.c
> > @@ -110,21 +110,32 @@ static int intel_dp_mst_atomic_check(struct
> > drm_connector *connector,
> >  	struct drm_connector_state *old_conn_state;
> >  	struct drm_crtc *old_crtc;
> >  	struct drm_crtc_state *crtc_state;
> > +	struct drm_dp_mst_topology_mgr *mgr;
> > +	struct drm_encoder *encoder;
> >  	int slots, ret = 0;
> > +	bool could_retrain = false;
> > +
> > +	if (new_conn_state->crtc) {
> > +		crtc_state = drm_atomic_get_new_crtc_state(
> > +		    state, new_conn_state->crtc);
> > +		if (crtc_state &&
> > drm_atomic_crtc_needs_modeset(crtc_state))
> > +			could_retrain = true;
> > +	}
> >  
> >  	old_conn_state = drm_atomic_get_old_connector_state(state,
> > connector);
> >  	old_crtc = old_conn_state->crtc;
> >  	if (!old_crtc)
> > -		return ret;
> > +		goto out;
> >  
> >  	crtc_state = drm_atomic_get_new_crtc_state(state, old_crtc);
> > -	slots = to_intel_crtc_state(crtc_state)->dp_m_n.tu;
> > -	if (drm_atomic_crtc_needs_modeset(crtc_state) && slots > 0) {
> > -		struct drm_dp_mst_topology_mgr *mgr;
> > -		struct drm_encoder *old_encoder;
> > +	if (!drm_atomic_crtc_needs_modeset(crtc_state))
> > +		goto out;
> > +	could_retrain = true;
> >  
> > -		old_encoder = old_conn_state->best_encoder;
> > -		mgr = &enc_to_mst(old_encoder)->primary->dp.mst_mgr;
> > +	slots = to_intel_crtc_state(crtc_state)->dp_m_n.tu;
> > +	if (slots > 0) {
> > +		encoder = old_conn_state->best_encoder;
> > +		mgr = &enc_to_mst(encoder)->primary->dp.mst_mgr;
> >  
> >  		ret = drm_dp_atomic_release_vcpi_slots(state, mgr,
> > slots);
> >  		if (ret)
> > @@ -132,6 +143,18 @@ static int intel_dp_mst_atomic_check(struct
> > drm_connector *connector,
> >  		else
> >  			to_intel_crtc_state(crtc_state)->dp_m_n.tu = 0;
> >  	}
> > +
> > +out:
> > +	if (could_retrain &&
> > +	    old_conn_state->link_status == DRM_MODE_LINK_STATUS_BAD) {
> > +		if (new_conn_state->best_encoder)
> > +			encoder = new_conn_state->best_encoder;
> > +		else
> > +			encoder = old_conn_state->best_encoder;
> > +
> > +		mgr = &enc_to_mst(encoder)->primary->dp.mst_mgr;
> > +		ret = drm_atomic_dp_mst_retrain_topology(state, mgr);
> > +	}
> >  	return ret;
> >  }
> >  
> > @@ -186,9 +209,12 @@ static void intel_mst_post_disable_dp(struct
> > intel_encoder *encoder,
> >  	intel_dp->active_mst_links--;
> >  
> >  	intel_mst->connector = NULL;
> > -	if (intel_dp->active_mst_links == 0)
> > +	if (intel_dp->active_mst_links == 0) {
> > +		intel_dp->mst_link_is_bad = false;
> > +
> >  		intel_dig_port->base.post_disable(&intel_dig_port->base,
> >  						  old_crtc_state, NULL);
> > +	}
> >  
> >  	DRM_DEBUG_KMS("active links %d\n", intel_dp->active_mst_links);
> >  }
> > diff --git a/drivers/gpu/drm/i915/intel_drv.h
> > b/drivers/gpu/drm/i915/intel_drv.h
> > index fc338529e918..f4a5861e4dff 100644
> > --- a/drivers/gpu/drm/i915/intel_drv.h
> > +++ b/drivers/gpu/drm/i915/intel_drv.h
> > @@ -1119,6 +1119,13 @@ struct intel_dp {
> >  	/* mst connector list */
> >  	struct intel_dp_mst_encoder *mst_encoders[I915_MAX_PIPES];
> >  	struct drm_dp_mst_topology_mgr mst_mgr;
> > +	/* We can't handle retraining from the dig workqueue, so... */
> > +	struct work_struct mst_retrain_work;
> > +	struct completion mst_retrain_completion;
> > +	/* Set when retraining the link at the current parameters is
> > +	 * impossible for an MST connection
> > +	 */
> > +	bool mst_link_is_bad;
> >  
> >  	uint32_t (*get_aux_clock_divider)(struct intel_dp *dp, int
> > index);
> >  	/*
> > @@ -1686,6 +1693,7 @@ void intel_dp_compute_rate(struct intel_dp
> > *intel_dp, int port_clock,
> >  bool intel_dp_source_supports_hbr2(struct intel_dp *intel_dp);
> >  bool
> >  intel_dp_get_link_status(struct intel_dp *intel_dp, uint8_t
> > link_status[DP_LINK_STATUS_SIZE]);
> > +int intel_dp_get_crtc_mask(struct intel_dp *intel_dp);
> >  
> >  static inline unsigned int intel_dp_unused_lane_mask(int lane_count)
> >  {
> > -- 
> > 2.14.3
> > 
> > _______________________________________________
> > dri-devel mailing list
> > dri-devel@lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/dri-devel
-- 
Cheers,
	Lyude Paul

