[PATCH 0/4] Link Training failure handling by sending Hotplug Uevent

[PATCH 0/4] Link Training failure handling by sending Hotplug Uevent

[Manasi Navare]

This patch series is a final revision of previous patch series for handling
link training failure. This has been polished in terms of the kernel documentation
based on review feedback.

One more patch is added to move sink's max link rate and lane count
to intel_dp and compute it at hotplug and only if link training fails else
keept it constant. This greatly simplifies the link train fallback logic
by changing the max link rate/lane count to the fallback values instead
of creating separate fallback values for link rate/lane count.

In general the idea is to if link training fails during or after atomic modeset,
then the driver sets the link-status property to BAD and sends a HOTPLUG
uevent to notify userspace that link status is BAD. The userspace can be modified
to be "link-status" property aware and on detecting link-status as BAD, it should
revalidate the modes and redo a modeset which in turn will retrain the link
at lower fallback values.

This has been validated and is proved to pass DP compliance uisng DPR-120.

Manasi Navare (4):
  drm: Add a new connector atomic property for link status
  drm/i915: Compute sink's max lane count/link BW at Hotplug
  drm/i915: Find fallback link rate/lane count
  drm/i915: Implement Link Rate fallback on Link training failure

 drivers/gpu/drm/drm_atomic.c                  | 10 ++++
 drivers/gpu/drm/drm_atomic_helper.c           | 15 ++++++
 drivers/gpu/drm/drm_connector.c               | 53 ++++++++++++++++++
 drivers/gpu/drm/i915/intel_dp.c               | 77 ++++++++++++++++++++++++++-
 drivers/gpu/drm/i915/intel_dp_link_training.c | 22 +++++++-
 drivers/gpu/drm/i915/intel_drv.h              |  9 ++++
 include/drm/drm_connector.h                   | 19 +++++++
 include/drm/drm_mode_config.h                 |  5 ++
 include/uapi/drm/drm_mode.h                   |  4 ++
 9 files changed, 210 insertions(+), 4 deletions(-)

-- 
1.9.1

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

[Manasi Navare]

At the time userspace does setcrtc, we've already promised the mode
would work. The promise is based on the theoretical capabilities of
the link, but it's possible we can't reach this in practice. The DP
spec describes how the link should be reduced, but we can't reduce
the link below the requirements of the mode. Black screen follows.

One idea would be to have setcrtc return a failure. However, it
already should not fail as the atomic checks have passed. It would
also conflict with the idea of making setcrtc asynchronous in the
future, returning before the actual mode setting and link training.

Another idea is to train the link "upfront" at hotplug time, before
pruning the mode list, so that we can do the pruning based on
practical not theoretical capabilities. However, the changes for link
training are pretty drastic, all for the sake of error handling and
DP compliance, when the most common happy day scenario is the current
approach of link training at mode setting time, using the optimal
parameters for the mode. It is also not certain all hardware could do
this without the pipe on; not even all our hardware can do this. Some
of this can be solved, but not trivially.

Both of the above ideas also fail to address link degradation *during*
operation.

The solution is to add a new "link-status" connector property in order
to address link training failure in a way that:
a) changes the current happy day scenario as little as possible, to
avoid regressions, b) can be implemented the same way by all drm
drivers, c) is still opt-in for the drivers and userspace, and opting
out doesn't regress the user experience, d) doesn't prevent drivers
from implementing better or alternate approaches, possibly without
userspace involvement. And, of course, handles all the issues presented.
In the usual happy day scenario, this is always "good". If something
fails during or after a mode set, the kernel driver can set the link
status to "bad" and issue a hotplug uevent for userspace to have it
re-check the valid modes through GET_CONNECTOR IOCTL, and try modeset
again. If the theoretical capabilities of the link can't be reached,
the mode list is trimmed based on that.

v4:
* Add comments in kernel-doc format (Daniel Vetter)
* Update the kernel-doc for link-status (Sean Paul)
v3:
* Fixed a build error (Jani Saarinen)
v2:
* Removed connector->link_status (Daniel Vetter)
* Set connector->state->link_status in drm_mode_connector_set_link_status_property
(Daniel Vetter)
* Set the connector_changed flag to true if connector->state->link_status changed.
* Reset link_status to GOOD in update_output_state (Daniel Vetter)
* Never allow userspace to set link status from Good To Bad (Daniel Vetter)

Acked-by: Tony Cheng <tony.cheng@amd.com>
Acked-by: Harry Wentland <harry.wentland@amd.com>
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>
Cc: Sean Paul <seanpaul@chromium.org>
Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
---
 drivers/gpu/drm/drm_atomic.c        | 10 +++++++
 drivers/gpu/drm/drm_atomic_helper.c | 15 +++++++++++
 drivers/gpu/drm/drm_connector.c     | 53 +++++++++++++++++++++++++++++++++++++
 include/drm/drm_connector.h         | 19 +++++++++++++
 include/drm/drm_mode_config.h       |  5 ++++
 include/uapi/drm/drm_mode.h         |  4 +++
 6 files changed, 106 insertions(+)

diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
index 19d7bcb..70a5152 100644
--- a/drivers/gpu/drm/drm_atomic.c
+++ b/drivers/gpu/drm/drm_atomic.c
@@ -1087,6 +1087,14 @@ int drm_atomic_connector_set_property(struct drm_connector *connector,
 		 * now?) atomic writes to DPMS property:
 		 */
 		return -EINVAL;
+	} else if (property == config->link_status_property) {
+		/* Never downgrade from GOOD to BAD on userspace's request here,
+		 * only hw issues can do that.
+		 */
+		if (state->link_status == DRM_LINK_STATUS_GOOD)
+			return 0;
+		state->link_status = val;
+		return 0;
 	} else if (connector->funcs->atomic_set_property) {
 		return connector->funcs->atomic_set_property(connector,
 				state, property, val);
@@ -1135,6 +1143,8 @@ static void drm_atomic_connector_print_state(struct drm_printer *p,
 		*val = (state->crtc) ? state->crtc->base.id : 0;
 	} else if (property == config->dpms_property) {
 		*val = connector->dpms;
+	} else if (property == config->link_status_property) {
+		*val = state->link_status;
 	} else if (connector->funcs->atomic_get_property) {
 		return connector->funcs->atomic_get_property(connector,
 				state, property, val);
diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index 494680c..3d6c1ce 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->state->link_status !=
+			    connector_state->link_status)
+				crtc_state->connectors_changed = true;
+		}
 	}
 
 	/*
@@ -2258,6 +2265,8 @@ static int update_output_state(struct drm_atomic_state *state,
 								NULL);
 			if (ret)
 				return ret;
+			/* Make sure legacy setCrtc always re-trains */
+			conn_state->link_status = DRM_LINK_STATUS_GOOD;
 		}
 	}
 
@@ -2301,6 +2310,12 @@ static int update_output_state(struct drm_atomic_state *state,
  *
  * Provides a default crtc set_config handler using the atomic driver interface.
  *
+ * NOTE: For backwards compatibility with old userspace this automatically
+ * resets the "link-status" property to GOOD, to force any link
+ * re-training. The SETCRTC ioctl does not define whether an update does
+ * need a full modeset or just a plane update, hence we're allowed to do
+ * that. See also drm_mode_connector_set_link_status_property().
+ *
  * Returns:
  * Returns 0 on success, negative errno numbers on failure.
  */
diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
index 5a45262..eee038a 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
@@ -625,6 +635,11 @@ int drm_display_info_set_bus_formats(struct drm_display_info *info,
  * 	tiling and virtualize both &drm_crtc and &drm_plane if needed. Drivers
  * 	should update this value using drm_mode_connector_set_tile_property().
  * 	Userspace cannot change this property.
+ * link-status:
+ *      Connector link-status property to indicate the status of link. The default
+ *      value of link-status is "GOOD". If something fails during or after modeset,
+ *      the kernel driver may set this to "BAD" and issue a hotplug uevent. Drivers
+ *      should update this value using drm_mode_connector_set_link_status_property().
  *
  * Connectors also have one standardized atomic property:
  *
@@ -666,6 +681,13 @@ 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;
 }
 
@@ -995,6 +1017,37 @@ int drm_mode_connector_update_edid_property(struct drm_connector *connector,
 }
 EXPORT_SYMBOL(drm_mode_connector_update_edid_property);
 
+/**
+ * drm_mode_connector_set_link_status_property - Set link status property of a connector
+ * @connector: drm connector
+ * @link_status: new value of link status property (0: Good, 1: Bad)
+ *
+ * In usual working scenario, this link status property will always be set to
+ * "GOOD". If something fails during or after a mode set, the kernel driver
+ * may set this link status property to "BAD". The caller then needs to send a
+ * hotplug uevent for userspace to re-check the valid modes through
+ * GET_CONNECTOR_IOCTL and retry modeset.
+ *
+ * Note: Drivers cannot rely on userspace to support this property and
+ * issue a modeset. As such, they may choose to handle issues (like
+ * re-training a link) without userspace's intervention.
+ *
+ * The reason for adding this property is to handle link training failures, but
+ * it is not limited to DP or link training. For example, if we implement
+ * asynchronous setcrtc, this property can be used to report any failures in that.
+ */
+void drm_mode_connector_set_link_status_property(struct drm_connector *connector,
+						 uint64_t link_status)
+{
+	struct drm_device *dev = connector->dev;
+
+	drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
+	connector->state->link_status = link_status;
+	drm_modeset_unlock(&dev->mode_config.connection_mutex);
+
+}
+EXPORT_SYMBOL(drm_mode_connector_set_link_status_property);
+
 int drm_mode_connector_set_obj_prop(struct drm_mode_object *obj,
 				    struct drm_property *property,
 				    uint64_t value)
diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
index 1218a0c..64e07c5 100644
--- a/include/drm/drm_connector.h
+++ b/include/drm/drm_connector.h
@@ -90,6 +90,17 @@ enum subpixel_order {
 };
 
 /**
+ * enum drm_link_status - connector's link_status property value
+ *
+ * This enum is used as the connector's link status property value.
+ * It is set to the values defined in uapi.
+ */
+enum drm_link_status {
+	DRM_LINK_STATUS_GOOD = DRM_MODE_LINK_STATUS_GOOD,
+	DRM_LINK_STATUS_BAD = DRM_MODE_LINK_STATUS_BAD,
+};
+
+/**
  * struct drm_display_info - runtime data about the connected sink
  *
  * Describes a given display (e.g. CRT or flat panel) and its limitations. For
@@ -213,6 +224,12 @@ struct drm_connector_state {
 
 	struct drm_encoder *best_encoder;
 
+	/**
+	 * @link_status: Connector link_status to keep track of whether link is
+	 * GOOD or BAD to notify userspace if retraining is necessary.
+	 */
+	enum drm_link_status link_status;
+
 	struct drm_atomic_state *state;
 };
 
@@ -776,6 +793,8 @@ int drm_mode_connector_set_path_property(struct drm_connector *connector,
 int drm_mode_connector_set_tile_property(struct drm_connector *connector);
 int drm_mode_connector_update_edid_property(struct drm_connector *connector,
 					    const struct edid *edid);
+void drm_mode_connector_set_link_status_property(struct drm_connector *connector,
+						 uint64_t link_status);
 
 /**
  * struct drm_tile_group - Tile group metadata
diff --git a/include/drm/drm_mode_config.h b/include/drm/drm_mode_config.h
index bf9991b..86faee4 100644
--- a/include/drm/drm_mode_config.h
+++ b/include/drm/drm_mode_config.h
@@ -431,6 +431,11 @@ 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 728790b..309c478 100644
--- a/include/uapi/drm/drm_mode.h
+++ b/include/uapi/drm/drm_mode.h
@@ -123,6 +123,10 @@
 #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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[PATCH 2/4] drm/i915: Compute sink's max lane count/link BW at Hotplug

[Manasi Navare]

Sink's capabilities are advertised through DPCD registers and get
updated only on hotplug. So they should be computed only once in the
long pulse handler and saved off in intel_dp structure for the use
later. For this reason two new fields max_sink_lane_count and
max_sink_link_bw are added to intel_dp structure.

This also simplifies the fallback link rate/lane count logic
to handle link training failure. In that case, the max_sink_link_bw
and max_sink_lane_count can be reccomputed to match the fallback
values lowering the sink capabilities due to link train failure.

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  | 10 ++++++++--
 drivers/gpu/drm/i915/intel_drv.h |  4 ++++
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index db75bb9..434dc7d 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -156,7 +156,7 @@ static u8 intel_dp_max_lane_count(struct intel_dp *intel_dp)
 	u8 source_max, sink_max;
 
 	source_max = intel_dig_port->max_lanes;
-	sink_max = drm_dp_max_lane_count(intel_dp->dpcd);
+	sink_max = intel_dp->max_sink_lane_count;
 
 	return min(source_max, sink_max);
 }
@@ -213,7 +213,7 @@ static u8 intel_dp_max_lane_count(struct intel_dp *intel_dp)
 
 	*sink_rates = default_rates;
 
-	return (intel_dp_max_link_bw(intel_dp) >> 3) + 1;
+	return (intel_dp->max_sink_link_bw >> 3) + 1;
 }
 
 static int
@@ -4395,6 +4395,12 @@ static bool intel_digital_port_connected(struct drm_i915_private *dev_priv,
 		      yesno(intel_dp_source_supports_hbr2(intel_dp)),
 		      yesno(drm_dp_tps3_supported(intel_dp->dpcd)));
 
+	/* Set the max lane count for sink */
+	intel_dp->max_sink_lane_count = drm_dp_max_lane_count(intel_dp->dpcd);
+
+	/* Set the max link BW for sink */
+	intel_dp->max_sink_link_bw = intel_dp_max_link_bw(intel_dp);
+
 	intel_dp_print_rates(intel_dp);
 
 	intel_dp_read_desc(intel_dp);
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index fd77a3b..b6526ad 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -906,6 +906,10 @@ struct intel_dp {
 	/* sink rates as reported by DP_SUPPORTED_LINK_RATES */
 	uint8_t num_sink_rates;
 	int sink_rates[DP_MAX_SUPPORTED_RATES];
+	/* Max lane count for the sink as per DPCD registers */
+	uint8_t max_sink_lane_count;
+	/* Max link BW for the sink as per DPCD registers */
+	int max_sink_link_bw;
 	/* sink or branch descriptor */
 	struct intel_dp_desc desc;
 	struct drm_dp_aux aux;
-- 
1.9.1

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[PATCH 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 and limits the max
link_rate and lane_count values to these fallback values.

v6:
* Cap the max link rate and lane count to the max
values obtained during fallback link training (Daniel Vetter)
v5:
* Start the fallback at the lane count value passed not
the max lane count (Jani Nikula)
v4:
* Remove the redundant variable link_train_failed
v3:
* Remove fallback_link_rate_index variable, just obtain
that using the helper intel_dp_link_rate_index (Jani Nikula)
v2:
Squash the patch that returns the link rate index (Jani Nikula)

Acked-by: Tony Cheng <tony.cheng@amd.com>
Acked-by: Harry Wentland <harry.wentland@amd.com>
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  | 40 ++++++++++++++++++++++++++++++++++++++++
 drivers/gpu/drm/i915/intel_drv.h |  2 ++
 2 files changed, 42 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 434dc7d..b5c7526f 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -278,6 +278,46 @@ 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;
+}
+
+int 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;
+
+	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->max_sink_link_bw = drm_dp_link_rate_to_bw_code(common_rates[link_rate_index - 1]);
+		intel_dp->max_sink_lane_count = lane_count;
+	} else if (lane_count > 1) {
+		intel_dp->max_sink_link_bw = intel_dp_max_link_bw(intel_dp);
+		intel_dp->max_sink_lane_count = lane_count >> 1;
+	} else {
+		DRM_ERROR("Link Training Unsuccessful\n");
+		return -1;
+	}
+
+	return 0;
+}
+
 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 b6526ad..47e3671 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -1400,6 +1400,8 @@ bool intel_dp_init_connector(struct intel_digital_port *intel_dig_port,
 void intel_dp_set_link_params(struct intel_dp *intel_dp,
 			      int link_rate, uint8_t lane_count,
 			      bool link_mst);
+int 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 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.

v9:
* Use the trimmed max values of link rate/lane count based on
link train fallback (Daniel Vetter)
v8:
* Set link_status to BAD first and then call mode_valid (Jani Nikula)
v7:
Remove the redundant variable in previous patch itself
v6:
* Obtain link rate index from fallback_link_rate using
the helper intel_dp_link_rate_index (Jani Nikula)
* Include fallback within intel_dp_start_link_train (Jani Nikula)
v5:
* Move set link status to drm core (Daniel Vetter, Jani Nikula)
v4:
* Add fallback support for non DDI platforms too
* Set connector->link status inside set_link_status function
(Jani Nikula)
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)

Acked-by: Tony Cheng <tony.cheng@amd.com>
Acked-by: Harry Wentland <Harry.wentland@amd.com>
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/i915/intel_dp.c               | 27 +++++++++++++++++++++++++++
 drivers/gpu/drm/i915/intel_dp_link_training.c | 22 ++++++++++++++++++++--
 drivers/gpu/drm/i915/intel_drv.h              |  3 +++
 3 files changed, 50 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index b5c7526f..404da32 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -5676,6 +5676,29 @@ 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;
+
+	intel_connector = container_of(work, typeof(*intel_connector),
+				       modeset_retry_work);
+	connector = &intel_connector->base;
+	DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n", connector->base.id,
+		      connector->name);
+
+	/* Grab the locks before changing connector property*/
+	mutex_lock(&connector->dev->mode_config.mutex);
+	/* Set connector link status to BAD and send a Uevent to notify
+	 * userspace to do a modeset.
+	 */
+	drm_mode_connector_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)
@@ -5688,6 +5711,10 @@ 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..955b239 100644
--- a/drivers/gpu/drm/i915/intel_dp_link_training.c
+++ b/drivers/gpu/drm/i915/intel_dp_link_training.c
@@ -313,6 +313,24 @@ void intel_dp_stop_link_train(struct intel_dp *intel_dp)
 void
 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);
+	struct intel_connector *intel_connector = intel_dp->attached_connector;
+
+	if (!intel_dp_link_training_clock_recovery(intel_dp))
+		goto failure_handling;
+	if (!intel_dp_link_training_channel_equalization(intel_dp))
+		goto failure_handling;
+
+	DRM_DEBUG_KMS("Link Training Passed at Link Rate = %d, Lane count = %d",
+		      intel_dp->link_rate, intel_dp->lane_count);
+	return;
+
+ failure_handling:
+	DRM_DEBUG_KMS("Link Training failed at link rate = %d, lane count = %d",
+		      intel_dp->link_rate, intel_dp->lane_count);
+	if (!intel_dp_get_link_train_fallback_values(intel_dp,
+						     intel_dp->link_rate,
+						     intel_dp->lane_count))
+		/* Schedule a Hotplug Uevent to userspace to start modeset */
+		schedule_work(&intel_connector->modeset_retry_work);
+	return;
 }
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index 47e3671..9d6f7ee 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -315,6 +315,9 @@ 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 {
-- 
1.9.1

