[PATCH v2 0/4] Handle link training failure during modeset for DDI

[PATCH v2 0/4] Handle link training failure during modeset for DDI

[Manasi Navare]

Link training failure is handled by lowering the link rate/lane count
as per the Dp Spec 1.2 and sending a hotplug uevent to userspace to notify
that it needs to redo a modeset. This is notified by setting connector link
status property which should be tracked by userspace to take the action.

This behaviour complies with Dp spec as tested by DP compliance test suite.

Manasi Navare (4):
  drm: Add a new connector property for link status
  drm/i915: Set link status property for DP connector
  drm/i915: Find fallback link rate/lane count
  drm/i915: Implement Link Rate fallback on Link training failure

 drivers/gpu/drm/drm_atomic_helper.c           |   4 +
 drivers/gpu/drm/drm_connector.c               |  17 ++++
 drivers/gpu/drm/i915/intel_ddi.c              |  23 ++++-
 drivers/gpu/drm/i915/intel_dp.c               | 128 +++++++++++++++++++++++++-
 drivers/gpu/drm/i915/intel_dp_link_training.c |  12 ++-
 drivers/gpu/drm/i915/intel_drv.h              |  13 ++-
 include/drm/drm_connector.h                   |   4 +-
 include/drm/drm_crtc.h                        |   5 +
 include/uapi/drm/drm_mode.h                   |   4 +
 9 files changed, 201 insertions(+), 9 deletions(-)

-- 
1.9.1

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[PATCH v2 1/4] drm: Add a new connector property for link status

[Manasi Navare]

A new default connector property is added for keeping
track of whether the link is good (link training passed) or
link is bad (link training  failed). If the link status property
is not good, then userspace should fire off a new modeset at the current
mode even if there have not been any changes in the mode list
or connector status.
Also add link status connector member corersponding to the
decoded value of link status property.

v3: Add link status member to store property value locally
(Ville Syrjala)
v2:
* Make this a default connector property (Daniel Vetter)

Cc: dri-devel@lists.freedesktop.org
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Daniel Vetter <daniel.vetter@intel.com>
Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
---
 drivers/gpu/drm/drm_connector.c | 17 +++++++++++++++++
 include/drm/drm_connector.h     |  4 +++-
 include/drm/drm_crtc.h          |  5 +++++
 include/uapi/drm/drm_mode.h     |  4 ++++
 4 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
index 2db7fb5..d4e852f 100644
--- a/drivers/gpu/drm/drm_connector.c
+++ b/drivers/gpu/drm/drm_connector.c
@@ -243,6 +243,10 @@ int drm_connector_init(struct drm_device *dev,
 	drm_object_attach_property(&connector->base,
 				      config->dpms_property, 0);
 
+	drm_object_attach_property(&connector->base,
+				   config->link_status_property,
+				   0);
+
 	if (drm_core_check_feature(dev, DRIVER_ATOMIC)) {
 		drm_object_attach_property(&connector->base, config->prop_crtc_id, 0);
 	}
@@ -506,6 +510,12 @@ const char *drm_get_subpixel_order_name(enum subpixel_order order)
 };
 DRM_ENUM_NAME_FN(drm_get_dpms_name, drm_dpms_enum_list)
 
+static const struct drm_prop_enum_list drm_link_status_enum_list[] = {
+	{ DRM_MODE_LINK_STATUS_GOOD, "Good" },
+	{ DRM_MODE_LINK_STATUS_BAD, "Bad" },
+};
+DRM_ENUM_NAME_FN(drm_get_link_status_name, drm_link_status_enum_list)
+
 /**
  * drm_display_info_set_bus_formats - set the supported bus formats
  * @info: display info to store bus formats in
@@ -622,6 +632,13 @@ int drm_connector_create_standard_properties(struct drm_device *dev)
 		return -ENOMEM;
 	dev->mode_config.tile_property = prop;
 
+	prop = drm_property_create_enum(dev, 0, "link-status",
+					drm_link_status_enum_list,
+					ARRAY_SIZE(drm_link_status_enum_list));
+	if (!prop)
+		return -ENOMEM;
+	dev->mode_config.link_status_property = prop;
+
 	return 0;
 }
 
diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
index ac9d7d8..90387a1 100644
--- a/include/drm/drm_connector.h
+++ b/include/drm/drm_connector.h
@@ -682,6 +682,9 @@ struct drm_connector {
 	uint8_t num_h_tile, num_v_tile;
 	uint8_t tile_h_loc, tile_v_loc;
 	uint16_t tile_h_size, tile_v_size;
+
+	/* Connector Link status for link training */
+	bool link_status;
 };
 
 #define obj_to_connector(x) container_of(x, struct drm_connector, base)
@@ -754,7 +757,6 @@ int drm_mode_create_tv_properties(struct drm_device *dev,
 int drm_mode_create_scaling_mode_property(struct drm_device *dev);
 int drm_mode_create_aspect_ratio_property(struct drm_device *dev);
 int drm_mode_create_suggested_offset_properties(struct drm_device *dev);
-
 int drm_mode_connector_set_path_property(struct drm_connector *connector,
 					 const char *path);
 int drm_mode_connector_set_tile_property(struct drm_connector *connector);
diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
index fa1aa21..b86ca19 100644
--- a/include/drm/drm_crtc.h
+++ b/include/drm/drm_crtc.h
@@ -1151,6 +1151,11 @@ struct drm_mode_config {
 	 */
 	struct drm_property *tile_property;
 	/**
+	 * @link_status_property: Default connector property for link status
+	 * of a connector as a result of link training.
+	 */
+	struct drm_property *link_status_property;
+	/**
 	 * @plane_type_property: Default plane property to differentiate
 	 * CURSOR, PRIMARY and OVERLAY legacy uses of planes.
 	 */
diff --git a/include/uapi/drm/drm_mode.h b/include/uapi/drm/drm_mode.h
index 084b50a..f1b0afd 100644
--- a/include/uapi/drm/drm_mode.h
+++ b/include/uapi/drm/drm_mode.h
@@ -121,6 +121,10 @@
 #define DRM_MODE_DIRTY_ON       1
 #define DRM_MODE_DIRTY_ANNOTATE 2
 
+/* Link Status options */
+#define DRM_MODE_LINK_STATUS_GOOD	0
+#define DRM_MODE_LINK_STATUS_BAD	1
+
 struct drm_mode_modeinfo {
 	__u32 clock;
 	__u16 hdisplay;
-- 
1.9.1

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Re: [PATCH v2 1/4] drm: Add a new connector property for link status

[Jani Nikula]

On Sat, 29 Oct 2016, Manasi Navare <manasi.d.navare@intel.com> wrote:
> A new default connector property is added for keeping
> track of whether the link is good (link training passed) or
> link is bad (link training  failed). If the link status property
> is not good, then userspace should fire off a new modeset at the current
> mode even if there have not been any changes in the mode list
> or connector status.
> Also add link status connector member corersponding to the
> decoded value of link status property.

I'm still a bit uneasy about the name "link status", because I want it
to be evident that this is not just about display port link
layer. However, I don't have a good counter proposal, and it's easy to
change once we agree on everything else.

>
> v3: Add link status member to store property value locally
> (Ville Syrjala)
> v2:
> * Make this a default connector property (Daniel Vetter)
>
> Cc: dri-devel@lists.freedesktop.org
> Cc: Jani Nikula <jani.nikula@linux.intel.com>
> Cc: Daniel Vetter <daniel.vetter@intel.com>
> Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
> Cc: Chris Wilson <chris@chris-wilson.co.uk>
> Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
> ---
>  drivers/gpu/drm/drm_connector.c | 17 +++++++++++++++++
>  include/drm/drm_connector.h     |  4 +++-
>  include/drm/drm_crtc.h          |  5 +++++
>  include/uapi/drm/drm_mode.h     |  4 ++++
>  4 files changed, 29 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
> index 2db7fb5..d4e852f 100644
> --- a/drivers/gpu/drm/drm_connector.c
> +++ b/drivers/gpu/drm/drm_connector.c
> @@ -243,6 +243,10 @@ int drm_connector_init(struct drm_device *dev,
>  	drm_object_attach_property(&connector->base,
>  				      config->dpms_property, 0);
>  
> +	drm_object_attach_property(&connector->base,
> +				   config->link_status_property,
> +				   0);
> +
>  	if (drm_core_check_feature(dev, DRIVER_ATOMIC)) {
>  		drm_object_attach_property(&connector->base, config->prop_crtc_id, 0);
>  	}
> @@ -506,6 +510,12 @@ const char *drm_get_subpixel_order_name(enum subpixel_order order)
>  };
>  DRM_ENUM_NAME_FN(drm_get_dpms_name, drm_dpms_enum_list)
>  
> +static const struct drm_prop_enum_list drm_link_status_enum_list[] = {
> +	{ DRM_MODE_LINK_STATUS_GOOD, "Good" },
> +	{ DRM_MODE_LINK_STATUS_BAD, "Bad" },
> +};
> +DRM_ENUM_NAME_FN(drm_get_link_status_name, drm_link_status_enum_list)
> +
>  /**
>   * drm_display_info_set_bus_formats - set the supported bus formats
>   * @info: display info to store bus formats in
> @@ -622,6 +632,13 @@ int drm_connector_create_standard_properties(struct drm_device *dev)
>  		return -ENOMEM;
>  	dev->mode_config.tile_property = prop;
>  
> +	prop = drm_property_create_enum(dev, 0, "link-status",
> +					drm_link_status_enum_list,
> +					ARRAY_SIZE(drm_link_status_enum_list));
> +	if (!prop)
> +		return -ENOMEM;
> +	dev->mode_config.link_status_property = prop;
> +
>  	return 0;
>  }
>  
> diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
> index ac9d7d8..90387a1 100644
> --- a/include/drm/drm_connector.h
> +++ b/include/drm/drm_connector.h
> @@ -682,6 +682,9 @@ struct drm_connector {
>  	uint8_t num_h_tile, num_v_tile;
>  	uint8_t tile_h_loc, tile_v_loc;
>  	uint16_t tile_h_size, tile_v_size;
> +
> +	/* Connector Link status for link training */

Drop the "link training" bit, this is not just about DP.

> +	bool link_status;

What does it mean for link status to be true or false? Which one is good
and which one is bad? Please either name this differently, or make this
an int and expect it to have the same values as the property.

>  };
>  
>  #define obj_to_connector(x) container_of(x, struct drm_connector, base)
> @@ -754,7 +757,6 @@ int drm_mode_create_tv_properties(struct drm_device *dev,
>  int drm_mode_create_scaling_mode_property(struct drm_device *dev);
>  int drm_mode_create_aspect_ratio_property(struct drm_device *dev);
>  int drm_mode_create_suggested_offset_properties(struct drm_device *dev);
> -
>  int drm_mode_connector_set_path_property(struct drm_connector *connector,
>  					 const char *path);
>  int drm_mode_connector_set_tile_property(struct drm_connector *connector);
> diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
> index fa1aa21..b86ca19 100644
> --- a/include/drm/drm_crtc.h
> +++ b/include/drm/drm_crtc.h
> @@ -1151,6 +1151,11 @@ struct drm_mode_config {
>  	 */
>  	struct drm_property *tile_property;
>  	/**
> +	 * @link_status_property: Default connector property for link status
> +	 * of a connector as a result of link training.

Same about "link training".

> +	 */
> +	struct drm_property *link_status_property;
> +	/**
>  	 * @plane_type_property: Default plane property to differentiate
>  	 * CURSOR, PRIMARY and OVERLAY legacy uses of planes.
>  	 */
> diff --git a/include/uapi/drm/drm_mode.h b/include/uapi/drm/drm_mode.h
> index 084b50a..f1b0afd 100644
> --- a/include/uapi/drm/drm_mode.h
> +++ b/include/uapi/drm/drm_mode.h
> @@ -121,6 +121,10 @@
>  #define DRM_MODE_DIRTY_ON       1
>  #define DRM_MODE_DIRTY_ANNOTATE 2
>  
> +/* Link Status options */
> +#define DRM_MODE_LINK_STATUS_GOOD	0
> +#define DRM_MODE_LINK_STATUS_BAD	1
> +
>  struct drm_mode_modeinfo {
>  	__u32 clock;
>  	__u16 hdisplay;

-- 
Jani Nikula, Intel Open Source Technology Center
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[PATCH v3 1/4] drm: Add a new connector property for link status

[Manasi Navare]

A new default connector property is added for keeping
track of whether the link is good (link training passed) or
link is bad (link training  failed). If the link status property
is not good, then userspace should fire off a new modeset at the current
mode even if there have not been any changes in the mode list
or connector status.
Also add link status connector member corersponding to the
decoded value of link status property.

v3:
* Drop "link training" from description since this is
not specific to DP (Jani Nikula)
* Add link status member to store property value locally
(Ville Syrjala)
v2:
* Make this a default connector property (Daniel Vetter)

Cc: dri-devel@lists.freedesktop.org
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Daniel Vetter <daniel.vetter@intel.com>
Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
---
 drivers/gpu/drm/drm_connector.c | 17 +++++++++++++++++
 include/drm/drm_connector.h     |  7 ++++++-
 include/drm/drm_crtc.h          |  5 +++++
 include/uapi/drm/drm_mode.h     |  4 ++++
 4 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
index 2db7fb5..d4e852f 100644
--- a/drivers/gpu/drm/drm_connector.c
+++ b/drivers/gpu/drm/drm_connector.c
@@ -243,6 +243,10 @@ int drm_connector_init(struct drm_device *dev,
 	drm_object_attach_property(&connector->base,
 				      config->dpms_property, 0);
 
+	drm_object_attach_property(&connector->base,
+				   config->link_status_property,
+				   0);
+
 	if (drm_core_check_feature(dev, DRIVER_ATOMIC)) {
 		drm_object_attach_property(&connector->base, config->prop_crtc_id, 0);
 	}
@@ -506,6 +510,12 @@ const char *drm_get_subpixel_order_name(enum subpixel_order order)
 };
 DRM_ENUM_NAME_FN(drm_get_dpms_name, drm_dpms_enum_list)
 
+static const struct drm_prop_enum_list drm_link_status_enum_list[] = {
+	{ DRM_MODE_LINK_STATUS_GOOD, "Good" },
+	{ DRM_MODE_LINK_STATUS_BAD, "Bad" },
+};
+DRM_ENUM_NAME_FN(drm_get_link_status_name, drm_link_status_enum_list)
+
 /**
  * drm_display_info_set_bus_formats - set the supported bus formats
  * @info: display info to store bus formats in
@@ -622,6 +632,13 @@ int drm_connector_create_standard_properties(struct drm_device *dev)
 		return -ENOMEM;
 	dev->mode_config.tile_property = prop;
 
+	prop = drm_property_create_enum(dev, 0, "link-status",
+					drm_link_status_enum_list,
+					ARRAY_SIZE(drm_link_status_enum_list));
+	if (!prop)
+		return -ENOMEM;
+	dev->mode_config.link_status_property = prop;
+
 	return 0;
 }
 
diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
index ac9d7d8..5c335e8 100644
--- a/include/drm/drm_connector.h
+++ b/include/drm/drm_connector.h
@@ -682,6 +682,12 @@ struct drm_connector {
 	uint8_t num_h_tile, num_v_tile;
 	uint8_t tile_h_loc, tile_v_loc;
 	uint16_t tile_h_size, tile_v_size;
+
+	/* Connector Link status
+	 * 0: If the link is Good
+	 * 1: If the link is Bad
+	 */
+	int link_status;
 };
 
 #define obj_to_connector(x) container_of(x, struct drm_connector, base)
@@ -754,7 +760,6 @@ int drm_mode_create_tv_properties(struct drm_device *dev,
 int drm_mode_create_scaling_mode_property(struct drm_device *dev);
 int drm_mode_create_aspect_ratio_property(struct drm_device *dev);
 int drm_mode_create_suggested_offset_properties(struct drm_device *dev);
-
 int drm_mode_connector_set_path_property(struct drm_connector *connector,
 					 const char *path);
 int drm_mode_connector_set_tile_property(struct drm_connector *connector);
diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
index fa1aa21..737f4d3 100644
--- a/include/drm/drm_crtc.h
+++ b/include/drm/drm_crtc.h
@@ -1151,6 +1151,11 @@ struct drm_mode_config {
 	 */
 	struct drm_property *tile_property;
 	/**
+	 * @link_status_property: Default connector property for link status
+	 * of a connector
+	 */
+	struct drm_property *link_status_property;
+	/**
 	 * @plane_type_property: Default plane property to differentiate
 	 * CURSOR, PRIMARY and OVERLAY legacy uses of planes.
 	 */
diff --git a/include/uapi/drm/drm_mode.h b/include/uapi/drm/drm_mode.h
index 084b50a..f1b0afd 100644
--- a/include/uapi/drm/drm_mode.h
+++ b/include/uapi/drm/drm_mode.h
@@ -121,6 +121,10 @@
 #define DRM_MODE_DIRTY_ON       1
 #define DRM_MODE_DIRTY_ANNOTATE 2
 
+/* Link Status options */
+#define DRM_MODE_LINK_STATUS_GOOD	0
+#define DRM_MODE_LINK_STATUS_BAD	1
+
 struct drm_mode_modeinfo {
 	__u32 clock;
 	__u16 hdisplay;
-- 
1.9.1

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Re: [PATCH v3 1/4] drm: Add a new connector property for link status

[Jani Nikula]

On Mon, 31 Oct 2016, Manasi Navare <manasi.d.navare@intel.com> wrote:
> A new default connector property is added for keeping
> track of whether the link is good (link training passed) or
> link is bad (link training  failed). If the link status property
> is not good, then userspace should fire off a new modeset at the current
> mode even if there have not been any changes in the mode list
> or connector status.
> Also add link status connector member corersponding to the
> decoded value of link status property.

I think it would be good to expand on this, both in the commit message
and documentation. This is UABI after all.

When is the property changed, who changes it, what is the userspace
expected to do when the status goes from good to bad, how does userspace
notice it's gone bad (uevents).

While we want this for handling DP link training failures during mode
setting according to the DP spec, in a way that can pass the CTS, it's
also needed for async mode sets.

BR,
Jani.



>
> v3:
> * Drop "link training" from description since this is
> not specific to DP (Jani Nikula)
> * Add link status member to store property value locally
> (Ville Syrjala)
> v2:
> * Make this a default connector property (Daniel Vetter)
>
> Cc: dri-devel@lists.freedesktop.org
> Cc: Jani Nikula <jani.nikula@linux.intel.com>
> Cc: Daniel Vetter <daniel.vetter@intel.com>
> Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
> Cc: Chris Wilson <chris@chris-wilson.co.uk>
> Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
> ---
>  drivers/gpu/drm/drm_connector.c | 17 +++++++++++++++++
>  include/drm/drm_connector.h     |  7 ++++++-
>  include/drm/drm_crtc.h          |  5 +++++
>  include/uapi/drm/drm_mode.h     |  4 ++++
>  4 files changed, 32 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
> index 2db7fb5..d4e852f 100644
> --- a/drivers/gpu/drm/drm_connector.c
> +++ b/drivers/gpu/drm/drm_connector.c
> @@ -243,6 +243,10 @@ int drm_connector_init(struct drm_device *dev,
>  	drm_object_attach_property(&connector->base,
>  				      config->dpms_property, 0);
>  
> +	drm_object_attach_property(&connector->base,
> +				   config->link_status_property,
> +				   0);
> +
>  	if (drm_core_check_feature(dev, DRIVER_ATOMIC)) {
>  		drm_object_attach_property(&connector->base, config->prop_crtc_id, 0);
>  	}
> @@ -506,6 +510,12 @@ const char *drm_get_subpixel_order_name(enum subpixel_order order)
>  };
>  DRM_ENUM_NAME_FN(drm_get_dpms_name, drm_dpms_enum_list)
>  
> +static const struct drm_prop_enum_list drm_link_status_enum_list[] = {
> +	{ DRM_MODE_LINK_STATUS_GOOD, "Good" },
> +	{ DRM_MODE_LINK_STATUS_BAD, "Bad" },
> +};
> +DRM_ENUM_NAME_FN(drm_get_link_status_name, drm_link_status_enum_list)
> +
>  /**
>   * drm_display_info_set_bus_formats - set the supported bus formats
>   * @info: display info to store bus formats in
> @@ -622,6 +632,13 @@ int drm_connector_create_standard_properties(struct drm_device *dev)
>  		return -ENOMEM;
>  	dev->mode_config.tile_property = prop;
>  
> +	prop = drm_property_create_enum(dev, 0, "link-status",
> +					drm_link_status_enum_list,
> +					ARRAY_SIZE(drm_link_status_enum_list));
> +	if (!prop)
> +		return -ENOMEM;
> +	dev->mode_config.link_status_property = prop;
> +
>  	return 0;
>  }
>  
> diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
> index ac9d7d8..5c335e8 100644
> --- a/include/drm/drm_connector.h
> +++ b/include/drm/drm_connector.h
> @@ -682,6 +682,12 @@ struct drm_connector {
>  	uint8_t num_h_tile, num_v_tile;
>  	uint8_t tile_h_loc, tile_v_loc;
>  	uint16_t tile_h_size, tile_v_size;
> +
> +	/* Connector Link status
> +	 * 0: If the link is Good
> +	 * 1: If the link is Bad
> +	 */
> +	int link_status;
>  };
>  
>  #define obj_to_connector(x) container_of(x, struct drm_connector, base)
> @@ -754,7 +760,6 @@ int drm_mode_create_tv_properties(struct drm_device *dev,
>  int drm_mode_create_scaling_mode_property(struct drm_device *dev);
>  int drm_mode_create_aspect_ratio_property(struct drm_device *dev);
>  int drm_mode_create_suggested_offset_properties(struct drm_device *dev);
> -
>  int drm_mode_connector_set_path_property(struct drm_connector *connector,
>  					 const char *path);
>  int drm_mode_connector_set_tile_property(struct drm_connector *connector);
> diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
> index fa1aa21..737f4d3 100644
> --- a/include/drm/drm_crtc.h
> +++ b/include/drm/drm_crtc.h
> @@ -1151,6 +1151,11 @@ struct drm_mode_config {
>  	 */
>  	struct drm_property *tile_property;
>  	/**
> +	 * @link_status_property: Default connector property for link status
> +	 * of a connector
> +	 */
> +	struct drm_property *link_status_property;
> +	/**
>  	 * @plane_type_property: Default plane property to differentiate
>  	 * CURSOR, PRIMARY and OVERLAY legacy uses of planes.
>  	 */
> diff --git a/include/uapi/drm/drm_mode.h b/include/uapi/drm/drm_mode.h
> index 084b50a..f1b0afd 100644
> --- a/include/uapi/drm/drm_mode.h
> +++ b/include/uapi/drm/drm_mode.h
> @@ -121,6 +121,10 @@
>  #define DRM_MODE_DIRTY_ON       1
>  #define DRM_MODE_DIRTY_ANNOTATE 2
>  
> +/* Link Status options */
> +#define DRM_MODE_LINK_STATUS_GOOD	0
> +#define DRM_MODE_LINK_STATUS_BAD	1
> +
>  struct drm_mode_modeinfo {
>  	__u32 clock;
>  	__u16 hdisplay;

-- 
Jani Nikula, Intel Open Source Technology Center
_______________________________________________
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dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel

[PATCH v2 2/4] drm/i915: Set link status property for DP connector

[Manasi Navare]

This defines a helper function to set the property value.
This will be used to set the link status to Bad in case
of link training failures.

v2:
* Simplify the return value (Jani Nikula)

Cc: dri-devel@lists.freedesktop.org
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Daniel Vetter <daniel.vetter@intel.com>
Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
---
 drivers/gpu/drm/i915/intel_dp.c  | 11 +++++++++++
 drivers/gpu/drm/i915/intel_drv.h |  2 ++
 2 files changed, 13 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 1063afe..2b6f51c 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -4640,6 +4640,17 @@ static int intel_dp_get_modes(struct drm_connector *connector)
 	return 0;
 }
 