Re: [PATCH v3 1/5] drm/i915: Move DP modeset retry work into intel_dp

[Ville Syrjälä]

On Fri, Mar 09, 2018 at 04:32:27PM -0500, Lyude Paul wrote:
> While having the modeset_retry_work in intel_connector makes sense with
> SST, this paradigm doesn't make a whole ton of sense when it comes to
> MST since we have to deal with multiple connectors. In most cases, it's
> more useful to just use the intel_dp struct since it indicates whether
> or not we're dealing with an MST device, along with being able to easily
> trace the intel_dp struct back to it's respective connector (if there is
> any). So, move the modeset_retry_work function out of the
> intel_connector struct and into intel_dp.
> 
> Signed-off-by: Lyude Paul <lyude@redhat.com>
> Reviewed-by: Manasi Navare <manasi.d.navare@intel.com>
> Cc: Manasi Navare <manasi.d.navare@intel.com>
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> V2:
>  - Remove accidental duplicate modeset_retry_work in intel_connector
> V3:
>  - Also check against eDP in intel_hpd_poll_fini() - mdnavare
> Signed-off-by: Lyude Paul <lyude@redhat.com>
> ---
>  drivers/gpu/drm/i915/intel_display.c          | 25 +++++++++++++++++++++++--
>  drivers/gpu/drm/i915/intel_dp.c               | 10 ++++------
>  drivers/gpu/drm/i915/intel_dp_link_training.c |  2 +-
>  drivers/gpu/drm/i915/intel_drv.h              |  6 +++---
>  4 files changed, 31 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index f424fff477f6..3b7fa430a84a 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -15394,16 +15394,37 @@ static void intel_hpd_poll_fini(struct drm_device *dev)
>  {
>  	struct intel_connector *connector;
>  	struct drm_connector_list_iter conn_iter;
> +	struct work_struct *work;
> +	int conn_type;
>  
>  	/* Kill all the work that may have been queued by hpd. */
>  	drm_connector_list_iter_begin(dev, &conn_iter);
>  	for_each_intel_connector_iter(connector, &conn_iter) {
> -		if (connector->modeset_retry_work.func)
> -			cancel_work_sync(&connector->modeset_retry_work);
>  		if (connector->hdcp_shim) {
>  			cancel_delayed_work_sync(&connector->hdcp_check_work);
>  			cancel_work_sync(&connector->hdcp_prop_work);
>  		}
> +
> +		conn_type = connector->base.connector_type;
> +		if (conn_type != DRM_MODE_CONNECTOR_eDP &&
> +		    conn_type != DRM_MODE_CONNECTOR_DisplayPort)
> +			continue;
> +
> +		if (connector->mst_port) {
> +			work = &connector->mst_port->modeset_retry_work;
> +		} else {
> +			struct intel_encoder *intel_encoder =
> +				connector->encoder;
> +			struct intel_dp *intel_dp;
> +
> +			if (!intel_encoder)
> +				continue;
> +
> +			intel_dp = enc_to_intel_dp(&intel_encoder->base);
> +			work = &intel_dp->modeset_retry_work;
> +		}
> +
> +		cancel_work_sync(work);

Why are we even walking the connectors for this? Can't we just
walk the encoders instead?