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Re: [Intel-gfx] [PATCH 1/4] drm: Add a new connector atomic property for link status

[Daniel Vetter]

On Mon, Dec 05, 2016 at 04:27:35PM -0800, Manasi Navare wrote:
> At the time userspace does setcrtc, we've already promised the mode
> would work. The promise is based on the theoretical capabilities of
> the link, but it's possible we can't reach this in practice. The DP
> spec describes how the link should be reduced, but we can't reduce
> the link below the requirements of the mode. Black screen follows.
> 
> One idea would be to have setcrtc return a failure. However, it
> already should not fail as the atomic checks have passed. It would
> also conflict with the idea of making setcrtc asynchronous in the
> future, returning before the actual mode setting and link training.
> 
> Another idea is to train the link "upfront" at hotplug time, before
> pruning the mode list, so that we can do the pruning based on
> practical not theoretical capabilities. However, the changes for link
> training are pretty drastic, all for the sake of error handling and
> DP compliance, when the most common happy day scenario is the current
> approach of link training at mode setting time, using the optimal
> parameters for the mode. It is also not certain all hardware could do
> this without the pipe on; not even all our hardware can do this. Some
> of this can be solved, but not trivially.
> 
> Both of the above ideas also fail to address link degradation *during*
> operation.
> 
> The solution is to add a new "link-status" connector property in order
> to address link training failure in a way that:
> a) changes the current happy day scenario as little as possible, to
> avoid regressions, b) can be implemented the same way by all drm
> drivers, c) is still opt-in for the drivers and userspace, and opting
> out doesn't regress the user experience, d) doesn't prevent drivers
> from implementing better or alternate approaches, possibly without
> userspace involvement. And, of course, handles all the issues presented.
> In the usual happy day scenario, this is always "good". If something
> fails during or after a mode set, the kernel driver can set the link
> status to "bad" and issue a hotplug uevent for userspace to have it
> re-check the valid modes through GET_CONNECTOR IOCTL, and try modeset
> again. If the theoretical capabilities of the link can't be reached,
> the mode list is trimmed based on that.
> 
> v4:
> * Add comments in kernel-doc format (Daniel Vetter)
> * Update the kernel-doc for link-status (Sean Paul)
> v3:
> * Fixed a build error (Jani Saarinen)
> v2:
> * Removed connector->link_status (Daniel Vetter)
> * Set connector->state->link_status in drm_mode_connector_set_link_status_property
> (Daniel Vetter)
> * Set the connector_changed flag to true if connector->state->link_status changed.
> * Reset link_status to GOOD in update_output_state (Daniel Vetter)
> * Never allow userspace to set link status from Good To Bad (Daniel Vetter)
> 
> Acked-by: Tony Cheng <tony.cheng@amd.com>
> Acked-by: Harry Wentland <harry.wentland@amd.com>
> 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>
> Cc: Sean Paul <seanpaul@chromium.org>

Didn't Sean r-b this already?

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

Looks all nice and tidy, great work.

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

Can be merged as soon as we have an ack from Martin that the -modesetting
side is ready to go too.
-Daniel

> ---
>  drivers/gpu/drm/drm_atomic.c        | 10 +++++++
>  drivers/gpu/drm/drm_atomic_helper.c | 15 +++++++++++
>  drivers/gpu/drm/drm_connector.c     | 53 +++++++++++++++++++++++++++++++++++++
>  include/drm/drm_connector.h         | 19 +++++++++++++
>  include/drm/drm_mode_config.h       |  5 ++++
>  include/uapi/drm/drm_mode.h         |  4 +++
>  6 files changed, 106 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
> index 19d7bcb..70a5152 100644
> --- a/drivers/gpu/drm/drm_atomic.c
> +++ b/drivers/gpu/drm/drm_atomic.c
> @@ -1087,6 +1087,14 @@ int drm_atomic_connector_set_property(struct drm_connector *connector,
>  		 * now?) atomic writes to DPMS property:
>  		 */
>  		return -EINVAL;
> +	} else if (property == config->link_status_property) {
> +		/* Never downgrade from GOOD to BAD on userspace's request here,
> +		 * only hw issues can do that.
> +		 */
> +		if (state->link_status == DRM_LINK_STATUS_GOOD)
> +			return 0;
> +		state->link_status = val;
> +		return 0;
>  	} else if (connector->funcs->atomic_set_property) {
>  		return connector->funcs->atomic_set_property(connector,
>  				state, property, val);
> @@ -1135,6 +1143,8 @@ static void drm_atomic_connector_print_state(struct drm_printer *p,
>  		*val = (state->crtc) ? state->crtc->base.id : 0;
>  	} else if (property == config->dpms_property) {
>  		*val = connector->dpms;
> +	} else if (property == config->link_status_property) {
> +		*val = state->link_status;
>  	} else if (connector->funcs->atomic_get_property) {
>  		return connector->funcs->atomic_get_property(connector,
>  				state, property, val);
> diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> index 494680c..3d6c1ce 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->state->link_status !=
> +			    connector_state->link_status)
> +				crtc_state->connectors_changed = true;
> +		}
>  	}
>  
>  	/*
> @@ -2258,6 +2265,8 @@ static int update_output_state(struct drm_atomic_state *state,
>  								NULL);
>  			if (ret)
>  				return ret;
> +			/* Make sure legacy setCrtc always re-trains */
> +			conn_state->link_status = DRM_LINK_STATUS_GOOD;
>  		}
>  	}
>  
> @@ -2301,6 +2310,12 @@ static int update_output_state(struct drm_atomic_state *state,
>   *
>   * Provides a default crtc set_config handler using the atomic driver interface.
>   *
> + * NOTE: For backwards compatibility with old userspace this automatically
> + * resets the "link-status" property to GOOD, to force any link
> + * re-training. The SETCRTC ioctl does not define whether an update does
> + * need a full modeset or just a plane update, hence we're allowed to do
> + * that. See also drm_mode_connector_set_link_status_property().
> + *
>   * Returns:
>   * Returns 0 on success, negative errno numbers on failure.
>   */
> diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
> index 5a45262..eee038a 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
> @@ -625,6 +635,11 @@ int drm_display_info_set_bus_formats(struct drm_display_info *info,
>   * 	tiling and virtualize both &drm_crtc and &drm_plane if needed. Drivers
>   * 	should update this value using drm_mode_connector_set_tile_property().
>   * 	Userspace cannot change this property.
> + * link-status:
> + *      Connector link-status property to indicate the status of link. The default
> + *      value of link-status is "GOOD". If something fails during or after modeset,
> + *      the kernel driver may set this to "BAD" and issue a hotplug uevent. Drivers
> + *      should update this value using drm_mode_connector_set_link_status_property().
>   *
>   * Connectors also have one standardized atomic property:
>   *
> @@ -666,6 +681,13 @@ 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;
>  }
>  
> @@ -995,6 +1017,37 @@ int drm_mode_connector_update_edid_property(struct drm_connector *connector,
>  }
>  EXPORT_SYMBOL(drm_mode_connector_update_edid_property);
>  
> +/**
> + * drm_mode_connector_set_link_status_property - Set link status property of a connector
> + * @connector: drm connector
> + * @link_status: new value of link status property (0: Good, 1: Bad)
> + *
> + * In usual working scenario, this link status property will always be set to
> + * "GOOD". If something fails during or after a mode set, the kernel driver
> + * may set this link status property to "BAD". The caller then needs to send a
> + * hotplug uevent for userspace to re-check the valid modes through
> + * GET_CONNECTOR_IOCTL and retry modeset.
> + *
> + * Note: Drivers cannot rely on userspace to support this property and
> + * issue a modeset. As such, they may choose to handle issues (like
> + * re-training a link) without userspace's intervention.
> + *
> + * The reason for adding this property is to handle link training failures, but
> + * it is not limited to DP or link training. For example, if we implement
> + * asynchronous setcrtc, this property can be used to report any failures in that.
> + */
> +void drm_mode_connector_set_link_status_property(struct drm_connector *connector,
> +						 uint64_t link_status)
> +{
> +	struct drm_device *dev = connector->dev;
> +
> +	drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
> +	connector->state->link_status = link_status;
> +	drm_modeset_unlock(&dev->mode_config.connection_mutex);
> +
> +}
> +EXPORT_SYMBOL(drm_mode_connector_set_link_status_property);
> +
>  int drm_mode_connector_set_obj_prop(struct drm_mode_object *obj,
>  				    struct drm_property *property,
>  				    uint64_t value)
> diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
> index 1218a0c..64e07c5 100644
> --- a/include/drm/drm_connector.h
> +++ b/include/drm/drm_connector.h
> @@ -90,6 +90,17 @@ enum subpixel_order {
>  };
>  
>  /**
> + * enum drm_link_status - connector's link_status property value
> + *
> + * This enum is used as the connector's link status property value.
> + * It is set to the values defined in uapi.
> + */
> +enum drm_link_status {
> +	DRM_LINK_STATUS_GOOD = DRM_MODE_LINK_STATUS_GOOD,
> +	DRM_LINK_STATUS_BAD = DRM_MODE_LINK_STATUS_BAD,
> +};
> +
> +/**
>   * struct drm_display_info - runtime data about the connected sink
>   *
>   * Describes a given display (e.g. CRT or flat panel) and its limitations. For
> @@ -213,6 +224,12 @@ struct drm_connector_state {
>  
>  	struct drm_encoder *best_encoder;
>  
> +	/**
> +	 * @link_status: Connector link_status to keep track of whether link is
> +	 * GOOD or BAD to notify userspace if retraining is necessary.
> +	 */
> +	enum drm_link_status link_status;
> +
>  	struct drm_atomic_state *state;
>  };
>  
> @@ -776,6 +793,8 @@ int drm_mode_connector_set_path_property(struct drm_connector *connector,
>  int drm_mode_connector_set_tile_property(struct drm_connector *connector);
>  int drm_mode_connector_update_edid_property(struct drm_connector *connector,
>  					    const struct edid *edid);
> +void drm_mode_connector_set_link_status_property(struct drm_connector *connector,
> +						 uint64_t link_status);
>  
>  /**
>   * struct drm_tile_group - Tile group metadata
> diff --git a/include/drm/drm_mode_config.h b/include/drm/drm_mode_config.h
> index bf9991b..86faee4 100644
> --- a/include/drm/drm_mode_config.h
> +++ b/include/drm/drm_mode_config.h
> @@ -431,6 +431,11 @@ 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 728790b..309c478 100644
> --- a/include/uapi/drm/drm_mode.h
> +++ b/include/uapi/drm/drm_mode.h
> @@ -123,6 +123,10 @@
>  #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
> 
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/intel-gfx

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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Re: [Intel-gfx] [PATCH 1/4] drm: Add a new connector atomic property for link status

[Manasi Navare]

On Tue, Dec 06, 2016 at 08:23:05AM +0100, Daniel Vetter wrote:
> On Mon, Dec 05, 2016 at 04:27:35PM -0800, Manasi Navare wrote:
> > At the time userspace does setcrtc, we've already promised the mode
> > would work. The promise is based on the theoretical capabilities of
> > the link, but it's possible we can't reach this in practice. The DP
> > spec describes how the link should be reduced, but we can't reduce
> > the link below the requirements of the mode. Black screen follows.
> > 
> > One idea would be to have setcrtc return a failure. However, it
> > already should not fail as the atomic checks have passed. It would
> > also conflict with the idea of making setcrtc asynchronous in the
> > future, returning before the actual mode setting and link training.
> > 
> > Another idea is to train the link "upfront" at hotplug time, before
> > pruning the mode list, so that we can do the pruning based on
> > practical not theoretical capabilities. However, the changes for link
> > training are pretty drastic, all for the sake of error handling and
> > DP compliance, when the most common happy day scenario is the current
> > approach of link training at mode setting time, using the optimal
> > parameters for the mode. It is also not certain all hardware could do
> > this without the pipe on; not even all our hardware can do this. Some
> > of this can be solved, but not trivially.
> > 
> > Both of the above ideas also fail to address link degradation *during*
> > operation.
> > 
> > The solution is to add a new "link-status" connector property in order
> > to address link training failure in a way that:
> > a) changes the current happy day scenario as little as possible, to
> > avoid regressions, b) can be implemented the same way by all drm
> > drivers, c) is still opt-in for the drivers and userspace, and opting
> > out doesn't regress the user experience, d) doesn't prevent drivers
> > from implementing better or alternate approaches, possibly without
> > userspace involvement. And, of course, handles all the issues presented.
> > In the usual happy day scenario, this is always "good". If something
> > fails during or after a mode set, the kernel driver can set the link
> > status to "bad" and issue a hotplug uevent for userspace to have it
> > re-check the valid modes through GET_CONNECTOR IOCTL, and try modeset
> > again. If the theoretical capabilities of the link can't be reached,
> > the mode list is trimmed based on that.
> > 
> > v4:
> > * Add comments in kernel-doc format (Daniel Vetter)
> > * Update the kernel-doc for link-status (Sean Paul)
> > v3:
> > * Fixed a build error (Jani Saarinen)
> > v2:
> > * Removed connector->link_status (Daniel Vetter)
> > * Set connector->state->link_status in drm_mode_connector_set_link_status_property
> > (Daniel Vetter)
> > * Set the connector_changed flag to true if connector->state->link_status changed.
> > * Reset link_status to GOOD in update_output_state (Daniel Vetter)
> > * Never allow userspace to set link status from Good To Bad (Daniel Vetter)
> > 
> > Acked-by: Tony Cheng <tony.cheng@amd.com>
> > Acked-by: Harry Wentland <harry.wentland@amd.com>
> > 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>
> > Cc: Sean Paul <seanpaul@chromium.org>
> 
> Didn't Sean r-b this already?
> 
> > Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
> 
> Looks all nice and tidy, great work.
> 
> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> 
> Can be merged as soon as we have an ack from Martin that the -modesetting
> side is ready to go too.
> -Daniel
>

Thanks Daniel. 
And yes I missed Sean Paul's r-b. I will add yours and his r-b and resubmit
the patch.