+int
+intel_dp_set_link_status_property(struct drm_connector *connector,
+				  uint64_t val)
+{
+	struct drm_device *dev = connector->dev;
+
+	return drm_object_property_set_value(&connector->base,
+					     dev->mode_config.link_status_property,
+					     val);
+}
+
 static int
 intel_dp_connector_register(struct drm_connector *connector)
 {
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index 2616d92..3cb7481 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -1391,6 +1391,8 @@ u32 skl_plane_stride(const struct drm_framebuffer *fb, int plane,
 bool intel_dp_init(struct drm_device *dev, i915_reg_t output_reg, enum port port);
 bool intel_dp_init_connector(struct intel_digital_port *intel_dig_port,
 			     struct intel_connector *intel_connector);
+int intel_dp_set_link_status_property(struct drm_connector *connector,
+				      uint64_t val);
 void intel_dp_set_link_params(struct intel_dp *intel_dp,
 			      int link_rate, uint8_t lane_count,
 			      bool link_mst);
-- 
1.9.1

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Re: [PATCH v2 2/4] drm/i915: Set link status property for DP connector

[Jani Nikula]

On Sat, 29 Oct 2016, Manasi Navare <manasi.d.navare@intel.com> wrote:
> This defines a helper function to set the property value.
> This will be used to set the link status to Bad in case
> of link training failures.
>
> v2:
> * Simplify the return value (Jani Nikula)
>
> Cc: dri-devel@lists.freedesktop.org
> Cc: Jani Nikula <jani.nikula@linux.intel.com>
> Cc: Daniel Vetter <daniel.vetter@intel.com>
> Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
> Cc: Chris Wilson <chris@chris-wilson.co.uk>
> Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>

Reviewed-by: Jani Nikula <jani.nikula@intel.com>


> ---
>  drivers/gpu/drm/i915/intel_dp.c  | 11 +++++++++++
>  drivers/gpu/drm/i915/intel_drv.h |  2 ++
>  2 files changed, 13 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 1063afe..2b6f51c 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -4640,6 +4640,17 @@ static int intel_dp_get_modes(struct drm_connector *connector)
>  	return 0;
>  }
>  
> +int
> +intel_dp_set_link_status_property(struct drm_connector *connector,
> +				  uint64_t val)
> +{
> +	struct drm_device *dev = connector->dev;
> +
> +	return drm_object_property_set_value(&connector->base,
> +					     dev->mode_config.link_status_property,
> +					     val);
> +}
> +
>  static int
>  intel_dp_connector_register(struct drm_connector *connector)
>  {
> diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> index 2616d92..3cb7481 100644
> --- a/drivers/gpu/drm/i915/intel_drv.h
> +++ b/drivers/gpu/drm/i915/intel_drv.h
> @@ -1391,6 +1391,8 @@ u32 skl_plane_stride(const struct drm_framebuffer *fb, int plane,
>  bool intel_dp_init(struct drm_device *dev, i915_reg_t output_reg, enum port port);
>  bool intel_dp_init_connector(struct intel_digital_port *intel_dig_port,
>  			     struct intel_connector *intel_connector);
> +int intel_dp_set_link_status_property(struct drm_connector *connector,
> +				      uint64_t val);
>  void intel_dp_set_link_params(struct intel_dp *intel_dp,
>  			      int link_rate, uint8_t lane_count,
>  			      bool link_mst);

-- 
Jani Nikula, Intel Open Source Technology Center
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[PATCH v2 3/4] drm/i915: Find fallback link rate/lane count

[Manasi Navare]

If link training fails, then we need to fallback to lower
link rate first and if link training fails at RBR, then
fallback to lower lane count.
This function finds the next lower link rate/lane count
value after link training failure.

v2:
Squash the patch that returns the link rate index (Jani Nikula)

Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Daniel Vetter <daniel.vetter@intel.com>
Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
---
 drivers/gpu/drm/i915/intel_dp.c  | 43 ++++++++++++++++++++++++++++++++++++++++
 drivers/gpu/drm/i915/intel_drv.h |  6 ++++++
 2 files changed, 49 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 2b6f51c..fb4fcdd 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -288,6 +288,49 @@ static int intel_dp_common_rates(struct intel_dp *intel_dp,
 			       common_rates);
 }
 
+static int intel_dp_link_rate_index(struct intel_dp *intel_dp,
+				    int *common_rates, int link_rate)
+{
+	int common_len;
+	int index;
+
+	common_len = intel_dp_common_rates(intel_dp, common_rates);
+	for (index = 0; index < common_len; index++) {
+		if (link_rate == common_rates[common_len - index - 1])
+			return common_len - index - 1;
+	}
+
+	return -1;
+}
+
+void intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp,
+					     int link_rate, uint8_t lane_count)
+{
+	int common_rates[DP_MAX_SUPPORTED_RATES] = {};
+	int common_len;
+	int link_rate_index = -1;
+
+	if (!intel_dp->link_train_failed)
+		return;
+
+	common_len = intel_dp_common_rates(intel_dp, common_rates);
+	link_rate_index = intel_dp_link_rate_index(intel_dp,
+						   common_rates,
+						   link_rate);
+	if (link_rate_index > 0) {
+		intel_dp->fallback_link_rate_index = link_rate_index - 1;
+		intel_dp->fallback_link_rate = common_rates[intel_dp->fallback_link_rate_index];
+		intel_dp->fallback_lane_count = intel_dp_max_lane_count(intel_dp);
+	} else if (lane_count > 1) {
+		intel_dp->fallback_link_rate_index = common_len - 1;
+		intel_dp->fallback_link_rate = common_rates[intel_dp->fallback_link_rate_index];
+		intel_dp->fallback_lane_count = lane_count >> 1;
+	} else {
+		DRM_ERROR("Link Training Unsuccessful\n");
+		intel_dp->link_train_failed = false;
+	}
+}
+
 static enum drm_mode_status
 intel_dp_mode_valid(struct drm_connector *connector,
 		    struct drm_display_mode *mode)
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index 3cb7481..bc25b2b 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -897,6 +897,10 @@ struct intel_dp {
 	uint32_t DP;
 	int link_rate;
 	uint8_t lane_count;
+	int fallback_link_rate;
+	uint8_t fallback_lane_count;
+	int fallback_link_rate_index;
+	bool link_train_failed;
 	uint8_t sink_count;
 	bool link_mst;
 	bool has_audio;
@@ -1396,6 +1400,8 @@ int intel_dp_set_link_status_property(struct drm_connector *connector,
 void intel_dp_set_link_params(struct intel_dp *intel_dp,
 			      int link_rate, uint8_t lane_count,
 			      bool link_mst);
+void intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp,
+					     int link_rate, uint8_t lane_count);
 void intel_dp_start_link_train(struct intel_dp *intel_dp);
 void intel_dp_stop_link_train(struct intel_dp *intel_dp);
 void intel_dp_sink_dpms(struct intel_dp *intel_dp, int mode);
-- 
1.9.1

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[PATCH v2 4/4] drm/i915: Implement Link Rate fallback on Link training failure

[Manasi Navare]

If link training at a link rate optimal for a particular
mode fails during modeset's atomic commit phase, then we
let the modeset complete and then retry. We save the link rate
value at which link training failed, update the link status property
to "BAD" and use a lower link rate to prune the modes. It will redo
the modeset on the current mode at lower link rate or if the current
mode gets pruned due to lower link constraints then, it will send a
hotplug uevent for userspace to handle it.

This is also required to pass DP CTS tests 4.3.1.3, 4.3.1.4,
4.3.1.6.

v2:
* Squashed a few patches (Jani Nikula)

Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Daniel Vetter <daniel.vetter@intel.com>
Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
---
 drivers/gpu/drm/drm_atomic_helper.c           |  4 ++
 drivers/gpu/drm/i915/intel_ddi.c              | 23 ++++++++-
 drivers/gpu/drm/i915/intel_dp.c               | 74 +++++++++++++++++++++++++--
 drivers/gpu/drm/i915/intel_dp_link_training.c | 12 +++--
 drivers/gpu/drm/i915/intel_drv.h              |  5 +-
 5 files changed, 110 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index 75ad01d..a3df3a4 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -519,6 +519,10 @@ static int handle_conflicting_encoders(struct drm_atomic_state *state,
 					       connector_state);
 		if (ret)
 			return ret;
+
+		crtc_state = drm_atomic_get_existing_crtc_state(state, connector->state->crtc);
+		if (connector->link_status == DRM_MODE_LINK_STATUS_BAD)
+			crtc_state->connectors_changed = true;
 	}
 
 	/*
diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
index 938ac4d..319eeca 100644
--- a/drivers/gpu/drm/i915/intel_ddi.c
+++ b/drivers/gpu/drm/i915/intel_ddi.c
@@ -1684,6 +1684,8 @@ static void intel_ddi_pre_enable_dp(struct intel_encoder *encoder,
 	struct intel_dp *intel_dp = enc_to_intel_dp(&encoder->base);
 	struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
 	enum port port = intel_ddi_get_encoder_port(encoder);
+	struct intel_connector *intel_connector = intel_dp->attached_connector;
+	struct drm_connector *connector = &intel_connector->base;
 
 	intel_dp_set_link_params(intel_dp, link_rate, lane_count,
 				 link_mst);
@@ -1694,7 +1696,26 @@ static void intel_ddi_pre_enable_dp(struct intel_encoder *encoder,
 	intel_prepare_dp_ddi_buffers(encoder);
 	intel_ddi_init_dp_buf_reg(encoder);
 	intel_dp_sink_dpms(intel_dp, DRM_MODE_DPMS_ON);
-	intel_dp_start_link_train(intel_dp);
+	if (!intel_dp_start_link_train(intel_dp)) {
+		DRM_DEBUG_KMS("Link Training failed at link rate = %d, lane count = %d",
+			      link_rate, lane_count);
+		intel_dp->link_train_failed = true;
+		intel_dp_get_link_train_fallback_values(intel_dp, link_rate,
+							lane_count);
+		/* Schedule a Hotplug Uevent to userspace to start modeset */
+		schedule_work(&intel_connector->modeset_retry_work);
+	} else {
+		DRM_DEBUG_KMS("Link Training Passed at Link Rate = %d, Lane count = %d",
+			      link_rate, lane_count);
+		intel_dp->link_train_failed = false;
+		intel_dp->fallback_link_rate_index = -1;
+		intel_dp->fallback_link_rate = 0;
+		intel_dp->fallback_lane_count = 0;
+		connector->link_status = DRM_MODE_LINK_STATUS_GOOD;
+		intel_dp_set_link_status_property(connector,
+						  DRM_MODE_LINK_STATUS_GOOD);
+	}
+
 	if (port != PORT_A || INTEL_GEN(dev_priv) >= 9)
 		intel_dp_stop_link_train(intel_dp);
 }
diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index fb4fcdd..d1f0e2c 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -354,8 +354,14 @@ void intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp,
 		target_clock = fixed_mode->clock;
 	}
 
-	max_link_clock = intel_dp_max_link_rate(intel_dp);
-	max_lanes = intel_dp_max_lane_count(intel_dp);
+	/* Prune the modes using the fallback link rate/lane count */
+	if (intel_dp->link_train_failed) {
+		max_link_clock = intel_dp->fallback_link_rate;
+		max_lanes = intel_dp->fallback_lane_count;
+	} else {
+		max_link_clock = intel_dp_max_link_rate(intel_dp);
+		max_lanes = intel_dp_max_lane_count(intel_dp);
+	}
 
 	max_rate = intel_dp_max_data_rate(max_link_clock, max_lanes);
 	mode_rate = intel_dp_link_required(target_clock, 18);
@@ -1640,6 +1646,12 @@ static int intel_dp_compute_bpp(struct intel_dp *intel_dp,
 	if (adjusted_mode->flags & DRM_MODE_FLAG_DBLCLK)
 		return false;
 
+	/* Fall back to lower link rate in case of failure in previous modeset */
+	if (intel_dp->link_train_failed) {
+		min_lane_count = max_lane_count = intel_dp->fallback_lane_count;
+		min_clock = max_clock = intel_dp->fallback_link_rate_index;
+	}
+
 	DRM_DEBUG_KMS("DP link computation with max lane count %i "
 		      "max bw %d pixel clock %iKHz\n",
 		      max_lane_count, common_rates[max_clock],
@@ -4423,6 +4435,13 @@ static bool intel_digital_port_connected(struct drm_i915_private *dev_priv,
 		intel_dp->compliance_test_active = 0;
 		intel_dp->compliance_test_type = 0;
 		intel_dp->compliance_test_data = 0;
+		intel_dp->link_train_failed = false;
+		intel_dp->fallback_link_rate_index = -1;
+		intel_dp->fallback_link_rate = 0;
+		intel_dp->fallback_lane_count = 0;
+		connector->link_status = DRM_MODE_LINK_STATUS_GOOD;
+		intel_dp_set_link_status_property(connector,
+						  DRM_MODE_LINK_STATUS_GOOD);
 
 		if (intel_dp->is_mst) {
 			DRM_DEBUG_KMS("MST device may have disappeared %d vs %d\n",
@@ -4514,8 +4533,12 @@ static bool intel_digital_port_connected(struct drm_i915_private *dev_priv,
 	DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n",
 		      connector->base.id, connector->name);
 
+	/* If this is a retry due to link trianing failure */
+	if (status == connector_status_connected && intel_dp->link_train_failed)
+		return status;
+
 	/* If full detect is not performed yet, do a full detect */
-	if (!intel_dp->detect_done)
+	if (!intel_dp->detect_done && !intel_dp->link_train_failed)
 		status = intel_dp_long_pulse(intel_dp->attached_connector);
 
 	intel_dp->detect_done = false;
@@ -5692,6 +5715,47 @@ static bool intel_edp_init_connector(struct intel_dp *intel_dp,
 	return false;
 }
 
+static void intel_dp_modeset_retry_work_fn(struct work_struct *work)
+{
+	struct intel_connector *intel_connector;
+	struct drm_connector *connector;
+	struct drm_display_mode *mode;
+	bool verbose_prune = true;
+	bool reprobe = false;
+
+	intel_connector = container_of(work, typeof(*intel_connector),
+				       modeset_retry_work);
+	connector = &intel_connector->base;
+
+	/* Grab the locks before changing connector property*/
+	mutex_lock(&connector->dev->mode_config.mutex);
+	DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n", connector->base.id,
+		      connector->name);
+	list_for_each_entry(mode, &connector->modes, head) {
+		mode->status = intel_dp_mode_valid(connector,
+						   mode);
+		if (mode->status != MODE_OK)
+			reprobe = true;
+	}
+	drm_mode_prune_invalid(connector->dev, &connector->modes,
+			       verbose_prune);
+
+	/* Set connector link status to BAD only if modeset required
+	 * for the current mode, if mode list changed then just send uevent
+	 * so that it can reprobe the connectors and validate modes and do
+	 * a modeset on a different valid mode.
+	 */
+	if (!reprobe) {
+		connector->link_status = DRM_MODE_LINK_STATUS_BAD;
+		intel_dp_set_link_status_property(connector,
+						  DRM_MODE_LINK_STATUS_BAD);
+	}
+	mutex_unlock(&connector->dev->mode_config.mutex);
+
+	/* Send Hotplug uevent so userspace can reprobe */
+	drm_kms_helper_hotplug_event(connector->dev);
+}
+
 bool
 intel_dp_init_connector(struct intel_digital_port *intel_dig_port,
 			struct intel_connector *intel_connector)
@@ -5704,6 +5768,10 @@ static bool intel_edp_init_connector(struct intel_dp *intel_dp,
 	enum port port = intel_dig_port->port;
 	int type;
 
+	/* Initialize the work for modeset in case of link train failure */
+	INIT_WORK(&intel_connector->modeset_retry_work,
+		  intel_dp_modeset_retry_work_fn);
+
 	if (WARN(intel_dig_port->max_lanes < 1,
 		 "Not enough lanes (%d) for DP on port %c\n",
 		 intel_dig_port->max_lanes, port_name(port)))
diff --git a/drivers/gpu/drm/i915/intel_dp_link_training.c b/drivers/gpu/drm/i915/intel_dp_link_training.c
index 0048b52..10f81ab 100644
--- a/drivers/gpu/drm/i915/intel_dp_link_training.c
+++ b/drivers/gpu/drm/i915/intel_dp_link_training.c
@@ -310,9 +310,15 @@ void intel_dp_stop_link_train(struct intel_dp *intel_dp)
 				DP_TRAINING_PATTERN_DISABLE);
 }
 
-void
+bool
 intel_dp_start_link_train(struct intel_dp *intel_dp)
 {
-	intel_dp_link_training_clock_recovery(intel_dp);
-	intel_dp_link_training_channel_equalization(intel_dp);
+	bool ret;
+
+	if (intel_dp_link_training_clock_recovery(intel_dp)) {
+		ret = intel_dp_link_training_channel_equalization(intel_dp);
+		if (ret)
+			return true;
+	}
+	return false;
 }
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index bc25b2b..a54e9b7 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -312,6 +312,9 @@ struct intel_connector {
 	void *port; /* store this opaque as its illegal to dereference it */
 
 	struct intel_dp *mst_port;
+
+	/* Work struct to schedule a uevent on link train failure */
+	struct work_struct modeset_retry_work;
 };
 
 struct dpll {
@@ -1402,7 +1405,7 @@ void intel_dp_set_link_params(struct intel_dp *intel_dp,
 			      bool link_mst);
 void intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp,
 					     int link_rate, uint8_t lane_count);
-void intel_dp_start_link_train(struct intel_dp *intel_dp);
+bool intel_dp_start_link_train(struct intel_dp *intel_dp);
 void intel_dp_stop_link_train(struct intel_dp *intel_dp);
 void intel_dp_sink_dpms(struct intel_dp *intel_dp, int mode);
 void intel_dp_encoder_reset(struct drm_encoder *encoder);
-- 
1.9.1

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Re: [PATCH v2 4/4] drm/i915: Implement Link Rate fallback on Link training failure

[Jani Nikula]

On Sat, 29 Oct 2016, Manasi Navare <manasi.d.navare@intel.com> wrote:
> If link training at a link rate optimal for a particular
> mode fails during modeset's atomic commit phase, then we
> let the modeset complete and then retry. We save the link rate
> value at which link training failed, update the link status property
> to "BAD" and use a lower link rate to prune the modes. It will redo
> the modeset on the current mode at lower link rate or if the current
> mode gets pruned due to lower link constraints then, it will send a
> hotplug uevent for userspace to handle it.
>
> This is also required to pass DP CTS tests 4.3.1.3, 4.3.1.4,
> 4.3.1.6.
>
> v2:
> * Squashed a few patches (Jani Nikula)
>
> Cc: Jani Nikula <jani.nikula@linux.intel.com>
> Cc: Daniel Vetter <daniel.vetter@intel.com>
> Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
> Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
> ---
>  drivers/gpu/drm/drm_atomic_helper.c           |  4 ++
>  drivers/gpu/drm/i915/intel_ddi.c              | 23 ++++++++-
>  drivers/gpu/drm/i915/intel_dp.c               | 74 +++++++++++++++++++++++++--
>  drivers/gpu/drm/i915/intel_dp_link_training.c | 12 +++--
>  drivers/gpu/drm/i915/intel_drv.h              |  5 +-
>  5 files changed, 110 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> index 75ad01d..a3df3a4 100644
> --- a/drivers/gpu/drm/drm_atomic_helper.c
> +++ b/drivers/gpu/drm/drm_atomic_helper.c
> @@ -519,6 +519,10 @@ static int handle_conflicting_encoders(struct drm_atomic_state *state,
>  					       connector_state);
>  		if (ret)
>  			return ret;
> +
> +		crtc_state = drm_atomic_get_existing_crtc_state(state, connector->state->crtc);
> +		if (connector->link_status == DRM_MODE_LINK_STATUS_BAD)
> +			crtc_state->connectors_changed = true;
>  	}
>  
>  	/*
> diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
> index 938ac4d..319eeca 100644
> --- a/drivers/gpu/drm/i915/intel_ddi.c
> +++ b/drivers/gpu/drm/i915/intel_ddi.c
> @@ -1684,6 +1684,8 @@ static void intel_ddi_pre_enable_dp(struct intel_encoder *encoder,
>  	struct intel_dp *intel_dp = enc_to_intel_dp(&encoder->base);
>  	struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
>  	enum port port = intel_ddi_get_encoder_port(encoder);
> +	struct intel_connector *intel_connector = intel_dp->attached_connector;
> +	struct drm_connector *connector = &intel_connector->base;
>  
>  	intel_dp_set_link_params(intel_dp, link_rate, lane_count,
>  				 link_mst);
> @@ -1694,7 +1696,26 @@ static void intel_ddi_pre_enable_dp(struct intel_encoder *encoder,
>  	intel_prepare_dp_ddi_buffers(encoder);
>  	intel_ddi_init_dp_buf_reg(encoder);
>  	intel_dp_sink_dpms(intel_dp, DRM_MODE_DPMS_ON);
> -	intel_dp_start_link_train(intel_dp);
> +	if (!intel_dp_start_link_train(intel_dp)) {
> +		DRM_DEBUG_KMS("Link Training failed at link rate = %d, lane count = %d",
> +			      link_rate, lane_count);
> +		intel_dp->link_train_failed = true;
> +		intel_dp_get_link_train_fallback_values(intel_dp, link_rate,
> +							lane_count);
> +		/* Schedule a Hotplug Uevent to userspace to start modeset */
> +		schedule_work(&intel_connector->modeset_retry_work);

This is not just about DDI. Need to do this for the other cases too.

> +	} else {
> +		DRM_DEBUG_KMS("Link Training Passed at Link Rate = %d, Lane count = %d",
> +			      link_rate, lane_count);
> +		intel_dp->link_train_failed = false;
> +		intel_dp->fallback_link_rate_index = -1;
> +		intel_dp->fallback_link_rate = 0;
> +		intel_dp->fallback_lane_count = 0;
> +		connector->link_status = DRM_MODE_LINK_STATUS_GOOD;
> +		intel_dp_set_link_status_property(connector,
> +						  DRM_MODE_LINK_STATUS_GOOD);

Looks like you never actually read connector->link_status... Why do you
need both connector->link_status and intel_dp->link_train_failed? Do you
think you have 4 states? What are they? Can't this all be in sync with
the property?

> +	}
> +
>  	if (port != PORT_A || INTEL_GEN(dev_priv) >= 9)
>  		intel_dp_stop_link_train(intel_dp);
>  }
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index fb4fcdd..d1f0e2c 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -354,8 +354,14 @@ void intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp,
>  		target_clock = fixed_mode->clock;
>  	}
>  
> -	max_link_clock = intel_dp_max_link_rate(intel_dp);
> -	max_lanes = intel_dp_max_lane_count(intel_dp);
> +	/* Prune the modes using the fallback link rate/lane count */
> +	if (intel_dp->link_train_failed) {
> +		max_link_clock = intel_dp->fallback_link_rate;
> +		max_lanes = intel_dp->fallback_lane_count;
> +	} else {
> +		max_link_clock = intel_dp_max_link_rate(intel_dp);
> +		max_lanes = intel_dp_max_lane_count(intel_dp);
> +	}
>  
>  	max_rate = intel_dp_max_data_rate(max_link_clock, max_lanes);
>  	mode_rate = intel_dp_link_required(target_clock, 18);
> @@ -1640,6 +1646,12 @@ static int intel_dp_compute_bpp(struct intel_dp *intel_dp,
>  	if (adjusted_mode->flags & DRM_MODE_FLAG_DBLCLK)
>  		return false;
>  
> +	/* Fall back to lower link rate in case of failure in previous modeset */
> +	if (intel_dp->link_train_failed) {
> +		min_lane_count = max_lane_count = intel_dp->fallback_lane_count;
> +		min_clock = max_clock = intel_dp->fallback_link_rate_index;
> +	}
> +

My general feeling is that there's starting to be a bit too much special
casing around the fallback values. I'm not decided we need to fix this
right away in this series, or whether it can be follow-up work.

One idea is to compute the common rates and lanes once when they're
first needed, and all of the helpers would use that info. The fallback
code would just trim those, and the conditional fallback stuff could be
removed from all over the place.