>  	}
>  	drm_connector_list_iter_end(&conn_iter);
>  }
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 4dd1b2287dd6..5abf0c95725a 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -6261,12 +6261,10 @@ static bool intel_edp_init_connector(struct intel_dp *intel_dp,
>  
>  static void intel_dp_modeset_retry_work_fn(struct work_struct *work)
>  {
> -	struct intel_connector *intel_connector;
> -	struct drm_connector *connector;
> +	struct intel_dp *intel_dp = container_of(work, typeof(*intel_dp),
> +						 modeset_retry_work);
> +	struct drm_connector *connector = &intel_dp->attached_connector->base;
>  
> -	intel_connector = container_of(work, typeof(*intel_connector),
> -				       modeset_retry_work);
> -	connector = &intel_connector->base;
>  	DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n", connector->base.id,
>  		      connector->name);
>  
> @@ -6295,7 +6293,7 @@ intel_dp_init_connector(struct intel_digital_port *intel_dig_port,
>  	int type;
>  
>  	/* Initialize the work for modeset in case of link train failure */
> -	INIT_WORK(&intel_connector->modeset_retry_work,
> +	INIT_WORK(&intel_dp->modeset_retry_work,
>  		  intel_dp_modeset_retry_work_fn);
>  
>  	if (WARN(intel_dig_port->max_lanes < 1,
> diff --git a/drivers/gpu/drm/i915/intel_dp_link_training.c b/drivers/gpu/drm/i915/intel_dp_link_training.c
> index f59b59bb0a21..2cfa58ce1f95 100644
> --- a/drivers/gpu/drm/i915/intel_dp_link_training.c
> +++ b/drivers/gpu/drm/i915/intel_dp_link_training.c
> @@ -340,7 +340,7 @@ intel_dp_start_link_train(struct intel_dp *intel_dp)
>  							     intel_dp->link_rate,
>  							     intel_dp->lane_count))
>  			/* Schedule a Hotplug Uevent to userspace to start modeset */
> -			schedule_work(&intel_connector->modeset_retry_work);
> +			schedule_work(&intel_dp->modeset_retry_work);
>  	} else {
>  		DRM_ERROR("[CONNECTOR:%d:%s] Link Training failed at link rate = %d, lane count = %d",
>  			  intel_connector->base.base.id,
> diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> index 83e5ca889d9c..3f19dc80997f 100644
> --- a/drivers/gpu/drm/i915/intel_drv.h
> +++ b/drivers/gpu/drm/i915/intel_drv.h
> @@ -406,9 +406,6 @@ struct intel_connector {
>  
>  	struct intel_dp *mst_port;
>  
> -	/* Work struct to schedule a uevent on link train failure */
> -	struct work_struct modeset_retry_work;
> -
>  	const struct intel_hdcp_shim *hdcp_shim;
>  	struct mutex hdcp_mutex;
>  	uint64_t hdcp_value; /* protected by hdcp_mutex */
> @@ -1135,6 +1132,9 @@ struct intel_dp {
>  
>  	/* Displayport compliance testing */
>  	struct intel_dp_compliance compliance;
> +
> +	/* Work struct to schedule a uevent on link train failure */
> +	struct work_struct modeset_retry_work;
>  };
>  
>  struct intel_lspcon {
> -- 
> 2.14.3

-- 
Ville Syrjälä
Intel OTC

Re: [PATCH v3 1/5] drm/i915: Move DP modeset retry work into intel_dp

[Lyude Paul]