Manasi

 
> > ---
> >  drivers/gpu/drm/drm_atomic.c        | 10 +++++++
> >  drivers/gpu/drm/drm_atomic_helper.c | 15 +++++++++++
> >  drivers/gpu/drm/drm_connector.c     | 53 +++++++++++++++++++++++++++++++++++++
> >  include/drm/drm_connector.h         | 19 +++++++++++++
> >  include/drm/drm_mode_config.h       |  5 ++++
> >  include/uapi/drm/drm_mode.h         |  4 +++
> >  6 files changed, 106 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
> > index 19d7bcb..70a5152 100644
> > --- a/drivers/gpu/drm/drm_atomic.c
> > +++ b/drivers/gpu/drm/drm_atomic.c
> > @@ -1087,6 +1087,14 @@ int drm_atomic_connector_set_property(struct drm_connector *connector,
> >  		 * now?) atomic writes to DPMS property:
> >  		 */
> >  		return -EINVAL;
> > +	} else if (property == config->link_status_property) {
> > +		/* Never downgrade from GOOD to BAD on userspace's request here,
> > +		 * only hw issues can do that.
> > +		 */
> > +		if (state->link_status == DRM_LINK_STATUS_GOOD)
> > +			return 0;
> > +		state->link_status = val;
> > +		return 0;
> >  	} else if (connector->funcs->atomic_set_property) {
> >  		return connector->funcs->atomic_set_property(connector,
> >  				state, property, val);
> > @@ -1135,6 +1143,8 @@ static void drm_atomic_connector_print_state(struct drm_printer *p,
> >  		*val = (state->crtc) ? state->crtc->base.id : 0;
> >  	} else if (property == config->dpms_property) {
> >  		*val = connector->dpms;
> > +	} else if (property == config->link_status_property) {
> > +		*val = state->link_status;
> >  	} else if (connector->funcs->atomic_get_property) {
> >  		return connector->funcs->atomic_get_property(connector,
> >  				state, property, val);
> > diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> > index 494680c..3d6c1ce 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->state->link_status !=
> > +			    connector_state->link_status)
> > +				crtc_state->connectors_changed = true;
> > +		}
> >  	}
> >  
> >  	/*
> > @@ -2258,6 +2265,8 @@ static int update_output_state(struct drm_atomic_state *state,
> >  								NULL);
> >  			if (ret)
> >  				return ret;
> > +			/* Make sure legacy setCrtc always re-trains */
> > +			conn_state->link_status = DRM_LINK_STATUS_GOOD;
> >  		}
> >  	}
> >  
> > @@ -2301,6 +2310,12 @@ static int update_output_state(struct drm_atomic_state *state,
> >   *
> >   * Provides a default crtc set_config handler using the atomic driver interface.
> >   *
> > + * NOTE: For backwards compatibility with old userspace this automatically
> > + * resets the "link-status" property to GOOD, to force any link
> > + * re-training. The SETCRTC ioctl does not define whether an update does
> > + * need a full modeset or just a plane update, hence we're allowed to do
> > + * that. See also drm_mode_connector_set_link_status_property().
> > + *
> >   * Returns:
> >   * Returns 0 on success, negative errno numbers on failure.
> >   */
> > diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
> > index 5a45262..eee038a 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
> > @@ -625,6 +635,11 @@ int drm_display_info_set_bus_formats(struct drm_display_info *info,
> >   * 	tiling and virtualize both &drm_crtc and &drm_plane if needed. Drivers
> >   * 	should update this value using drm_mode_connector_set_tile_property().
> >   * 	Userspace cannot change this property.
> > + * link-status:
> > + *      Connector link-status property to indicate the status of link. The default
> > + *      value of link-status is "GOOD". If something fails during or after modeset,
> > + *      the kernel driver may set this to "BAD" and issue a hotplug uevent. Drivers
> > + *      should update this value using drm_mode_connector_set_link_status_property().
> >   *
> >   * Connectors also have one standardized atomic property:
> >   *
> > @@ -666,6 +681,13 @@ 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;
> >  }
> >  
> > @@ -995,6 +1017,37 @@ int drm_mode_connector_update_edid_property(struct drm_connector *connector,
> >  }
> >  EXPORT_SYMBOL(drm_mode_connector_update_edid_property);
> >  
> > +/**
> > + * drm_mode_connector_set_link_status_property - Set link status property of a connector
> > + * @connector: drm connector
> > + * @link_status: new value of link status property (0: Good, 1: Bad)
> > + *
> > + * In usual working scenario, this link status property will always be set to
> > + * "GOOD". If something fails during or after a mode set, the kernel driver
> > + * may set this link status property to "BAD". The caller then needs to send a
> > + * hotplug uevent for userspace to re-check the valid modes through
> > + * GET_CONNECTOR_IOCTL and retry modeset.
> > + *
> > + * Note: Drivers cannot rely on userspace to support this property and
> > + * issue a modeset. As such, they may choose to handle issues (like
> > + * re-training a link) without userspace's intervention.
> > + *
> > + * The reason for adding this property is to handle link training failures, but
> > + * it is not limited to DP or link training. For example, if we implement
> > + * asynchronous setcrtc, this property can be used to report any failures in that.
> > + */
> > +void drm_mode_connector_set_link_status_property(struct drm_connector *connector,
> > +						 uint64_t link_status)
> > +{
> > +	struct drm_device *dev = connector->dev;
> > +
> > +	drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
> > +	connector->state->link_status = link_status;
> > +	drm_modeset_unlock(&dev->mode_config.connection_mutex);
> > +
> > +}
> > +EXPORT_SYMBOL(drm_mode_connector_set_link_status_property);
> > +
> >  int drm_mode_connector_set_obj_prop(struct drm_mode_object *obj,
> >  				    struct drm_property *property,
> >  				    uint64_t value)
> > diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
> > index 1218a0c..64e07c5 100644
> > --- a/include/drm/drm_connector.h
> > +++ b/include/drm/drm_connector.h
> > @@ -90,6 +90,17 @@ enum subpixel_order {
> >  };
> >  
> >  /**
> > + * enum drm_link_status - connector's link_status property value
> > + *
> > + * This enum is used as the connector's link status property value.
> > + * It is set to the values defined in uapi.
> > + */
> > +enum drm_link_status {
> > +	DRM_LINK_STATUS_GOOD = DRM_MODE_LINK_STATUS_GOOD,
> > +	DRM_LINK_STATUS_BAD = DRM_MODE_LINK_STATUS_BAD,
> > +};
> > +
> > +/**
> >   * struct drm_display_info - runtime data about the connected sink
> >   *
> >   * Describes a given display (e.g. CRT or flat panel) and its limitations. For
> > @@ -213,6 +224,12 @@ struct drm_connector_state {
> >  
> >  	struct drm_encoder *best_encoder;
> >  
> > +	/**
> > +	 * @link_status: Connector link_status to keep track of whether link is
> > +	 * GOOD or BAD to notify userspace if retraining is necessary.
> > +	 */
> > +	enum drm_link_status link_status;
> > +
> >  	struct drm_atomic_state *state;
> >  };
> >  
> > @@ -776,6 +793,8 @@ int drm_mode_connector_set_path_property(struct drm_connector *connector,
> >  int drm_mode_connector_set_tile_property(struct drm_connector *connector);
> >  int drm_mode_connector_update_edid_property(struct drm_connector *connector,
> >  					    const struct edid *edid);
> > +void drm_mode_connector_set_link_status_property(struct drm_connector *connector,
> > +						 uint64_t link_status);
> >  
> >  /**
> >   * struct drm_tile_group - Tile group metadata
> > diff --git a/include/drm/drm_mode_config.h b/include/drm/drm_mode_config.h
> > index bf9991b..86faee4 100644
> > --- a/include/drm/drm_mode_config.h
> > +++ b/include/drm/drm_mode_config.h
> > @@ -431,6 +431,11 @@ 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 728790b..309c478 100644
> > --- a/include/uapi/drm/drm_mode.h
> > +++ b/include/uapi/drm/drm_mode.h
> > @@ -123,6 +123,10 @@
> >  #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
> > 
> > _______________________________________________
> > Intel-gfx mailing list
> > Intel-gfx@lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/intel-gfx
> 
> -- 
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch
_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel

[PATCH v4 1/4] drm: Add a new connector atomic property for link status

[Manasi Navare]

At the time userspace does setcrtc, we've already promised the mode
would work. The promise is based on the theoretical capabilities of
the link, but it's possible we can't reach this in practice. The DP
spec describes how the link should be reduced, but we can't reduce
the link below the requirements of the mode. Black screen follows.

One idea would be to have setcrtc return a failure. However, it
already should not fail as the atomic checks have passed. It would
also conflict with the idea of making setcrtc asynchronous in the
future, returning before the actual mode setting and link training.

Another idea is to train the link "upfront" at hotplug time, before
pruning the mode list, so that we can do the pruning based on
practical not theoretical capabilities. However, the changes for link
training are pretty drastic, all for the sake of error handling and
DP compliance, when the most common happy day scenario is the current
approach of link training at mode setting time, using the optimal
parameters for the mode. It is also not certain all hardware could do
this without the pipe on; not even all our hardware can do this. Some
of this can be solved, but not trivially.

Both of the above ideas also fail to address link degradation *during*
operation.

The solution is to add a new "link-status" connector property in order
to address link training failure in a way that:
a) changes the current happy day scenario as little as possible, to
avoid regressions, b) can be implemented the same way by all drm
drivers, c) is still opt-in for the drivers and userspace, and opting
out doesn't regress the user experience, d) doesn't prevent drivers
from implementing better or alternate approaches, possibly without
userspace involvement. And, of course, handles all the issues presented.
In the usual happy day scenario, this is always "good". If something
fails during or after a mode set, the kernel driver can set the link
status to "bad" and issue a hotplug uevent for userspace to have it
re-check the valid modes through GET_CONNECTOR IOCTL, and try modeset
again. If the theoretical capabilities of the link can't be reached,
the mode list is trimmed based on that.

v4:
* Add comments in kernel-doc format (Daniel Vetter)
* Update the kernel-doc for link-status (Sean Paul)
v3:
* Fixed a build error (Jani Saarinen)
v2:
* Removed connector->link_status (Daniel Vetter)
* Set connector->state->link_status in drm_mode_connector_set_link_status_property
(Daniel Vetter)
* Set the connector_changed flag to true if connector->state->link_status changed.
* Reset link_status to GOOD in update_output_state (Daniel Vetter)
* Never allow userspace to set link status from Good To Bad (Daniel Vetter)

Reviewed-by: Sean Paul <seanpaul@chromium.org>
Reviewed-by: Daniel Vetter  <daniel.vetter@ffwll.ch>
Acked-by: Tony Cheng <tony.cheng@amd.com>
Acked-by: Harry Wentland <harry.wentland@amd.com>
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>
Cc: Sean Paul <seanpaul@chromium.org>
Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
---
 drivers/gpu/drm/drm_atomic.c        | 10 +++++++
 drivers/gpu/drm/drm_atomic_helper.c | 15 +++++++++++
 drivers/gpu/drm/drm_connector.c     | 53 +++++++++++++++++++++++++++++++++++++
 include/drm/drm_connector.h         | 19 +++++++++++++
 include/drm/drm_mode_config.h       |  5 ++++
 include/uapi/drm/drm_mode.h         |  4 +++
 6 files changed, 106 insertions(+)

diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
index 19d7bcb..70a5152 100644
--- a/drivers/gpu/drm/drm_atomic.c
+++ b/drivers/gpu/drm/drm_atomic.c
@@ -1087,6 +1087,14 @@ int drm_atomic_connector_set_property(struct drm_connector *connector,
 		 * now?) atomic writes to DPMS property:
 		 */
 		return -EINVAL;
+	} else if (property == config->link_status_property) {
+		/* Never downgrade from GOOD to BAD on userspace's request here,
+		 * only hw issues can do that.
+		 */
+		if (state->link_status == DRM_LINK_STATUS_GOOD)
+			return 0;
+		state->link_status = val;
+		return 0;
 	} else if (connector->funcs->atomic_set_property) {
 		return connector->funcs->atomic_set_property(connector,
 				state, property, val);
@@ -1135,6 +1143,8 @@ static void drm_atomic_connector_print_state(struct drm_printer *p,
 		*val = (state->crtc) ? state->crtc->base.id : 0;
 	} else if (property == config->dpms_property) {
 		*val = connector->dpms;
+	} else if (property == config->link_status_property) {
+		*val = state->link_status;
 	} else if (connector->funcs->atomic_get_property) {
 		return connector->funcs->atomic_get_property(connector,
 				state, property, val);
diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index 494680c..3d6c1ce 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->state->link_status !=
+			    connector_state->link_status)
+				crtc_state->connectors_changed = true;
+		}
 	}
 
 	/*
@@ -2258,6 +2265,8 @@ static int update_output_state(struct drm_atomic_state *state,
 								NULL);
 			if (ret)
 				return ret;
+			/* Make sure legacy setCrtc always re-trains */
+			conn_state->link_status = DRM_LINK_STATUS_GOOD;
 		}
 	}
 
@@ -2301,6 +2310,12 @@ static int update_output_state(struct drm_atomic_state *state,
  *
  * Provides a default crtc set_config handler using the atomic driver interface.
  *
+ * NOTE: For backwards compatibility with old userspace this automatically
+ * resets the "link-status" property to GOOD, to force any link
+ * re-training. The SETCRTC ioctl does not define whether an update does
+ * need a full modeset or just a plane update, hence we're allowed to do
+ * that. See also drm_mode_connector_set_link_status_property().
+ *
  * Returns:
  * Returns 0 on success, negative errno numbers on failure.
  */
diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
index 5a45262..eee038a 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
@@ -625,6 +635,11 @@ int drm_display_info_set_bus_formats(struct drm_display_info *info,
  * 	tiling and virtualize both &drm_crtc and &drm_plane if needed. Drivers
  * 	should update this value using drm_mode_connector_set_tile_property().
  * 	Userspace cannot change this property.
+ * link-status:
+ *      Connector link-status property to indicate the status of link. The default
+ *      value of link-status is "GOOD". If something fails during or after modeset,
+ *      the kernel driver may set this to "BAD" and issue a hotplug uevent. Drivers
+ *      should update this value using drm_mode_connector_set_link_status_property().
  *
  * Connectors also have one standardized atomic property:
  *
@@ -666,6 +681,13 @@ 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;
 }
 
@@ -995,6 +1017,37 @@ int drm_mode_connector_update_edid_property(struct drm_connector *connector,
 }
 EXPORT_SYMBOL(drm_mode_connector_update_edid_property);
 
+/**
+ * drm_mode_connector_set_link_status_property - Set link status property of a connector
+ * @connector: drm connector
+ * @link_status: new value of link status property (0: Good, 1: Bad)
+ *
+ * In usual working scenario, this link status property will always be set to
+ * "GOOD". If something fails during or after a mode set, the kernel driver
+ * may set this link status property to "BAD". The caller then needs to send a
+ * hotplug uevent for userspace to re-check the valid modes through
+ * GET_CONNECTOR_IOCTL and retry modeset.
+ *
+ * Note: Drivers cannot rely on userspace to support this property and
+ * issue a modeset. As such, they may choose to handle issues (like
+ * re-training a link) without userspace's intervention.
+ *
+ * The reason for adding this property is to handle link training failures, but
+ * it is not limited to DP or link training. For example, if we implement
+ * asynchronous setcrtc, this property can be used to report any failures in that.
+ */
+void drm_mode_connector_set_link_status_property(struct drm_connector *connector,
+						 uint64_t link_status)
+{
+	struct drm_device *dev = connector->dev;
+
+	drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
+	connector->state->link_status = link_status;
+	drm_modeset_unlock(&dev->mode_config.connection_mutex);
+
+}
+EXPORT_SYMBOL(drm_mode_connector_set_link_status_property);
+
 int drm_mode_connector_set_obj_prop(struct drm_mode_object *obj,
 				    struct drm_property *property,
 				    uint64_t value)
diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
index 1218a0c..64e07c5 100644
--- a/include/drm/drm_connector.h
+++ b/include/drm/drm_connector.h
@@ -90,6 +90,17 @@ enum subpixel_order {
 };
 
 /**
+ * enum drm_link_status - connector's link_status property value
+ *
+ * This enum is used as the connector's link status property value.
+ * It is set to the values defined in uapi.
+ */
+enum drm_link_status {
+	DRM_LINK_STATUS_GOOD = DRM_MODE_LINK_STATUS_GOOD,
+	DRM_LINK_STATUS_BAD = DRM_MODE_LINK_STATUS_BAD,
+};
+
+/**
  * struct drm_display_info - runtime data about the connected sink
  *
  * Describes a given display (e.g. CRT or flat panel) and its limitations. For
@@ -213,6 +224,12 @@ struct drm_connector_state {
 
 	struct drm_encoder *best_encoder;
 
+	/**
+	 * @link_status: Connector link_status to keep track of whether link is
+	 * GOOD or BAD to notify userspace if retraining is necessary.
+	 */
+	enum drm_link_status link_status;
+
 	struct drm_atomic_state *state;
 };
 
@@ -776,6 +793,8 @@ int drm_mode_connector_set_path_property(struct drm_connector *connector,
 int drm_mode_connector_set_tile_property(struct drm_connector *connector);
 int drm_mode_connector_update_edid_property(struct drm_connector *connector,
 					    const struct edid *edid);
+void drm_mode_connector_set_link_status_property(struct drm_connector *connector,
+						 uint64_t link_status);
 
 /**
  * struct drm_tile_group - Tile group metadata
diff --git a/include/drm/drm_mode_config.h b/include/drm/drm_mode_config.h
index bf9991b..86faee4 100644
--- a/include/drm/drm_mode_config.h
+++ b/include/drm/drm_mode_config.h
@@ -431,6 +431,11 @@ 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 728790b..309c478 100644
--- a/include/uapi/drm/drm_mode.h
+++ b/include/uapi/drm/drm_mode.h
@@ -123,6 +123,10 @@
 #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 v4 1/4] drm: Add a new connector atomic property for link status

[Jani Nikula]

On Tue, 06 Dec 2016, Manasi Navare <manasi.d.navare@intel.com> wrote:
> At the time userspace does setcrtc, we've already promised the mode
> would work. The promise is based on the theoretical capabilities of
> the link, but it's possible we can't reach this in practice. The DP
> spec describes how the link should be reduced, but we can't reduce
> the link below the requirements of the mode. Black screen follows.
>
> One idea would be to have setcrtc return a failure. However, it
> already should not fail as the atomic checks have passed. It would
> also conflict with the idea of making setcrtc asynchronous in the
> future, returning before the actual mode setting and link training.
>
> Another idea is to train the link "upfront" at hotplug time, before
> pruning the mode list, so that we can do the pruning based on
> practical not theoretical capabilities. However, the changes for link
> training are pretty drastic, all for the sake of error handling and
> DP compliance, when the most common happy day scenario is the current
> approach of link training at mode setting time, using the optimal
> parameters for the mode. It is also not certain all hardware could do
> this without the pipe on; not even all our hardware can do this. Some
> of this can be solved, but not trivially.
>
> Both of the above ideas also fail to address link degradation *during*
> operation.
>
> The solution is to add a new "link-status" connector property in order
> to address link training failure in a way that:
> a) changes the current happy day scenario as little as possible, to
> avoid regressions, b) can be implemented the same way by all drm
> drivers, c) is still opt-in for the drivers and userspace, and opting
> out doesn't regress the user experience, d) doesn't prevent drivers
> from implementing better or alternate approaches, possibly without
> userspace involvement. And, of course, handles all the issues presented.
> In the usual happy day scenario, this is always "good". If something
> fails during or after a mode set, the kernel driver can set the link
> status to "bad" and issue a hotplug uevent for userspace to have it
> re-check the valid modes through GET_CONNECTOR IOCTL, and try modeset
> again. If the theoretical capabilities of the link can't be reached,
> the mode list is trimmed based on that.
>
> v4:
> * Add comments in kernel-doc format (Daniel Vetter)
> * Update the kernel-doc for link-status (Sean Paul)
> v3:
> * Fixed a build error (Jani Saarinen)
> v2:
> * Removed connector->link_status (Daniel Vetter)
> * Set connector->state->link_status in drm_mode_connector_set_link_status_property
> (Daniel Vetter)
> * Set the connector_changed flag to true if connector->state->link_status changed.
> * Reset link_status to GOOD in update_output_state (Daniel Vetter)
> * Never allow userspace to set link status from Good To Bad (Daniel Vetter)
>
> Reviewed-by: Sean Paul <seanpaul@chromium.org>
> Reviewed-by: Daniel Vetter  <daniel.vetter@ffwll.ch>
> Acked-by: Tony Cheng <tony.cheng@amd.com>
> Acked-by: Harry Wentland <harry.wentland@amd.com>
> 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>
> Cc: Sean Paul <seanpaul@chromium.org>
> Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
> ---
>  drivers/gpu/drm/drm_atomic.c        | 10 +++++++
>  drivers/gpu/drm/drm_atomic_helper.c | 15 +++++++++++
>  drivers/gpu/drm/drm_connector.c     | 53 +++++++++++++++++++++++++++++++++++++
>  include/drm/drm_connector.h         | 19 +++++++++++++
>  include/drm/drm_mode_config.h       |  5 ++++
>  include/uapi/drm/drm_mode.h         |  4 +++
>  6 files changed, 106 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
> index 19d7bcb..70a5152 100644
> --- a/drivers/gpu/drm/drm_atomic.c
> +++ b/drivers/gpu/drm/drm_atomic.c
> @@ -1087,6 +1087,14 @@ int drm_atomic_connector_set_property(struct drm_connector *connector,
>  		 * now?) atomic writes to DPMS property:
>  		 */
>  		return -EINVAL;
> +	} else if (property == config->link_status_property) {
> +		/* Never downgrade from GOOD to BAD on userspace's request here,
> +		 * only hw issues can do that.
> +		 */
> +		if (state->link_status == DRM_LINK_STATUS_GOOD)
> +			return 0;

Is it conceivable we'd want to support the userspace requesting the
change from GOOD to BAD at a later point in time? If yes, perhaps the
right answer here is to return an error on GOOD->BAD transition, so the
userspace can distinguish between the kernel rejecting vs. accepting the
property set?