>  	DRM_DEBUG_KMS("DP link computation with max lane count %i "
>  		      "max bw %d pixel clock %iKHz\n",
>  		      max_lane_count, common_rates[max_clock],
> @@ -4423,6 +4435,13 @@ static bool intel_digital_port_connected(struct drm_i915_private *dev_priv,
>  		intel_dp->compliance_test_active = 0;
>  		intel_dp->compliance_test_type = 0;
>  		intel_dp->compliance_test_data = 0;
> +		intel_dp->link_train_failed = false;
> +		intel_dp->fallback_link_rate_index = -1;
> +		intel_dp->fallback_link_rate = 0;
> +		intel_dp->fallback_lane_count = 0;
> +		connector->link_status = DRM_MODE_LINK_STATUS_GOOD;
> +		intel_dp_set_link_status_property(connector,
> +						  DRM_MODE_LINK_STATUS_GOOD);
>  
>  		if (intel_dp->is_mst) {
>  			DRM_DEBUG_KMS("MST device may have disappeared %d vs %d\n",
> @@ -4514,8 +4533,12 @@ static bool intel_digital_port_connected(struct drm_i915_private *dev_priv,
>  	DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n",
>  		      connector->base.id, connector->name);
>  
> +	/* If this is a retry due to link trianing failure */
> +	if (status == connector_status_connected && intel_dp->link_train_failed)
> +		return status;
> +
>  	/* If full detect is not performed yet, do a full detect */
> -	if (!intel_dp->detect_done)
> +	if (!intel_dp->detect_done && !intel_dp->link_train_failed)
>  		status = intel_dp_long_pulse(intel_dp->attached_connector);
>  
>  	intel_dp->detect_done = false;
> @@ -5692,6 +5715,47 @@ static bool intel_edp_init_connector(struct intel_dp *intel_dp,
>  	return false;
>  }
>  
> +static void intel_dp_modeset_retry_work_fn(struct work_struct *work)
> +{
> +	struct intel_connector *intel_connector;
> +	struct drm_connector *connector;
> +	struct drm_display_mode *mode;
> +	bool verbose_prune = true;
> +	bool reprobe = false;
> +
> +	intel_connector = container_of(work, typeof(*intel_connector),
> +				       modeset_retry_work);
> +	connector = &intel_connector->base;
> +
> +	/* Grab the locks before changing connector property*/
> +	mutex_lock(&connector->dev->mode_config.mutex);
> +	DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n", connector->base.id,
> +		      connector->name);
> +	list_for_each_entry(mode, &connector->modes, head) {
> +		mode->status = intel_dp_mode_valid(connector,
> +						   mode);
> +		if (mode->status != MODE_OK)
> +			reprobe = true;
> +	}
> +	drm_mode_prune_invalid(connector->dev, &connector->modes,
> +			       verbose_prune);
> +
> +	/* Set connector link status to BAD only if modeset required
> +	 * for the current mode, if mode list changed then just send uevent
> +	 * so that it can reprobe the connectors and validate modes and do
> +	 * a modeset on a different valid mode.
> +	 */
> +	if (!reprobe) {
> +		connector->link_status = DRM_MODE_LINK_STATUS_BAD;
> +		intel_dp_set_link_status_property(connector,
> +						  DRM_MODE_LINK_STATUS_BAD);
> +	}


I think the link status property should be set to bad unconditionally
here. If the current link is bad, it is bad right now independent of
modes fitting into the fallback link parameters.

Which makes me think, unless I'm missing something, that you might be
able to prune the invalid modes and set the property right away when
link training fails, and only use the work to do
drm_kms_helper_hotplug_event.

> +	mutex_unlock(&connector->dev->mode_config.mutex);
> +
> +	/* Send Hotplug uevent so userspace can reprobe */
> +	drm_kms_helper_hotplug_event(connector->dev);
> +}
> +
>  bool
>  intel_dp_init_connector(struct intel_digital_port *intel_dig_port,
>  			struct intel_connector *intel_connector)
> @@ -5704,6 +5768,10 @@ static bool intel_edp_init_connector(struct intel_dp *intel_dp,
>  	enum port port = intel_dig_port->port;
>  	int type;
>  
> +	/* Initialize the work for modeset in case of link train failure */
> +	INIT_WORK(&intel_connector->modeset_retry_work,
> +		  intel_dp_modeset_retry_work_fn);
> +
>  	if (WARN(intel_dig_port->max_lanes < 1,
>  		 "Not enough lanes (%d) for DP on port %c\n",
>  		 intel_dig_port->max_lanes, port_name(port)))
> diff --git a/drivers/gpu/drm/i915/intel_dp_link_training.c b/drivers/gpu/drm/i915/intel_dp_link_training.c
> index 0048b52..10f81ab 100644
> --- a/drivers/gpu/drm/i915/intel_dp_link_training.c
> +++ b/drivers/gpu/drm/i915/intel_dp_link_training.c
> @@ -310,9 +310,15 @@ void intel_dp_stop_link_train(struct intel_dp *intel_dp)
>  				DP_TRAINING_PATTERN_DISABLE);
>  }
>  
> -void
> +bool
>  intel_dp_start_link_train(struct intel_dp *intel_dp)
>  {
> -	intel_dp_link_training_clock_recovery(intel_dp);
> -	intel_dp_link_training_channel_equalization(intel_dp);
> +	bool ret;
> +
> +	if (intel_dp_link_training_clock_recovery(intel_dp)) {
> +		ret = intel_dp_link_training_channel_equalization(intel_dp);
> +		if (ret)
> +			return true;
> +	}
> +	return false;
>  }
> diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> index bc25b2b..a54e9b7 100644
> --- a/drivers/gpu/drm/i915/intel_drv.h
> +++ b/drivers/gpu/drm/i915/intel_drv.h
> @@ -312,6 +312,9 @@ struct intel_connector {
>  	void *port; /* store this opaque as its illegal to dereference it */
>  
>  	struct intel_dp *mst_port;
> +
> +	/* Work struct to schedule a uevent on link train failure */
> +	struct work_struct modeset_retry_work;
>  };
>  
>  struct dpll {
> @@ -1402,7 +1405,7 @@ void intel_dp_set_link_params(struct intel_dp *intel_dp,
>  			      bool link_mst);
>  void intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp,
>  					     int link_rate, uint8_t lane_count);
> -void intel_dp_start_link_train(struct intel_dp *intel_dp);
> +bool intel_dp_start_link_train(struct intel_dp *intel_dp);
>  void intel_dp_stop_link_train(struct intel_dp *intel_dp);
>  void intel_dp_sink_dpms(struct intel_dp *intel_dp, int mode);
>  void intel_dp_encoder_reset(struct drm_encoder *encoder);

-- 
Jani Nikula, Intel Open Source Technology Center
_______________________________________________
Intel-gfx mailing list
Intel-gfx@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/intel-gfx

Re: [PATCH v2 4/4] drm/i915: Implement Link Rate fallback on Link training failure

[Manasi Navare]

On Tue, Nov 01, 2016 at 10:49:14AM +0200, Jani Nikula wrote:
> On Sat, 29 Oct 2016, Manasi Navare <manasi.d.navare@intel.com> wrote:
> > If link training at a link rate optimal for a particular
> > mode fails during modeset's atomic commit phase, then we
> > let the modeset complete and then retry. We save the link rate
> > value at which link training failed, update the link status property
> > to "BAD" and use a lower link rate to prune the modes. It will redo
> > the modeset on the current mode at lower link rate or if the current
> > mode gets pruned due to lower link constraints then, it will send a
> > hotplug uevent for userspace to handle it.
> >
> > This is also required to pass DP CTS tests 4.3.1.3, 4.3.1.4,
> > 4.3.1.6.
> >
> > v2:
> > * Squashed a few patches (Jani Nikula)
> >
> > Cc: Jani Nikula <jani.nikula@linux.intel.com>
> > Cc: Daniel Vetter <daniel.vetter@intel.com>
> > Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
> > Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
> > ---
> >  drivers/gpu/drm/drm_atomic_helper.c           |  4 ++
> >  drivers/gpu/drm/i915/intel_ddi.c              | 23 ++++++++-
> >  drivers/gpu/drm/i915/intel_dp.c               | 74 +++++++++++++++++++++++++--
> >  drivers/gpu/drm/i915/intel_dp_link_training.c | 12 +++--
> >  drivers/gpu/drm/i915/intel_drv.h              |  5 +-
> >  5 files changed, 110 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> > index 75ad01d..a3df3a4 100644
> > --- a/drivers/gpu/drm/drm_atomic_helper.c
> > +++ b/drivers/gpu/drm/drm_atomic_helper.c
> > @@ -519,6 +519,10 @@ static int handle_conflicting_encoders(struct drm_atomic_state *state,
> >  					       connector_state);
> >  		if (ret)
> >  			return ret;
> > +
> > +		crtc_state = drm_atomic_get_existing_crtc_state(state, connector->state->crtc);
> > +		if (connector->link_status == DRM_MODE_LINK_STATUS_BAD)
> > +			crtc_state->connectors_changed = true;
> >  	}
> >  
> >  	/*
> > diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
> > index 938ac4d..319eeca 100644
> > --- a/drivers/gpu/drm/i915/intel_ddi.c
> > +++ b/drivers/gpu/drm/i915/intel_ddi.c
> > @@ -1684,6 +1684,8 @@ static void intel_ddi_pre_enable_dp(struct intel_encoder *encoder,
> >  	struct intel_dp *intel_dp = enc_to_intel_dp(&encoder->base);
> >  	struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
> >  	enum port port = intel_ddi_get_encoder_port(encoder);
> > +	struct intel_connector *intel_connector = intel_dp->attached_connector;
> > +	struct drm_connector *connector = &intel_connector->base;
> >  
> >  	intel_dp_set_link_params(intel_dp, link_rate, lane_count,
> >  				 link_mst);
> > @@ -1694,7 +1696,26 @@ static void intel_ddi_pre_enable_dp(struct intel_encoder *encoder,
> >  	intel_prepare_dp_ddi_buffers(encoder);
> >  	intel_ddi_init_dp_buf_reg(encoder);
> >  	intel_dp_sink_dpms(intel_dp, DRM_MODE_DPMS_ON);
> > -	intel_dp_start_link_train(intel_dp);
> > +	if (!intel_dp_start_link_train(intel_dp)) {
> > +		DRM_DEBUG_KMS("Link Training failed at link rate = %d, lane count = %d",
> > +			      link_rate, lane_count);
> > +		intel_dp->link_train_failed = true;
> > +		intel_dp_get_link_train_fallback_values(intel_dp, link_rate,
> > +							lane_count);
> > +		/* Schedule a Hotplug Uevent to userspace to start modeset */
> > +		schedule_work(&intel_connector->modeset_retry_work);
> 
> This is not just about DDI. Need to do this for the other cases too.
>

Yes, first series will g out for adding this support for DDI, then more patches
to expand it to non DDI platforms.

 
> > +	} else {
> > +		DRM_DEBUG_KMS("Link Training Passed at Link Rate = %d, Lane count = %d",
> > +			      link_rate, lane_count);
> > +		intel_dp->link_train_failed = false;
> > +		intel_dp->fallback_link_rate_index = -1;
> > +		intel_dp->fallback_link_rate = 0;
> > +		intel_dp->fallback_lane_count = 0;
> > +		connector->link_status = DRM_MODE_LINK_STATUS_GOOD;
> > +		intel_dp_set_link_status_property(connector,
> > +						  DRM_MODE_LINK_STATUS_GOOD);
> 
> Looks like you never actually read connector->link_status... Why do you
> need both connector->link_status and intel_dp->link_train_failed? Do you
> think you have 4 states? What are they? Can't this all be in sync with
> the property?
> 

This connector->link_status member of drm_Connector gets read in
drm_atomic_helper_check_modeset() in the driver where it reads this
and sets crtc_state->connector_Changed to true if this link_status
has changed.
This is required so that the driver does a complete modeset.
This connector->link_status was in sync with the property. But reading the
drm_object property in drm_atomic_helper_Check_modeset was causing the system to
not boot.
intel_dp->link_train_failed also just indicates if the link failed, I will have to see
if i can just use connector->link_status for this purpose. 

> > +	}
> > +
> >  	if (port != PORT_A || INTEL_GEN(dev_priv) >= 9)
> >  		intel_dp_stop_link_train(intel_dp);
> >  }
> > diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> > index fb4fcdd..d1f0e2c 100644
> > --- a/drivers/gpu/drm/i915/intel_dp.c
> > +++ b/drivers/gpu/drm/i915/intel_dp.c
> > @@ -354,8 +354,14 @@ void intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp,
> >  		target_clock = fixed_mode->clock;
> >  	}
> >  
> > -	max_link_clock = intel_dp_max_link_rate(intel_dp);
> > -	max_lanes = intel_dp_max_lane_count(intel_dp);
> > +	/* Prune the modes using the fallback link rate/lane count */
> > +	if (intel_dp->link_train_failed) {
> > +		max_link_clock = intel_dp->fallback_link_rate;
> > +		max_lanes = intel_dp->fallback_lane_count;
> > +	} else {
> > +		max_link_clock = intel_dp_max_link_rate(intel_dp);
> > +		max_lanes = intel_dp_max_lane_count(intel_dp);
> > +	}
> >  
> >  	max_rate = intel_dp_max_data_rate(max_link_clock, max_lanes);
> >  	mode_rate = intel_dp_link_required(target_clock, 18);
> > @@ -1640,6 +1646,12 @@ static int intel_dp_compute_bpp(struct intel_dp *intel_dp,
> >  	if (adjusted_mode->flags & DRM_MODE_FLAG_DBLCLK)
> >  		return false;
> >  
> > +	/* Fall back to lower link rate in case of failure in previous modeset */
> > +	if (intel_dp->link_train_failed) {
> > +		min_lane_count = max_lane_count = intel_dp->fallback_lane_count;
> > +		min_clock = max_clock = intel_dp->fallback_link_rate_index;
> > +	}
> > +
> 
> My general feeling is that there's starting to be a bit too much special
> casing around the fallback values. I'm not decided we need to fix this
> right away in this series, or whether it can be follow-up work.
> 
> One idea is to compute the common rates and lanes once when they're
> first needed, and all of the helpers would use that info. The fallback
> code would just trim those, and the conditional fallback stuff could be
> removed from all over the place.
>

These fallback values get computed in a separate helper function that I have
added intel_dp_get_link_train_fallback_values. It is the previous patch. 
I store the fallback values in intel_dp one at a time because for that
iteration of modeset we only need to try the fallback_link_rate
and fallback_lane_count so we dont need an array here.
Are you suggesting just changing the common_rates array itself to get trimmed to use the trimmed
fallback values after link training fails? Could you please elaborate your thought?


 
> >  	DRM_DEBUG_KMS("DP link computation with max lane count %i "
> >  		      "max bw %d pixel clock %iKHz\n",
> >  		      max_lane_count, common_rates[max_clock],
> > @@ -4423,6 +4435,13 @@ static bool intel_digital_port_connected(struct drm_i915_private *dev_priv,
> >  		intel_dp->compliance_test_active = 0;
> >  		intel_dp->compliance_test_type = 0;
> >  		intel_dp->compliance_test_data = 0;
> > +		intel_dp->link_train_failed = false;
> > +		intel_dp->fallback_link_rate_index = -1;
> > +		intel_dp->fallback_link_rate = 0;
> > +		intel_dp->fallback_lane_count = 0;
> > +		connector->link_status = DRM_MODE_LINK_STATUS_GOOD;
> > +		intel_dp_set_link_status_property(connector,
> > +						  DRM_MODE_LINK_STATUS_GOOD);
> >  
> >  		if (intel_dp->is_mst) {
> >  			DRM_DEBUG_KMS("MST device may have disappeared %d vs %d\n",
> > @@ -4514,8 +4533,12 @@ static bool intel_digital_port_connected(struct drm_i915_private *dev_priv,
> >  	DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n",
> >  		      connector->base.id, connector->name);
> >  
> > +	/* If this is a retry due to link trianing failure */
> > +	if (status == connector_status_connected && intel_dp->link_train_failed)
> > +		return status;
> > +
> >  	/* If full detect is not performed yet, do a full detect */
> > -	if (!intel_dp->detect_done)
> > +	if (!intel_dp->detect_done && !intel_dp->link_train_failed)
> >  		status = intel_dp_long_pulse(intel_dp->attached_connector);
> >  
> >  	intel_dp->detect_done = false;
> > @@ -5692,6 +5715,47 @@ static bool intel_edp_init_connector(struct intel_dp *intel_dp,
> >  	return false;
> >  }
> >  
> > +static void intel_dp_modeset_retry_work_fn(struct work_struct *work)
> > +{
> > +	struct intel_connector *intel_connector;
> > +	struct drm_connector *connector;
> > +	struct drm_display_mode *mode;
> > +	bool verbose_prune = true;
> > +	bool reprobe = false;
> > +
> > +	intel_connector = container_of(work, typeof(*intel_connector),
> > +				       modeset_retry_work);
> > +	connector = &intel_connector->base;
> > +
> > +	/* Grab the locks before changing connector property*/
> > +	mutex_lock(&connector->dev->mode_config.mutex);
> > +	DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n", connector->base.id,
> > +		      connector->name);
> > +	list_for_each_entry(mode, &connector->modes, head) {
> > +		mode->status = intel_dp_mode_valid(connector,
> > +						   mode);
> > +		if (mode->status != MODE_OK)
> > +			reprobe = true;
> > +	}
> > +	drm_mode_prune_invalid(connector->dev, &connector->modes,
> > +			       verbose_prune);
> > +
> > +	/* Set connector link status to BAD only if modeset required
> > +	 * for the current mode, if mode list changed then just send uevent
> > +	 * so that it can reprobe the connectors and validate modes and do
> > +	 * a modeset on a different valid mode.
> > +	 */
> > +	if (!reprobe) {
> > +		connector->link_status = DRM_MODE_LINK_STATUS_BAD;
> > +		intel_dp_set_link_status_property(connector,
> > +						  DRM_MODE_LINK_STATUS_BAD);
> > +	}
> 
> 
> I think the link status property should be set to bad unconditionally
> here. If the current link is bad, it is bad right now independent of
> modes fitting into the fallback link parameters.
> 
> Which makes me think, unless I'm missing something, that you might be
> able to prune the invalid modes and set the property right away when
> link training fails, and only use the work to do
> drm_kms_helper_hotplug_event.
>

The problem with setting the link_status property BAD irrespective of the 
mode pruning is that, if the modes gets pruned and we set the link_sttaus to BAD
Chris Wilson's driver checks that the link status is BAD and he first tries to attempt
the modeset at the current mode without calling mode_valid, and that results in a failure
in enocder->compute_config since now the mode does not fit and the pipe cannot be 
configured. This creates a lot of warnings/errors/kernel crash eventually. 
So the best way is to set the link status as bad only when we want to force the modeset
at the current mode, if the modes get pruned then in any case userspace will do another modeset
at the next lower mode.

Manasi 
> > +	mutex_unlock(&connector->dev->mode_config.mutex);
> > +
> > +	/* Send Hotplug uevent so userspace can reprobe */
> > +	drm_kms_helper_hotplug_event(connector->dev);
> > +}
> > +
> >  bool
> >  intel_dp_init_connector(struct intel_digital_port *intel_dig_port,
> >  			struct intel_connector *intel_connector)
> > @@ -5704,6 +5768,10 @@ static bool intel_edp_init_connector(struct intel_dp *intel_dp,
> >  	enum port port = intel_dig_port->port;
> >  	int type;
> >  
> > +	/* Initialize the work for modeset in case of link train failure */
> > +	INIT_WORK(&intel_connector->modeset_retry_work,
> > +		  intel_dp_modeset_retry_work_fn);
> > +
> >  	if (WARN(intel_dig_port->max_lanes < 1,
> >  		 "Not enough lanes (%d) for DP on port %c\n",
> >  		 intel_dig_port->max_lanes, port_name(port)))
> > diff --git a/drivers/gpu/drm/i915/intel_dp_link_training.c b/drivers/gpu/drm/i915/intel_dp_link_training.c
> > index 0048b52..10f81ab 100644
> > --- a/drivers/gpu/drm/i915/intel_dp_link_training.c
> > +++ b/drivers/gpu/drm/i915/intel_dp_link_training.c
> > @@ -310,9 +310,15 @@ void intel_dp_stop_link_train(struct intel_dp *intel_dp)
> >  				DP_TRAINING_PATTERN_DISABLE);
> >  }
> >  
> > -void
> > +bool
> >  intel_dp_start_link_train(struct intel_dp *intel_dp)
> >  {
> > -	intel_dp_link_training_clock_recovery(intel_dp);
> > -	intel_dp_link_training_channel_equalization(intel_dp);
> > +	bool ret;
> > +
> > +	if (intel_dp_link_training_clock_recovery(intel_dp)) {
> > +		ret = intel_dp_link_training_channel_equalization(intel_dp);
> > +		if (ret)
> > +			return true;
> > +	}
> > +	return false;
> >  }
> > diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> > index bc25b2b..a54e9b7 100644
> > --- a/drivers/gpu/drm/i915/intel_drv.h
> > +++ b/drivers/gpu/drm/i915/intel_drv.h
> > @@ -312,6 +312,9 @@ struct intel_connector {
> >  	void *port; /* store this opaque as its illegal to dereference it */
> >  
> >  	struct intel_dp *mst_port;
> > +
> > +	/* Work struct to schedule a uevent on link train failure */
> > +	struct work_struct modeset_retry_work;
> >  };
> >  
> >  struct dpll {
> > @@ -1402,7 +1405,7 @@ void intel_dp_set_link_params(struct intel_dp *intel_dp,
> >  			      bool link_mst);
> >  void intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp,
> >  					     int link_rate, uint8_t lane_count);
> > -void intel_dp_start_link_train(struct intel_dp *intel_dp);
> > +bool intel_dp_start_link_train(struct intel_dp *intel_dp);
> >  void intel_dp_stop_link_train(struct intel_dp *intel_dp);
> >  void intel_dp_sink_dpms(struct intel_dp *intel_dp, int mode);
> >  void intel_dp_encoder_reset(struct drm_encoder *encoder);
> 
> -- 
> Jani Nikula, Intel Open Source Technology Center
_______________________________________________
Intel-gfx mailing list
Intel-gfx@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/intel-gfx

Re: [PATCH v2 4/4] drm/i915: Implement Link Rate fallback on Link training failure

[Jani Nikula]

On Tue, 01 Nov 2016, Manasi Navare <manasi.d.navare@intel.com> wrote:
> On Tue, Nov 01, 2016 at 10:49:14AM +0200, Jani Nikula wrote:
>> On Sat, 29 Oct 2016, Manasi Navare <manasi.d.navare@intel.com> wrote:
>> > If link training at a link rate optimal for a particular
>> > mode fails during modeset's atomic commit phase, then we
>> > let the modeset complete and then retry. We save the link rate
>> > value at which link training failed, update the link status property
>> > to "BAD" and use a lower link rate to prune the modes. It will redo
>> > the modeset on the current mode at lower link rate or if the current
>> > mode gets pruned due to lower link constraints then, it will send a
>> > hotplug uevent for userspace to handle it.
>> >
>> > This is also required to pass DP CTS tests 4.3.1.3, 4.3.1.4,
>> > 4.3.1.6.
>> >
>> > v2:
>> > * Squashed a few patches (Jani Nikula)
>> >
>> > Cc: Jani Nikula <jani.nikula@linux.intel.com>
>> > Cc: Daniel Vetter <daniel.vetter@intel.com>
>> > Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
>> > Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
>> > ---
>> >  drivers/gpu/drm/drm_atomic_helper.c           |  4 ++
>> >  drivers/gpu/drm/i915/intel_ddi.c              | 23 ++++++++-
>> >  drivers/gpu/drm/i915/intel_dp.c               | 74 +++++++++++++++++++++++++--
>> >  drivers/gpu/drm/i915/intel_dp_link_training.c | 12 +++--
>> >  drivers/gpu/drm/i915/intel_drv.h              |  5 +-
>> >  5 files changed, 110 insertions(+), 8 deletions(-)
>> >
>> > diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
>> > index 75ad01d..a3df3a4 100644
>> > --- a/drivers/gpu/drm/drm_atomic_helper.c
>> > +++ b/drivers/gpu/drm/drm_atomic_helper.c
>> > @@ -519,6 +519,10 @@ static int handle_conflicting_encoders(struct drm_atomic_state *state,
>> >  					       connector_state);
>> >  		if (ret)
>> >  			return ret;
>> > +
>> > +		crtc_state = drm_atomic_get_existing_crtc_state(state, connector->state->crtc);
>> > +		if (connector->link_status == DRM_MODE_LINK_STATUS_BAD)
>> > +			crtc_state->connectors_changed = true;
>> >  	}
>> >  
>> >  	/*
>> > diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
>> > index 938ac4d..319eeca 100644
>> > --- a/drivers/gpu/drm/i915/intel_ddi.c
>> > +++ b/drivers/gpu/drm/i915/intel_ddi.c
>> > @@ -1684,6 +1684,8 @@ static void intel_ddi_pre_enable_dp(struct intel_encoder *encoder,
>> >  	struct intel_dp *intel_dp = enc_to_intel_dp(&encoder->base);
>> >  	struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
>> >  	enum port port = intel_ddi_get_encoder_port(encoder);
>> > +	struct intel_connector *intel_connector = intel_dp->attached_connector;
>> > +	struct drm_connector *connector = &intel_connector->base;
>> >  
>> >  	intel_dp_set_link_params(intel_dp, link_rate, lane_count,
>> >  				 link_mst);
>> > @@ -1694,7 +1696,26 @@ static void intel_ddi_pre_enable_dp(struct intel_encoder *encoder,
>> >  	intel_prepare_dp_ddi_buffers(encoder);
>> >  	intel_ddi_init_dp_buf_reg(encoder);
>> >  	intel_dp_sink_dpms(intel_dp, DRM_MODE_DPMS_ON);
>> > -	intel_dp_start_link_train(intel_dp);
>> > +	if (!intel_dp_start_link_train(intel_dp)) {
>> > +		DRM_DEBUG_KMS("Link Training failed at link rate = %d, lane count = %d",
>> > +			      link_rate, lane_count);
>> > +		intel_dp->link_train_failed = true;
>> > +		intel_dp_get_link_train_fallback_values(intel_dp, link_rate,
>> > +							lane_count);
>> > +		/* Schedule a Hotplug Uevent to userspace to start modeset */
>> > +		schedule_work(&intel_connector->modeset_retry_work);
>> 
>> This is not just about DDI. Need to do this for the other cases too.
>>
>
> Yes, first series will g out for adding this support for DDI, then more patches
> to expand it to non DDI platforms.
>
>  
>> > +	} else {
>> > +		DRM_DEBUG_KMS("Link Training Passed at Link Rate = %d, Lane count = %d",
>> > +			      link_rate, lane_count);
>> > +		intel_dp->link_train_failed = false;
>> > +		intel_dp->fallback_link_rate_index = -1;
>> > +		intel_dp->fallback_link_rate = 0;
>> > +		intel_dp->fallback_lane_count = 0;
>> > +		connector->link_status = DRM_MODE_LINK_STATUS_GOOD;
>> > +		intel_dp_set_link_status_property(connector,
>> > +						  DRM_MODE_LINK_STATUS_GOOD);
>> 
>> Looks like you never actually read connector->link_status... Why do you
>> need both connector->link_status and intel_dp->link_train_failed? Do you
>> think you have 4 states? What are they? Can't this all be in sync with
>> the property?
>> 
>
> This connector->link_status member of drm_Connector gets read in
> drm_atomic_helper_check_modeset() in the driver where it reads this
> and sets crtc_state->connector_Changed to true if this link_status
> has changed.
> This is required so that the driver does a complete modeset.
> This connector->link_status was in sync with the property. But reading the
> drm_object property in drm_atomic_helper_Check_modeset was causing the system to
> not boot.
> intel_dp->link_train_failed also just indicates if the link failed, I will have to see
> if i can just use connector->link_status for this purpose. 