On Mon, 2018-03-12 at 23:01 +0200, Ville Syrjälä wrote:
> On Fri, Mar 09, 2018 at 04:32:27PM -0500, Lyude Paul wrote:
> > While having the modeset_retry_work in intel_connector makes sense with
> > SST, this paradigm doesn't make a whole ton of sense when it comes to
> > MST since we have to deal with multiple connectors. In most cases, it's
> > more useful to just use the intel_dp struct since it indicates whether
> > or not we're dealing with an MST device, along with being able to easily
> > trace the intel_dp struct back to it's respective connector (if there is
> > any). So, move the modeset_retry_work function out of the
> > intel_connector struct and into intel_dp.
> > 
> > Signed-off-by: Lyude Paul <lyude@redhat.com>
> > Reviewed-by: Manasi Navare <manasi.d.navare@intel.com>
> > Cc: Manasi Navare <manasi.d.navare@intel.com>
> > Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > 
> > V2:
> >  - Remove accidental duplicate modeset_retry_work in intel_connector
> > V3:
> >  - Also check against eDP in intel_hpd_poll_fini() - mdnavare
> > Signed-off-by: Lyude Paul <lyude@redhat.com>
> > ---
> >  drivers/gpu/drm/i915/intel_display.c          | 25 +++++++++++++++++++++++-
> > -
> >  drivers/gpu/drm/i915/intel_dp.c               | 10 ++++------
> >  drivers/gpu/drm/i915/intel_dp_link_training.c |  2 +-
> >  drivers/gpu/drm/i915/intel_drv.h              |  6 +++---
> >  4 files changed, 31 insertions(+), 12 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/intel_display.c
> > b/drivers/gpu/drm/i915/intel_display.c
> > index f424fff477f6..3b7fa430a84a 100644
> > --- a/drivers/gpu/drm/i915/intel_display.c
> > +++ b/drivers/gpu/drm/i915/intel_display.c
> > @@ -15394,16 +15394,37 @@ static void intel_hpd_poll_fini(struct drm_device
> > *dev)
> >  {
> >  	struct intel_connector *connector;
> >  	struct drm_connector_list_iter conn_iter;
> > +	struct work_struct *work;
> > +	int conn_type;
> >  
> >  	/* Kill all the work that may have been queued by hpd. */
> >  	drm_connector_list_iter_begin(dev, &conn_iter);
> >  	for_each_intel_connector_iter(connector, &conn_iter) {
> > -		if (connector->modeset_retry_work.func)
> > -			cancel_work_sync(&connector->modeset_retry_work);
> >  		if (connector->hdcp_shim) {
> >  			cancel_delayed_work_sync(&connector-
> > >hdcp_check_work);
> >  			cancel_work_sync(&connector->hdcp_prop_work);
> >  		}
> > +
> > +		conn_type = connector->base.connector_type;
> > +		if (conn_type != DRM_MODE_CONNECTOR_eDP &&
> > +		    conn_type != DRM_MODE_CONNECTOR_DisplayPort)
> > +			continue;
> > +
> > +		if (connector->mst_port) {
> > +			work = &connector->mst_port->modeset_retry_work;
> > +		} else {
> > +			struct intel_encoder *intel_encoder =
> > +				connector->encoder;
> > +			struct intel_dp *intel_dp;
> > +
> > +			if (!intel_encoder)
> > +				continue;
> > +
> > +			intel_dp = enc_to_intel_dp(&intel_encoder->base);
> > +			work = &intel_dp->modeset_retry_work;
> > +		}
> > +
> > +		cancel_work_sync(work);
> 
> Why are we even walking the connectors for this? Can't we just
> walk the encoders instead?
We could walk the encoders for this, but seeing as we're already walking the