BR,
Jani.


> +		state->link_status = val;
> +		return 0;
>  	} else if (connector->funcs->atomic_set_property) {
>  		return connector->funcs->atomic_set_property(connector,
>  				state, property, val);
> @@ -1135,6 +1143,8 @@ static void drm_atomic_connector_print_state(struct drm_printer *p,
>  		*val = (state->crtc) ? state->crtc->base.id : 0;
>  	} else if (property == config->dpms_property) {
>  		*val = connector->dpms;
> +	} else if (property == config->link_status_property) {
> +		*val = state->link_status;
>  	} else if (connector->funcs->atomic_get_property) {
>  		return connector->funcs->atomic_get_property(connector,
>  				state, property, val);
> diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> index 494680c..3d6c1ce 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->state->link_status !=
> +			    connector_state->link_status)
> +				crtc_state->connectors_changed = true;
> +		}
>  	}
>  
>  	/*
> @@ -2258,6 +2265,8 @@ static int update_output_state(struct drm_atomic_state *state,
>  								NULL);
>  			if (ret)
>  				return ret;
> +			/* Make sure legacy setCrtc always re-trains */
> +			conn_state->link_status = DRM_LINK_STATUS_GOOD;
>  		}
>  	}
>  
> @@ -2301,6 +2310,12 @@ static int update_output_state(struct drm_atomic_state *state,
>   *
>   * Provides a default crtc set_config handler using the atomic driver interface.
>   *
> + * NOTE: For backwards compatibility with old userspace this automatically
> + * resets the "link-status" property to GOOD, to force any link
> + * re-training. The SETCRTC ioctl does not define whether an update does
> + * need a full modeset or just a plane update, hence we're allowed to do
> + * that. See also drm_mode_connector_set_link_status_property().
> + *
>   * Returns:
>   * Returns 0 on success, negative errno numbers on failure.
>   */
> diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
> index 5a45262..eee038a 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
> @@ -625,6 +635,11 @@ int drm_display_info_set_bus_formats(struct drm_display_info *info,
>   * 	tiling and virtualize both &drm_crtc and &drm_plane if needed. Drivers
>   * 	should update this value using drm_mode_connector_set_tile_property().
>   * 	Userspace cannot change this property.
> + * link-status:
> + *      Connector link-status property to indicate the status of link. The default
> + *      value of link-status is "GOOD". If something fails during or after modeset,
> + *      the kernel driver may set this to "BAD" and issue a hotplug uevent. Drivers
> + *      should update this value using drm_mode_connector_set_link_status_property().
>   *
>   * Connectors also have one standardized atomic property:
>   *
> @@ -666,6 +681,13 @@ 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;
>  }
>  
> @@ -995,6 +1017,37 @@ int drm_mode_connector_update_edid_property(struct drm_connector *connector,
>  }
>  EXPORT_SYMBOL(drm_mode_connector_update_edid_property);
>  
> +/**
> + * drm_mode_connector_set_link_status_property - Set link status property of a connector
> + * @connector: drm connector
> + * @link_status: new value of link status property (0: Good, 1: Bad)
> + *
> + * In usual working scenario, this link status property will always be set to
> + * "GOOD". If something fails during or after a mode set, the kernel driver
> + * may set this link status property to "BAD". The caller then needs to send a
> + * hotplug uevent for userspace to re-check the valid modes through
> + * GET_CONNECTOR_IOCTL and retry modeset.
> + *
> + * Note: Drivers cannot rely on userspace to support this property and
> + * issue a modeset. As such, they may choose to handle issues (like
> + * re-training a link) without userspace's intervention.
> + *
> + * The reason for adding this property is to handle link training failures, but
> + * it is not limited to DP or link training. For example, if we implement
> + * asynchronous setcrtc, this property can be used to report any failures in that.
> + */
> +void drm_mode_connector_set_link_status_property(struct drm_connector *connector,
> +						 uint64_t link_status)
> +{
> +	struct drm_device *dev = connector->dev;
> +
> +	drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
> +	connector->state->link_status = link_status;
> +	drm_modeset_unlock(&dev->mode_config.connection_mutex);
> +
> +}
> +EXPORT_SYMBOL(drm_mode_connector_set_link_status_property);
> +
>  int drm_mode_connector_set_obj_prop(struct drm_mode_object *obj,
>  				    struct drm_property *property,
>  				    uint64_t value)
> diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
> index 1218a0c..64e07c5 100644
> --- a/include/drm/drm_connector.h
> +++ b/include/drm/drm_connector.h
> @@ -90,6 +90,17 @@ enum subpixel_order {
>  };
>  
>  /**
> + * enum drm_link_status - connector's link_status property value
> + *
> + * This enum is used as the connector's link status property value.
> + * It is set to the values defined in uapi.
> + */
> +enum drm_link_status {
> +	DRM_LINK_STATUS_GOOD = DRM_MODE_LINK_STATUS_GOOD,
> +	DRM_LINK_STATUS_BAD = DRM_MODE_LINK_STATUS_BAD,
> +};
> +
> +/**
>   * struct drm_display_info - runtime data about the connected sink
>   *
>   * Describes a given display (e.g. CRT or flat panel) and its limitations. For
> @@ -213,6 +224,12 @@ struct drm_connector_state {
>  
>  	struct drm_encoder *best_encoder;
>  
> +	/**
> +	 * @link_status: Connector link_status to keep track of whether link is
> +	 * GOOD or BAD to notify userspace if retraining is necessary.
> +	 */
> +	enum drm_link_status link_status;
> +
>  	struct drm_atomic_state *state;
>  };
>  
> @@ -776,6 +793,8 @@ int drm_mode_connector_set_path_property(struct drm_connector *connector,
>  int drm_mode_connector_set_tile_property(struct drm_connector *connector);
>  int drm_mode_connector_update_edid_property(struct drm_connector *connector,
>  					    const struct edid *edid);
> +void drm_mode_connector_set_link_status_property(struct drm_connector *connector,
> +						 uint64_t link_status);
>  
>  /**
>   * struct drm_tile_group - Tile group metadata
> diff --git a/include/drm/drm_mode_config.h b/include/drm/drm_mode_config.h
> index bf9991b..86faee4 100644
> --- a/include/drm/drm_mode_config.h
> +++ b/include/drm/drm_mode_config.h
> @@ -431,6 +431,11 @@ 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 728790b..309c478 100644
> --- a/include/uapi/drm/drm_mode.h
> +++ b/include/uapi/drm/drm_mode.h
> @@ -123,6 +123,10 @@
>  #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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Re: [Intel-gfx] [PATCH v4 1/4] drm: Add a new connector atomic property for link status

[Daniel Vetter]

On Thu, Dec 08, 2016 at 05:05:54PM +0200, Jani Nikula wrote:
> On Tue, 06 Dec 2016, Manasi Navare <manasi.d.navare@intel.com> wrote:
> > At the time userspace does setcrtc, we've already promised the mode
> > would work. The promise is based on the theoretical capabilities of
> > the link, but it's possible we can't reach this in practice. The DP
> > spec describes how the link should be reduced, but we can't reduce
> > the link below the requirements of the mode. Black screen follows.
> >
> > One idea would be to have setcrtc return a failure. However, it
> > already should not fail as the atomic checks have passed. It would
> > also conflict with the idea of making setcrtc asynchronous in the
> > future, returning before the actual mode setting and link training.
> >
> > Another idea is to train the link "upfront" at hotplug time, before
> > pruning the mode list, so that we can do the pruning based on
> > practical not theoretical capabilities. However, the changes for link
> > training are pretty drastic, all for the sake of error handling and
> > DP compliance, when the most common happy day scenario is the current
> > approach of link training at mode setting time, using the optimal
> > parameters for the mode. It is also not certain all hardware could do
> > this without the pipe on; not even all our hardware can do this. Some
> > of this can be solved, but not trivially.
> >
> > Both of the above ideas also fail to address link degradation *during*
> > operation.
> >
> > The solution is to add a new "link-status" connector property in order
> > to address link training failure in a way that:
> > a) changes the current happy day scenario as little as possible, to
> > avoid regressions, b) can be implemented the same way by all drm
> > drivers, c) is still opt-in for the drivers and userspace, and opting
> > out doesn't regress the user experience, d) doesn't prevent drivers
> > from implementing better or alternate approaches, possibly without
> > userspace involvement. And, of course, handles all the issues presented.
> > In the usual happy day scenario, this is always "good". If something
> > fails during or after a mode set, the kernel driver can set the link
> > status to "bad" and issue a hotplug uevent for userspace to have it
> > re-check the valid modes through GET_CONNECTOR IOCTL, and try modeset
> > again. If the theoretical capabilities of the link can't be reached,
> > the mode list is trimmed based on that.
> >
> > v4:
> > * Add comments in kernel-doc format (Daniel Vetter)
> > * Update the kernel-doc for link-status (Sean Paul)
> > v3:
> > * Fixed a build error (Jani Saarinen)
> > v2:
> > * Removed connector->link_status (Daniel Vetter)
> > * Set connector->state->link_status in drm_mode_connector_set_link_status_property
> > (Daniel Vetter)
> > * Set the connector_changed flag to true if connector->state->link_status changed.
> > * Reset link_status to GOOD in update_output_state (Daniel Vetter)
> > * Never allow userspace to set link status from Good To Bad (Daniel Vetter)
> >
> > Reviewed-by: Sean Paul <seanpaul@chromium.org>
> > Reviewed-by: Daniel Vetter  <daniel.vetter@ffwll.ch>
> > Acked-by: Tony Cheng <tony.cheng@amd.com>
> > Acked-by: Harry Wentland <harry.wentland@amd.com>
> > 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>
> > Cc: Sean Paul <seanpaul@chromium.org>
> > Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
> > ---
> >  drivers/gpu/drm/drm_atomic.c        | 10 +++++++
> >  drivers/gpu/drm/drm_atomic_helper.c | 15 +++++++++++
> >  drivers/gpu/drm/drm_connector.c     | 53 +++++++++++++++++++++++++++++++++++++
> >  include/drm/drm_connector.h         | 19 +++++++++++++
> >  include/drm/drm_mode_config.h       |  5 ++++
> >  include/uapi/drm/drm_mode.h         |  4 +++
> >  6 files changed, 106 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
> > index 19d7bcb..70a5152 100644
> > --- a/drivers/gpu/drm/drm_atomic.c
> > +++ b/drivers/gpu/drm/drm_atomic.c
> > @@ -1087,6 +1087,14 @@ int drm_atomic_connector_set_property(struct drm_connector *connector,
> >  		 * now?) atomic writes to DPMS property:
> >  		 */
> >  		return -EINVAL;
> > +	} else if (property == config->link_status_property) {
> > +		/* Never downgrade from GOOD to BAD on userspace's request here,
> > +		 * only hw issues can do that.
> > +		 */
> > +		if (state->link_status == DRM_LINK_STATUS_GOOD)
> > +			return 0;
> 
> Is it conceivable we'd want to support the userspace requesting the
> change from GOOD to BAD at a later point in time? If yes, perhaps the
> right answer here is to return an error on GOOD->BAD transition, so the
> userspace can distinguish between the kernel rejecting vs. accepting the
> property set?

One of the design ideas behind atomic is that userspace doesn't need to be
able to understand all properties, but still needs to be able to restore
the state it wants on VT switch. Or as a "pls reset my display to boot-up
state because my compositor made a mess of it". That's why e.g. the
various fence ptr properties read back as 0, and the fence fd input
parameters read back as -1, to make sure dumb save/restore doesn't do
something stupid.

Same idea here for silently rejecting a good->bad transition: We don't
want userspace to accidentally break the display when it restores state.
At least that's been my thinking behind suggesting this. Might want to
document that somewhere a bit better.

> 
> BR,
> Jani.
> 
> 
> > +		state->link_status = val;
> > +		return 0;
> >  	} else if (connector->funcs->atomic_set_property) {
> >  		return connector->funcs->atomic_set_property(connector,
> >  				state, property, val);
> > @@ -1135,6 +1143,8 @@ static void drm_atomic_connector_print_state(struct drm_printer *p,
> >  		*val = (state->crtc) ? state->crtc->base.id : 0;
> >  	} else if (property == config->dpms_property) {
> >  		*val = connector->dpms;
> > +	} else if (property == config->link_status_property) {
> > +		*val = state->link_status;
> >  	} else if (connector->funcs->atomic_get_property) {
> >  		return connector->funcs->atomic_get_property(connector,
> >  				state, property, val);
> > diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> > index 494680c..3d6c1ce 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->state->link_status !=
> > +			    connector_state->link_status)
> > +				crtc_state->connectors_changed = true;
> > +		}
> >  	}
> >  
> >  	/*
> > @@ -2258,6 +2265,8 @@ static int update_output_state(struct drm_atomic_state *state,
> >  								NULL);
> >  			if (ret)
> >  				return ret;
> > +			/* Make sure legacy setCrtc always re-trains */
> > +			conn_state->link_status = DRM_LINK_STATUS_GOOD;
> >  		}
> >  	}
> >  
> > @@ -2301,6 +2310,12 @@ static int update_output_state(struct drm_atomic_state *state,
> >   *
> >   * Provides a default crtc set_config handler using the atomic driver interface.
> >   *
> > + * NOTE: For backwards compatibility with old userspace this automatically
> > + * resets the "link-status" property to GOOD, to force any link
> > + * re-training. The SETCRTC ioctl does not define whether an update does
> > + * need a full modeset or just a plane update, hence we're allowed to do
> > + * that. See also drm_mode_connector_set_link_status_property().
> > + *
> >   * Returns:
> >   * Returns 0 on success, negative errno numbers on failure.
> >   */
> > diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
> > index 5a45262..eee038a 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
> > @@ -625,6 +635,11 @@ int drm_display_info_set_bus_formats(struct drm_display_info *info,
> >   * 	tiling and virtualize both &drm_crtc and &drm_plane if needed. Drivers
> >   * 	should update this value using drm_mode_connector_set_tile_property().
> >   * 	Userspace cannot change this property.
> > + * link-status:
> > + *      Connector link-status property to indicate the status of link. The default
> > + *      value of link-status is "GOOD". If something fails during or after modeset,
> > + *      the kernel driver may set this to "BAD" and issue a hotplug uevent. Drivers
> > + *      should update this value using drm_mode_connector_set_link_status_property().

E.g. by adding here "Note that userspace trying to change from GOOD to BAD
is silently rejected, to avoid a dumb save/restore for e.g. VT switching
from upsetting the display state."

Does that sound good?