Please do. Usually if you add more than one variable for essentially the
same thing, you'll end up having combinations of the variables (states)
that you should not be in. At least you should have a clear idea what
the states are where link_train_failed and link_status disagree.

>
>> > +	}
>> > +
>> >  	if (port != PORT_A || INTEL_GEN(dev_priv) >= 9)
>> >  		intel_dp_stop_link_train(intel_dp);
>> >  }
>> > diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
>> > index fb4fcdd..d1f0e2c 100644
>> > --- a/drivers/gpu/drm/i915/intel_dp.c
>> > +++ b/drivers/gpu/drm/i915/intel_dp.c
>> > @@ -354,8 +354,14 @@ void intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp,
>> >  		target_clock = fixed_mode->clock;
>> >  	}
>> >  
>> > -	max_link_clock = intel_dp_max_link_rate(intel_dp);
>> > -	max_lanes = intel_dp_max_lane_count(intel_dp);
>> > +	/* Prune the modes using the fallback link rate/lane count */
>> > +	if (intel_dp->link_train_failed) {
>> > +		max_link_clock = intel_dp->fallback_link_rate;
>> > +		max_lanes = intel_dp->fallback_lane_count;
>> > +	} else {
>> > +		max_link_clock = intel_dp_max_link_rate(intel_dp);
>> > +		max_lanes = intel_dp_max_lane_count(intel_dp);
>> > +	}
>> >  
>> >  	max_rate = intel_dp_max_data_rate(max_link_clock, max_lanes);
>> >  	mode_rate = intel_dp_link_required(target_clock, 18);
>> > @@ -1640,6 +1646,12 @@ static int intel_dp_compute_bpp(struct intel_dp *intel_dp,
>> >  	if (adjusted_mode->flags & DRM_MODE_FLAG_DBLCLK)
>> >  		return false;
>> >  
>> > +	/* Fall back to lower link rate in case of failure in previous modeset */
>> > +	if (intel_dp->link_train_failed) {
>> > +		min_lane_count = max_lane_count = intel_dp->fallback_lane_count;
>> > +		min_clock = max_clock = intel_dp->fallback_link_rate_index;
>> > +	}
>> > +
>> 
>> My general feeling is that there's starting to be a bit too much special
>> casing around the fallback values. I'm not decided we need to fix this
>> right away in this series, or whether it can be follow-up work.
>> 
>> One idea is to compute the common rates and lanes once when they're
>> first needed, and all of the helpers would use that info. The fallback
>> code would just trim those, and the conditional fallback stuff could be
>> removed from all over the place.
>>
>
> These fallback values get computed in a separate helper function that
> I have added intel_dp_get_link_train_fallback_values. It is the
> previous patch.  I store the fallback values in intel_dp one at a time
> because for that iteration of modeset we only need to try the
> fallback_link_rate and fallback_lane_count so we dont need an array
> here.

Sure. I'm *not* referring to my earlier suggestion of storing failing
link rate, lane count pairs (although I think we'll need that
eventually).

> Are you suggesting just changing the common_rates array itself to get
> trimmed to use the trimmed fallback values after link training fails?
> Could you please elaborate your thought?

I'm not saying you should change this now. But having a lot of code
check some fallback stuff is ugly and error prone. I'm just documenting
the ideas to make this better.

I think this could be fixed by storing the common rates array and max
lanes in intel_dp, instead of having them locally in a few functions,
and then making the link rate and lane counting functions aware of the
fallback stuff. Either the functions would check for the fallbacks,
centralizing the checks in one place, and/or the fallback code would
modify the common values stored in intel_dp, so that the link rate and
lane counting functions would just work with the fallbacks. Code would
be simpler overall.

>  
>> >  	DRM_DEBUG_KMS("DP link computation with max lane count %i "
>> >  		      "max bw %d pixel clock %iKHz\n",
>> >  		      max_lane_count, common_rates[max_clock],
>> > @@ -4423,6 +4435,13 @@ static bool intel_digital_port_connected(struct drm_i915_private *dev_priv,
>> >  		intel_dp->compliance_test_active = 0;
>> >  		intel_dp->compliance_test_type = 0;
>> >  		intel_dp->compliance_test_data = 0;
>> > +		intel_dp->link_train_failed = false;
>> > +		intel_dp->fallback_link_rate_index = -1;
>> > +		intel_dp->fallback_link_rate = 0;
>> > +		intel_dp->fallback_lane_count = 0;
>> > +		connector->link_status = DRM_MODE_LINK_STATUS_GOOD;
>> > +		intel_dp_set_link_status_property(connector,
>> > +						  DRM_MODE_LINK_STATUS_GOOD);
>> >  
>> >  		if (intel_dp->is_mst) {
>> >  			DRM_DEBUG_KMS("MST device may have disappeared %d vs %d\n",
>> > @@ -4514,8 +4533,12 @@ static bool intel_digital_port_connected(struct drm_i915_private *dev_priv,
>> >  	DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n",
>> >  		      connector->base.id, connector->name);
>> >  
>> > +	/* If this is a retry due to link trianing failure */
>> > +	if (status == connector_status_connected && intel_dp->link_train_failed)
>> > +		return status;
>> > +
>> >  	/* If full detect is not performed yet, do a full detect */
>> > -	if (!intel_dp->detect_done)
>> > +	if (!intel_dp->detect_done && !intel_dp->link_train_failed)
>> >  		status = intel_dp_long_pulse(intel_dp->attached_connector);
>> >  
>> >  	intel_dp->detect_done = false;
>> > @@ -5692,6 +5715,47 @@ static bool intel_edp_init_connector(struct intel_dp *intel_dp,
>> >  	return false;
>> >  }
>> >  
>> > +static void intel_dp_modeset_retry_work_fn(struct work_struct *work)
>> > +{
>> > +	struct intel_connector *intel_connector;
>> > +	struct drm_connector *connector;
>> > +	struct drm_display_mode *mode;
>> > +	bool verbose_prune = true;
>> > +	bool reprobe = false;
>> > +
>> > +	intel_connector = container_of(work, typeof(*intel_connector),
>> > +				       modeset_retry_work);
>> > +	connector = &intel_connector->base;
>> > +
>> > +	/* Grab the locks before changing connector property*/
>> > +	mutex_lock(&connector->dev->mode_config.mutex);
>> > +	DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n", connector->base.id,
>> > +		      connector->name);
>> > +	list_for_each_entry(mode, &connector->modes, head) {
>> > +		mode->status = intel_dp_mode_valid(connector,
>> > +						   mode);
>> > +		if (mode->status != MODE_OK)
>> > +			reprobe = true;
>> > +	}
>> > +	drm_mode_prune_invalid(connector->dev, &connector->modes,
>> > +			       verbose_prune);
>> > +
>> > +	/* Set connector link status to BAD only if modeset required
>> > +	 * for the current mode, if mode list changed then just send uevent
>> > +	 * so that it can reprobe the connectors and validate modes and do
>> > +	 * a modeset on a different valid mode.
>> > +	 */
>> > +	if (!reprobe) {
>> > +		connector->link_status = DRM_MODE_LINK_STATUS_BAD;
>> > +		intel_dp_set_link_status_property(connector,
>> > +						  DRM_MODE_LINK_STATUS_BAD);
>> > +	}
>> 
>> 
>> I think the link status property should be set to bad unconditionally
>> here. If the current link is bad, it is bad right now independent of
>> modes fitting into the fallback link parameters.
>> 
>> Which makes me think, unless I'm missing something, that you might be
>> able to prune the invalid modes and set the property right away when
>> link training fails, and only use the work to do
>> drm_kms_helper_hotplug_event.
>>
>
> The problem with setting the link_status property BAD irrespective of
> the mode pruning is that, if the modes gets pruned and we set the
> link_sttaus to BAD Chris Wilson's driver checks that the link status
> is BAD and he first tries to attempt the modeset at the current mode
> without calling mode_valid, and that results in a failure in
> enocder->compute_config since now the mode does not fit and the pipe
> cannot be configured. This creates a lot of warnings/errors/kernel
> crash eventually.  So the best way is to set the link status as bad
> only when we want to force the modeset at the current mode, if the
> modes get pruned then in any case userspace will do another modeset at
> the next lower mode.

Why would the userspace driver retry the same mode without refreshing
the mode list first if link status is bad?

If the link is bad, the link is *bad*, regardless of whether the current
mode might eventually work or not. An interface that reports good on
some values of bad is inconsistent (related reading [1]). IMO the
userspace should first figure out if the current mode is valid or not,
and then decide what to do.

Chris, any comments?

Side note, the kernel must not crash depending on what the userspace
does.

BR,
Jani.


[1] http://sweng.the-davies.net/Home/rustys-api-design-manifesto

>
> Manasi 
>> > +	mutex_unlock(&connector->dev->mode_config.mutex);
>> > +
>> > +	/* Send Hotplug uevent so userspace can reprobe */
>> > +	drm_kms_helper_hotplug_event(connector->dev);
>> > +}
>> > +
>> >  bool
>> >  intel_dp_init_connector(struct intel_digital_port *intel_dig_port,
>> >  			struct intel_connector *intel_connector)
>> > @@ -5704,6 +5768,10 @@ static bool intel_edp_init_connector(struct intel_dp *intel_dp,
>> >  	enum port port = intel_dig_port->port;
>> >  	int type;
>> >  
>> > +	/* Initialize the work for modeset in case of link train failure */
>> > +	INIT_WORK(&intel_connector->modeset_retry_work,
>> > +		  intel_dp_modeset_retry_work_fn);
>> > +
>> >  	if (WARN(intel_dig_port->max_lanes < 1,
>> >  		 "Not enough lanes (%d) for DP on port %c\n",
>> >  		 intel_dig_port->max_lanes, port_name(port)))
>> > diff --git a/drivers/gpu/drm/i915/intel_dp_link_training.c b/drivers/gpu/drm/i915/intel_dp_link_training.c
>> > index 0048b52..10f81ab 100644
>> > --- a/drivers/gpu/drm/i915/intel_dp_link_training.c
>> > +++ b/drivers/gpu/drm/i915/intel_dp_link_training.c
>> > @@ -310,9 +310,15 @@ void intel_dp_stop_link_train(struct intel_dp *intel_dp)
>> >  				DP_TRAINING_PATTERN_DISABLE);
>> >  }
>> >  
>> > -void
>> > +bool
>> >  intel_dp_start_link_train(struct intel_dp *intel_dp)
>> >  {
>> > -	intel_dp_link_training_clock_recovery(intel_dp);
>> > -	intel_dp_link_training_channel_equalization(intel_dp);
>> > +	bool ret;
>> > +
>> > +	if (intel_dp_link_training_clock_recovery(intel_dp)) {
>> > +		ret = intel_dp_link_training_channel_equalization(intel_dp);
>> > +		if (ret)
>> > +			return true;
>> > +	}
>> > +	return false;
>> >  }
>> > diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
>> > index bc25b2b..a54e9b7 100644
>> > --- a/drivers/gpu/drm/i915/intel_drv.h
>> > +++ b/drivers/gpu/drm/i915/intel_drv.h
>> > @@ -312,6 +312,9 @@ struct intel_connector {
>> >  	void *port; /* store this opaque as its illegal to dereference it */
>> >  
>> >  	struct intel_dp *mst_port;
>> > +
>> > +	/* Work struct to schedule a uevent on link train failure */
>> > +	struct work_struct modeset_retry_work;
>> >  };
>> >  
>> >  struct dpll {
>> > @@ -1402,7 +1405,7 @@ void intel_dp_set_link_params(struct intel_dp *intel_dp,
>> >  			      bool link_mst);
>> >  void intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp,
>> >  					     int link_rate, uint8_t lane_count);
>> > -void intel_dp_start_link_train(struct intel_dp *intel_dp);
>> > +bool intel_dp_start_link_train(struct intel_dp *intel_dp);
>> >  void intel_dp_stop_link_train(struct intel_dp *intel_dp);
>> >  void intel_dp_sink_dpms(struct intel_dp *intel_dp, int mode);
>> >  void intel_dp_encoder_reset(struct drm_encoder *encoder);
>> 
>> -- 
>> Jani Nikula, Intel Open Source Technology Center

-- 
Jani Nikula, Intel Open Source Technology Center
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Re: [PATCH v2 4/4] drm/i915: Implement Link Rate fallback on Link training failure

[Manasi Navare]

On Tue, Nov 01, 2016 at 09:16:28PM +0200, Jani Nikula wrote:
> On Tue, 01 Nov 2016, Manasi Navare <manasi.d.navare@intel.com> wrote:
> > On Tue, Nov 01, 2016 at 10:49:14AM +0200, Jani Nikula wrote:
> >> On Sat, 29 Oct 2016, Manasi Navare <manasi.d.navare@intel.com> wrote:
> >> > If link training at a link rate optimal for a particular
> >> > mode fails during modeset's atomic commit phase, then we
> >> > let the modeset complete and then retry. We save the link rate
> >> > value at which link training failed, update the link status property
> >> > to "BAD" and use a lower link rate to prune the modes. It will redo
> >> > the modeset on the current mode at lower link rate or if the current
> >> > mode gets pruned due to lower link constraints then, it will send a
> >> > hotplug uevent for userspace to handle it.
> >> >
> >> > This is also required to pass DP CTS tests 4.3.1.3, 4.3.1.4,
> >> > 4.3.1.6.
> >> >
> >> > v2:
> >> > * Squashed a few patches (Jani Nikula)
> >> >
> >> > Cc: Jani Nikula <jani.nikula@linux.intel.com>
> >> > Cc: Daniel Vetter <daniel.vetter@intel.com>
> >> > Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
> >> > Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
> >> > ---
> >> >  drivers/gpu/drm/drm_atomic_helper.c           |  4 ++
> >> >  drivers/gpu/drm/i915/intel_ddi.c              | 23 ++++++++-
> >> >  drivers/gpu/drm/i915/intel_dp.c               | 74 +++++++++++++++++++++++++--
> >> >  drivers/gpu/drm/i915/intel_dp_link_training.c | 12 +++--
> >> >  drivers/gpu/drm/i915/intel_drv.h              |  5 +-
> >> >  5 files changed, 110 insertions(+), 8 deletions(-)
> >> >
> >> > diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> >> > index 75ad01d..a3df3a4 100644
> >> > --- a/drivers/gpu/drm/drm_atomic_helper.c
> >> > +++ b/drivers/gpu/drm/drm_atomic_helper.c
> >> > @@ -519,6 +519,10 @@ static int handle_conflicting_encoders(struct drm_atomic_state *state,
> >> >  					       connector_state);
> >> >  		if (ret)
> >> >  			return ret;
> >> > +
> >> > +		crtc_state = drm_atomic_get_existing_crtc_state(state, connector->state->crtc);
> >> > +		if (connector->link_status == DRM_MODE_LINK_STATUS_BAD)
> >> > +			crtc_state->connectors_changed = true;
> >> >  	}
> >> >  
> >> >  	/*
> >> > diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
> >> > index 938ac4d..319eeca 100644
> >> > --- a/drivers/gpu/drm/i915/intel_ddi.c
> >> > +++ b/drivers/gpu/drm/i915/intel_ddi.c
> >> > @@ -1684,6 +1684,8 @@ static void intel_ddi_pre_enable_dp(struct intel_encoder *encoder,
> >> >  	struct intel_dp *intel_dp = enc_to_intel_dp(&encoder->base);
> >> >  	struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
> >> >  	enum port port = intel_ddi_get_encoder_port(encoder);
> >> > +	struct intel_connector *intel_connector = intel_dp->attached_connector;
> >> > +	struct drm_connector *connector = &intel_connector->base;
> >> >  
> >> >  	intel_dp_set_link_params(intel_dp, link_rate, lane_count,
> >> >  				 link_mst);
> >> > @@ -1694,7 +1696,26 @@ static void intel_ddi_pre_enable_dp(struct intel_encoder *encoder,
> >> >  	intel_prepare_dp_ddi_buffers(encoder);
> >> >  	intel_ddi_init_dp_buf_reg(encoder);
> >> >  	intel_dp_sink_dpms(intel_dp, DRM_MODE_DPMS_ON);
> >> > -	intel_dp_start_link_train(intel_dp);
> >> > +	if (!intel_dp_start_link_train(intel_dp)) {
> >> > +		DRM_DEBUG_KMS("Link Training failed at link rate = %d, lane count = %d",
> >> > +			      link_rate, lane_count);
> >> > +		intel_dp->link_train_failed = true;
> >> > +		intel_dp_get_link_train_fallback_values(intel_dp, link_rate,
> >> > +							lane_count);
> >> > +		/* Schedule a Hotplug Uevent to userspace to start modeset */
> >> > +		schedule_work(&intel_connector->modeset_retry_work);
> >> 
> >> This is not just about DDI. Need to do this for the other cases too.
> >>
> >
> > Yes, first series will g out for adding this support for DDI, then more patches
> > to expand it to non DDI platforms.
> >
> >  
> >> > +	} else {
> >> > +		DRM_DEBUG_KMS("Link Training Passed at Link Rate = %d, Lane count = %d",
> >> > +			      link_rate, lane_count);
> >> > +		intel_dp->link_train_failed = false;
> >> > +		intel_dp->fallback_link_rate_index = -1;
> >> > +		intel_dp->fallback_link_rate = 0;
> >> > +		intel_dp->fallback_lane_count = 0;
> >> > +		connector->link_status = DRM_MODE_LINK_STATUS_GOOD;
> >> > +		intel_dp_set_link_status_property(connector,
> >> > +						  DRM_MODE_LINK_STATUS_GOOD);
> >> 
> >> Looks like you never actually read connector->link_status... Why do you
> >> need both connector->link_status and intel_dp->link_train_failed? Do you
> >> think you have 4 states? What are they? Can't this all be in sync with
> >> the property?
> >> 
> >
> > This connector->link_status member of drm_Connector gets read in
> > drm_atomic_helper_check_modeset() in the driver where it reads this
> > and sets crtc_state->connector_Changed to true if this link_status
> > has changed.
> > This is required so that the driver does a complete modeset.
> > This connector->link_status was in sync with the property. But reading the
> > drm_object property in drm_atomic_helper_Check_modeset was causing the system to
> > not boot.
> > intel_dp->link_train_failed also just indicates if the link failed, I will have to see
> > if i can just use connector->link_status for this purpose. 
> 
> Please do. Usually if you add more than one variable for essentially the
> same thing, you'll end up having combinations of the variables (states)
> that you should not be in. At least you should have a clear idea what
> the states are where link_train_failed and link_status disagree.
>

I will try to converge these.
How do we handle the case where it has tried all possible fallback values,
lowest link rate and lowest lane count, now the link is still bad,
DPR expects driver to stop link training with ERROR that link training
is unsuccessful even after trying fallback. In this case we should not
try to retrain again and in that case I was just setting link_train_failed
to false again. Do you have any suggestions on how to handle this case, do we
send the uevent in this case as well? But then we dont have fallback values since
we have exhausted all fallback values.

 
> >
> >> > +	}
> >> > +
> >> >  	if (port != PORT_A || INTEL_GEN(dev_priv) >= 9)
> >> >  		intel_dp_stop_link_train(intel_dp);
> >> >  }
> >> > diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> >> > index fb4fcdd..d1f0e2c 100644
> >> > --- a/drivers/gpu/drm/i915/intel_dp.c
> >> > +++ b/drivers/gpu/drm/i915/intel_dp.c
> >> > @@ -354,8 +354,14 @@ void intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp,
> >> >  		target_clock = fixed_mode->clock;
> >> >  	}
> >> >  
> >> > -	max_link_clock = intel_dp_max_link_rate(intel_dp);
> >> > -	max_lanes = intel_dp_max_lane_count(intel_dp);
> >> > +	/* Prune the modes using the fallback link rate/lane count */
> >> > +	if (intel_dp->link_train_failed) {
> >> > +		max_link_clock = intel_dp->fallback_link_rate;
> >> > +		max_lanes = intel_dp->fallback_lane_count;
> >> > +	} else {
> >> > +		max_link_clock = intel_dp_max_link_rate(intel_dp);
> >> > +		max_lanes = intel_dp_max_lane_count(intel_dp);
> >> > +	}
> >> >  
> >> >  	max_rate = intel_dp_max_data_rate(max_link_clock, max_lanes);
> >> >  	mode_rate = intel_dp_link_required(target_clock, 18);
> >> > @@ -1640,6 +1646,12 @@ static int intel_dp_compute_bpp(struct intel_dp *intel_dp,
> >> >  	if (adjusted_mode->flags & DRM_MODE_FLAG_DBLCLK)
> >> >  		return false;
> >> >  
> >> > +	/* Fall back to lower link rate in case of failure in previous modeset */
> >> > +	if (intel_dp->link_train_failed) {
> >> > +		min_lane_count = max_lane_count = intel_dp->fallback_lane_count;
> >> > +		min_clock = max_clock = intel_dp->fallback_link_rate_index;
> >> > +	}
> >> > +
> >> 
> >> My general feeling is that there's starting to be a bit too much special
> >> casing around the fallback values. I'm not decided we need to fix this
> >> right away in this series, or whether it can be follow-up work.
> >> 
> >> One idea is to compute the common rates and lanes once when they're
> >> first needed, and all of the helpers would use that info. The fallback
> >> code would just trim those, and the conditional fallback stuff could be
> >> removed from all over the place.
> >>
> >
> > These fallback values get computed in a separate helper function that
> > I have added intel_dp_get_link_train_fallback_values. It is the
> > previous patch.  I store the fallback values in intel_dp one at a time
> > because for that iteration of modeset we only need to try the
> > fallback_link_rate and fallback_lane_count so we dont need an array
> > here.
> 
> Sure. I'm *not* referring to my earlier suggestion of storing failing
> link rate, lane count pairs (although I think we'll need that
> eventually).
> 
> > Are you suggesting just changing the common_rates array itself to get
> > trimmed to use the trimmed fallback values after link training fails?
> > Could you please elaborate your thought?
> 
> I'm not saying you should change this now. But having a lot of code
> check some fallback stuff is ugly and error prone. I'm just documenting
> the ideas to make this better.
> 
> I think this could be fixed by storing the common rates array and max
> lanes in intel_dp, instead of having them locally in a few functions,
> and then making the link rate and lane counting functions aware of the
> fallback stuff. Either the functions would check for the fallbacks,
> centralizing the checks in one place, and/or the fallback code would
> modify the common values stored in intel_dp, so that the link rate and
> lane counting functions would just work with the fallbacks. Code would
> be simpler overall.
> 

Again this might involve a lot more changes since we would have to change
all the helper functions that curerntly calculate max lanes and common_rates
but this can definitely be done in the next round of clean up after these 
patches land. But nevertheless I will see if I can update the common_rates
array now with fallback values instead of storing fallbck values separately
in the intel_dp structure.