connectors for the HDCP prop doesn't it make more sense to just stick our code
there? or is there a simpler solution for this I'm missing
> 
> >  	}
> >  	drm_connector_list_iter_end(&conn_iter);
> >  }
> > diff --git a/drivers/gpu/drm/i915/intel_dp.c
> > b/drivers/gpu/drm/i915/intel_dp.c
> > index 4dd1b2287dd6..5abf0c95725a 100644
> > --- a/drivers/gpu/drm/i915/intel_dp.c
> > +++ b/drivers/gpu/drm/i915/intel_dp.c
> > @@ -6261,12 +6261,10 @@ static bool intel_edp_init_connector(struct intel_dp
> > *intel_dp,
> >  
> >  static void intel_dp_modeset_retry_work_fn(struct work_struct *work)
> >  {
> > -	struct intel_connector *intel_connector;
> > -	struct drm_connector *connector;
> > +	struct intel_dp *intel_dp = container_of(work, typeof(*intel_dp),
> > +						 modeset_retry_work);
> > +	struct drm_connector *connector = &intel_dp->attached_connector-
> > >base;
> >  
> > -	intel_connector = container_of(work, typeof(*intel_connector),
> > -				       modeset_retry_work);
> > -	connector = &intel_connector->base;
> >  	DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n", connector->base.id,
> >  		      connector->name);
> >  
> > @@ -6295,7 +6293,7 @@ intel_dp_init_connector(struct intel_digital_port
> > *intel_dig_port,
> >  	int type;
> >  
> >  	/* Initialize the work for modeset in case of link train failure */
> > -	INIT_WORK(&intel_connector->modeset_retry_work,
> > +	INIT_WORK(&intel_dp->modeset_retry_work,
> >  		  intel_dp_modeset_retry_work_fn);
> >  
> >  	if (WARN(intel_dig_port->max_lanes < 1,
> > diff --git a/drivers/gpu/drm/i915/intel_dp_link_training.c
> > b/drivers/gpu/drm/i915/intel_dp_link_training.c
> > index f59b59bb0a21..2cfa58ce1f95 100644
> > --- a/drivers/gpu/drm/i915/intel_dp_link_training.c
> > +++ b/drivers/gpu/drm/i915/intel_dp_link_training.c
> > @@ -340,7 +340,7 @@ intel_dp_start_link_train(struct intel_dp *intel_dp)
> >  							     intel_dp-
> > >link_rate,
> >  							     intel_dp-
> > >lane_count))
> >  			/* Schedule a Hotplug Uevent to userspace to start
> > modeset */
> > -			schedule_work(&intel_connector-
> > >modeset_retry_work);
> > +			schedule_work(&intel_dp->modeset_retry_work);
> >  	} else {
> >  		DRM_ERROR("[CONNECTOR:%d:%s] Link Training failed at link
> > rate = %d, lane count = %d",
> >  			  intel_connector->base.base.id,
> > diff --git a/drivers/gpu/drm/i915/intel_drv.h
> > b/drivers/gpu/drm/i915/intel_drv.h
> > index 83e5ca889d9c..3f19dc80997f 100644
> > --- a/drivers/gpu/drm/i915/intel_drv.h
> > +++ b/drivers/gpu/drm/i915/intel_drv.h
> > @@ -406,9 +406,6 @@ struct intel_connector {
> >  
> >  	struct intel_dp *mst_port;
> >  
> > -	/* Work struct to schedule a uevent on link train failure */
> > -	struct work_struct modeset_retry_work;
> > -
> >  	const struct intel_hdcp_shim *hdcp_shim;
> >  	struct mutex hdcp_mutex;
> >  	uint64_t hdcp_value; /* protected by hdcp_mutex */
> > @@ -1135,6 +1132,9 @@ struct intel_dp {
> >  
> >  	/* Displayport compliance testing */
> >  	struct intel_dp_compliance compliance;
> > +
> > +	/* Work struct to schedule a uevent on link train failure */
> > +	struct work_struct modeset_retry_work;
> >  };
> >  
> >  struct intel_lspcon {
> > -- 
> > 2.14.3
> 
> 