Cheers, Daniel

> >   *
> >   * Connectors also have one standardized atomic property:
> >   *
> > @@ -666,6 +681,13 @@ 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;
> >  }
> >  
> > @@ -995,6 +1017,37 @@ int drm_mode_connector_update_edid_property(struct drm_connector *connector,
> >  }
> >  EXPORT_SYMBOL(drm_mode_connector_update_edid_property);
> >  
> > +/**
> > + * drm_mode_connector_set_link_status_property - Set link status property of a connector
> > + * @connector: drm connector
> > + * @link_status: new value of link status property (0: Good, 1: Bad)
> > + *
> > + * In usual working scenario, this link status property will always be set to
> > + * "GOOD". If something fails during or after a mode set, the kernel driver
> > + * may set this link status property to "BAD". The caller then needs to send a
> > + * hotplug uevent for userspace to re-check the valid modes through
> > + * GET_CONNECTOR_IOCTL and retry modeset.
> > + *
> > + * Note: Drivers cannot rely on userspace to support this property and
> > + * issue a modeset. As such, they may choose to handle issues (like
> > + * re-training a link) without userspace's intervention.
> > + *
> > + * The reason for adding this property is to handle link training failures, but
> > + * it is not limited to DP or link training. For example, if we implement
> > + * asynchronous setcrtc, this property can be used to report any failures in that.
> > + */
> > +void drm_mode_connector_set_link_status_property(struct drm_connector *connector,
> > +						 uint64_t link_status)
> > +{
> > +	struct drm_device *dev = connector->dev;
> > +
> > +	drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
> > +	connector->state->link_status = link_status;
> > +	drm_modeset_unlock(&dev->mode_config.connection_mutex);
> > +
> > +}
> > +EXPORT_SYMBOL(drm_mode_connector_set_link_status_property);
> > +
> >  int drm_mode_connector_set_obj_prop(struct drm_mode_object *obj,
> >  				    struct drm_property *property,
> >  				    uint64_t value)
> > diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
> > index 1218a0c..64e07c5 100644
> > --- a/include/drm/drm_connector.h
> > +++ b/include/drm/drm_connector.h
> > @@ -90,6 +90,17 @@ enum subpixel_order {
> >  };
> >  
> >  /**
> > + * enum drm_link_status - connector's link_status property value
> > + *
> > + * This enum is used as the connector's link status property value.
> > + * It is set to the values defined in uapi.
> > + */
> > +enum drm_link_status {
> > +	DRM_LINK_STATUS_GOOD = DRM_MODE_LINK_STATUS_GOOD,
> > +	DRM_LINK_STATUS_BAD = DRM_MODE_LINK_STATUS_BAD,
> > +};
> > +
> > +/**
> >   * struct drm_display_info - runtime data about the connected sink
> >   *
> >   * Describes a given display (e.g. CRT or flat panel) and its limitations. For
> > @@ -213,6 +224,12 @@ struct drm_connector_state {
> >  
> >  	struct drm_encoder *best_encoder;
> >  
> > +	/**
> > +	 * @link_status: Connector link_status to keep track of whether link is
> > +	 * GOOD or BAD to notify userspace if retraining is necessary.
> > +	 */
> > +	enum drm_link_status link_status;
> > +
> >  	struct drm_atomic_state *state;
> >  };
> >  
> > @@ -776,6 +793,8 @@ int drm_mode_connector_set_path_property(struct drm_connector *connector,
> >  int drm_mode_connector_set_tile_property(struct drm_connector *connector);
> >  int drm_mode_connector_update_edid_property(struct drm_connector *connector,
> >  					    const struct edid *edid);
> > +void drm_mode_connector_set_link_status_property(struct drm_connector *connector,
> > +						 uint64_t link_status);
> >  
> >  /**
> >   * struct drm_tile_group - Tile group metadata
> > diff --git a/include/drm/drm_mode_config.h b/include/drm/drm_mode_config.h
> > index bf9991b..86faee4 100644
> > --- a/include/drm/drm_mode_config.h
> > +++ b/include/drm/drm_mode_config.h
> > @@ -431,6 +431,11 @@ 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 728790b..309c478 100644
> > --- a/include/uapi/drm/drm_mode.h
> > +++ b/include/uapi/drm/drm_mode.h
> > @@ -123,6 +123,10 @@
> >  #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
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/intel-gfx

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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Re: [PATCH 2/4] drm/i915: Compute sink's max lane count/link BW at Hotplug

[Manasi Navare]

Jani,

Could you please review this patch? This is the patch that
calculates the max sink link rate and max sink lane count only
once at hotplug and then anytime the max lane count and common rates are requested,
the helper functions use these values.
This simplifies the fallback logic since we can go ahead and update
the max sink link rate and lane count to these fallback lower
values since link training failed so thus capping the max values
to fallback values.
This is better than defining common_rates array in intel_dp, because
its easier to update the max link rate vs going and updating and
resizing the whole array.
Also with this approach the helper functions do not change.

Regards
Manasi

On Mon, Dec 05, 2016 at 04:27:36PM -0800, Manasi Navare wrote:
> Sink's capabilities are advertised through DPCD registers and get
> updated only on hotplug. So they should be computed only once in the
> long pulse handler and saved off in intel_dp structure for the use
> later. For this reason two new fields max_sink_lane_count and
> max_sink_link_bw are added to intel_dp structure.
> 
> This also simplifies the fallback link rate/lane count logic
> to handle link training failure. In that case, the max_sink_link_bw
> and max_sink_lane_count can be reccomputed to match the fallback
> values lowering the sink capabilities due to link train failure.
> 
> 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  | 10 ++++++++--
>  drivers/gpu/drm/i915/intel_drv.h |  4 ++++
>  2 files changed, 12 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index db75bb9..434dc7d 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -156,7 +156,7 @@ static u8 intel_dp_max_lane_count(struct intel_dp *intel_dp)
>  	u8 source_max, sink_max;
>  
>  	source_max = intel_dig_port->max_lanes;
> -	sink_max = drm_dp_max_lane_count(intel_dp->dpcd);
> +	sink_max = intel_dp->max_sink_lane_count;
>  
>  	return min(source_max, sink_max);
>  }
> @@ -213,7 +213,7 @@ static u8 intel_dp_max_lane_count(struct intel_dp *intel_dp)
>  
>  	*sink_rates = default_rates;
>  
> -	return (intel_dp_max_link_bw(intel_dp) >> 3) + 1;
> +	return (intel_dp->max_sink_link_bw >> 3) + 1;
>  }
>  
>  static int
> @@ -4395,6 +4395,12 @@ static bool intel_digital_port_connected(struct drm_i915_private *dev_priv,
>  		      yesno(intel_dp_source_supports_hbr2(intel_dp)),
>  		      yesno(drm_dp_tps3_supported(intel_dp->dpcd)));
>  
> +	/* Set the max lane count for sink */
> +	intel_dp->max_sink_lane_count = drm_dp_max_lane_count(intel_dp->dpcd);
> +
> +	/* Set the max link BW for sink */
> +	intel_dp->max_sink_link_bw = intel_dp_max_link_bw(intel_dp);
> +
>  	intel_dp_print_rates(intel_dp);
>  
>  	intel_dp_read_desc(intel_dp);
> diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> index fd77a3b..b6526ad 100644
> --- a/drivers/gpu/drm/i915/intel_drv.h
> +++ b/drivers/gpu/drm/i915/intel_drv.h
> @@ -906,6 +906,10 @@ struct intel_dp {
>  	/* sink rates as reported by DP_SUPPORTED_LINK_RATES */
>  	uint8_t num_sink_rates;
>  	int sink_rates[DP_MAX_SUPPORTED_RATES];
> +	/* Max lane count for the sink as per DPCD registers */
> +	uint8_t max_sink_lane_count;
> +	/* Max link BW for the sink as per DPCD registers */
> +	int max_sink_link_bw;
>  	/* sink or branch descriptor */
>  	struct intel_dp_desc desc;
>  	struct drm_dp_aux aux;
> -- 
> 1.9.1
> 
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Re: [PATCH 3/4] drm/i915: Find fallback link rate/lane count

[Manasi Navare]

Hi Jani,

This patch uses the simplified fallback logic where
if link train fails, we first lower the max sink link rate
to a lower value until it reaches RBR keeping the max lane count
unchanged and then lower the lane count and set max lane count to
this lowered lane count and resetting the link rate to the max
sink link rate based on DPCD values.
Because this directly goes and updates the max link rate
and max lane count values on fallback, we do not need
any special case for fallback during intel_dp_compute_config.

Manasi

On Mon, Dec 05, 2016 at 04:27:37PM -0800, Manasi Navare wrote:
> 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 and limits the max
> link_rate and lane_count values to these fallback values.
> 
> v6:
> * Cap the max link rate and lane count to the max
> values obtained during fallback link training (Daniel Vetter)
> v5:
> * Start the fallback at the lane count value passed not
> the max lane count (Jani Nikula)
> v4:
> * Remove the redundant variable link_train_failed
> v3:
> * Remove fallback_link_rate_index variable, just obtain
> that using the helper intel_dp_link_rate_index (Jani Nikula)
> v2:
> Squash the patch that returns the link rate index (Jani Nikula)
> 
> Acked-by: Tony Cheng <tony.cheng@amd.com>
> Acked-by: Harry Wentland <harry.wentland@amd.com>
> 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  | 40 ++++++++++++++++++++++++++++++++++++++++
>  drivers/gpu/drm/i915/intel_drv.h |  2 ++
>  2 files changed, 42 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 434dc7d..b5c7526f 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -278,6 +278,46 @@ 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;
> +}
> +
> +int 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;
> +
> +	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->max_sink_link_bw = drm_dp_link_rate_to_bw_code(common_rates[link_rate_index - 1]);
> +		intel_dp->max_sink_lane_count = lane_count;
> +	} else if (lane_count > 1) {
> +		intel_dp->max_sink_link_bw = intel_dp_max_link_bw(intel_dp);
> +		intel_dp->max_sink_lane_count = lane_count >> 1;
> +	} else {
> +		DRM_ERROR("Link Training Unsuccessful\n");
> +		return -1;
> +	}
> +
> +	return 0;
> +}
> +
>  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 b6526ad..47e3671 100644
> --- a/drivers/gpu/drm/i915/intel_drv.h
> +++ b/drivers/gpu/drm/i915/intel_drv.h
> @@ -1400,6 +1400,8 @@ bool intel_dp_init_connector(struct intel_digital_port *intel_dig_port,
>  void intel_dp_set_link_params(struct intel_dp *intel_dp,
>  			      int link_rate, uint8_t lane_count,
>  			      bool link_mst);
> +int 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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Re: [PATCH 4/4] drm/i915: Implement Link Rate fallback on Link training failure

[Manasi Navare]

Hi Jani,

Could you please review this patch?
This patch was changed a bit from the last time you reviewed it
based on feedback from Sean Paul that the driver need not
validate the modes and prune the mode on link training failure.
Instead it should just send the hotplug uevent after setting link status
to BAD and then userspace driver should take care of validating the modes
again before modeset. So the i915_modeset_work_fn removed the calls to
intel_dp_mode_valid() and prune_mode_invalid().
There are no other functional changes in this patch from the previous
reviewed version.
Daniel has already ACKED this, but need your formal r-b.

Regards
Manasi

On Mon, Dec 05, 2016 at 04:27:38PM -0800, 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.
> 
> v9:
> * Use the trimmed max values of link rate/lane count based on
> link train fallback (Daniel Vetter)
> v8:
> * Set link_status to BAD first and then call mode_valid (Jani Nikula)
> v7:
> Remove the redundant variable in previous patch itself
> v6:
> * Obtain link rate index from fallback_link_rate using
> the helper intel_dp_link_rate_index (Jani Nikula)
> * Include fallback within intel_dp_start_link_train (Jani Nikula)
> v5:
> * Move set link status to drm core (Daniel Vetter, Jani Nikula)
> v4:
> * Add fallback support for non DDI platforms too
> * Set connector->link status inside set_link_status function
> (Jani Nikula)
> 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)
> 
> Acked-by: Tony Cheng <tony.cheng@amd.com>
> Acked-by: Harry Wentland <Harry.wentland@amd.com>
> 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/i915/intel_dp.c               | 27 +++++++++++++++++++++++++++
>  drivers/gpu/drm/i915/intel_dp_link_training.c | 22 ++++++++++++++++++++--
>  drivers/gpu/drm/i915/intel_drv.h              |  3 +++
>  3 files changed, 50 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index b5c7526f..404da32 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -5676,6 +5676,29 @@ 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;
> +
> +	intel_connector = container_of(work, typeof(*intel_connector),
> +				       modeset_retry_work);
> +	connector = &intel_connector->base;
> +	DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n", connector->base.id,
> +		      connector->name);
> +
> +	/* Grab the locks before changing connector property*/
> +	mutex_lock(&connector->dev->mode_config.mutex);
> +	/* Set connector link status to BAD and send a Uevent to notify
> +	 * userspace to do a modeset.
> +	 */
> +	drm_mode_connector_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)
> @@ -5688,6 +5711,10 @@ 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..955b239 100644
> --- a/drivers/gpu/drm/i915/intel_dp_link_training.c
> +++ b/drivers/gpu/drm/i915/intel_dp_link_training.c
> @@ -313,6 +313,24 @@ void intel_dp_stop_link_train(struct intel_dp *intel_dp)
>  void
>  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);
> +	struct intel_connector *intel_connector = intel_dp->attached_connector;
> +
> +	if (!intel_dp_link_training_clock_recovery(intel_dp))
> +		goto failure_handling;
> +	if (!intel_dp_link_training_channel_equalization(intel_dp))
> +		goto failure_handling;
> +
> +	DRM_DEBUG_KMS("Link Training Passed at Link Rate = %d, Lane count = %d",
> +		      intel_dp->link_rate, intel_dp->lane_count);
> +	return;
> +
> + failure_handling:
> +	DRM_DEBUG_KMS("Link Training failed at link rate = %d, lane count = %d",
> +		      intel_dp->link_rate, intel_dp->lane_count);
> +	if (!intel_dp_get_link_train_fallback_values(intel_dp,
> +						     intel_dp->link_rate,
> +						     intel_dp->lane_count))
> +		/* Schedule a Hotplug Uevent to userspace to start modeset */
> +		schedule_work(&intel_connector->modeset_retry_work);
> +	return;
>  }
> diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> index 47e3671..9d6f7ee 100644
> --- a/drivers/gpu/drm/i915/intel_drv.h
> +++ b/drivers/gpu/drm/i915/intel_drv.h
> @@ -315,6 +315,9 @@ 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 {
> -- 
> 1.9.1
> 
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[PATCH v5 1/4] drm: Add a new connector atomic property for link status

[Manasi Navare]

At the time userspace does setcrtc, we've already promised the mode
would work. The promise is based on the theoretical capabilities of
the link, but it's possible we can't reach this in practice. The DP
spec describes how the link should be reduced, but we can't reduce
the link below the requirements of the mode. Black screen follows.

One idea would be to have setcrtc return a failure. However, it
already should not fail as the atomic checks have passed. It would
also conflict with the idea of making setcrtc asynchronous in the
future, returning before the actual mode setting and link training.

Another idea is to train the link "upfront" at hotplug time, before
pruning the mode list, so that we can do the pruning based on
practical not theoretical capabilities. However, the changes for link
training are pretty drastic, all for the sake of error handling and
DP compliance, when the most common happy day scenario is the current
approach of link training at mode setting time, using the optimal
parameters for the mode. It is also not certain all hardware could do
this without the pipe on; not even all our hardware can do this. Some
of this can be solved, but not trivially.

Both of the above ideas also fail to address link degradation *during*
operation.

The solution is to add a new "link-status" connector property in order
to address link training failure in a way that:
a) changes the current happy day scenario as little as possible, to
avoid regressions, b) can be implemented the same way by all drm
drivers, c) is still opt-in for the drivers and userspace, and opting
out doesn't regress the user experience, d) doesn't prevent drivers
from implementing better or alternate approaches, possibly without
userspace involvement. And, of course, handles all the issues presented.
In the usual happy day scenario, this is always "good". If something
fails during or after a mode set, the kernel driver can set the link
status to "bad" and issue a hotplug uevent for userspace to have it
re-check the valid modes through GET_CONNECTOR IOCTL, and try modeset
again. If the theoretical capabilities of the link can't be reached,
the mode list is trimmed based on that.

v5:
* Clarify doc for silent rejection of atomic properties by driver (Daniel Vetter)
v4:
* Add comments in kernel-doc format (Daniel Vetter)
* Update the kernel-doc for link-status (Sean Paul)
v3:
* Fixed a build error (Jani Saarinen)
v2:
* Removed connector->link_status (Daniel Vetter)
* Set connector->state->link_status in drm_mode_connector_set_link_status_property
(Daniel Vetter)
* Set the connector_changed flag to true if connector->state->link_status changed.
* Reset link_status to GOOD in update_output_state (Daniel Vetter)
* Never allow userspace to set link status from Good To Bad (Daniel Vetter)

Reviewed-by: Sean Paul <seanpaul@chromium.org>
Reviewed-by: Daniel Vetter  <daniel.vetter@ffwll.ch>
Acked-by: Tony Cheng <tony.cheng@amd.com>
Acked-by: Harry Wentland <harry.wentland@amd.com>
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>
Cc: Sean Paul <seanpaul@chromium.org>
Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
---
 drivers/gpu/drm/drm_atomic.c        | 18 +++++++++++++
 drivers/gpu/drm/drm_atomic_helper.c | 15 +++++++++++
 drivers/gpu/drm/drm_connector.c     | 53 +++++++++++++++++++++++++++++++++++++
 include/drm/drm_connector.h         | 19 +++++++++++++
 include/drm/drm_mode_config.h       |  5 ++++
 include/uapi/drm/drm_mode.h         |  4 +++
 6 files changed, 114 insertions(+)

diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
index 72fa5b2..34eddb9 100644
--- a/drivers/gpu/drm/drm_atomic.c
+++ b/drivers/gpu/drm/drm_atomic.c
@@ -1087,6 +1087,22 @@ int drm_atomic_connector_set_property(struct drm_connector *connector,
 		 * now?) atomic writes to DPMS property:
 		 */
 		return -EINVAL;
+	} else if (property == config->link_status_property) {
+		/* Never downgrade from GOOD to BAD on userspace's request here,
+		 * only hw issues can do that.
+		 *
+		 * For an atomic property the userspace doesn't need to be able
+		 * to understand all the properties, but needs to be able to
+		 * restore the state itw ants on VT switch. So if the userspace
+		 * tries to change the link_status from GOOD to BAD, driver
+		 * silently rejects it and returns a 0. This prevents userspace
+		 * from accidently breaking  the display when it restores the
+		 * state.
+		 */
+		if (state->link_status == DRM_LINK_STATUS_GOOD)
+			return 0;
+		state->link_status = val;
+		return 0;
 	} else if (connector->funcs->atomic_set_property) {
 		return connector->funcs->atomic_set_property(connector,
 				state, property, val);
@@ -1135,6 +1151,8 @@ static void drm_atomic_connector_print_state(struct drm_printer *p,
 		*val = (state->crtc) ? state->crtc->base.id : 0;
 	} else if (property == config->dpms_property) {
 		*val = connector->dpms;
+	} else if (property == config->link_status_property) {
+		*val = state->link_status;
 	} else if (connector->funcs->atomic_get_property) {
 		return connector->funcs->atomic_get_property(connector,
 				state, property, val);
diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index 23767df..5e7af63 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->state->link_status !=
+			    connector_state->link_status)
+				crtc_state->connectors_changed = true;
+		}
 	}
 
 	/*
@@ -2255,6 +2262,8 @@ static int update_output_state(struct drm_atomic_state *state,
 								NULL);
 			if (ret)
 				return ret;
+			/* Make sure legacy setCrtc always re-trains */
+			conn_state->link_status = DRM_LINK_STATUS_GOOD;
 		}
 	}
 