Manasi
> >  
> >> >  	DRM_DEBUG_KMS("DP link computation with max lane count %i "
> >> >  		      "max bw %d pixel clock %iKHz\n",
> >> >  		      max_lane_count, common_rates[max_clock],
> >> > @@ -4423,6 +4435,13 @@ static bool intel_digital_port_connected(struct drm_i915_private *dev_priv,
> >> >  		intel_dp->compliance_test_active = 0;
> >> >  		intel_dp->compliance_test_type = 0;
> >> >  		intel_dp->compliance_test_data = 0;
> >> > +		intel_dp->link_train_failed = false;
> >> > +		intel_dp->fallback_link_rate_index = -1;
> >> > +		intel_dp->fallback_link_rate = 0;
> >> > +		intel_dp->fallback_lane_count = 0;
> >> > +		connector->link_status = DRM_MODE_LINK_STATUS_GOOD;
> >> > +		intel_dp_set_link_status_property(connector,
> >> > +						  DRM_MODE_LINK_STATUS_GOOD);
> >> >  
> >> >  		if (intel_dp->is_mst) {
> >> >  			DRM_DEBUG_KMS("MST device may have disappeared %d vs %d\n",
> >> > @@ -4514,8 +4533,12 @@ static bool intel_digital_port_connected(struct drm_i915_private *dev_priv,
> >> >  	DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n",
> >> >  		      connector->base.id, connector->name);
> >> >  
> >> > +	/* If this is a retry due to link trianing failure */
> >> > +	if (status == connector_status_connected && intel_dp->link_train_failed)
> >> > +		return status;
> >> > +
> >> >  	/* If full detect is not performed yet, do a full detect */
> >> > -	if (!intel_dp->detect_done)
> >> > +	if (!intel_dp->detect_done && !intel_dp->link_train_failed)
> >> >  		status = intel_dp_long_pulse(intel_dp->attached_connector);
> >> >  
> >> >  	intel_dp->detect_done = false;
> >> > @@ -5692,6 +5715,47 @@ static bool intel_edp_init_connector(struct intel_dp *intel_dp,
> >> >  	return false;
> >> >  }
> >> >  
> >> > +static void intel_dp_modeset_retry_work_fn(struct work_struct *work)
> >> > +{
> >> > +	struct intel_connector *intel_connector;
> >> > +	struct drm_connector *connector;
> >> > +	struct drm_display_mode *mode;
> >> > +	bool verbose_prune = true;
> >> > +	bool reprobe = false;
> >> > +
> >> > +	intel_connector = container_of(work, typeof(*intel_connector),
> >> > +				       modeset_retry_work);
> >> > +	connector = &intel_connector->base;
> >> > +
> >> > +	/* Grab the locks before changing connector property*/
> >> > +	mutex_lock(&connector->dev->mode_config.mutex);
> >> > +	DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n", connector->base.id,
> >> > +		      connector->name);
> >> > +	list_for_each_entry(mode, &connector->modes, head) {
> >> > +		mode->status = intel_dp_mode_valid(connector,
> >> > +						   mode);
> >> > +		if (mode->status != MODE_OK)
> >> > +			reprobe = true;
> >> > +	}
> >> > +	drm_mode_prune_invalid(connector->dev, &connector->modes,
> >> > +			       verbose_prune);
> >> > +
> >> > +	/* Set connector link status to BAD only if modeset required
> >> > +	 * for the current mode, if mode list changed then just send uevent
> >> > +	 * so that it can reprobe the connectors and validate modes and do
> >> > +	 * a modeset on a different valid mode.
> >> > +	 */
> >> > +	if (!reprobe) {
> >> > +		connector->link_status = DRM_MODE_LINK_STATUS_BAD;
> >> > +		intel_dp_set_link_status_property(connector,
> >> > +						  DRM_MODE_LINK_STATUS_BAD);
> >> > +	}
> >> 
> >> 
> >> I think the link status property should be set to bad unconditionally
> >> here. If the current link is bad, it is bad right now independent of
> >> modes fitting into the fallback link parameters.
> >> 
> >> Which makes me think, unless I'm missing something, that you might be
> >> able to prune the invalid modes and set the property right away when
> >> link training fails, and only use the work to do
> >> drm_kms_helper_hotplug_event.
> >>
> >
> > The problem with setting the link_status property BAD irrespective of
> > the mode pruning is that, if the modes gets pruned and we set the
> > link_sttaus to BAD Chris Wilson's driver checks that the link status
> > is BAD and he first tries to attempt the modeset at the current mode
> > without calling mode_valid, and that results in a failure in
> > enocder->compute_config since now the mode does not fit and the pipe
> > cannot be configured. This creates a lot of warnings/errors/kernel
> > crash eventually.  So the best way is to set the link status as bad
> > only when we want to force the modeset at the current mode, if the
> > modes get pruned then in any case userspace will do another modeset at
> > the next lower mode.
> 
> Why would the userspace driver retry the same mode without refreshing
> the mode list first if link status is bad?
> 
> If the link is bad, the link is *bad*, regardless of whether the current
> mode might eventually work or not. An interface that reports good on
> some values of bad is inconsistent (related reading [1]). IMO the
> userspace should first figure out if the current mode is valid or not,
> and then decide what to do.
> 
> Chris, any comments?
> 
> Side note, the kernel must not crash depending on what the userspace
> does.
> 
> BR,
> Jani.
> 

Chris, yes I think it is a good idea to always call mode_valid first on recieveing
link_status as BAD and then calling setcrtc to set the current mode or whatever valid mode
is. Then I would not need to set link status BAD conditionally in the driver.
Could you make this change in your link_status patch and resend it to me?

Manasi

> 
> [1] http://sweng.the-davies.net/Home/rustys-api-design-manifesto
> 
> >
> > Manasi 
> >> > +	mutex_unlock(&connector->dev->mode_config.mutex);
> >> > +
> >> > +	/* Send Hotplug uevent so userspace can reprobe */
> >> > +	drm_kms_helper_hotplug_event(connector->dev);
> >> > +}
> >> > +
> >> >  bool
> >> >  intel_dp_init_connector(struct intel_digital_port *intel_dig_port,
> >> >  			struct intel_connector *intel_connector)
> >> > @@ -5704,6 +5768,10 @@ static bool intel_edp_init_connector(struct intel_dp *intel_dp,
> >> >  	enum port port = intel_dig_port->port;
> >> >  	int type;
> >> >  
> >> > +	/* Initialize the work for modeset in case of link train failure */
> >> > +	INIT_WORK(&intel_connector->modeset_retry_work,
> >> > +		  intel_dp_modeset_retry_work_fn);
> >> > +
> >> >  	if (WARN(intel_dig_port->max_lanes < 1,
> >> >  		 "Not enough lanes (%d) for DP on port %c\n",
> >> >  		 intel_dig_port->max_lanes, port_name(port)))
> >> > diff --git a/drivers/gpu/drm/i915/intel_dp_link_training.c b/drivers/gpu/drm/i915/intel_dp_link_training.c
> >> > index 0048b52..10f81ab 100644
> >> > --- a/drivers/gpu/drm/i915/intel_dp_link_training.c
> >> > +++ b/drivers/gpu/drm/i915/intel_dp_link_training.c
> >> > @@ -310,9 +310,15 @@ void intel_dp_stop_link_train(struct intel_dp *intel_dp)
> >> >  				DP_TRAINING_PATTERN_DISABLE);
> >> >  }
> >> >  
> >> > -void
> >> > +bool
> >> >  intel_dp_start_link_train(struct intel_dp *intel_dp)
> >> >  {
> >> > -	intel_dp_link_training_clock_recovery(intel_dp);
> >> > -	intel_dp_link_training_channel_equalization(intel_dp);
> >> > +	bool ret;
> >> > +
> >> > +	if (intel_dp_link_training_clock_recovery(intel_dp)) {
> >> > +		ret = intel_dp_link_training_channel_equalization(intel_dp);
> >> > +		if (ret)
> >> > +			return true;
> >> > +	}
> >> > +	return false;
> >> >  }
> >> > diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> >> > index bc25b2b..a54e9b7 100644
> >> > --- a/drivers/gpu/drm/i915/intel_drv.h
> >> > +++ b/drivers/gpu/drm/i915/intel_drv.h
> >> > @@ -312,6 +312,9 @@ struct intel_connector {
> >> >  	void *port; /* store this opaque as its illegal to dereference it */
> >> >  
> >> >  	struct intel_dp *mst_port;
> >> > +
> >> > +	/* Work struct to schedule a uevent on link train failure */
> >> > +	struct work_struct modeset_retry_work;
> >> >  };
> >> >  
> >> >  struct dpll {
> >> > @@ -1402,7 +1405,7 @@ void intel_dp_set_link_params(struct intel_dp *intel_dp,
> >> >  			      bool link_mst);
> >> >  void intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp,
> >> >  					     int link_rate, uint8_t lane_count);
> >> > -void intel_dp_start_link_train(struct intel_dp *intel_dp);
> >> > +bool intel_dp_start_link_train(struct intel_dp *intel_dp);
> >> >  void intel_dp_stop_link_train(struct intel_dp *intel_dp);
> >> >  void intel_dp_sink_dpms(struct intel_dp *intel_dp, int mode);
> >> >  void intel_dp_encoder_reset(struct drm_encoder *encoder);
> >> 
> >> -- 
> >> Jani Nikula, Intel Open Source Technology Center
> 
> -- 
> Jani Nikula, Intel Open Source Technology Center
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Re: [PATCH v2 4/4] drm/i915: Implement Link Rate fallback on Link training failure

[Manasi Navare]

On Tue, Nov 01, 2016 at 12:34:37PM -0700, Manasi Navare wrote:
> On Tue, Nov 01, 2016 at 09:16:28PM +0200, Jani Nikula wrote:
> > On Tue, 01 Nov 2016, Manasi Navare <manasi.d.navare@intel.com> wrote:
> > > On Tue, Nov 01, 2016 at 10:49:14AM +0200, Jani Nikula wrote:
> > >> On Sat, 29 Oct 2016, Manasi Navare <manasi.d.navare@intel.com> wrote:
> > >> > If link training at a link rate optimal for a particular
> > >> > mode fails during modeset's atomic commit phase, then we
> > >> > let the modeset complete and then retry. We save the link rate
> > >> > value at which link training failed, update the link status property
> > >> > to "BAD" and use a lower link rate to prune the modes. It will redo
> > >> > the modeset on the current mode at lower link rate or if the current
> > >> > mode gets pruned due to lower link constraints then, it will send a
> > >> > hotplug uevent for userspace to handle it.
> > >> >
> > >> > This is also required to pass DP CTS tests 4.3.1.3, 4.3.1.4,
> > >> > 4.3.1.6.
> > >> >
> > >> > v2:
> > >> > * Squashed a few patches (Jani Nikula)
> > >> >
> > >> > Cc: Jani Nikula <jani.nikula@linux.intel.com>
> > >> > Cc: Daniel Vetter <daniel.vetter@intel.com>
> > >> > Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
> > >> > Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
> > >> > ---
> > >> >  drivers/gpu/drm/drm_atomic_helper.c           |  4 ++
> > >> >  drivers/gpu/drm/i915/intel_ddi.c              | 23 ++++++++-
> > >> >  drivers/gpu/drm/i915/intel_dp.c               | 74 +++++++++++++++++++++++++--
> > >> >  drivers/gpu/drm/i915/intel_dp_link_training.c | 12 +++--
> > >> >  drivers/gpu/drm/i915/intel_drv.h              |  5 +-
> > >> >  5 files changed, 110 insertions(+), 8 deletions(-)
> > >> >
> > >> > diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> > >> > index 75ad01d..a3df3a4 100644
> > >> > --- a/drivers/gpu/drm/drm_atomic_helper.c
> > >> > +++ b/drivers/gpu/drm/drm_atomic_helper.c
> > >> > @@ -519,6 +519,10 @@ static int handle_conflicting_encoders(struct drm_atomic_state *state,
> > >> >  					       connector_state);
> > >> >  		if (ret)
> > >> >  			return ret;
> > >> > +
> > >> > +		crtc_state = drm_atomic_get_existing_crtc_state(state, connector->state->crtc);
> > >> > +		if (connector->link_status == DRM_MODE_LINK_STATUS_BAD)
> > >> > +			crtc_state->connectors_changed = true;
> > >> >  	}
> > >> >  
> > >> >  	/*
> > >> > diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
> > >> > index 938ac4d..319eeca 100644
> > >> > --- a/drivers/gpu/drm/i915/intel_ddi.c
> > >> > +++ b/drivers/gpu/drm/i915/intel_ddi.c
> > >> > @@ -1684,6 +1684,8 @@ static void intel_ddi_pre_enable_dp(struct intel_encoder *encoder,
> > >> >  	struct intel_dp *intel_dp = enc_to_intel_dp(&encoder->base);
> > >> >  	struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
> > >> >  	enum port port = intel_ddi_get_encoder_port(encoder);
> > >> > +	struct intel_connector *intel_connector = intel_dp->attached_connector;
> > >> > +	struct drm_connector *connector = &intel_connector->base;
> > >> >  
> > >> >  	intel_dp_set_link_params(intel_dp, link_rate, lane_count,
> > >> >  				 link_mst);
> > >> > @@ -1694,7 +1696,26 @@ static void intel_ddi_pre_enable_dp(struct intel_encoder *encoder,
> > >> >  	intel_prepare_dp_ddi_buffers(encoder);
> > >> >  	intel_ddi_init_dp_buf_reg(encoder);
> > >> >  	intel_dp_sink_dpms(intel_dp, DRM_MODE_DPMS_ON);
> > >> > -	intel_dp_start_link_train(intel_dp);
> > >> > +	if (!intel_dp_start_link_train(intel_dp)) {
> > >> > +		DRM_DEBUG_KMS("Link Training failed at link rate = %d, lane count = %d",
> > >> > +			      link_rate, lane_count);
> > >> > +		intel_dp->link_train_failed = true;
> > >> > +		intel_dp_get_link_train_fallback_values(intel_dp, link_rate,
> > >> > +							lane_count);
> > >> > +		/* Schedule a Hotplug Uevent to userspace to start modeset */
> > >> > +		schedule_work(&intel_connector->modeset_retry_work);
> > >> 
> > >> This is not just about DDI. Need to do this for the other cases too.
> > >>
> > >
> > > Yes, first series will g out for adding this support for DDI, then more patches
> > > to expand it to non DDI platforms.
> > >
> > >  
> > >> > +	} else {
> > >> > +		DRM_DEBUG_KMS("Link Training Passed at Link Rate = %d, Lane count = %d",
> > >> > +			      link_rate, lane_count);
> > >> > +		intel_dp->link_train_failed = false;
> > >> > +		intel_dp->fallback_link_rate_index = -1;
> > >> > +		intel_dp->fallback_link_rate = 0;
> > >> > +		intel_dp->fallback_lane_count = 0;
> > >> > +		connector->link_status = DRM_MODE_LINK_STATUS_GOOD;
> > >> > +		intel_dp_set_link_status_property(connector,
> > >> > +						  DRM_MODE_LINK_STATUS_GOOD);
> > >> 
> > >> Looks like you never actually read connector->link_status... Why do you
> > >> need both connector->link_status and intel_dp->link_train_failed? Do you
> > >> think you have 4 states? What are they? Can't this all be in sync with
> > >> the property?
> > >> 
> > >
> > > This connector->link_status member of drm_Connector gets read in
> > > drm_atomic_helper_check_modeset() in the driver where it reads this
> > > and sets crtc_state->connector_Changed to true if this link_status
> > > has changed.
> > > This is required so that the driver does a complete modeset.
> > > This connector->link_status was in sync with the property. But reading the
> > > drm_object property in drm_atomic_helper_Check_modeset was causing the system to
> > > not boot.
> > > intel_dp->link_train_failed also just indicates if the link failed, I will have to see
> > > if i can just use connector->link_status for this purpose. 
> > 
> > Please do. Usually if you add more than one variable for essentially the
> > same thing, you'll end up having combinations of the variables (states)
> > that you should not be in. At least you should have a clear idea what
> > the states are where link_train_failed and link_status disagree.
> >
> 
> I will try to converge these.
> How do we handle the case where it has tried all possible fallback values,
> lowest link rate and lowest lane count, now the link is still bad,
> DPR expects driver to stop link training with ERROR that link training
> is unsuccessful even after trying fallback. In this case we should not
> try to retrain again and in that case I was just setting link_train_failed
> to false again. Do you have any suggestions on how to handle this case, do we
> send the uevent in this case as well? But then we dont have fallback values since
> we have exhausted all fallback values.
> 
>  
> > >
> > >> > +	}
> > >> > +
> > >> >  	if (port != PORT_A || INTEL_GEN(dev_priv) >= 9)
> > >> >  		intel_dp_stop_link_train(intel_dp);
> > >> >  }
> > >> > diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> > >> > index fb4fcdd..d1f0e2c 100644
> > >> > --- a/drivers/gpu/drm/i915/intel_dp.c
> > >> > +++ b/drivers/gpu/drm/i915/intel_dp.c
> > >> > @@ -354,8 +354,14 @@ void intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp,
> > >> >  		target_clock = fixed_mode->clock;
> > >> >  	}
> > >> >  
> > >> > -	max_link_clock = intel_dp_max_link_rate(intel_dp);
> > >> > -	max_lanes = intel_dp_max_lane_count(intel_dp);
> > >> > +	/* Prune the modes using the fallback link rate/lane count */
> > >> > +	if (intel_dp->link_train_failed) {
> > >> > +		max_link_clock = intel_dp->fallback_link_rate;
> > >> > +		max_lanes = intel_dp->fallback_lane_count;
> > >> > +	} else {
> > >> > +		max_link_clock = intel_dp_max_link_rate(intel_dp);
> > >> > +		max_lanes = intel_dp_max_lane_count(intel_dp);
> > >> > +	}
> > >> >  
> > >> >  	max_rate = intel_dp_max_data_rate(max_link_clock, max_lanes);
> > >> >  	mode_rate = intel_dp_link_required(target_clock, 18);
> > >> > @@ -1640,6 +1646,12 @@ static int intel_dp_compute_bpp(struct intel_dp *intel_dp,
> > >> >  	if (adjusted_mode->flags & DRM_MODE_FLAG_DBLCLK)
> > >> >  		return false;
> > >> >  
> > >> > +	/* Fall back to lower link rate in case of failure in previous modeset */
> > >> > +	if (intel_dp->link_train_failed) {
> > >> > +		min_lane_count = max_lane_count = intel_dp->fallback_lane_count;
> > >> > +		min_clock = max_clock = intel_dp->fallback_link_rate_index;
> > >> > +	}
> > >> > +
> > >> 
> > >> My general feeling is that there's starting to be a bit too much special
> > >> casing around the fallback values. I'm not decided we need to fix this
> > >> right away in this series, or whether it can be follow-up work.
> > >> 
> > >> One idea is to compute the common rates and lanes once when they're
> > >> first needed, and all of the helpers would use that info. The fallback
> > >> code would just trim those, and the conditional fallback stuff could be
> > >> removed from all over the place.
> > >>
> > >
> > > These fallback values get computed in a separate helper function that
> > > I have added intel_dp_get_link_train_fallback_values. It is the
> > > previous patch.  I store the fallback values in intel_dp one at a time
> > > because for that iteration of modeset we only need to try the
> > > fallback_link_rate and fallback_lane_count so we dont need an array
> > > here.
> > 
> > Sure. I'm *not* referring to my earlier suggestion of storing failing
> > link rate, lane count pairs (although I think we'll need that
> > eventually).
> > 
> > > Are you suggesting just changing the common_rates array itself to get
> > > trimmed to use the trimmed fallback values after link training fails?
> > > Could you please elaborate your thought?
> > 
> > I'm not saying you should change this now. But having a lot of code
> > check some fallback stuff is ugly and error prone. I'm just documenting
> > the ideas to make this better.
> > 
> > I think this could be fixed by storing the common rates array and max
> > lanes in intel_dp, instead of having them locally in a few functions,
> > and then making the link rate and lane counting functions aware of the
> > fallback stuff. Either the functions would check for the fallbacks,
> > centralizing the checks in one place, and/or the fallback code would
> > modify the common values stored in intel_dp, so that the link rate and
> > lane counting functions would just work with the fallbacks. Code would
> > be simpler overall.
> > 
> 
> Again this might involve a lot more changes since we would have to change
> all the helper functions that curerntly calculate max lanes and common_rates
> but this can definitely be done in the next round of clean up after these 
> patches land. But nevertheless I will see if I can update the common_rates
> array now with fallback values instead of storing fallbck values separately
> in the intel_dp structure.
> 
> Manasi
> > >  
> > >> >  	DRM_DEBUG_KMS("DP link computation with max lane count %i "
> > >> >  		      "max bw %d pixel clock %iKHz\n",
> > >> >  		      max_lane_count, common_rates[max_clock],
> > >> > @@ -4423,6 +4435,13 @@ static bool intel_digital_port_connected(struct drm_i915_private *dev_priv,
> > >> >  		intel_dp->compliance_test_active = 0;
> > >> >  		intel_dp->compliance_test_type = 0;
> > >> >  		intel_dp->compliance_test_data = 0;
> > >> > +		intel_dp->link_train_failed = false;
> > >> > +		intel_dp->fallback_link_rate_index = -1;
> > >> > +		intel_dp->fallback_link_rate = 0;
> > >> > +		intel_dp->fallback_lane_count = 0;
> > >> > +		connector->link_status = DRM_MODE_LINK_STATUS_GOOD;
> > >> > +		intel_dp_set_link_status_property(connector,
> > >> > +						  DRM_MODE_LINK_STATUS_GOOD);
> > >> >  
> > >> >  		if (intel_dp->is_mst) {
> > >> >  			DRM_DEBUG_KMS("MST device may have disappeared %d vs %d\n",
> > >> > @@ -4514,8 +4533,12 @@ static bool intel_digital_port_connected(struct drm_i915_private *dev_priv,
> > >> >  	DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n",
> > >> >  		      connector->base.id, connector->name);
> > >> >  
> > >> > +	/* If this is a retry due to link trianing failure */
> > >> > +	if (status == connector_status_connected && intel_dp->link_train_failed)
> > >> > +		return status;
> > >> > +
> > >> >  	/* If full detect is not performed yet, do a full detect */
> > >> > -	if (!intel_dp->detect_done)
> > >> > +	if (!intel_dp->detect_done && !intel_dp->link_train_failed)
> > >> >  		status = intel_dp_long_pulse(intel_dp->attached_connector);
> > >> >  
> > >> >  	intel_dp->detect_done = false;
> > >> > @@ -5692,6 +5715,47 @@ static bool intel_edp_init_connector(struct intel_dp *intel_dp,
> > >> >  	return false;
> > >> >  }
> > >> >  
> > >> > +static void intel_dp_modeset_retry_work_fn(struct work_struct *work)
> > >> > +{
> > >> > +	struct intel_connector *intel_connector;
> > >> > +	struct drm_connector *connector;
> > >> > +	struct drm_display_mode *mode;
> > >> > +	bool verbose_prune = true;
> > >> > +	bool reprobe = false;
> > >> > +
> > >> > +	intel_connector = container_of(work, typeof(*intel_connector),
> > >> > +				       modeset_retry_work);
> > >> > +	connector = &intel_connector->base;
> > >> > +
> > >> > +	/* Grab the locks before changing connector property*/
> > >> > +	mutex_lock(&connector->dev->mode_config.mutex);
> > >> > +	DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n", connector->base.id,
> > >> > +		      connector->name);
> > >> > +	list_for_each_entry(mode, &connector->modes, head) {
> > >> > +		mode->status = intel_dp_mode_valid(connector,
> > >> > +						   mode);
> > >> > +		if (mode->status != MODE_OK)
> > >> > +			reprobe = true;
> > >> > +	}
> > >> > +	drm_mode_prune_invalid(connector->dev, &connector->modes,
> > >> > +			       verbose_prune);
> > >> > +
> > >> > +	/* Set connector link status to BAD only if modeset required
> > >> > +	 * for the current mode, if mode list changed then just send uevent
> > >> > +	 * so that it can reprobe the connectors and validate modes and do
> > >> > +	 * a modeset on a different valid mode.
> > >> > +	 */
> > >> > +	if (!reprobe) {
> > >> > +		connector->link_status = DRM_MODE_LINK_STATUS_BAD;
> > >> > +		intel_dp_set_link_status_property(connector,
> > >> > +						  DRM_MODE_LINK_STATUS_BAD);
> > >> > +	}
> > >> 
> > >> 
> > >> I think the link status property should be set to bad unconditionally
> > >> here. If the current link is bad, it is bad right now independent of
> > >> modes fitting into the fallback link parameters.
> > >> 
> > >> Which makes me think, unless I'm missing something, that you might be
> > >> able to prune the invalid modes and set the property right away when
> > >> link training fails, and only use the work to do
> > >> drm_kms_helper_hotplug_event.
> > >>
> > >
> > > The problem with setting the link_status property BAD irrespective of
> > > the mode pruning is that, if the modes gets pruned and we set the
> > > link_sttaus to BAD Chris Wilson's driver checks that the link status
> > > is BAD and he first tries to attempt the modeset at the current mode
> > > without calling mode_valid, and that results in a failure in
> > > enocder->compute_config since now the mode does not fit and the pipe
> > > cannot be configured. This creates a lot of warnings/errors/kernel
> > > crash eventually.  So the best way is to set the link status as bad
> > > only when we want to force the modeset at the current mode, if the
> > > modes get pruned then in any case userspace will do another modeset at
> > > the next lower mode.
> > 
> > Why would the userspace driver retry the same mode without refreshing
> > the mode list first if link status is bad?
> > 
> > If the link is bad, the link is *bad*, regardless of whether the current
> > mode might eventually work or not. An interface that reports good on
> > some values of bad is inconsistent (related reading [1]). IMO the
> > userspace should first figure out if the current mode is valid or not,
> > and then decide what to do.
> > 
> > Chris, any comments?
> > 
> > Side note, the kernel must not crash depending on what the userspace
> > does.
> > 
> > BR,
> > Jani.
> > 
> 
> Chris, yes I think it is a good idea to always call mode_valid first on recieveing
> link_status as BAD and then calling setcrtc to set the current mode or whatever valid mode
> is. Then I would not need to set link status BAD conditionally in the driver.
> Could you make this change in your link_status patch and resend it to me?
> 
> Manasi


Chris,
I was able to further investigate this and I found the problem in my code,
where I had to add a check that only if crtc is present, it will try to configure
the pipe else it will return EINVAL to userspace at much earlier stage and
that fixed the kernel errors (NULL dereferencing) that I was seeing.
So Jani, now I can set the link_status to bad unconditionally and send
a hotplug uevent. I will make these changes and submit the new revision
of patches.