Re: [PATCH v3 1/5] drm/i915: Move DP modeset retry work into intel_dp

[Ville Syrjälä]

On Tue, Mar 13, 2018 at 07:24:20PM -0400, Lyude Paul wrote:
> On Mon, 2018-03-12 at 23:01 +0200, Ville Syrjälä wrote:
> > On Fri, Mar 09, 2018 at 04:32:27PM -0500, Lyude Paul wrote:
> > > While having the modeset_retry_work in intel_connector makes sense with
> > > SST, this paradigm doesn't make a whole ton of sense when it comes to
> > > MST since we have to deal with multiple connectors. In most cases, it's
> > > more useful to just use the intel_dp struct since it indicates whether
> > > or not we're dealing with an MST device, along with being able to easily
> > > trace the intel_dp struct back to it's respective connector (if there is
> > > any). So, move the modeset_retry_work function out of the
> > > intel_connector struct and into intel_dp.
> > > 
> > > Signed-off-by: Lyude Paul <lyude@redhat.com>
> > > Reviewed-by: Manasi Navare <manasi.d.navare@intel.com>
> > > Cc: Manasi Navare <manasi.d.navare@intel.com>
> > > Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > > 
> > > V2:
> > >  - Remove accidental duplicate modeset_retry_work in intel_connector
> > > V3:
> > >  - Also check against eDP in intel_hpd_poll_fini() - mdnavare
> > > Signed-off-by: Lyude Paul <lyude@redhat.com>
> > > ---
> > >  drivers/gpu/drm/i915/intel_display.c          | 25 +++++++++++++++++++++++-
> > > -
> > >  drivers/gpu/drm/i915/intel_dp.c               | 10 ++++------
> > >  drivers/gpu/drm/i915/intel_dp_link_training.c |  2 +-
> > >  drivers/gpu/drm/i915/intel_drv.h              |  6 +++---
> > >  4 files changed, 31 insertions(+), 12 deletions(-)
> > > 
> > > diff --git a/drivers/gpu/drm/i915/intel_display.c
> > > b/drivers/gpu/drm/i915/intel_display.c
> > > index f424fff477f6..3b7fa430a84a 100644
> > > --- a/drivers/gpu/drm/i915/intel_display.c
> > > +++ b/drivers/gpu/drm/i915/intel_display.c
> > > @@ -15394,16 +15394,37 @@ static void intel_hpd_poll_fini(struct drm_device
> > > *dev)
> > >  {
> > >  	struct intel_connector *connector;
> > >  	struct drm_connector_list_iter conn_iter;
> > > +	struct work_struct *work;
> > > +	int conn_type;
> > >  
> > >  	/* Kill all the work that may have been queued by hpd. */
> > >  	drm_connector_list_iter_begin(dev, &conn_iter);
> > >  	for_each_intel_connector_iter(connector, &conn_iter) {
> > > -		if (connector->modeset_retry_work.func)
> > > -			cancel_work_sync(&connector->modeset_retry_work);
> > >  		if (connector->hdcp_shim) {
> > >  			cancel_delayed_work_sync(&connector-
> > > >hdcp_check_work);
> > >  			cancel_work_sync(&connector->hdcp_prop_work);
> > >  		}
> > > +
> > > +		conn_type = connector->base.connector_type;
> > > +		if (conn_type != DRM_MODE_CONNECTOR_eDP &&
> > > +		    conn_type != DRM_MODE_CONNECTOR_DisplayPort)
> > > +			continue;
> > > +
> > > +		if (connector->mst_port) {
> > > +			work = &connector->mst_port->modeset_retry_work;
> > > +		} else {
> > > +			struct intel_encoder *intel_encoder =
> > > +				connector->encoder;
> > > +			struct intel_dp *intel_dp;
> > > +
> > > +			if (!intel_encoder)
> > > +				continue;
> > > +
> > > +			intel_dp = enc_to_intel_dp(&intel_encoder->base);
> > > +			work = &intel_dp->modeset_retry_work;
> > > +		}
> > > +
> > > +		cancel_work_sync(work);
> > 
> > Why are we even walking the connectors for this? Can't we just
> > walk the encoders instead?
> We could walk the encoders for this, but seeing as we're already walking the
> connectors for the HDCP prop doesn't it make more sense to just stick our code
> there? or is there a simpler solution for this I'm missing

I think walking the encoders when you want encoders is a lot cleaner.
Keeps the snr much higher.