@@ -2298,6 +2307,12 @@ static int update_output_state(struct drm_atomic_state *state,
  *
  * Provides a default crtc set_config handler using the atomic driver interface.
  *
+ * NOTE: For backwards compatibility with old userspace this automatically
+ * resets the "link-status" property to GOOD, to force any link
+ * re-training. The SETCRTC ioctl does not define whether an update does
+ * need a full modeset or just a plane update, hence we're allowed to do
+ * that. See also drm_mode_connector_set_link_status_property().
+ *
  * Returns:
  * Returns 0 on success, negative errno numbers on failure.
  */
diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
index 5a45262..eee038a 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
@@ -625,6 +635,11 @@ int drm_display_info_set_bus_formats(struct drm_display_info *info,
  * 	tiling and virtualize both &drm_crtc and &drm_plane if needed. Drivers
  * 	should update this value using drm_mode_connector_set_tile_property().
  * 	Userspace cannot change this property.
+ * link-status:
+ *      Connector link-status property to indicate the status of link. The default
+ *      value of link-status is "GOOD". If something fails during or after modeset,
+ *      the kernel driver may set this to "BAD" and issue a hotplug uevent. Drivers
+ *      should update this value using drm_mode_connector_set_link_status_property().
  *
  * Connectors also have one standardized atomic property:
  *
@@ -666,6 +681,13 @@ 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;
 }
 
@@ -995,6 +1017,37 @@ int drm_mode_connector_update_edid_property(struct drm_connector *connector,
 }
 EXPORT_SYMBOL(drm_mode_connector_update_edid_property);
 
+/**
+ * drm_mode_connector_set_link_status_property - Set link status property of a connector
+ * @connector: drm connector
+ * @link_status: new value of link status property (0: Good, 1: Bad)
+ *
+ * In usual working scenario, this link status property will always be set to
+ * "GOOD". If something fails during or after a mode set, the kernel driver
+ * may set this link status property to "BAD". The caller then needs to send a
+ * hotplug uevent for userspace to re-check the valid modes through
+ * GET_CONNECTOR_IOCTL and retry modeset.
+ *
+ * Note: Drivers cannot rely on userspace to support this property and
+ * issue a modeset. As such, they may choose to handle issues (like
+ * re-training a link) without userspace's intervention.
+ *
+ * The reason for adding this property is to handle link training failures, but
+ * it is not limited to DP or link training. For example, if we implement
+ * asynchronous setcrtc, this property can be used to report any failures in that.
+ */
+void drm_mode_connector_set_link_status_property(struct drm_connector *connector,
+						 uint64_t link_status)
+{
+	struct drm_device *dev = connector->dev;
+
+	drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
+	connector->state->link_status = link_status;
+	drm_modeset_unlock(&dev->mode_config.connection_mutex);
+
+}
+EXPORT_SYMBOL(drm_mode_connector_set_link_status_property);
+
 int drm_mode_connector_set_obj_prop(struct drm_mode_object *obj,
 				    struct drm_property *property,
 				    uint64_t value)
diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
index 1218a0c..64e07c5 100644
--- a/include/drm/drm_connector.h
+++ b/include/drm/drm_connector.h
@@ -90,6 +90,17 @@ enum subpixel_order {
 };
 
 /**
+ * enum drm_link_status - connector's link_status property value
+ *
+ * This enum is used as the connector's link status property value.
+ * It is set to the values defined in uapi.
+ */
+enum drm_link_status {
+	DRM_LINK_STATUS_GOOD = DRM_MODE_LINK_STATUS_GOOD,
+	DRM_LINK_STATUS_BAD = DRM_MODE_LINK_STATUS_BAD,
+};
+
+/**
  * struct drm_display_info - runtime data about the connected sink
  *
  * Describes a given display (e.g. CRT or flat panel) and its limitations. For
@@ -213,6 +224,12 @@ struct drm_connector_state {
 
 	struct drm_encoder *best_encoder;
 
+	/**
+	 * @link_status: Connector link_status to keep track of whether link is
+	 * GOOD or BAD to notify userspace if retraining is necessary.
+	 */
+	enum drm_link_status link_status;
+
 	struct drm_atomic_state *state;
 };
 
@@ -776,6 +793,8 @@ int drm_mode_connector_set_path_property(struct drm_connector *connector,
 int drm_mode_connector_set_tile_property(struct drm_connector *connector);
 int drm_mode_connector_update_edid_property(struct drm_connector *connector,
 					    const struct edid *edid);
+void drm_mode_connector_set_link_status_property(struct drm_connector *connector,
+						 uint64_t link_status);
 
 /**
  * struct drm_tile_group - Tile group metadata
diff --git a/include/drm/drm_mode_config.h b/include/drm/drm_mode_config.h
index bf9991b..86faee4 100644
--- a/include/drm/drm_mode_config.h
+++ b/include/drm/drm_mode_config.h
@@ -431,6 +431,11 @@ 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 728790b..309c478 100644
--- a/include/uapi/drm/drm_mode.h
+++ b/include/uapi/drm/drm_mode.h
@@ -123,6 +123,10 @@
 #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 v5 1/4] drm: Add a new connector atomic property for link status

[Sean Paul]

<snip>

> diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
> index 72fa5b2..34eddb9 100644
> --- a/drivers/gpu/drm/drm_atomic.c
> +++ b/drivers/gpu/drm/drm_atomic.c
> @@ -1087,6 +1087,22 @@ int drm_atomic_connector_set_property(struct drm_connector *connector,
>                  * now?) atomic writes to DPMS property:
>                  */
>                 return -EINVAL;
> +       } else if (property == config->link_status_property) {
> +               /* Never downgrade from GOOD to BAD on userspace's request here,
> +                * only hw issues can do that.
> +                *
> +                * For an atomic property the userspace doesn't need to be able
> +                * to understand all the properties, but needs to be able to
> +                * restore the state itw ants on VT switch. So if the userspace

s/itw ants/it wants/

<snip>
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[PATCH v6 1/4] drm: Add a new connector atomic property for link status

[Manasi Navare]

At the time userspace does setcrtc, we've already promised the mode
would work. The promise is based on the theoretical capabilities of
the link, but it's possible we can't reach this in practice. The DP
spec describes how the link should be reduced, but we can't reduce
the link below the requirements of the mode. Black screen follows.

One idea would be to have setcrtc return a failure. However, it
already should not fail as the atomic checks have passed. It would
also conflict with the idea of making setcrtc asynchronous in the
future, returning before the actual mode setting and link training.

Another idea is to train the link "upfront" at hotplug time, before
pruning the mode list, so that we can do the pruning based on
practical not theoretical capabilities. However, the changes for link
training are pretty drastic, all for the sake of error handling and
DP compliance, when the most common happy day scenario is the current
approach of link training at mode setting time, using the optimal
parameters for the mode. It is also not certain all hardware could do
this without the pipe on; not even all our hardware can do this. Some
of this can be solved, but not trivially.

Both of the above ideas also fail to address link degradation *during*
operation.

The solution is to add a new "link-status" connector property in order
to address link training failure in a way that:
a) changes the current happy day scenario as little as possible, to
avoid regressions, b) can be implemented the same way by all drm
drivers, c) is still opt-in for the drivers and userspace, and opting
out doesn't regress the user experience, d) doesn't prevent drivers
from implementing better or alternate approaches, possibly without
userspace involvement. And, of course, handles all the issues presented.
In the usual happy day scenario, this is always "good". If something
fails during or after a mode set, the kernel driver can set the link
status to "bad" and issue a hotplug uevent for userspace to have it
re-check the valid modes through GET_CONNECTOR IOCTL, and try modeset
again. If the theoretical capabilities of the link can't be reached,
the mode list is trimmed based on that.

v6:
* Fix a typo in kernel doc (Sean Paul)
v5:
* Clarify doc for silent rejection of atomic properties by driver (Daniel Vetter)
v4:
* Add comments in kernel-doc format (Daniel Vetter)
* Update the kernel-doc for link-status (Sean Paul)
v3:
* Fixed a build error (Jani Saarinen)
v2:
* Removed connector->link_status (Daniel Vetter)
* Set connector->state->link_status in drm_mode_connector_set_link_status_property
(Daniel Vetter)
* Set the connector_changed flag to true if connector->state->link_status changed.
* Reset link_status to GOOD in update_output_state (Daniel Vetter)
* Never allow userspace to set link status from Good To Bad (Daniel Vetter)

Reviewed-by: Sean Paul <seanpaul@chromium.org>
Reviewed-by: Daniel Vetter  <daniel.vetter@ffwll.ch>
Acked-by: Tony Cheng <tony.cheng@amd.com>
Acked-by: Harry Wentland <harry.wentland@amd.com>
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>
Cc: Sean Paul <seanpaul@chromium.org>
Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
---
 drivers/gpu/drm/drm_atomic.c        | 18 +++++++++++++
 drivers/gpu/drm/drm_atomic_helper.c | 15 +++++++++++
 drivers/gpu/drm/drm_connector.c     | 53 +++++++++++++++++++++++++++++++++++++
 include/drm/drm_connector.h         | 19 +++++++++++++
 include/drm/drm_mode_config.h       |  5 ++++
 include/uapi/drm/drm_mode.h         |  4 +++
 6 files changed, 114 insertions(+)

diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
index 72fa5b2..673f3af 100644
--- a/drivers/gpu/drm/drm_atomic.c
+++ b/drivers/gpu/drm/drm_atomic.c
@@ -1087,6 +1087,22 @@ int drm_atomic_connector_set_property(struct drm_connector *connector,
 		 * now?) atomic writes to DPMS property:
 		 */
 		return -EINVAL;
+	} else if (property == config->link_status_property) {
+		/* Never downgrade from GOOD to BAD on userspace's request here,
+		 * only hw issues can do that.
+		 *
+		 * For an atomic property the userspace doesn't need to be able
+		 * to understand all the properties, but needs to be able to
+		 * restore the state it wants on VT switch. So if the userspace
+		 * tries to change the link_status from GOOD to BAD, driver
+		 * silently rejects it and returns a 0. This prevents userspace
+		 * from accidently breaking  the display when it restores the
+		 * state.
+		 */
+		if (state->link_status == DRM_LINK_STATUS_GOOD)
+			return 0;
+		state->link_status = val;
+		return 0;
 	} else if (connector->funcs->atomic_set_property) {
 		return connector->funcs->atomic_set_property(connector,
 				state, property, val);
@@ -1135,6 +1151,8 @@ static void drm_atomic_connector_print_state(struct drm_printer *p,
 		*val = (state->crtc) ? state->crtc->base.id : 0;
 	} else if (property == config->dpms_property) {
 		*val = connector->dpms;
+	} else if (property == config->link_status_property) {
+		*val = state->link_status;
 	} else if (connector->funcs->atomic_get_property) {
 		return connector->funcs->atomic_get_property(connector,
 				state, property, val);
diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index 23767df..5e7af63 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->state->link_status !=
+			    connector_state->link_status)
+				crtc_state->connectors_changed = true;
+		}
 	}
 
 	/*
@@ -2255,6 +2262,8 @@ static int update_output_state(struct drm_atomic_state *state,
 								NULL);
 			if (ret)
 				return ret;
+			/* Make sure legacy setCrtc always re-trains */
+			conn_state->link_status = DRM_LINK_STATUS_GOOD;
 		}
 	}
 
@@ -2298,6 +2307,12 @@ static int update_output_state(struct drm_atomic_state *state,
  *
  * Provides a default crtc set_config handler using the atomic driver interface.
  *
+ * NOTE: For backwards compatibility with old userspace this automatically
+ * resets the "link-status" property to GOOD, to force any link
+ * re-training. The SETCRTC ioctl does not define whether an update does
+ * need a full modeset or just a plane update, hence we're allowed to do
+ * that. See also drm_mode_connector_set_link_status_property().
+ *
  * Returns:
  * Returns 0 on success, negative errno numbers on failure.
  */
diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
index 5a45262..eee038a 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
@@ -625,6 +635,11 @@ int drm_display_info_set_bus_formats(struct drm_display_info *info,
  * 	tiling and virtualize both &drm_crtc and &drm_plane if needed. Drivers
  * 	should update this value using drm_mode_connector_set_tile_property().
  * 	Userspace cannot change this property.
+ * link-status:
+ *      Connector link-status property to indicate the status of link. The default
+ *      value of link-status is "GOOD". If something fails during or after modeset,
+ *      the kernel driver may set this to "BAD" and issue a hotplug uevent. Drivers
+ *      should update this value using drm_mode_connector_set_link_status_property().
  *
  * Connectors also have one standardized atomic property:
  *
@@ -666,6 +681,13 @@ 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;
 }
 
@@ -995,6 +1017,37 @@ int drm_mode_connector_update_edid_property(struct drm_connector *connector,
 }
 EXPORT_SYMBOL(drm_mode_connector_update_edid_property);
 
+/**
+ * drm_mode_connector_set_link_status_property - Set link status property of a connector
+ * @connector: drm connector
+ * @link_status: new value of link status property (0: Good, 1: Bad)
+ *
+ * In usual working scenario, this link status property will always be set to
+ * "GOOD". If something fails during or after a mode set, the kernel driver
+ * may set this link status property to "BAD". The caller then needs to send a
+ * hotplug uevent for userspace to re-check the valid modes through
+ * GET_CONNECTOR_IOCTL and retry modeset.
+ *
+ * Note: Drivers cannot rely on userspace to support this property and
+ * issue a modeset. As such, they may choose to handle issues (like
+ * re-training a link) without userspace's intervention.
+ *
+ * The reason for adding this property is to handle link training failures, but
+ * it is not limited to DP or link training. For example, if we implement
+ * asynchronous setcrtc, this property can be used to report any failures in that.
+ */
+void drm_mode_connector_set_link_status_property(struct drm_connector *connector,
+						 uint64_t link_status)
+{
+	struct drm_device *dev = connector->dev;
+
+	drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
+	connector->state->link_status = link_status;
+	drm_modeset_unlock(&dev->mode_config.connection_mutex);
+
+}
+EXPORT_SYMBOL(drm_mode_connector_set_link_status_property);
+
 int drm_mode_connector_set_obj_prop(struct drm_mode_object *obj,
 				    struct drm_property *property,
 				    uint64_t value)
diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
index 1218a0c..64e07c5 100644
--- a/include/drm/drm_connector.h
+++ b/include/drm/drm_connector.h
@@ -90,6 +90,17 @@ enum subpixel_order {
 };
 
 /**
+ * enum drm_link_status - connector's link_status property value
+ *
+ * This enum is used as the connector's link status property value.
+ * It is set to the values defined in uapi.
+ */
+enum drm_link_status {
+	DRM_LINK_STATUS_GOOD = DRM_MODE_LINK_STATUS_GOOD,
+	DRM_LINK_STATUS_BAD = DRM_MODE_LINK_STATUS_BAD,
+};
+
+/**
  * struct drm_display_info - runtime data about the connected sink
  *
  * Describes a given display (e.g. CRT or flat panel) and its limitations. For
@@ -213,6 +224,12 @@ struct drm_connector_state {
 
 	struct drm_encoder *best_encoder;
 
+	/**
+	 * @link_status: Connector link_status to keep track of whether link is
+	 * GOOD or BAD to notify userspace if retraining is necessary.
+	 */
+	enum drm_link_status link_status;
+
 	struct drm_atomic_state *state;
 };
 
@@ -776,6 +793,8 @@ int drm_mode_connector_set_path_property(struct drm_connector *connector,
 int drm_mode_connector_set_tile_property(struct drm_connector *connector);
 int drm_mode_connector_update_edid_property(struct drm_connector *connector,
 					    const struct edid *edid);
+void drm_mode_connector_set_link_status_property(struct drm_connector *connector,
+						 uint64_t link_status);
 
 /**
  * struct drm_tile_group - Tile group metadata
diff --git a/include/drm/drm_mode_config.h b/include/drm/drm_mode_config.h
index bf9991b..86faee4 100644
--- a/include/drm/drm_mode_config.h
+++ b/include/drm/drm_mode_config.h
@@ -431,6 +431,11 @@ 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 728790b..309c478 100644
--- a/include/uapi/drm/drm_mode.h
+++ b/include/uapi/drm/drm_mode.h
@@ -123,6 +123,10 @@
 #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 v5 1/4] drm: Add a new connector atomic property for link status

[Manasi Navare]

Thanks Sean.
Done, fixed the typo and submitted the patch.

Regards
Manasi

On Thu, Dec 08, 2016 at 02:36:25PM -0500, Sean Paul wrote:
> <snip>
> 
> > diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
> > index 72fa5b2..34eddb9 100644
> > --- a/drivers/gpu/drm/drm_atomic.c
> > +++ b/drivers/gpu/drm/drm_atomic.c
> > @@ -1087,6 +1087,22 @@ int drm_atomic_connector_set_property(struct drm_connector *connector,
> >                  * now?) atomic writes to DPMS property:
> >                  */
> >                 return -EINVAL;
> > +       } else if (property == config->link_status_property) {
> > +               /* Never downgrade from GOOD to BAD on userspace's request here,
> > +                * only hw issues can do that.
> > +                *
> > +                * For an atomic property the userspace doesn't need to be able
> > +                * to understand all the properties, but needs to be able to
> > +                * restore the state itw ants on VT switch. So if the userspace
> 
> s/itw ants/it wants/
> 
> <snip>
> _______________________________________________
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> dri-devel@lists.freedesktop.org
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Re: [PATCH 2/4] drm/i915: Compute sink's max lane count/link BW at Hotplug

[Jani Nikula]

On Tue, 06 Dec 2016, Manasi Navare <manasi.d.navare@intel.com> wrote:
> Sink's capabilities are advertised through DPCD registers and get
> updated only on hotplug. So they should be computed only once in the
> long pulse handler and saved off in intel_dp structure for the use
> later. For this reason two new fields max_sink_lane_count and
> max_sink_link_bw are added to intel_dp structure.
>
> This also simplifies the fallback link rate/lane count logic
> to handle link training failure. In that case, the max_sink_link_bw
> and max_sink_lane_count can be reccomputed to match the fallback
> values lowering the sink capabilities due to link train failure.
>
> 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>

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

Eventually we may want to call the fields *link* rates, because that's
what they'll effectively be. Transient values that don't reflect the
sink or source capabilities, but the link capabilities.