Chris, your link_status patch is good to go!

Manasi
> 
> > 
> > [1] http://sweng.the-davies.net/Home/rustys-api-design-manifesto
> > 
> > >
> > > Manasi 
> > >> > +	mutex_unlock(&connector->dev->mode_config.mutex);
> > >> > +
> > >> > +	/* Send Hotplug uevent so userspace can reprobe */
> > >> > +	drm_kms_helper_hotplug_event(connector->dev);
> > >> > +}
> > >> > +
> > >> >  bool
> > >> >  intel_dp_init_connector(struct intel_digital_port *intel_dig_port,
> > >> >  			struct intel_connector *intel_connector)
> > >> > @@ -5704,6 +5768,10 @@ static bool intel_edp_init_connector(struct intel_dp *intel_dp,
> > >> >  	enum port port = intel_dig_port->port;
> > >> >  	int type;
> > >> >  
> > >> > +	/* Initialize the work for modeset in case of link train failure */
> > >> > +	INIT_WORK(&intel_connector->modeset_retry_work,
> > >> > +		  intel_dp_modeset_retry_work_fn);
> > >> > +
> > >> >  	if (WARN(intel_dig_port->max_lanes < 1,
> > >> >  		 "Not enough lanes (%d) for DP on port %c\n",
> > >> >  		 intel_dig_port->max_lanes, port_name(port)))
> > >> > diff --git a/drivers/gpu/drm/i915/intel_dp_link_training.c b/drivers/gpu/drm/i915/intel_dp_link_training.c
> > >> > index 0048b52..10f81ab 100644
> > >> > --- a/drivers/gpu/drm/i915/intel_dp_link_training.c
> > >> > +++ b/drivers/gpu/drm/i915/intel_dp_link_training.c
> > >> > @@ -310,9 +310,15 @@ void intel_dp_stop_link_train(struct intel_dp *intel_dp)
> > >> >  				DP_TRAINING_PATTERN_DISABLE);
> > >> >  }
> > >> >  
> > >> > -void
> > >> > +bool
> > >> >  intel_dp_start_link_train(struct intel_dp *intel_dp)
> > >> >  {
> > >> > -	intel_dp_link_training_clock_recovery(intel_dp);
> > >> > -	intel_dp_link_training_channel_equalization(intel_dp);
> > >> > +	bool ret;
> > >> > +
> > >> > +	if (intel_dp_link_training_clock_recovery(intel_dp)) {
> > >> > +		ret = intel_dp_link_training_channel_equalization(intel_dp);
> > >> > +		if (ret)
> > >> > +			return true;
> > >> > +	}
> > >> > +	return false;
> > >> >  }
> > >> > diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> > >> > index bc25b2b..a54e9b7 100644
> > >> > --- a/drivers/gpu/drm/i915/intel_drv.h
> > >> > +++ b/drivers/gpu/drm/i915/intel_drv.h
> > >> > @@ -312,6 +312,9 @@ struct intel_connector {
> > >> >  	void *port; /* store this opaque as its illegal to dereference it */
> > >> >  
> > >> >  	struct intel_dp *mst_port;
> > >> > +
> > >> > +	/* Work struct to schedule a uevent on link train failure */
> > >> > +	struct work_struct modeset_retry_work;
> > >> >  };
> > >> >  
> > >> >  struct dpll {
> > >> > @@ -1402,7 +1405,7 @@ void intel_dp_set_link_params(struct intel_dp *intel_dp,
> > >> >  			      bool link_mst);
> > >> >  void intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp,
> > >> >  					     int link_rate, uint8_t lane_count);
> > >> > -void intel_dp_start_link_train(struct intel_dp *intel_dp);
> > >> > +bool intel_dp_start_link_train(struct intel_dp *intel_dp);
> > >> >  void intel_dp_stop_link_train(struct intel_dp *intel_dp);
> > >> >  void intel_dp_sink_dpms(struct intel_dp *intel_dp, int mode);
> > >> >  void intel_dp_encoder_reset(struct drm_encoder *encoder);
> > >> 
> > >> -- 
> > >> Jani Nikula, Intel Open Source Technology Center
> > 
> > -- 
> > Jani Nikula, Intel Open Source Technology Center
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/intel-gfx
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[PATCH v3 4/4] drm/i915: Implement Link Rate fallback on Link training failure

[Manasi Navare]

If link training at a link rate optimal for a particular
mode fails during modeset's atomic commit phase, then we
let the modeset complete and then retry. We save the link rate
value at which link training failed, update the link status property
to "BAD" and use a lower link rate to prune the modes. It will redo
the modeset on the current mode at lower link rate or if the current
mode gets pruned due to lower link constraints then, it will send a
hotplug uevent for userspace to handle it.

This is also required to pass DP CTS tests 4.3.1.3, 4.3.1.4,
4.3.1.6.

v3:
* Set link status property to BAd unconditionally (Jani Nikula)
* Dont use two separate variables link_train_failed and link_status
to indicate same thing (Jani Nikula)
v2:
* Squashed a few patches (Jani Nikula)

Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Daniel Vetter <daniel.vetter@intel.com>
Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
---
 drivers/gpu/drm/drm_atomic_helper.c           |  7 +++
 drivers/gpu/drm/i915/intel_ddi.c              | 22 ++++++++-
 drivers/gpu/drm/i915/intel_dp.c               | 70 ++++++++++++++++++++++++---
 drivers/gpu/drm/i915/intel_dp_link_training.c | 12 +++--
 drivers/gpu/drm/i915/intel_drv.h              |  6 ++-
 5 files changed, 105 insertions(+), 12 deletions(-)

diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index 75ad01d..94b0b3a 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -519,6 +519,13 @@ static int handle_conflicting_encoders(struct drm_atomic_state *state,
 					       connector_state);
 		if (ret)
 			return ret;
+
+		if (connector->state->crtc) {
+			crtc_state = drm_atomic_get_existing_crtc_state(state,
+									connector->state->crtc);
+			if (connector->link_status == DRM_MODE_LINK_STATUS_BAD)
+				crtc_state->connectors_changed = true;
+		}
 	}
 
 	/*
diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
index 938ac4d..a59f8d2 100644
--- a/drivers/gpu/drm/i915/intel_ddi.c
+++ b/drivers/gpu/drm/i915/intel_ddi.c
@@ -1684,6 +1684,8 @@ static void intel_ddi_pre_enable_dp(struct intel_encoder *encoder,
 	struct intel_dp *intel_dp = enc_to_intel_dp(&encoder->base);
 	struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
 	enum port port = intel_ddi_get_encoder_port(encoder);
+	struct intel_connector *intel_connector = intel_dp->attached_connector;
+	struct drm_connector *connector = &intel_connector->base;
 
 	intel_dp_set_link_params(intel_dp, link_rate, lane_count,
 				 link_mst);
@@ -1694,7 +1696,25 @@ static void intel_ddi_pre_enable_dp(struct intel_encoder *encoder,
 	intel_prepare_dp_ddi_buffers(encoder);
 	intel_ddi_init_dp_buf_reg(encoder);
 	intel_dp_sink_dpms(intel_dp, DRM_MODE_DPMS_ON);
-	intel_dp_start_link_train(intel_dp);
+	if (!intel_dp_start_link_train(intel_dp)) {
+		DRM_DEBUG_KMS("Link Training failed at link rate = %d, lane count = %d",
+			      link_rate, lane_count);
+		connector->link_status = DRM_MODE_LINK_STATUS_BAD;
+		intel_dp_get_link_train_fallback_values(intel_dp, link_rate,
+							lane_count);
+		/* Schedule a Hotplug Uevent to userspace to start modeset */
+		schedule_work(&intel_connector->modeset_retry_work);
+	} else {
+		DRM_DEBUG_KMS("Link Training Passed at Link Rate = %d, Lane count = %d",
+			      link_rate, lane_count);
+		intel_dp->fallback_link_rate_index = -1;
+		intel_dp->fallback_link_rate = 0;
+		intel_dp->fallback_lane_count = 0;
+		connector->link_status = DRM_MODE_LINK_STATUS_GOOD;
+		intel_dp_set_link_status_property(connector,
+						  DRM_MODE_LINK_STATUS_GOOD);
+	}
+
 	if (port != PORT_A || INTEL_GEN(dev_priv) >= 9)
 		intel_dp_stop_link_train(intel_dp);
 }
diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index fb4fcdd..659b17f 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -310,9 +310,6 @@ void intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp,
 	int common_len;
 	int link_rate_index = -1;
 
-	if (!intel_dp->link_train_failed)
-		return;
-
 	common_len = intel_dp_common_rates(intel_dp, common_rates);
 	link_rate_index = intel_dp_link_rate_index(intel_dp,
 						   common_rates,
@@ -327,7 +324,6 @@ void intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp,
 		intel_dp->fallback_lane_count = lane_count >> 1;
 	} else {
 		DRM_ERROR("Link Training Unsuccessful\n");
-		intel_dp->link_train_failed = false;
 	}
 }
 
@@ -354,8 +350,14 @@ void intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp,
 		target_clock = fixed_mode->clock;
 	}
 
-	max_link_clock = intel_dp_max_link_rate(intel_dp);
-	max_lanes = intel_dp_max_lane_count(intel_dp);
+	/* Prune the modes using the fallback link rate/lane count */
+	if (connector->link_status == DRM_MODE_LINK_STATUS_BAD) {
+		max_link_clock = intel_dp->fallback_link_rate;
+		max_lanes = intel_dp->fallback_lane_count;
+	} else {
+		max_link_clock = intel_dp_max_link_rate(intel_dp);
+		max_lanes = intel_dp_max_lane_count(intel_dp);
+	}
 
 	max_rate = intel_dp_max_data_rate(max_link_clock, max_lanes);
 	mode_rate = intel_dp_link_required(target_clock, 18);
@@ -1593,6 +1595,7 @@ static int intel_dp_compute_bpp(struct intel_dp *intel_dp,
 	enum port port = dp_to_dig_port(intel_dp)->port;
 	struct intel_crtc *intel_crtc = to_intel_crtc(pipe_config->base.crtc);
 	struct intel_connector *intel_connector = intel_dp->attached_connector;
+	struct drm_connector *connector = &intel_connector->base;
 	int lane_count, clock;
 	int min_lane_count = 1;
 	int max_lane_count = intel_dp_max_lane_count(intel_dp);
@@ -1640,6 +1643,12 @@ static int intel_dp_compute_bpp(struct intel_dp *intel_dp,
 	if (adjusted_mode->flags & DRM_MODE_FLAG_DBLCLK)
 		return false;
 
+	/* Fall back to lower link rate in case of failure in previous modeset */
+	if (connector->link_status == DRM_MODE_LINK_STATUS_BAD) {
+		min_lane_count = max_lane_count = intel_dp->fallback_lane_count;
+		min_clock = max_clock = intel_dp->fallback_link_rate_index;
+	}
+
 	DRM_DEBUG_KMS("DP link computation with max lane count %i "
 		      "max bw %d pixel clock %iKHz\n",
 		      max_lane_count, common_rates[max_clock],
@@ -4423,6 +4432,12 @@ static bool intel_digital_port_connected(struct drm_i915_private *dev_priv,
 		intel_dp->compliance_test_active = 0;
 		intel_dp->compliance_test_type = 0;
 		intel_dp->compliance_test_data = 0;
+		intel_dp->fallback_link_rate_index = -1;
+		intel_dp->fallback_link_rate = 0;
+		intel_dp->fallback_lane_count = 0;
+		connector->link_status = DRM_MODE_LINK_STATUS_GOOD;
+		intel_dp_set_link_status_property(connector,
+						  DRM_MODE_LINK_STATUS_GOOD);
 
 		if (intel_dp->is_mst) {
 			DRM_DEBUG_KMS("MST device may have disappeared %d vs %d\n",
@@ -4514,6 +4529,11 @@ static bool intel_digital_port_connected(struct drm_i915_private *dev_priv,
 	DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n",
 		      connector->base.id, connector->name);
 
+	/* If this is a retry due to link trianing failure */
+	if (status == connector_status_connected &&
+	    connector->link_status == DRM_MODE_LINK_STATUS_BAD)
+		return status;
+
 	/* If full detect is not performed yet, do a full detect */
 	if (!intel_dp->detect_done)
 		status = intel_dp_long_pulse(intel_dp->attached_connector);
@@ -5692,6 +5712,40 @@ static bool intel_edp_init_connector(struct intel_dp *intel_dp,
 	return false;
 }
 
+static void intel_dp_modeset_retry_work_fn(struct work_struct *work)
+{
+	struct intel_connector *intel_connector;
+	struct drm_connector *connector;
+	struct drm_display_mode *mode;
+	bool verbose_prune = true;
+
+	intel_connector = container_of(work, typeof(*intel_connector),
+				       modeset_retry_work);
+	connector = &intel_connector->base;
+
+	/* Grab the locks before changing connector property*/
+	mutex_lock(&connector->dev->mode_config.mutex);
+	DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n", connector->base.id,
+		      connector->name);
+	list_for_each_entry(mode, &connector->modes, head) {
+		mode->status = intel_dp_mode_valid(connector,
+						   mode);
+	}
+	drm_mode_prune_invalid(connector->dev, &connector->modes,
+			       verbose_prune);
+
+	/* Set connector link status to BAD and send a Uevent to notify
+	 * userspace to do a modeset.
+	 */
+	connector->link_status = DRM_MODE_LINK_STATUS_BAD;
+	intel_dp_set_link_status_property(connector,
+					  DRM_MODE_LINK_STATUS_BAD);
+	mutex_unlock(&connector->dev->mode_config.mutex);
+
+	/* Send Hotplug uevent so userspace can reprobe */
+	drm_kms_helper_hotplug_event(connector->dev);
+}
+
 bool
 intel_dp_init_connector(struct intel_digital_port *intel_dig_port,
 			struct intel_connector *intel_connector)
@@ -5704,6 +5758,10 @@ static bool intel_edp_init_connector(struct intel_dp *intel_dp,
 	enum port port = intel_dig_port->port;
 	int type;
 
+	/* Initialize the work for modeset in case of link train failure */
+	INIT_WORK(&intel_connector->modeset_retry_work,
+		  intel_dp_modeset_retry_work_fn);
+
 	if (WARN(intel_dig_port->max_lanes < 1,
 		 "Not enough lanes (%d) for DP on port %c\n",
 		 intel_dig_port->max_lanes, port_name(port)))
diff --git a/drivers/gpu/drm/i915/intel_dp_link_training.c b/drivers/gpu/drm/i915/intel_dp_link_training.c
index 0048b52..10f81ab 100644
--- a/drivers/gpu/drm/i915/intel_dp_link_training.c
+++ b/drivers/gpu/drm/i915/intel_dp_link_training.c
@@ -310,9 +310,15 @@ void intel_dp_stop_link_train(struct intel_dp *intel_dp)
 				DP_TRAINING_PATTERN_DISABLE);
 }
 
-void
+bool
 intel_dp_start_link_train(struct intel_dp *intel_dp)
 {
-	intel_dp_link_training_clock_recovery(intel_dp);
-	intel_dp_link_training_channel_equalization(intel_dp);
+	bool ret;
+
+	if (intel_dp_link_training_clock_recovery(intel_dp)) {
+		ret = intel_dp_link_training_channel_equalization(intel_dp);
+		if (ret)
+			return true;
+	}
+	return false;
 }
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index bc25b2b..c0378a9 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -312,6 +312,9 @@ struct intel_connector {
 	void *port; /* store this opaque as its illegal to dereference it */
 
 	struct intel_dp *mst_port;
+
+	/* Work struct to schedule a uevent on link train failure */
+	struct work_struct modeset_retry_work;
 };
 
 struct dpll {
@@ -900,7 +903,6 @@ struct intel_dp {
 	int fallback_link_rate;
 	uint8_t fallback_lane_count;
 	int fallback_link_rate_index;
-	bool link_train_failed;
 	uint8_t sink_count;
 	bool link_mst;
 	bool has_audio;
@@ -1402,7 +1404,7 @@ void intel_dp_set_link_params(struct intel_dp *intel_dp,
 			      bool link_mst);
 void intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp,
 					     int link_rate, uint8_t lane_count);
-void intel_dp_start_link_train(struct intel_dp *intel_dp);
+bool intel_dp_start_link_train(struct intel_dp *intel_dp);
 void intel_dp_stop_link_train(struct intel_dp *intel_dp);
 void intel_dp_sink_dpms(struct intel_dp *intel_dp, int mode);
 void intel_dp_encoder_reset(struct drm_encoder *encoder);
-- 
1.9.1

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Re: [PATCH v3 4/4] drm/i915: Implement Link Rate fallback on Link training failure

[Manasi Navare]

Jani, could you please take a look at this patch? 
I have addressed your comments on the previous revision.
The common_rates array can be moved into Intel dp
structure in a follow up patch since that would require changes
in a lot of places other than the link rate fallback implementation.