> > 
> > >  	}
> > >  	drm_connector_list_iter_end(&conn_iter);
> > >  }
> > > diff --git a/drivers/gpu/drm/i915/intel_dp.c
> > > b/drivers/gpu/drm/i915/intel_dp.c
> > > index 4dd1b2287dd6..5abf0c95725a 100644
> > > --- a/drivers/gpu/drm/i915/intel_dp.c
> > > +++ b/drivers/gpu/drm/i915/intel_dp.c
> > > @@ -6261,12 +6261,10 @@ static bool intel_edp_init_connector(struct intel_dp
> > > *intel_dp,
> > >  
> > >  static void intel_dp_modeset_retry_work_fn(struct work_struct *work)
> > >  {
> > > -	struct intel_connector *intel_connector;
> > > -	struct drm_connector *connector;
> > > +	struct intel_dp *intel_dp = container_of(work, typeof(*intel_dp),
> > > +						 modeset_retry_work);
> > > +	struct drm_connector *connector = &intel_dp->attached_connector-
> > > >base;
> > >  
> > > -	intel_connector = container_of(work, typeof(*intel_connector),
> > > -				       modeset_retry_work);
> > > -	connector = &intel_connector->base;
> > >  	DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n", connector->base.id,
> > >  		      connector->name);
> > >  
> > > @@ -6295,7 +6293,7 @@ intel_dp_init_connector(struct intel_digital_port
> > > *intel_dig_port,
> > >  	int type;
> > >  
> > >  	/* Initialize the work for modeset in case of link train failure */
> > > -	INIT_WORK(&intel_connector->modeset_retry_work,
> > > +	INIT_WORK(&intel_dp->modeset_retry_work,
> > >  		  intel_dp_modeset_retry_work_fn);
> > >  
> > >  	if (WARN(intel_dig_port->max_lanes < 1,
> > > diff --git a/drivers/gpu/drm/i915/intel_dp_link_training.c
> > > b/drivers/gpu/drm/i915/intel_dp_link_training.c
> > > index f59b59bb0a21..2cfa58ce1f95 100644
> > > --- a/drivers/gpu/drm/i915/intel_dp_link_training.c
> > > +++ b/drivers/gpu/drm/i915/intel_dp_link_training.c
> > > @@ -340,7 +340,7 @@ intel_dp_start_link_train(struct intel_dp *intel_dp)
> > >  							     intel_dp-
> > > >link_rate,
> > >  							     intel_dp-
> > > >lane_count))
> > >  			/* Schedule a Hotplug Uevent to userspace to start
> > > modeset */
> > > -			schedule_work(&intel_connector-
> > > >modeset_retry_work);
> > > +			schedule_work(&intel_dp->modeset_retry_work);
> > >  	} else {
> > >  		DRM_ERROR("[CONNECTOR:%d:%s] Link Training failed at link
> > > rate = %d, lane count = %d",
> > >  			  intel_connector->base.base.id,
> > > diff --git a/drivers/gpu/drm/i915/intel_drv.h
> > > b/drivers/gpu/drm/i915/intel_drv.h
> > > index 83e5ca889d9c..3f19dc80997f 100644
> > > --- a/drivers/gpu/drm/i915/intel_drv.h
> > > +++ b/drivers/gpu/drm/i915/intel_drv.h
> > > @@ -406,9 +406,6 @@ struct intel_connector {
> > >  
> > >  	struct intel_dp *mst_port;
> > >  
> > > -	/* Work struct to schedule a uevent on link train failure */
> > > -	struct work_struct modeset_retry_work;
> > > -
> > >  	const struct intel_hdcp_shim *hdcp_shim;
> > >  	struct mutex hdcp_mutex;
> > >  	uint64_t hdcp_value; /* protected by hdcp_mutex */
> > > @@ -1135,6 +1132,9 @@ struct intel_dp {
> > >  
> > >  	/* Displayport compliance testing */
> > >  	struct intel_dp_compliance compliance;
> > > +
> > > +	/* Work struct to schedule a uevent on link train failure */
> > > +	struct work_struct modeset_retry_work;
> > >  };
> > >  
> > >  struct intel_lspcon {
> > > -- 
> > > 2.14.3
> > 
> > 

-- 
Ville Syrjälä
Intel OTC