> ---
>  drivers/gpu/drm/i915/intel_dp.c  | 10 ++++++++--
>  drivers/gpu/drm/i915/intel_drv.h |  4 ++++
>  2 files changed, 12 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index db75bb9..434dc7d 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -156,7 +156,7 @@ static u8 intel_dp_max_lane_count(struct intel_dp *intel_dp)
>  	u8 source_max, sink_max;
>  
>  	source_max = intel_dig_port->max_lanes;
> -	sink_max = drm_dp_max_lane_count(intel_dp->dpcd);
> +	sink_max = intel_dp->max_sink_lane_count;
>  
>  	return min(source_max, sink_max);
>  }
> @@ -213,7 +213,7 @@ static u8 intel_dp_max_lane_count(struct intel_dp *intel_dp)
>  
>  	*sink_rates = default_rates;
>  
> -	return (intel_dp_max_link_bw(intel_dp) >> 3) + 1;
> +	return (intel_dp->max_sink_link_bw >> 3) + 1;
>  }
>  
>  static int
> @@ -4395,6 +4395,12 @@ static bool intel_digital_port_connected(struct drm_i915_private *dev_priv,
>  		      yesno(intel_dp_source_supports_hbr2(intel_dp)),
>  		      yesno(drm_dp_tps3_supported(intel_dp->dpcd)));
>  
> +	/* Set the max lane count for sink */
> +	intel_dp->max_sink_lane_count = drm_dp_max_lane_count(intel_dp->dpcd);
> +
> +	/* Set the max link BW for sink */
> +	intel_dp->max_sink_link_bw = intel_dp_max_link_bw(intel_dp);
> +
>  	intel_dp_print_rates(intel_dp);
>  
>  	intel_dp_read_desc(intel_dp);
> diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> index fd77a3b..b6526ad 100644
> --- a/drivers/gpu/drm/i915/intel_drv.h
> +++ b/drivers/gpu/drm/i915/intel_drv.h
> @@ -906,6 +906,10 @@ struct intel_dp {
>  	/* sink rates as reported by DP_SUPPORTED_LINK_RATES */
>  	uint8_t num_sink_rates;
>  	int sink_rates[DP_MAX_SUPPORTED_RATES];
> +	/* Max lane count for the sink as per DPCD registers */
> +	uint8_t max_sink_lane_count;
> +	/* Max link BW for the sink as per DPCD registers */
> +	int max_sink_link_bw;
>  	/* sink or branch descriptor */
>  	struct intel_dp_desc desc;
>  	struct drm_dp_aux aux;

-- 
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Re: [PATCH 2/4] drm/i915: Compute sink's max lane count/link BW at Hotplug

[Manasi Navare]

On Thu, Dec 08, 2016 at 11:23:39PM +0200, Jani Nikula wrote:
> On Tue, 06 Dec 2016, Manasi Navare <manasi.d.navare@intel.com> wrote:
> > Sink's capabilities are advertised through DPCD registers and get
> > updated only on hotplug. So they should be computed only once in the
> > long pulse handler and saved off in intel_dp structure for the use
> > later. For this reason two new fields max_sink_lane_count and
> > max_sink_link_bw are added to intel_dp structure.
> >
> > This also simplifies the fallback link rate/lane count logic
> > to handle link training failure. In that case, the max_sink_link_bw
> > and max_sink_lane_count can be reccomputed to match the fallback
> > values lowering the sink capabilities due to link train failure.
> >
> > 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>
> 
> Reviewed-by: Jani Nikula <jani.nikula@intel.com>
> 
> Eventually we may want to call the fields *link* rates, because that's
> what they'll effectively be. Transient values that don't reflect the
> sink or source capabilities, but the link capabilities.
>

Thanks Jani for your r-b.
Yes I agree, should I change the name to link_rate instead of sink_link_rate now?
The only reason I kept it as sink_link_rate is because we go ahead and calculate
the link capabilities later based on common link rate.

Regards
Manasi 
> > ---
> >  drivers/gpu/drm/i915/intel_dp.c  | 10 ++++++++--
> >  drivers/gpu/drm/i915/intel_drv.h |  4 ++++
> >  2 files changed, 12 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> > index db75bb9..434dc7d 100644
> > --- a/drivers/gpu/drm/i915/intel_dp.c
> > +++ b/drivers/gpu/drm/i915/intel_dp.c
> > @@ -156,7 +156,7 @@ static u8 intel_dp_max_lane_count(struct intel_dp *intel_dp)
> >  	u8 source_max, sink_max;
> >  
> >  	source_max = intel_dig_port->max_lanes;
> > -	sink_max = drm_dp_max_lane_count(intel_dp->dpcd);
> > +	sink_max = intel_dp->max_sink_lane_count;
> >  
> >  	return min(source_max, sink_max);
> >  }
> > @@ -213,7 +213,7 @@ static u8 intel_dp_max_lane_count(struct intel_dp *intel_dp)
> >  
> >  	*sink_rates = default_rates;
> >  
> > -	return (intel_dp_max_link_bw(intel_dp) >> 3) + 1;
> > +	return (intel_dp->max_sink_link_bw >> 3) + 1;
> >  }
> >  
> >  static int
> > @@ -4395,6 +4395,12 @@ static bool intel_digital_port_connected(struct drm_i915_private *dev_priv,
> >  		      yesno(intel_dp_source_supports_hbr2(intel_dp)),
> >  		      yesno(drm_dp_tps3_supported(intel_dp->dpcd)));
> >  
> > +	/* Set the max lane count for sink */
> > +	intel_dp->max_sink_lane_count = drm_dp_max_lane_count(intel_dp->dpcd);
> > +
> > +	/* Set the max link BW for sink */
> > +	intel_dp->max_sink_link_bw = intel_dp_max_link_bw(intel_dp);
> > +
> >  	intel_dp_print_rates(intel_dp);
> >  
> >  	intel_dp_read_desc(intel_dp);
> > diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> > index fd77a3b..b6526ad 100644
> > --- a/drivers/gpu/drm/i915/intel_drv.h
> > +++ b/drivers/gpu/drm/i915/intel_drv.h
> > @@ -906,6 +906,10 @@ struct intel_dp {
> >  	/* sink rates as reported by DP_SUPPORTED_LINK_RATES */
> >  	uint8_t num_sink_rates;
> >  	int sink_rates[DP_MAX_SUPPORTED_RATES];
> > +	/* Max lane count for the sink as per DPCD registers */
> > +	uint8_t max_sink_lane_count;
> > +	/* Max link BW for the sink as per DPCD registers */
> > +	int max_sink_link_bw;
> >  	/* sink or branch descriptor */
> >  	struct intel_dp_desc desc;
> >  	struct drm_dp_aux aux;
> 
> -- 
> Jani Nikula, Intel Open Source Technology Center
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Re: [PATCH 3/4] drm/i915: Find fallback link rate/lane count

[Jani Nikula]

On Tue, 06 Dec 2016, Manasi Navare <manasi.d.navare@intel.com> wrote:
> 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 and limits the max
> link_rate and lane_count values to these fallback values.
>
> v6:
> * Cap the max link rate and lane count to the max
> values obtained during fallback link training (Daniel Vetter)
> v5:
> * Start the fallback at the lane count value passed not
> the max lane count (Jani Nikula)
> v4:
> * Remove the redundant variable link_train_failed
> v3:
> * Remove fallback_link_rate_index variable, just obtain
> that using the helper intel_dp_link_rate_index (Jani Nikula)
> v2:
> Squash the patch that returns the link rate index (Jani Nikula)
>
> Acked-by: Tony Cheng <tony.cheng@amd.com>
> Acked-by: Harry Wentland <harry.wentland@amd.com>
> 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  | 40 ++++++++++++++++++++++++++++++++++++++++
>  drivers/gpu/drm/i915/intel_drv.h |  2 ++
>  2 files changed, 42 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 434dc7d..b5c7526f 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -278,6 +278,46 @@ 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;

Probably somewhere in the history of the patch series there was a time
when it was necessary to search for the rates in reverse order. What
possible benefit could that offer at this point?

> +	}
> +
> +	return -1;
> +}
> +
> +int 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] = {};

No need to initialize because you initialize it a couple of lines later.

> +	int common_len;
> +	int link_rate_index = -1;

No need to initialize because you initialize it a couple of lines later.

> +
> +	common_len = intel_dp_common_rates(intel_dp, common_rates);
> +	link_rate_index = intel_dp_link_rate_index(intel_dp,
> +						   common_rates,
> +						   link_rate);

Please stop and think, and don't rush each new iteration of the patches.

What's wrong with the above lines? Please think about it. Answer at the
end of the mail (*).

> +	if (link_rate_index > 0) {
> +		intel_dp->max_sink_link_bw = drm_dp_link_rate_to_bw_code(common_rates[link_rate_index - 1]);
> +		intel_dp->max_sink_lane_count = lane_count;
> +	} else if (lane_count > 1) {
> +		intel_dp->max_sink_link_bw = intel_dp_max_link_bw(intel_dp);
> +		intel_dp->max_sink_lane_count = lane_count >> 1;
> +	} else {
> +		DRM_ERROR("Link Training Unsuccessful\n");
> +		return -1;
> +	}
> +
> +	return 0;
> +}
> +
>  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 b6526ad..47e3671 100644
> --- a/drivers/gpu/drm/i915/intel_drv.h
> +++ b/drivers/gpu/drm/i915/intel_drv.h
> @@ -1400,6 +1400,8 @@ bool intel_dp_init_connector(struct intel_digital_port *intel_dig_port,
>  void intel_dp_set_link_params(struct intel_dp *intel_dp,
>  			      int link_rate, uint8_t lane_count,
>  			      bool link_mst);
> +int 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);


(*) You do intel_dp_common_rates(intel_dp, common_rates) twice, for no
reason at all.

-- 
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Re: [PATCH 2/4] drm/i915: Compute sink's max lane count/link BW at Hotplug

[Manasi Navare]

Daniel, can we merge this patch?
It has no dependency on other link train patches,
it is just a clean up for the existing driver code that
uses max link rate and lane count values.
Other link train patches have dependency on this thats why
it was part of the series.
But it would be great if this gets merged so that i dont have to
rebase it tremendously after 3 weeks when I am back and plus
its good for the driver to start using this clean up. This kind
of clean up was long due.

Regards
Manasi

On Thu, Dec 08, 2016 at 11:23:39PM +0200, Jani Nikula wrote:
> On Tue, 06 Dec 2016, Manasi Navare <manasi.d.navare@intel.com> wrote:
> > Sink's capabilities are advertised through DPCD registers and get
> > updated only on hotplug. So they should be computed only once in the
> > long pulse handler and saved off in intel_dp structure for the use
> > later. For this reason two new fields max_sink_lane_count and
> > max_sink_link_bw are added to intel_dp structure.
> >
> > This also simplifies the fallback link rate/lane count logic
> > to handle link training failure. In that case, the max_sink_link_bw
> > and max_sink_lane_count can be reccomputed to match the fallback
> > values lowering the sink capabilities due to link train failure.
> >
> > 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>
> 
> Reviewed-by: Jani Nikula <jani.nikula@intel.com>
> 
> Eventually we may want to call the fields *link* rates, because that's
> what they'll effectively be. Transient values that don't reflect the
> sink or source capabilities, but the link capabilities.
> 
> > ---
> >  drivers/gpu/drm/i915/intel_dp.c  | 10 ++++++++--
> >  drivers/gpu/drm/i915/intel_drv.h |  4 ++++
> >  2 files changed, 12 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> > index db75bb9..434dc7d 100644
> > --- a/drivers/gpu/drm/i915/intel_dp.c
> > +++ b/drivers/gpu/drm/i915/intel_dp.c
> > @@ -156,7 +156,7 @@ static u8 intel_dp_max_lane_count(struct intel_dp *intel_dp)
> >  	u8 source_max, sink_max;
> >  
> >  	source_max = intel_dig_port->max_lanes;
> > -	sink_max = drm_dp_max_lane_count(intel_dp->dpcd);
> > +	sink_max = intel_dp->max_sink_lane_count;
> >  
> >  	return min(source_max, sink_max);
> >  }
> > @@ -213,7 +213,7 @@ static u8 intel_dp_max_lane_count(struct intel_dp *intel_dp)
> >  
> >  	*sink_rates = default_rates;
> >  
> > -	return (intel_dp_max_link_bw(intel_dp) >> 3) + 1;
> > +	return (intel_dp->max_sink_link_bw >> 3) + 1;
> >  }
> >  
> >  static int
> > @@ -4395,6 +4395,12 @@ static bool intel_digital_port_connected(struct drm_i915_private *dev_priv,
> >  		      yesno(intel_dp_source_supports_hbr2(intel_dp)),
> >  		      yesno(drm_dp_tps3_supported(intel_dp->dpcd)));
> >  
> > +	/* Set the max lane count for sink */
> > +	intel_dp->max_sink_lane_count = drm_dp_max_lane_count(intel_dp->dpcd);
> > +
> > +	/* Set the max link BW for sink */
> > +	intel_dp->max_sink_link_bw = intel_dp_max_link_bw(intel_dp);
> > +
> >  	intel_dp_print_rates(intel_dp);
> >  
> >  	intel_dp_read_desc(intel_dp);
> > diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> > index fd77a3b..b6526ad 100644
> > --- a/drivers/gpu/drm/i915/intel_drv.h
> > +++ b/drivers/gpu/drm/i915/intel_drv.h
> > @@ -906,6 +906,10 @@ struct intel_dp {
> >  	/* sink rates as reported by DP_SUPPORTED_LINK_RATES */
> >  	uint8_t num_sink_rates;
> >  	int sink_rates[DP_MAX_SUPPORTED_RATES];
> > +	/* Max lane count for the sink as per DPCD registers */
> > +	uint8_t max_sink_lane_count;
> > +	/* Max link BW for the sink as per DPCD registers */
> > +	int max_sink_link_bw;
> >  	/* sink or branch descriptor */
> >  	struct intel_dp_desc desc;
> >  	struct drm_dp_aux aux;
> 
> -- 
> Jani Nikula, Intel Open Source Technology Center
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Re: [PATCH 4/4] drm/i915: Implement Link Rate fallback on Link training failure

[Jani Nikula]

On Tue, 06 Dec 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.
>
> v9:
> * Use the trimmed max values of link rate/lane count based on
> link train fallback (Daniel Vetter)
> v8:
> * Set link_status to BAD first and then call mode_valid (Jani Nikula)
> v7:
> Remove the redundant variable in previous patch itself
> v6:
> * Obtain link rate index from fallback_link_rate using
> the helper intel_dp_link_rate_index (Jani Nikula)
> * Include fallback within intel_dp_start_link_train (Jani Nikula)
> v5:
> * Move set link status to drm core (Daniel Vetter, Jani Nikula)
> v4:
> * Add fallback support for non DDI platforms too
> * Set connector->link status inside set_link_status function
> (Jani Nikula)
> 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)
>
> Acked-by: Tony Cheng <tony.cheng@amd.com>
> Acked-by: Harry Wentland <Harry.wentland@amd.com>
> 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>

This is not a journey I'd like to do again, but I like the place where
we've finally arrived.

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

> ---
>  drivers/gpu/drm/i915/intel_dp.c               | 27 +++++++++++++++++++++++++++
>  drivers/gpu/drm/i915/intel_dp_link_training.c | 22 ++++++++++++++++++++--
>  drivers/gpu/drm/i915/intel_drv.h              |  3 +++
>  3 files changed, 50 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index b5c7526f..404da32 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -5676,6 +5676,29 @@ 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;
> +
> +	intel_connector = container_of(work, typeof(*intel_connector),
> +				       modeset_retry_work);
> +	connector = &intel_connector->base;
> +	DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n", connector->base.id,
> +		      connector->name);
> +
> +	/* Grab the locks before changing connector property*/
> +	mutex_lock(&connector->dev->mode_config.mutex);
> +	/* Set connector link status to BAD and send a Uevent to notify
> +	 * userspace to do a modeset.
> +	 */
> +	drm_mode_connector_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)
> @@ -5688,6 +5711,10 @@ 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..955b239 100644
> --- a/drivers/gpu/drm/i915/intel_dp_link_training.c
> +++ b/drivers/gpu/drm/i915/intel_dp_link_training.c
> @@ -313,6 +313,24 @@ void intel_dp_stop_link_train(struct intel_dp *intel_dp)
>  void
>  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);
> +	struct intel_connector *intel_connector = intel_dp->attached_connector;
> +
> +	if (!intel_dp_link_training_clock_recovery(intel_dp))
> +		goto failure_handling;
> +	if (!intel_dp_link_training_channel_equalization(intel_dp))
> +		goto failure_handling;
> +
> +	DRM_DEBUG_KMS("Link Training Passed at Link Rate = %d, Lane count = %d",
> +		      intel_dp->link_rate, intel_dp->lane_count);
> +	return;
> +
> + failure_handling:
> +	DRM_DEBUG_KMS("Link Training failed at link rate = %d, lane count = %d",
> +		      intel_dp->link_rate, intel_dp->lane_count);
> +	if (!intel_dp_get_link_train_fallback_values(intel_dp,
> +						     intel_dp->link_rate,
> +						     intel_dp->lane_count))
> +		/* Schedule a Hotplug Uevent to userspace to start modeset */
> +		schedule_work(&intel_connector->modeset_retry_work);
> +	return;
>  }
> diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> index 47e3671..9d6f7ee 100644
> --- a/drivers/gpu/drm/i915/intel_drv.h
> +++ b/drivers/gpu/drm/i915/intel_drv.h
> @@ -315,6 +315,9 @@ 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 {

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

[Manasi Navare]

On Thu, Dec 08, 2016 at 11:46:02PM +0200, Jani Nikula wrote:
> On Tue, 06 Dec 2016, Manasi Navare <manasi.d.navare@intel.com> wrote:
> > 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 and limits the max
> > link_rate and lane_count values to these fallback values.
> >
> > v6:
> > * Cap the max link rate and lane count to the max
> > values obtained during fallback link training (Daniel Vetter)
> > v5:
> > * Start the fallback at the lane count value passed not
> > the max lane count (Jani Nikula)
> > v4:
> > * Remove the redundant variable link_train_failed
> > v3:
> > * Remove fallback_link_rate_index variable, just obtain
> > that using the helper intel_dp_link_rate_index (Jani Nikula)
> > v2:
> > Squash the patch that returns the link rate index (Jani Nikula)
> >
> > Acked-by: Tony Cheng <tony.cheng@amd.com>
> > Acked-by: Harry Wentland <harry.wentland@amd.com>
> > 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  | 40 ++++++++++++++++++++++++++++++++++++++++
> >  drivers/gpu/drm/i915/intel_drv.h |  2 ++
> >  2 files changed, 42 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> > index 434dc7d..b5c7526f 100644
> > --- a/drivers/gpu/drm/i915/intel_dp.c
> > +++ b/drivers/gpu/drm/i915/intel_dp.c
> > @@ -278,6 +278,46 @@ 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;
> 
> Probably somewhere in the history of the patch series there was a time
> when it was necessary to search for the rates in reverse order. What
> possible benefit could that offer at this point?
>

The advantage here is that the link rate is more likely to match quicker
if we search in reverse order.