Regards
Manasi

On Wed, Nov 02, 2016 at 01:55:39PM -0700, Manasi Navare wrote:
> If link training at a link rate optimal for a particular
> mode fails during modeset's atomic commit phase, then we
> let the modeset complete and then retry. We save the link rate
> value at which link training failed, update the link status property
> to "BAD" and use a lower link rate to prune the modes. It will redo
> the modeset on the current mode at lower link rate or if the current
> mode gets pruned due to lower link constraints then, it will send a
> hotplug uevent for userspace to handle it.
> 
> This is also required to pass DP CTS tests 4.3.1.3, 4.3.1.4,
> 4.3.1.6.
> 
> v3:
> * Set link status property to BAd unconditionally (Jani Nikula)
> * Dont use two separate variables link_train_failed and link_status
> to indicate same thing (Jani Nikula)
> v2:
> * Squashed a few patches (Jani Nikula)
> 
> Cc: Jani Nikula <jani.nikula@linux.intel.com>
> Cc: Daniel Vetter <daniel.vetter@intel.com>
> Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
> Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
> ---
>  drivers/gpu/drm/drm_atomic_helper.c           |  7 +++
>  drivers/gpu/drm/i915/intel_ddi.c              | 22 ++++++++-
>  drivers/gpu/drm/i915/intel_dp.c               | 70 ++++++++++++++++++++++++---
>  drivers/gpu/drm/i915/intel_dp_link_training.c | 12 +++--
>  drivers/gpu/drm/i915/intel_drv.h              |  6 ++-
>  5 files changed, 105 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> index 75ad01d..94b0b3a 100644
> --- a/drivers/gpu/drm/drm_atomic_helper.c
> +++ b/drivers/gpu/drm/drm_atomic_helper.c
> @@ -519,6 +519,13 @@ static int handle_conflicting_encoders(struct drm_atomic_state *state,
>  					       connector_state);
>  		if (ret)
>  			return ret;
> +
> +		if (connector->state->crtc) {
> +			crtc_state = drm_atomic_get_existing_crtc_state(state,
> +									connector->state->crtc);
> +			if (connector->link_status == DRM_MODE_LINK_STATUS_BAD)
> +				crtc_state->connectors_changed = true;
> +		}
>  	}
>  
>  	/*
> diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
> index 938ac4d..a59f8d2 100644
> --- a/drivers/gpu/drm/i915/intel_ddi.c
> +++ b/drivers/gpu/drm/i915/intel_ddi.c
> @@ -1684,6 +1684,8 @@ static void intel_ddi_pre_enable_dp(struct intel_encoder *encoder,
>  	struct intel_dp *intel_dp = enc_to_intel_dp(&encoder->base);
>  	struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
>  	enum port port = intel_ddi_get_encoder_port(encoder);
> +	struct intel_connector *intel_connector = intel_dp->attached_connector;
> +	struct drm_connector *connector = &intel_connector->base;
>  
>  	intel_dp_set_link_params(intel_dp, link_rate, lane_count,
>  				 link_mst);
> @@ -1694,7 +1696,25 @@ static void intel_ddi_pre_enable_dp(struct intel_encoder *encoder,
>  	intel_prepare_dp_ddi_buffers(encoder);
>  	intel_ddi_init_dp_buf_reg(encoder);
>  	intel_dp_sink_dpms(intel_dp, DRM_MODE_DPMS_ON);
> -	intel_dp_start_link_train(intel_dp);
> +	if (!intel_dp_start_link_train(intel_dp)) {
> +		DRM_DEBUG_KMS("Link Training failed at link rate = %d, lane count = %d",
> +			      link_rate, lane_count);
> +		connector->link_status = DRM_MODE_LINK_STATUS_BAD;
> +		intel_dp_get_link_train_fallback_values(intel_dp, link_rate,
> +							lane_count);
> +		/* Schedule a Hotplug Uevent to userspace to start modeset */
> +		schedule_work(&intel_connector->modeset_retry_work);
> +	} else {
> +		DRM_DEBUG_KMS("Link Training Passed at Link Rate = %d, Lane count = %d",
> +			      link_rate, lane_count);
> +		intel_dp->fallback_link_rate_index = -1;
> +		intel_dp->fallback_link_rate = 0;
> +		intel_dp->fallback_lane_count = 0;
> +		connector->link_status = DRM_MODE_LINK_STATUS_GOOD;
> +		intel_dp_set_link_status_property(connector,
> +						  DRM_MODE_LINK_STATUS_GOOD);
> +	}
> +
>  	if (port != PORT_A || INTEL_GEN(dev_priv) >= 9)
>  		intel_dp_stop_link_train(intel_dp);
>  }
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index fb4fcdd..659b17f 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -310,9 +310,6 @@ void intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp,
>  	int common_len;
>  	int link_rate_index = -1;
>  
> -	if (!intel_dp->link_train_failed)
> -		return;
> -
>  	common_len = intel_dp_common_rates(intel_dp, common_rates);
>  	link_rate_index = intel_dp_link_rate_index(intel_dp,
>  						   common_rates,
> @@ -327,7 +324,6 @@ void intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp,
>  		intel_dp->fallback_lane_count = lane_count >> 1;
>  	} else {
>  		DRM_ERROR("Link Training Unsuccessful\n");
> -		intel_dp->link_train_failed = false;
>  	}
>  }
>  
> @@ -354,8 +350,14 @@ void intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp,
>  		target_clock = fixed_mode->clock;
>  	}
>  
> -	max_link_clock = intel_dp_max_link_rate(intel_dp);
> -	max_lanes = intel_dp_max_lane_count(intel_dp);
> +	/* Prune the modes using the fallback link rate/lane count */
> +	if (connector->link_status == DRM_MODE_LINK_STATUS_BAD) {
> +		max_link_clock = intel_dp->fallback_link_rate;
> +		max_lanes = intel_dp->fallback_lane_count;
> +	} else {
> +		max_link_clock = intel_dp_max_link_rate(intel_dp);
> +		max_lanes = intel_dp_max_lane_count(intel_dp);
> +	}
>  
>  	max_rate = intel_dp_max_data_rate(max_link_clock, max_lanes);
>  	mode_rate = intel_dp_link_required(target_clock, 18);
> @@ -1593,6 +1595,7 @@ static int intel_dp_compute_bpp(struct intel_dp *intel_dp,
>  	enum port port = dp_to_dig_port(intel_dp)->port;
>  	struct intel_crtc *intel_crtc = to_intel_crtc(pipe_config->base.crtc);
>  	struct intel_connector *intel_connector = intel_dp->attached_connector;
> +	struct drm_connector *connector = &intel_connector->base;
>  	int lane_count, clock;
>  	int min_lane_count = 1;
>  	int max_lane_count = intel_dp_max_lane_count(intel_dp);
> @@ -1640,6 +1643,12 @@ static int intel_dp_compute_bpp(struct intel_dp *intel_dp,
>  	if (adjusted_mode->flags & DRM_MODE_FLAG_DBLCLK)
>  		return false;
>  
> +	/* Fall back to lower link rate in case of failure in previous modeset */
> +	if (connector->link_status == DRM_MODE_LINK_STATUS_BAD) {
> +		min_lane_count = max_lane_count = intel_dp->fallback_lane_count;
> +		min_clock = max_clock = intel_dp->fallback_link_rate_index;
> +	}
> +
>  	DRM_DEBUG_KMS("DP link computation with max lane count %i "
>  		      "max bw %d pixel clock %iKHz\n",
>  		      max_lane_count, common_rates[max_clock],
> @@ -4423,6 +4432,12 @@ static bool intel_digital_port_connected(struct drm_i915_private *dev_priv,
>  		intel_dp->compliance_test_active = 0;
>  		intel_dp->compliance_test_type = 0;
>  		intel_dp->compliance_test_data = 0;
> +		intel_dp->fallback_link_rate_index = -1;
> +		intel_dp->fallback_link_rate = 0;
> +		intel_dp->fallback_lane_count = 0;
> +		connector->link_status = DRM_MODE_LINK_STATUS_GOOD;
> +		intel_dp_set_link_status_property(connector,
> +						  DRM_MODE_LINK_STATUS_GOOD);
>  
>  		if (intel_dp->is_mst) {
>  			DRM_DEBUG_KMS("MST device may have disappeared %d vs %d\n",
> @@ -4514,6 +4529,11 @@ static bool intel_digital_port_connected(struct drm_i915_private *dev_priv,
>  	DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n",
>  		      connector->base.id, connector->name);
>  
> +	/* If this is a retry due to link trianing failure */
> +	if (status == connector_status_connected &&
> +	    connector->link_status == DRM_MODE_LINK_STATUS_BAD)
> +		return status;
> +
>  	/* If full detect is not performed yet, do a full detect */
>  	if (!intel_dp->detect_done)
>  		status = intel_dp_long_pulse(intel_dp->attached_connector);
> @@ -5692,6 +5712,40 @@ static bool intel_edp_init_connector(struct intel_dp *intel_dp,
>  	return false;
>  }
>  
> +static void intel_dp_modeset_retry_work_fn(struct work_struct *work)
> +{
> +	struct intel_connector *intel_connector;
> +	struct drm_connector *connector;
> +	struct drm_display_mode *mode;
> +	bool verbose_prune = true;
> +
> +	intel_connector = container_of(work, typeof(*intel_connector),
> +				       modeset_retry_work);
> +	connector = &intel_connector->base;
> +
> +	/* Grab the locks before changing connector property*/
> +	mutex_lock(&connector->dev->mode_config.mutex);
> +	DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n", connector->base.id,
> +		      connector->name);
> +	list_for_each_entry(mode, &connector->modes, head) {
> +		mode->status = intel_dp_mode_valid(connector,
> +						   mode);
> +	}
> +	drm_mode_prune_invalid(connector->dev, &connector->modes,
> +			       verbose_prune);
> +
> +	/* Set connector link status to BAD and send a Uevent to notify
> +	 * userspace to do a modeset.
> +	 */
> +	connector->link_status = DRM_MODE_LINK_STATUS_BAD;
> +	intel_dp_set_link_status_property(connector,
> +					  DRM_MODE_LINK_STATUS_BAD);
> +	mutex_unlock(&connector->dev->mode_config.mutex);
> +
> +	/* Send Hotplug uevent so userspace can reprobe */
> +	drm_kms_helper_hotplug_event(connector->dev);
> +}
> +
>  bool
>  intel_dp_init_connector(struct intel_digital_port *intel_dig_port,
>  			struct intel_connector *intel_connector)
> @@ -5704,6 +5758,10 @@ static bool intel_edp_init_connector(struct intel_dp *intel_dp,
>  	enum port port = intel_dig_port->port;
>  	int type;
>  
> +	/* Initialize the work for modeset in case of link train failure */
> +	INIT_WORK(&intel_connector->modeset_retry_work,
> +		  intel_dp_modeset_retry_work_fn);
> +
>  	if (WARN(intel_dig_port->max_lanes < 1,
>  		 "Not enough lanes (%d) for DP on port %c\n",
>  		 intel_dig_port->max_lanes, port_name(port)))
> diff --git a/drivers/gpu/drm/i915/intel_dp_link_training.c b/drivers/gpu/drm/i915/intel_dp_link_training.c
> index 0048b52..10f81ab 100644
> --- a/drivers/gpu/drm/i915/intel_dp_link_training.c
> +++ b/drivers/gpu/drm/i915/intel_dp_link_training.c
> @@ -310,9 +310,15 @@ void intel_dp_stop_link_train(struct intel_dp *intel_dp)
>  				DP_TRAINING_PATTERN_DISABLE);
>  }
>  
> -void
> +bool
>  intel_dp_start_link_train(struct intel_dp *intel_dp)
>  {
> -	intel_dp_link_training_clock_recovery(intel_dp);
> -	intel_dp_link_training_channel_equalization(intel_dp);
> +	bool ret;
> +
> +	if (intel_dp_link_training_clock_recovery(intel_dp)) {
> +		ret = intel_dp_link_training_channel_equalization(intel_dp);
> +		if (ret)
> +			return true;
> +	}
> +	return false;
>  }
> diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> index bc25b2b..c0378a9 100644
> --- a/drivers/gpu/drm/i915/intel_drv.h
> +++ b/drivers/gpu/drm/i915/intel_drv.h
> @@ -312,6 +312,9 @@ struct intel_connector {
>  	void *port; /* store this opaque as its illegal to dereference it */
>  
>  	struct intel_dp *mst_port;
> +
> +	/* Work struct to schedule a uevent on link train failure */
> +	struct work_struct modeset_retry_work;
>  };
>  
>  struct dpll {
> @@ -900,7 +903,6 @@ struct intel_dp {
>  	int fallback_link_rate;
>  	uint8_t fallback_lane_count;
>  	int fallback_link_rate_index;
> -	bool link_train_failed;
>  	uint8_t sink_count;
>  	bool link_mst;
>  	bool has_audio;
> @@ -1402,7 +1404,7 @@ void intel_dp_set_link_params(struct intel_dp *intel_dp,
>  			      bool link_mst);
>  void intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp,
>  					     int link_rate, uint8_t lane_count);
> -void intel_dp_start_link_train(struct intel_dp *intel_dp);
> +bool intel_dp_start_link_train(struct intel_dp *intel_dp);
>  void intel_dp_stop_link_train(struct intel_dp *intel_dp);
>  void intel_dp_sink_dpms(struct intel_dp *intel_dp, int mode);
>  void intel_dp_encoder_reset(struct drm_encoder *encoder);
> -- 
> 1.9.1
> 
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Re: [PATCH v3 4/4] drm/i915: Implement Link Rate fallback on Link training failure

[Jani Nikula]

On Mon, 07 Nov 2016, Manasi Navare <manasi.d.navare@intel.com> wrote:
> Jani, could you please take a look at this patch? 
> I have addressed your comments on the previous revision.
> The common_rates array can be moved into Intel dp
> structure in a follow up patch since that would require changes
> in a lot of places other than the link rate fallback implementation.

I think this is looking good. I think you need to put this together in a
series that doesn't add something first, and then remove it, i.e. build
a coherent story from the start. It's not that many patches. Then you
need to post all patches on both intel-gfx and dri-devel, preferrably in
a fresh thread, not replying to previous versions. The thread is too
confusing now with so many versions.

Then we need to get r-b and acks for the drm changes. Daniel, can you
help with the last part?

BR,
Jani.


-- 
Jani Nikula, Intel Open Source Technology Center
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Re: [PATCH v3 4/4] drm/i915: Implement Link Rate fallback on Link training failure

[Jani Nikula]

On Wed, 02 Nov 2016, Manasi Navare <manasi.d.navare@intel.com> wrote:
> If link training at a link rate optimal for a particular
> mode fails during modeset's atomic commit phase, then we
> let the modeset complete and then retry. We save the link rate
> value at which link training failed, update the link status property
> to "BAD" and use a lower link rate to prune the modes. It will redo
> the modeset on the current mode at lower link rate or if the current
> mode gets pruned due to lower link constraints then, it will send a
> hotplug uevent for userspace to handle it.
>
> This is also required to pass DP CTS tests 4.3.1.3, 4.3.1.4,
> 4.3.1.6.
>
> v3:
> * Set link status property to BAd unconditionally (Jani Nikula)
> * Dont use two separate variables link_train_failed and link_status
> to indicate same thing (Jani Nikula)
> v2:
> * Squashed a few patches (Jani Nikula)
>
> Cc: Jani Nikula <jani.nikula@linux.intel.com>
> Cc: Daniel Vetter <daniel.vetter@intel.com>
> Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
> Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
> ---
>  drivers/gpu/drm/drm_atomic_helper.c           |  7 +++
>  drivers/gpu/drm/i915/intel_ddi.c              | 22 ++++++++-
>  drivers/gpu/drm/i915/intel_dp.c               | 70 ++++++++++++++++++++++++---
>  drivers/gpu/drm/i915/intel_dp_link_training.c | 12 +++--
>  drivers/gpu/drm/i915/intel_drv.h              |  6 ++-
>  5 files changed, 105 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> index 75ad01d..94b0b3a 100644
> --- a/drivers/gpu/drm/drm_atomic_helper.c
> +++ b/drivers/gpu/drm/drm_atomic_helper.c
> @@ -519,6 +519,13 @@ static int handle_conflicting_encoders(struct drm_atomic_state *state,
>  					       connector_state);
>  		if (ret)
>  			return ret;
> +
> +		if (connector->state->crtc) {
> +			crtc_state = drm_atomic_get_existing_crtc_state(state,
> +									connector->state->crtc);
> +			if (connector->link_status == DRM_MODE_LINK_STATUS_BAD)
> +				crtc_state->connectors_changed = true;
> +		}
>  	}

Could this be a separate patch? Anyway needs to be posted on dri-devel.

>  
>  	/*
> diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
> index 938ac4d..a59f8d2 100644
> --- a/drivers/gpu/drm/i915/intel_ddi.c
> +++ b/drivers/gpu/drm/i915/intel_ddi.c
> @@ -1684,6 +1684,8 @@ static void intel_ddi_pre_enable_dp(struct intel_encoder *encoder,
>  	struct intel_dp *intel_dp = enc_to_intel_dp(&encoder->base);
>  	struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
>  	enum port port = intel_ddi_get_encoder_port(encoder);
> +	struct intel_connector *intel_connector = intel_dp->attached_connector;
> +	struct drm_connector *connector = &intel_connector->base;
>  
>  	intel_dp_set_link_params(intel_dp, link_rate, lane_count,
>  				 link_mst);
> @@ -1694,7 +1696,25 @@ static void intel_ddi_pre_enable_dp(struct intel_encoder *encoder,
>  	intel_prepare_dp_ddi_buffers(encoder);
>  	intel_ddi_init_dp_buf_reg(encoder);
>  	intel_dp_sink_dpms(intel_dp, DRM_MODE_DPMS_ON);
> -	intel_dp_start_link_train(intel_dp);
> +	if (!intel_dp_start_link_train(intel_dp)) {
> +		DRM_DEBUG_KMS("Link Training failed at link rate = %d, lane count = %d",
> +			      link_rate, lane_count);
> +		connector->link_status = DRM_MODE_LINK_STATUS_BAD;

Why does this not use intel_dp_set_link_status_property()?

> +		intel_dp_get_link_train_fallback_values(intel_dp, link_rate,
> +							lane_count);
> +		/* Schedule a Hotplug Uevent to userspace to start modeset */
> +		schedule_work(&intel_connector->modeset_retry_work);
> +	} else {
> +		DRM_DEBUG_KMS("Link Training Passed at Link Rate = %d, Lane count = %d",
> +			      link_rate, lane_count);
> +		intel_dp->fallback_link_rate_index = -1;
> +		intel_dp->fallback_link_rate = 0;
> +		intel_dp->fallback_lane_count = 0;
> +		connector->link_status = DRM_MODE_LINK_STATUS_GOOD;
> +		intel_dp_set_link_status_property(connector,
> +						  DRM_MODE_LINK_STATUS_GOOD);
> +	}
> +
>  	if (port != PORT_A || INTEL_GEN(dev_priv) >= 9)
>  		intel_dp_stop_link_train(intel_dp);
>  }
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index fb4fcdd..659b17f 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -310,9 +310,6 @@ void intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp,
>  	int common_len;
>  	int link_rate_index = -1;
>  
> -	if (!intel_dp->link_train_failed)
> -		return;
> -

You add this in an earlier patch and now remove it?

>  	common_len = intel_dp_common_rates(intel_dp, common_rates);
>  	link_rate_index = intel_dp_link_rate_index(intel_dp,
>  						   common_rates,
> @@ -327,7 +324,6 @@ void intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp,
>  		intel_dp->fallback_lane_count = lane_count >> 1;
>  	} else {
>  		DRM_ERROR("Link Training Unsuccessful\n");
> -		intel_dp->link_train_failed = false;
>  	}
>  }
>  
> @@ -354,8 +350,14 @@ void intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp,
>  		target_clock = fixed_mode->clock;
>  	}
>  
> -	max_link_clock = intel_dp_max_link_rate(intel_dp);
> -	max_lanes = intel_dp_max_lane_count(intel_dp);
> +	/* Prune the modes using the fallback link rate/lane count */
> +	if (connector->link_status == DRM_MODE_LINK_STATUS_BAD) {
> +		max_link_clock = intel_dp->fallback_link_rate;
> +		max_lanes = intel_dp->fallback_lane_count;
> +	} else {
> +		max_link_clock = intel_dp_max_link_rate(intel_dp);
> +		max_lanes = intel_dp_max_lane_count(intel_dp);
> +	}
>  
>  	max_rate = intel_dp_max_data_rate(max_link_clock, max_lanes);
>  	mode_rate = intel_dp_link_required(target_clock, 18);
> @@ -1593,6 +1595,7 @@ static int intel_dp_compute_bpp(struct intel_dp *intel_dp,
>  	enum port port = dp_to_dig_port(intel_dp)->port;
>  	struct intel_crtc *intel_crtc = to_intel_crtc(pipe_config->base.crtc);
>  	struct intel_connector *intel_connector = intel_dp->attached_connector;
> +	struct drm_connector *connector = &intel_connector->base;
>  	int lane_count, clock;
>  	int min_lane_count = 1;
>  	int max_lane_count = intel_dp_max_lane_count(intel_dp);
> @@ -1640,6 +1643,12 @@ static int intel_dp_compute_bpp(struct intel_dp *intel_dp,
>  	if (adjusted_mode->flags & DRM_MODE_FLAG_DBLCLK)
>  		return false;
>  
> +	/* Fall back to lower link rate in case of failure in previous modeset */
> +	if (connector->link_status == DRM_MODE_LINK_STATUS_BAD) {
> +		min_lane_count = max_lane_count = intel_dp->fallback_lane_count;
> +		min_clock = max_clock = intel_dp->fallback_link_rate_index;
> +	}
> +
>  	DRM_DEBUG_KMS("DP link computation with max lane count %i "
>  		      "max bw %d pixel clock %iKHz\n",
>  		      max_lane_count, common_rates[max_clock],
> @@ -4423,6 +4432,12 @@ static bool intel_digital_port_connected(struct drm_i915_private *dev_priv,
>  		intel_dp->compliance_test_active = 0;
>  		intel_dp->compliance_test_type = 0;
>  		intel_dp->compliance_test_data = 0;
> +		intel_dp->fallback_link_rate_index = -1;
> +		intel_dp->fallback_link_rate = 0;
> +		intel_dp->fallback_lane_count = 0;
> +		connector->link_status = DRM_MODE_LINK_STATUS_GOOD;
> +		intel_dp_set_link_status_property(connector,
> +						  DRM_MODE_LINK_STATUS_GOOD);

Seems like it would be a good idea to have this
intel_dp_set_link_status_property() helper set connector->link_status
too.

>  
>  		if (intel_dp->is_mst) {
>  			DRM_DEBUG_KMS("MST device may have disappeared %d vs %d\n",
> @@ -4514,6 +4529,11 @@ static bool intel_digital_port_connected(struct drm_i915_private *dev_priv,
>  	DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n",
>  		      connector->base.id, connector->name);
>  
> +	/* If this is a retry due to link trianing failure */
> +	if (status == connector_status_connected &&
> +	    connector->link_status == DRM_MODE_LINK_STATUS_BAD)
> +		return status;
> +
>  	/* If full detect is not performed yet, do a full detect */
>  	if (!intel_dp->detect_done)
>  		status = intel_dp_long_pulse(intel_dp->attached_connector);
> @@ -5692,6 +5712,40 @@ static bool intel_edp_init_connector(struct intel_dp *intel_dp,
>  	return false;
>  }
>  
> +static void intel_dp_modeset_retry_work_fn(struct work_struct *work)
> +{
> +	struct intel_connector *intel_connector;
> +	struct drm_connector *connector;
> +	struct drm_display_mode *mode;
> +	bool verbose_prune = true;
> +
> +	intel_connector = container_of(work, typeof(*intel_connector),
> +				       modeset_retry_work);
> +	connector = &intel_connector->base;
> +
> +	/* Grab the locks before changing connector property*/
> +	mutex_lock(&connector->dev->mode_config.mutex);
> +	DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n", connector->base.id,
> +		      connector->name);
> +	list_for_each_entry(mode, &connector->modes, head) {
> +		mode->status = intel_dp_mode_valid(connector,
> +						   mode);
> +	}
> +	drm_mode_prune_invalid(connector->dev, &connector->modes,
> +			       verbose_prune);
> +
> +	/* Set connector link status to BAD and send a Uevent to notify
> +	 * userspace to do a modeset.
> +	 */
> +	connector->link_status = DRM_MODE_LINK_STATUS_BAD;
> +	intel_dp_set_link_status_property(connector,
> +					  DRM_MODE_LINK_STATUS_BAD);
> +	mutex_unlock(&connector->dev->mode_config.mutex);
> +
> +	/* Send Hotplug uevent so userspace can reprobe */
> +	drm_kms_helper_hotplug_event(connector->dev);
> +}
> +
>  bool
>  intel_dp_init_connector(struct intel_digital_port *intel_dig_port,
>  			struct intel_connector *intel_connector)
> @@ -5704,6 +5758,10 @@ static bool intel_edp_init_connector(struct intel_dp *intel_dp,
>  	enum port port = intel_dig_port->port;
>  	int type;
>  
> +	/* Initialize the work for modeset in case of link train failure */
> +	INIT_WORK(&intel_connector->modeset_retry_work,
> +		  intel_dp_modeset_retry_work_fn);
> +
>  	if (WARN(intel_dig_port->max_lanes < 1,
>  		 "Not enough lanes (%d) for DP on port %c\n",
>  		 intel_dig_port->max_lanes, port_name(port)))
> diff --git a/drivers/gpu/drm/i915/intel_dp_link_training.c b/drivers/gpu/drm/i915/intel_dp_link_training.c
> index 0048b52..10f81ab 100644
> --- a/drivers/gpu/drm/i915/intel_dp_link_training.c
> +++ b/drivers/gpu/drm/i915/intel_dp_link_training.c
> @@ -310,9 +310,15 @@ void intel_dp_stop_link_train(struct intel_dp *intel_dp)
>  				DP_TRAINING_PATTERN_DISABLE);
>  }
>  
> -void
> +bool
>  intel_dp_start_link_train(struct intel_dp *intel_dp)
>  {
> -	intel_dp_link_training_clock_recovery(intel_dp);
> -	intel_dp_link_training_channel_equalization(intel_dp);
> +	bool ret;
> +
> +	if (intel_dp_link_training_clock_recovery(intel_dp)) {
> +		ret = intel_dp_link_training_channel_equalization(intel_dp);
> +		if (ret)
> +			return true;
> +	}
> +	return false;
>  }
> diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> index bc25b2b..c0378a9 100644
> --- a/drivers/gpu/drm/i915/intel_drv.h
> +++ b/drivers/gpu/drm/i915/intel_drv.h
> @@ -312,6 +312,9 @@ struct intel_connector {
>  	void *port; /* store this opaque as its illegal to dereference it */
>  
>  	struct intel_dp *mst_port;
> +
> +	/* Work struct to schedule a uevent on link train failure */
> +	struct work_struct modeset_retry_work;
>  };
>  
>  struct dpll {
> @@ -900,7 +903,6 @@ struct intel_dp {
>  	int fallback_link_rate;
>  	uint8_t fallback_lane_count;
>  	int fallback_link_rate_index;
> -	bool link_train_failed;
>  	uint8_t sink_count;
>  	bool link_mst;
>  	bool has_audio;
> @@ -1402,7 +1404,7 @@ void intel_dp_set_link_params(struct intel_dp *intel_dp,
>  			      bool link_mst);
>  void intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp,
>  					     int link_rate, uint8_t lane_count);
> -void intel_dp_start_link_train(struct intel_dp *intel_dp);
> +bool intel_dp_start_link_train(struct intel_dp *intel_dp);
>  void intel_dp_stop_link_train(struct intel_dp *intel_dp);
>  void intel_dp_sink_dpms(struct intel_dp *intel_dp, int mode);
>  void intel_dp_encoder_reset(struct drm_encoder *encoder);

-- 
Jani Nikula, Intel Open Source Technology Center
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Re: [PATCH v3 4/4] drm/i915: Implement Link Rate fallback on Link training failure

[Manasi Navare]

On Wed, Nov 09, 2016 at 03:04:05PM +0200, Jani Nikula wrote:
> On Wed, 02 Nov 2016, Manasi Navare <manasi.d.navare@intel.com> wrote:
> > If link training at a link rate optimal for a particular
> > mode fails during modeset's atomic commit phase, then we
> > let the modeset complete and then retry. We save the link rate
> > value at which link training failed, update the link status property
> > to "BAD" and use a lower link rate to prune the modes. It will redo
> > the modeset on the current mode at lower link rate or if the current
> > mode gets pruned due to lower link constraints then, it will send a
> > hotplug uevent for userspace to handle it.
> >
> > This is also required to pass DP CTS tests 4.3.1.3, 4.3.1.4,
> > 4.3.1.6.
> >
> > v3:
> > * Set link status property to BAd unconditionally (Jani Nikula)
> > * Dont use two separate variables link_train_failed and link_status
> > to indicate same thing (Jani Nikula)
> > v2:
> > * Squashed a few patches (Jani Nikula)
> >
> > Cc: Jani Nikula <jani.nikula@linux.intel.com>
> > Cc: Daniel Vetter <daniel.vetter@intel.com>
> > Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
> > Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
> > ---
> >  drivers/gpu/drm/drm_atomic_helper.c           |  7 +++
> >  drivers/gpu/drm/i915/intel_ddi.c              | 22 ++++++++-
> >  drivers/gpu/drm/i915/intel_dp.c               | 70 ++++++++++++++++++++++++---
> >  drivers/gpu/drm/i915/intel_dp_link_training.c | 12 +++--
> >  drivers/gpu/drm/i915/intel_drv.h              |  6 ++-
> >  5 files changed, 105 insertions(+), 12 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> > index 75ad01d..94b0b3a 100644
> > --- a/drivers/gpu/drm/drm_atomic_helper.c
> > +++ b/drivers/gpu/drm/drm_atomic_helper.c
> > @@ -519,6 +519,13 @@ static int handle_conflicting_encoders(struct drm_atomic_state *state,
> >  					       connector_state);
> >  		if (ret)
> >  			return ret;
> > +
> > +		if (connector->state->crtc) {
> > +			crtc_state = drm_atomic_get_existing_crtc_state(state,
> > +									connector->state->crtc);
> > +			if (connector->link_status == DRM_MODE_LINK_STATUS_BAD)
> > +				crtc_state->connectors_changed = true;
> > +		}
> >  	}
> 
> Could this be a separate patch? Anyway needs to be posted on dri-devel.
>

Yes I agree, I will move this into a separate patch right after the patch
where I declare the connector link status.
 
> >  
> >  	/*
> > diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
> > index 938ac4d..a59f8d2 100644
> > --- a/drivers/gpu/drm/i915/intel_ddi.c
> > +++ b/drivers/gpu/drm/i915/intel_ddi.c
> > @@ -1684,6 +1684,8 @@ static void intel_ddi_pre_enable_dp(struct intel_encoder *encoder,
> >  	struct intel_dp *intel_dp = enc_to_intel_dp(&encoder->base);
> >  	struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
> >  	enum port port = intel_ddi_get_encoder_port(encoder);
> > +	struct intel_connector *intel_connector = intel_dp->attached_connector;
> > +	struct drm_connector *connector = &intel_connector->base;
> >  
> >  	intel_dp_set_link_params(intel_dp, link_rate, lane_count,
> >  				 link_mst);
> > @@ -1694,7 +1696,25 @@ static void intel_ddi_pre_enable_dp(struct intel_encoder *encoder,
> >  	intel_prepare_dp_ddi_buffers(encoder);
> >  	intel_ddi_init_dp_buf_reg(encoder);
> >  	intel_dp_sink_dpms(intel_dp, DRM_MODE_DPMS_ON);
> > -	intel_dp_start_link_train(intel_dp);
> > +	if (!intel_dp_start_link_train(intel_dp)) {
> > +		DRM_DEBUG_KMS("Link Training failed at link rate = %d, lane count = %d",
> > +			      link_rate, lane_count);
> > +		connector->link_status = DRM_MODE_LINK_STATUS_BAD;
> 
> Why does this not use intel_dp_set_link_status_property()?
> 

I will move this connector->link_status setting inside the set_link_status function.


> > +		intel_dp_get_link_train_fallback_values(intel_dp, link_rate,
> > +							lane_count);
> > +		/* Schedule a Hotplug Uevent to userspace to start modeset */
> > +		schedule_work(&intel_connector->modeset_retry_work);
> > +	} else {
> > +		DRM_DEBUG_KMS("Link Training Passed at Link Rate = %d, Lane count = %d",
> > +			      link_rate, lane_count);
> > +		intel_dp->fallback_link_rate_index = -1;
> > +		intel_dp->fallback_link_rate = 0;
> > +		intel_dp->fallback_lane_count = 0;
> > +		connector->link_status = DRM_MODE_LINK_STATUS_GOOD;
> > +		intel_dp_set_link_status_property(connector,
> > +						  DRM_MODE_LINK_STATUS_GOOD);
> > +	}
> > +
> >  	if (port != PORT_A || INTEL_GEN(dev_priv) >= 9)
> >  		intel_dp_stop_link_train(intel_dp);
> >  }
> > diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> > index fb4fcdd..659b17f 100644
> > --- a/drivers/gpu/drm/i915/intel_dp.c
> > +++ b/drivers/gpu/drm/i915/intel_dp.c
> > @@ -310,9 +310,6 @@ void intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp,
> >  	int common_len;
> >  	int link_rate_index = -1;
> >  
> > -	if (!intel_dp->link_train_failed)
> > -		return;
> > -
> 
> You add this in an earlier patch and now remove it?
>

I removed it to address the comment about not using link_train_failed and
link_status to indicate the same thing. But this will be cleaned up when I submit
a clean patch series so that it does not appear as added in previous patch and 
removed here.

 
> >  	common_len = intel_dp_common_rates(intel_dp, common_rates);
> >  	link_rate_index = intel_dp_link_rate_index(intel_dp,
> >  						   common_rates,
> > @@ -327,7 +324,6 @@ void intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp,
> >  		intel_dp->fallback_lane_count = lane_count >> 1;
> >  	} else {
> >  		DRM_ERROR("Link Training Unsuccessful\n");
> > -		intel_dp->link_train_failed = false;
> >  	}
> >  }
> >  
> > @@ -354,8 +350,14 @@ void intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp,
> >  		target_clock = fixed_mode->clock;
> >  	}
> >  
> > -	max_link_clock = intel_dp_max_link_rate(intel_dp);
> > -	max_lanes = intel_dp_max_lane_count(intel_dp);
> > +	/* Prune the modes using the fallback link rate/lane count */
> > +	if (connector->link_status == DRM_MODE_LINK_STATUS_BAD) {
> > +		max_link_clock = intel_dp->fallback_link_rate;
> > +		max_lanes = intel_dp->fallback_lane_count;
> > +	} else {
> > +		max_link_clock = intel_dp_max_link_rate(intel_dp);
> > +		max_lanes = intel_dp_max_lane_count(intel_dp);
> > +	}
> >  
> >  	max_rate = intel_dp_max_data_rate(max_link_clock, max_lanes);
> >  	mode_rate = intel_dp_link_required(target_clock, 18);
> > @@ -1593,6 +1595,7 @@ static int intel_dp_compute_bpp(struct intel_dp *intel_dp,
> >  	enum port port = dp_to_dig_port(intel_dp)->port;
> >  	struct intel_crtc *intel_crtc = to_intel_crtc(pipe_config->base.crtc);
> >  	struct intel_connector *intel_connector = intel_dp->attached_connector;
> > +	struct drm_connector *connector = &intel_connector->base;
> >  	int lane_count, clock;
> >  	int min_lane_count = 1;
> >  	int max_lane_count = intel_dp_max_lane_count(intel_dp);
> > @@ -1640,6 +1643,12 @@ static int intel_dp_compute_bpp(struct intel_dp *intel_dp,
> >  	if (adjusted_mode->flags & DRM_MODE_FLAG_DBLCLK)
> >  		return false;
> >  
> > +	/* Fall back to lower link rate in case of failure in previous modeset */
> > +	if (connector->link_status == DRM_MODE_LINK_STATUS_BAD) {
> > +		min_lane_count = max_lane_count = intel_dp->fallback_lane_count;
> > +		min_clock = max_clock = intel_dp->fallback_link_rate_index;
> > +	}
> > +
> >  	DRM_DEBUG_KMS("DP link computation with max lane count %i "
> >  		      "max bw %d pixel clock %iKHz\n",
> >  		      max_lane_count, common_rates[max_clock],
> > @@ -4423,6 +4432,12 @@ static bool intel_digital_port_connected(struct drm_i915_private *dev_priv,
> >  		intel_dp->compliance_test_active = 0;
> >  		intel_dp->compliance_test_type = 0;
> >  		intel_dp->compliance_test_data = 0;
> > +		intel_dp->fallback_link_rate_index = -1;
> > +		intel_dp->fallback_link_rate = 0;
> > +		intel_dp->fallback_lane_count = 0;
> > +		connector->link_status = DRM_MODE_LINK_STATUS_GOOD;
> > +		intel_dp_set_link_status_property(connector,
> > +						  DRM_MODE_LINK_STATUS_GOOD);
> 
> Seems like it would be a good idea to have this
> intel_dp_set_link_status_property() helper set connector->link_status
> too.
>

Yup, will do this change. 

Regards
Manasi 
> >  
> >  		if (intel_dp->is_mst) {
> >  			DRM_DEBUG_KMS("MST device may have disappeared %d vs %d\n",
> > @@ -4514,6 +4529,11 @@ static bool intel_digital_port_connected(struct drm_i915_private *dev_priv,
> >  	DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n",
> >  		      connector->base.id, connector->name);
> >  
> > +	/* If this is a retry due to link trianing failure */
> > +	if (status == connector_status_connected &&
> > +	    connector->link_status == DRM_MODE_LINK_STATUS_BAD)
> > +		return status;
> > +
> >  	/* If full detect is not performed yet, do a full detect */
> >  	if (!intel_dp->detect_done)
> >  		status = intel_dp_long_pulse(intel_dp->attached_connector);
> > @@ -5692,6 +5712,40 @@ static bool intel_edp_init_connector(struct intel_dp *intel_dp,
> >  	return false;
> >  }
> >  
> > +static void intel_dp_modeset_retry_work_fn(struct work_struct *work)
> > +{
> > +	struct intel_connector *intel_connector;
> > +	struct drm_connector *connector;
> > +	struct drm_display_mode *mode;
> > +	bool verbose_prune = true;
> > +
> > +	intel_connector = container_of(work, typeof(*intel_connector),
> > +				       modeset_retry_work);
> > +	connector = &intel_connector->base;
> > +
> > +	/* Grab the locks before changing connector property*/
> > +	mutex_lock(&connector->dev->mode_config.mutex);
> > +	DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n", connector->base.id,
> > +		      connector->name);
> > +	list_for_each_entry(mode, &connector->modes, head) {
> > +		mode->status = intel_dp_mode_valid(connector,
> > +						   mode);
> > +	}
> > +	drm_mode_prune_invalid(connector->dev, &connector->modes,
> > +			       verbose_prune);
> > +
> > +	/* Set connector link status to BAD and send a Uevent to notify
> > +	 * userspace to do a modeset.
> > +	 */
> > +	connector->link_status = DRM_MODE_LINK_STATUS_BAD;
> > +	intel_dp_set_link_status_property(connector,
> > +					  DRM_MODE_LINK_STATUS_BAD);
> > +	mutex_unlock(&connector->dev->mode_config.mutex);
> > +
> > +	/* Send Hotplug uevent so userspace can reprobe */
> > +	drm_kms_helper_hotplug_event(connector->dev);
> > +}
> > +
> >  bool
> >  intel_dp_init_connector(struct intel_digital_port *intel_dig_port,
> >  			struct intel_connector *intel_connector)
> > @@ -5704,6 +5758,10 @@ static bool intel_edp_init_connector(struct intel_dp *intel_dp,
> >  	enum port port = intel_dig_port->port;
> >  	int type;
> >  
> > +	/* Initialize the work for modeset in case of link train failure */
> > +	INIT_WORK(&intel_connector->modeset_retry_work,
> > +		  intel_dp_modeset_retry_work_fn);
> > +
> >  	if (WARN(intel_dig_port->max_lanes < 1,
> >  		 "Not enough lanes (%d) for DP on port %c\n",
> >  		 intel_dig_port->max_lanes, port_name(port)))
> > diff --git a/drivers/gpu/drm/i915/intel_dp_link_training.c b/drivers/gpu/drm/i915/intel_dp_link_training.c
> > index 0048b52..10f81ab 100644
> > --- a/drivers/gpu/drm/i915/intel_dp_link_training.c
> > +++ b/drivers/gpu/drm/i915/intel_dp_link_training.c
> > @@ -310,9 +310,15 @@ void intel_dp_stop_link_train(struct intel_dp *intel_dp)
> >  				DP_TRAINING_PATTERN_DISABLE);
> >  }
> >  
> > -void
> > +bool
> >  intel_dp_start_link_train(struct intel_dp *intel_dp)
> >  {
> > -	intel_dp_link_training_clock_recovery(intel_dp);
> > -	intel_dp_link_training_channel_equalization(intel_dp);
> > +	bool ret;
> > +
> > +	if (intel_dp_link_training_clock_recovery(intel_dp)) {
> > +		ret = intel_dp_link_training_channel_equalization(intel_dp);
> > +		if (ret)
> > +			return true;
> > +	}
> > +	return false;
> >  }
> > diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> > index bc25b2b..c0378a9 100644
> > --- a/drivers/gpu/drm/i915/intel_drv.h
> > +++ b/drivers/gpu/drm/i915/intel_drv.h
> > @@ -312,6 +312,9 @@ struct intel_connector {
> >  	void *port; /* store this opaque as its illegal to dereference it */
> >  
> >  	struct intel_dp *mst_port;
> > +
> > +	/* Work struct to schedule a uevent on link train failure */
> > +	struct work_struct modeset_retry_work;
> >  };
> >  
> >  struct dpll {
> > @@ -900,7 +903,6 @@ struct intel_dp {
> >  	int fallback_link_rate;
> >  	uint8_t fallback_lane_count;
> >  	int fallback_link_rate_index;
> > -	bool link_train_failed;
> >  	uint8_t sink_count;
> >  	bool link_mst;
> >  	bool has_audio;
> > @@ -1402,7 +1404,7 @@ void intel_dp_set_link_params(struct intel_dp *intel_dp,
> >  			      bool link_mst);
> >  void intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp,
> >  					     int link_rate, uint8_t lane_count);
> > -void intel_dp_start_link_train(struct intel_dp *intel_dp);
> > +bool intel_dp_start_link_train(struct intel_dp *intel_dp);
> >  void intel_dp_stop_link_train(struct intel_dp *intel_dp);
> >  void intel_dp_sink_dpms(struct intel_dp *intel_dp, int mode);
> >  void intel_dp_encoder_reset(struct drm_encoder *encoder);
> 
> -- 
> Jani Nikula, Intel Open Source Technology Center
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✗ Fi.CI.BAT: failure for Handle link training failure during modeset for DDI

[Patchwork]

== Series Details ==

Series: Handle link training failure during modeset for DDI
URL   : https://patchwork.freedesktop.org/series/14556/
State : failure

== Summary ==

Series 14556v1 Handle link training failure during modeset for DDI
https://patchwork.freedesktop.org/api/1.0/series/14556/revisions/1/mbox/

Test drv_module_reload_basic:
                pass       -> INCOMPLETE (fi-skl-6770hq)
                dmesg-warn -> PASS       (fi-hsw-4770)
Test kms_force_connector_basic:
        Subgroup force-edid:
                dmesg-warn -> PASS       (fi-snb-2520m)
Test kms_pipe_crc_basic:
        Subgroup bad-pipe:
                dmesg-warn -> PASS       (fi-ilk-650)

fi-bdw-5557u     total:241  pass:226  dwarn:0   dfail:0   fail:0   skip:15 
fi-bsw-n3050     total:241  pass:201  dwarn:0   dfail:0   fail:0   skip:40 
fi-bxt-t5700     total:241  pass:213  dwarn:0   dfail:0   fail:0   skip:28 
fi-byt-j1900     total:241  pass:213  dwarn:0   dfail:0   fail:0   skip:28 
fi-byt-n2820     total:241  pass:209  dwarn:0   dfail:0   fail:0   skip:32 
fi-hsw-4770      total:241  pass:221  dwarn:0   dfail:0   fail:0   skip:20 
fi-hsw-4770r     total:241  pass:220  dwarn:0   dfail:0   fail:0   skip:21 
fi-ilk-650       total:241  pass:187  dwarn:0   dfail:0   fail:0   skip:54 
fi-ivb-3520m     total:241  pass:218  dwarn:0   dfail:0   fail:0   skip:23 
fi-ivb-3770      total:241  pass:218  dwarn:0   dfail:0   fail:0   skip:23 
fi-kbl-7200u     total:241  pass:219  dwarn:0   dfail:0   fail:0   skip:22 
fi-skl-6260u     total:241  pass:227  dwarn:0   dfail:0   fail:0   skip:14 
fi-skl-6700hq    total:241  pass:220  dwarn:0   dfail:0   fail:0   skip:21 
fi-skl-6770hq    total:6    pass:5    dwarn:0   dfail:0   fail:0   skip:0  
fi-snb-2520m     total:241  pass:208  dwarn:0   dfail:0   fail:0   skip:33 
fi-snb-2600      total:241  pass:207  dwarn:0   dfail:0   fail:0   skip:34 

f3968d51ade8c02e8868c2608ea4adb5a4afe301 drm-intel-nightly: 2016y-10m-28d-19h-57m-33s UTC integration manifest
eac571a drm/i915: Implement Link Rate fallback on Link training failure
ff275dd drm/i915: Find fallback link rate/lane count
fd42134 drm/i915: Set link status property for DP connector
7a0359a drm: Add a new connector property for link status

== Logs ==

For more details see: https://intel-gfx-ci.01.org/CI/Patchwork_2854/
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✗ Fi.CI.BAT: failure for Handle link training failure during modeset for DDI (rev2)

[Patchwork]

== Series Details ==

Series: Handle link training failure during modeset for DDI (rev2)
URL   : https://patchwork.freedesktop.org/series/14556/
State : failure

== Summary ==

Series 14556v2 Handle link training failure during modeset for DDI
https://patchwork.freedesktop.org/api/1.0/series/14556/revisions/2/mbox/

Test drv_module_reload_basic:
                dmesg-warn -> PASS       (fi-ilk-650)
                dmesg-warn -> PASS       (fi-bdw-5557u)
                pass       -> INCOMPLETE (fi-skl-6770hq)
                dmesg-warn -> INCOMPLETE (fi-skl-6700k)
Test kms_cursor_legacy:
        Subgroup basic-busy-flip-before-cursor-legacy:
                pass       -> DMESG-WARN (fi-ilk-650)
        Subgroup basic-flip-before-cursor-varying-size:
                pass       -> DMESG-WARN (fi-ilk-650)
Test kms_force_connector_basic:
        Subgroup force-edid:
                dmesg-warn -> PASS       (fi-snb-2520m)
Test kms_pipe_crc_basic:
        Subgroup bad-nb-words-1:
                pass       -> DMESG-WARN (fi-ilk-650)
        Subgroup bad-nb-words-3:
                dmesg-warn -> PASS       (fi-ilk-650)
        Subgroup nonblocking-crc-pipe-a-frame-sequence:
                pass       -> DMESG-WARN (fi-ilk-650)
        Subgroup suspend-read-crc-pipe-a:
                dmesg-warn -> PASS       (fi-ilk-650)

fi-bdw-5557u     total:241  pass:226  dwarn:0   dfail:0   fail:0   skip:15 
fi-bsw-n3050     total:241  pass:201  dwarn:0   dfail:0   fail:0   skip:40 
fi-bxt-t5700     total:241  pass:213  dwarn:0   dfail:0   fail:0   skip:28 
fi-byt-j1900     total:241  pass:213  dwarn:0   dfail:0   fail:0   skip:28 
fi-byt-n2820     total:241  pass:209  dwarn:0   dfail:0   fail:0   skip:32 
fi-hsw-4770      total:241  pass:221  dwarn:0   dfail:0   fail:0   skip:20 
fi-hsw-4770r     total:241  pass:220  dwarn:0   dfail:0   fail:0   skip:21 
fi-ilk-650       total:241  pass:180  dwarn:7   dfail:0   fail:0   skip:54 
fi-ivb-3520m     total:241  pass:218  dwarn:0   dfail:0   fail:0   skip:23 
fi-ivb-3770      total:241  pass:218  dwarn:0   dfail:0   fail:0   skip:23 
fi-kbl-7200u     total:241  pass:219  dwarn:0   dfail:0   fail:0   skip:22 
fi-skl-6260u     total:241  pass:227  dwarn:0   dfail:0   fail:0   skip:14 
fi-skl-6700hq    total:241  pass:220  dwarn:0   dfail:0   fail:0   skip:21 
fi-skl-6700k     total:6    pass:5    dwarn:0   dfail:0   fail:0   skip:0  
fi-skl-6770hq    total:6    pass:5    dwarn:0   dfail:0   fail:0   skip:0  
fi-snb-2520m     total:241  pass:208  dwarn:0   dfail:0   fail:0   skip:33 
fi-snb-2600      total:241  pass:207  dwarn:0   dfail:0   fail:0   skip:34 

6a1197bcb5cc18a56ad4ae8e6d706a212bc3db7d drm-intel-nightly: 2016y-10m-31d-14h-58m-16s UTC integration manifest
d3c54ba drm/i915: Implement Link Rate fallback on Link training failure
14102d8 drm/i915: Find fallback link rate/lane count
8705bee drm/i915: Set link status property for DP connector
cd53886 drm: Add a new connector property for link status

== Logs ==

For more details see: https://intel-gfx-ci.01.org/CI/Patchwork_2867/
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✗ Fi.CI.BAT: failure for Handle link training failure during modeset for DDI (rev3)

[Patchwork]

== Series Details ==

Series: Handle link training failure during modeset for DDI (rev3)
URL   : https://patchwork.freedesktop.org/series/14556/
State : failure

== Summary ==

Series 14556v3 Handle link training failure during modeset for DDI
https://patchwork.freedesktop.org/api/1.0/series/14556/revisions/3/mbox/

Test drv_module_reload_basic:
                pass       -> INCOMPLETE (fi-skl-6770hq)
                dmesg-warn -> INCOMPLETE (fi-skl-6700k)

fi-bdw-5557u     total:241  pass:226  dwarn:0   dfail:0   fail:0   skip:15 
fi-bsw-n3050     total:241  pass:201  dwarn:0   dfail:0   fail:0   skip:40 
fi-byt-j1900     total:241  pass:213  dwarn:0   dfail:0   fail:0   skip:28 
fi-byt-n2820     total:241  pass:209  dwarn:0   dfail:0   fail:0   skip:32 
fi-hsw-4770      total:241  pass:221  dwarn:0   dfail:0   fail:0   skip:20 
fi-hsw-4770r     total:241  pass:220  dwarn:0   dfail:0   fail:0   skip:21 
fi-ilk-650       total:241  pass:187  dwarn:0   dfail:0   fail:0   skip:54 
fi-ivb-3520m     total:241  pass:218  dwarn:0   dfail:0   fail:0   skip:23 
fi-ivb-3770      total:241  pass:218  dwarn:0   dfail:0   fail:0   skip:23 
fi-kbl-7200u     total:241  pass:219  dwarn:0   dfail:0   fail:0   skip:22 
fi-skl-6260u     total:241  pass:227  dwarn:0   dfail:0   fail:0   skip:14 
fi-skl-6700hq    total:241  pass:220  dwarn:0   dfail:0   fail:0   skip:21 
fi-skl-6700k     total:6    pass:5    dwarn:0   dfail:0   fail:0   skip:0  
fi-skl-6770hq    total:6    pass:5    dwarn:0   dfail:0   fail:0   skip:0  
fi-snb-2520m     total:241  pass:208  dwarn:0   dfail:0   fail:0   skip:33 
fi-snb-2600      total:241  pass:207  dwarn:0   dfail:0   fail:0   skip:34 

bf6b989af8b0fde56a352d9005c97b2d8e3bbbe3 drm-intel-nightly: 2016y-11m-02d-15h-44m-03s UTC integration manifest
06564f1 drm/i915: Implement Link Rate fallback on Link training failure
3e2e35f drm/i915: Find fallback link rate/lane count
a4fc113 drm/i915: Set link status property for DP connector
0abe534 drm: Add a new connector property for link status

== Logs ==

For more details see: https://intel-gfx-ci.01.org/CI/Patchwork_2896/
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