 
> > +	}
> > +
> > +	return -1;
> > +}
> > +
> > +int 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] = {};
> 
> No need to initialize because you initialize it a couple of lines later.
>

Agreed
 
> > +	int common_len;
> > +	int link_rate_index = -1;
> 
> No need to initialize because you initialize it a couple of lines later.
> 
> > +
> > +	common_len = intel_dp_common_rates(intel_dp, common_rates);
> > +	link_rate_index = intel_dp_link_rate_index(intel_dp,
> > +						   common_rates,
> > +						   link_rate);
> 
> Please stop and think, and don't rush each new iteration of the patches.
> 
> What's wrong with the above lines? Please think about it. Answer at the
> end of the mail (*).
>

> > +	if (link_rate_index > 0) {
> > +		intel_dp->max_sink_link_bw = drm_dp_link_rate_to_bw_code(common_rates[link_rate_index - 1]);
> > +		intel_dp->max_sink_lane_count = lane_count;
> > +	} else if (lane_count > 1) {
> > +		intel_dp->max_sink_link_bw = intel_dp_max_link_bw(intel_dp);
> > +		intel_dp->max_sink_lane_count = lane_count >> 1;
> > +	} else {
> > +		DRM_ERROR("Link Training Unsuccessful\n");
> > +		return -1;
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> >  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 b6526ad..47e3671 100644
> > --- a/drivers/gpu/drm/i915/intel_drv.h
> > +++ b/drivers/gpu/drm/i915/intel_drv.h
> > @@ -1400,6 +1400,8 @@ bool intel_dp_init_connector(struct intel_digital_port *intel_dig_port,
> >  void intel_dp_set_link_params(struct intel_dp *intel_dp,
> >  			      int link_rate, uint8_t lane_count,
> >  			      bool link_mst);
> > +int 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);
> 
> 
> (*) You do intel_dp_common_rates(intel_dp, common_rates) twice, for no
> reason at all.
>

Actually the first call was to obtain the common_len which was needed earlier but
we no longer need it because of the simplified fallback logic modifying the
max sink link rate directly.
So yes I will remove the first call to intel_dp_common_rate()
Good catch! Thanks Jani.

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

[Manasi Navare]

On Thu, Dec 08, 2016 at 11:51:30PM +0200, Jani Nikula wrote:
> On Tue, 06 Dec 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.
> >
> > v9:
> > * Use the trimmed max values of link rate/lane count based on
> > link train fallback (Daniel Vetter)
> > v8:
> > * Set link_status to BAD first and then call mode_valid (Jani Nikula)
> > v7:
> > Remove the redundant variable in previous patch itself
> > v6:
> > * Obtain link rate index from fallback_link_rate using
> > the helper intel_dp_link_rate_index (Jani Nikula)
> > * Include fallback within intel_dp_start_link_train (Jani Nikula)
> > v5:
> > * Move set link status to drm core (Daniel Vetter, Jani Nikula)
> > v4:
> > * Add fallback support for non DDI platforms too
> > * Set connector->link status inside set_link_status function
> > (Jani Nikula)
> > 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)
> >
> > Acked-by: Tony Cheng <tony.cheng@amd.com>
> > Acked-by: Harry Wentland <Harry.wentland@amd.com>
> > 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>
> 
> This is not a journey I'd like to do again, but I like the place where
> we've finally arrived.
> 
> Reviewed-by: Jani Nikula <jani.nikula@intel.com>
>

Thanks a lot Jani for all the reviews till now. Its actually
been a great journey for me learning so many things from you. I would def like to do this
again.

Regards
Manasi

 
> > ---
> >  drivers/gpu/drm/i915/intel_dp.c               | 27 +++++++++++++++++++++++++++
> >  drivers/gpu/drm/i915/intel_dp_link_training.c | 22 ++++++++++++++++++++--
> >  drivers/gpu/drm/i915/intel_drv.h              |  3 +++
> >  3 files changed, 50 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> > index b5c7526f..404da32 100644
> > --- a/drivers/gpu/drm/i915/intel_dp.c
> > +++ b/drivers/gpu/drm/i915/intel_dp.c
> > @@ -5676,6 +5676,29 @@ 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;
> > +
> > +	intel_connector = container_of(work, typeof(*intel_connector),
> > +				       modeset_retry_work);
> > +	connector = &intel_connector->base;
> > +	DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n", connector->base.id,
> > +		      connector->name);
> > +
> > +	/* Grab the locks before changing connector property*/
> > +	mutex_lock(&connector->dev->mode_config.mutex);
> > +	/* Set connector link status to BAD and send a Uevent to notify
> > +	 * userspace to do a modeset.
> > +	 */
> > +	drm_mode_connector_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)
> > @@ -5688,6 +5711,10 @@ 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..955b239 100644
> > --- a/drivers/gpu/drm/i915/intel_dp_link_training.c
> > +++ b/drivers/gpu/drm/i915/intel_dp_link_training.c
> > @@ -313,6 +313,24 @@ void intel_dp_stop_link_train(struct intel_dp *intel_dp)
> >  void
> >  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);
> > +	struct intel_connector *intel_connector = intel_dp->attached_connector;
> > +
> > +	if (!intel_dp_link_training_clock_recovery(intel_dp))
> > +		goto failure_handling;
> > +	if (!intel_dp_link_training_channel_equalization(intel_dp))
> > +		goto failure_handling;
> > +
> > +	DRM_DEBUG_KMS("Link Training Passed at Link Rate = %d, Lane count = %d",
> > +		      intel_dp->link_rate, intel_dp->lane_count);
> > +	return;
> > +
> > + failure_handling:
> > +	DRM_DEBUG_KMS("Link Training failed at link rate = %d, lane count = %d",
> > +		      intel_dp->link_rate, intel_dp->lane_count);
> > +	if (!intel_dp_get_link_train_fallback_values(intel_dp,
> > +						     intel_dp->link_rate,
> > +						     intel_dp->lane_count))
> > +		/* Schedule a Hotplug Uevent to userspace to start modeset */
> > +		schedule_work(&intel_connector->modeset_retry_work);
> > +	return;
> >  }
> > diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> > index 47e3671..9d6f7ee 100644
> > --- a/drivers/gpu/drm/i915/intel_drv.h
> > +++ b/drivers/gpu/drm/i915/intel_drv.h
> > @@ -315,6 +315,9 @@ 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 {
> 
> -- 
> Jani Nikula, Intel Open Source Technology Center
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[PATCH v7 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 and limits the max
link_rate and lane_count values to these fallback values.

v7:
* Remove unnecessary intializations and remove redundant
call to intel_dp_common_rates (Jani Nikula)
v6:
* Cap the max link rate and lane count to the max
values obtained during fallback link training (Daniel Vetter)
v5:
* Start the fallback at the lane count value passed not
the max lane count (Jani Nikula)
v4:
* Remove the redundant variable link_train_failed
v3:
* Remove fallback_link_rate_index variable, just obtain
that using the helper intel_dp_link_rate_index (Jani Nikula)
v2:
Squash the patch that returns the link rate index (Jani Nikula)

Acked-by: Tony Cheng <tony.cheng@amd.com>
Acked-by: Harry Wentland <harry.wentland@amd.com>
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  | 38 ++++++++++++++++++++++++++++++++++++++
 drivers/gpu/drm/i915/intel_drv.h |  2 ++
 2 files changed, 40 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 434dc7d..1b5e0d0 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -278,6 +278,44 @@ 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;
+}
+
+int 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 link_rate_index;
+
+	link_rate_index = intel_dp_link_rate_index(intel_dp,
+						   common_rates,
+						   link_rate);
+	if (link_rate_index > 0) {
+		intel_dp->max_sink_link_bw = drm_dp_link_rate_to_bw_code(common_rates[link_rate_index - 1]);
+		intel_dp->max_sink_lane_count = lane_count;
+	} else if (lane_count > 1) {
+		intel_dp->max_sink_link_bw = intel_dp_max_link_bw(intel_dp);
+		intel_dp->max_sink_lane_count = lane_count >> 1;
+	} else {
+		DRM_ERROR("Link Training Unsuccessful\n");
+		return -1;
+	}
+
+	return 0;
+}
+
 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 377693e..0a20422 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -1400,6 +1400,8 @@ bool intel_dp_init_connector(struct intel_digital_port *intel_dig_port,
 void intel_dp_set_link_params(struct intel_dp *intel_dp,
 			      int link_rate, uint8_t lane_count,
 			      bool link_mst);
+int 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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Re: [PATCH v7 3/4] drm/i915: Find fallback link rate/lane count

[Jani Nikula]

On Fri, 09 Dec 2016, Manasi Navare <manasi.d.navare@intel.com> wrote:
> 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 and limits the max
> link_rate and lane_count values to these fallback values.
>
> v7:
> * Remove unnecessary intializations and remove redundant
> call to intel_dp_common_rates (Jani Nikula)
> v6:
> * Cap the max link rate and lane count to the max
> values obtained during fallback link training (Daniel Vetter)
> v5:
> * Start the fallback at the lane count value passed not
> the max lane count (Jani Nikula)
> v4:
> * Remove the redundant variable link_train_failed
> v3:
> * Remove fallback_link_rate_index variable, just obtain
> that using the helper intel_dp_link_rate_index (Jani Nikula)
> v2:
> Squash the patch that returns the link rate index (Jani Nikula)
>
> Acked-by: Tony Cheng <tony.cheng@amd.com>
> Acked-by: Harry Wentland <harry.wentland@amd.com>
> 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>

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


> ---
>  drivers/gpu/drm/i915/intel_dp.c  | 38 ++++++++++++++++++++++++++++++++++++++
>  drivers/gpu/drm/i915/intel_drv.h |  2 ++
>  2 files changed, 40 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 434dc7d..1b5e0d0 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -278,6 +278,44 @@ 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;
> +}
> +
> +int 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 link_rate_index;
> +
> +	link_rate_index = intel_dp_link_rate_index(intel_dp,
> +						   common_rates,
> +						   link_rate);
> +	if (link_rate_index > 0) {
> +		intel_dp->max_sink_link_bw = drm_dp_link_rate_to_bw_code(common_rates[link_rate_index - 1]);
> +		intel_dp->max_sink_lane_count = lane_count;
> +	} else if (lane_count > 1) {
> +		intel_dp->max_sink_link_bw = intel_dp_max_link_bw(intel_dp);
> +		intel_dp->max_sink_lane_count = lane_count >> 1;
> +	} else {
> +		DRM_ERROR("Link Training Unsuccessful\n");
> +		return -1;
> +	}
> +
> +	return 0;
> +}
> +
>  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 377693e..0a20422 100644
> --- a/drivers/gpu/drm/i915/intel_drv.h
> +++ b/drivers/gpu/drm/i915/intel_drv.h
> @@ -1400,6 +1400,8 @@ bool intel_dp_init_connector(struct intel_digital_port *intel_dig_port,
>  void intel_dp_set_link_params(struct intel_dp *intel_dp,
>  			      int link_rate, uint8_t lane_count,
>  			      bool link_mst);
> +int 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);

-- 
Jani Nikula, Intel Open Source Technology Center
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Re: [PATCH 2/4] drm/i915: Compute sink's max lane count/link BW at Hotplug

[Jani Nikula]

On Thu, 08 Dec 2016, Manasi Navare <manasi.d.navare@intel.com> wrote:
> Daniel, can we merge this patch?

Pushed this one to dinq, thanks for the patch.

BR,
Jani.


> It has no dependency on other link train patches,
> it is just a clean up for the existing driver code that
> uses max link rate and lane count values.
> Other link train patches have dependency on this thats why
> it was part of the series.
> But it would be great if this gets merged so that i dont have to
> rebase it tremendously after 3 weeks when I am back and plus
> its good for the driver to start using this clean up. This kind
> of clean up was long due.
>
> Regards
> Manasi
>
> On Thu, Dec 08, 2016 at 11:23:39PM +0200, Jani Nikula wrote:
>> On Tue, 06 Dec 2016, Manasi Navare <manasi.d.navare@intel.com> wrote:
>> > Sink's capabilities are advertised through DPCD registers and get
>> > updated only on hotplug. So they should be computed only once in the
>> > long pulse handler and saved off in intel_dp structure for the use
>> > later. For this reason two new fields max_sink_lane_count and
>> > max_sink_link_bw are added to intel_dp structure.
>> >
>> > This also simplifies the fallback link rate/lane count logic
>> > to handle link training failure. In that case, the max_sink_link_bw
>> > and max_sink_lane_count can be reccomputed to match the fallback
>> > values lowering the sink capabilities due to link train failure.
>> >
>> > 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>
>> 
>> Reviewed-by: Jani Nikula <jani.nikula@intel.com>
>> 
>> Eventually we may want to call the fields *link* rates, because that's
>> what they'll effectively be. Transient values that don't reflect the
>> sink or source capabilities, but the link capabilities.
>> 
>> > ---
>> >  drivers/gpu/drm/i915/intel_dp.c  | 10 ++++++++--
>> >  drivers/gpu/drm/i915/intel_drv.h |  4 ++++
>> >  2 files changed, 12 insertions(+), 2 deletions(-)
>> >
>> > diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
>> > index db75bb9..434dc7d 100644
>> > --- a/drivers/gpu/drm/i915/intel_dp.c
>> > +++ b/drivers/gpu/drm/i915/intel_dp.c
>> > @@ -156,7 +156,7 @@ static u8 intel_dp_max_lane_count(struct intel_dp *intel_dp)
>> >  	u8 source_max, sink_max;
>> >  
>> >  	source_max = intel_dig_port->max_lanes;
>> > -	sink_max = drm_dp_max_lane_count(intel_dp->dpcd);
>> > +	sink_max = intel_dp->max_sink_lane_count;
>> >  
>> >  	return min(source_max, sink_max);
>> >  }
>> > @@ -213,7 +213,7 @@ static u8 intel_dp_max_lane_count(struct intel_dp *intel_dp)
>> >  
>> >  	*sink_rates = default_rates;
>> >  
>> > -	return (intel_dp_max_link_bw(intel_dp) >> 3) + 1;
>> > +	return (intel_dp->max_sink_link_bw >> 3) + 1;
>> >  }
>> >  
>> >  static int
>> > @@ -4395,6 +4395,12 @@ static bool intel_digital_port_connected(struct drm_i915_private *dev_priv,
>> >  		      yesno(intel_dp_source_supports_hbr2(intel_dp)),
>> >  		      yesno(drm_dp_tps3_supported(intel_dp->dpcd)));
>> >  
>> > +	/* Set the max lane count for sink */
>> > +	intel_dp->max_sink_lane_count = drm_dp_max_lane_count(intel_dp->dpcd);
>> > +
>> > +	/* Set the max link BW for sink */
>> > +	intel_dp->max_sink_link_bw = intel_dp_max_link_bw(intel_dp);
>> > +
>> >  	intel_dp_print_rates(intel_dp);
>> >  
>> >  	intel_dp_read_desc(intel_dp);
>> > diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
>> > index fd77a3b..b6526ad 100644
>> > --- a/drivers/gpu/drm/i915/intel_drv.h
>> > +++ b/drivers/gpu/drm/i915/intel_drv.h
>> > @@ -906,6 +906,10 @@ struct intel_dp {
>> >  	/* sink rates as reported by DP_SUPPORTED_LINK_RATES */
>> >  	uint8_t num_sink_rates;
>> >  	int sink_rates[DP_MAX_SUPPORTED_RATES];
>> > +	/* Max lane count for the sink as per DPCD registers */
>> > +	uint8_t max_sink_lane_count;
>> > +	/* Max link BW for the sink as per DPCD registers */
>> > +	int max_sink_link_bw;
>> >  	/* sink or branch descriptor */
>> >  	struct intel_dp_desc desc;
>> >  	struct drm_dp_aux aux;
>> 
>> -- 
>> Jani Nikula, Intel Open Source Technology Center

-- 
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Re: [PATCH v7 3/4] drm/i915: Find fallback link rate/lane count

[Jani Nikula]

On Fri, 09 Dec 2016, Jani Nikula <jani.nikula@linux.intel.com> wrote:
> On Fri, 09 Dec 2016, Manasi Navare <manasi.d.navare@intel.com> wrote:
>> 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 and limits the max
>> link_rate and lane_count values to these fallback values.
>>
>> v7:
>> * Remove unnecessary intializations and remove redundant
>> call to intel_dp_common_rates (Jani Nikula)
>> v6:
>> * Cap the max link rate and lane count to the max
>> values obtained during fallback link training (Daniel Vetter)
>> v5:
>> * Start the fallback at the lane count value passed not
>> the max lane count (Jani Nikula)
>> v4:
>> * Remove the redundant variable link_train_failed
>> v3:
>> * Remove fallback_link_rate_index variable, just obtain
>> that using the helper intel_dp_link_rate_index (Jani Nikula)
>> v2:
>> Squash the patch that returns the link rate index (Jani Nikula)
>>
>> Acked-by: Tony Cheng <tony.cheng@amd.com>
>> Acked-by: Harry Wentland <harry.wentland@amd.com>
>> 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>
>
> Reviewed-by: Jani Nikula <jani.nikula@intel.com>

And pushed this one to dinq, thanks for the patch.

BR,
Jani.

>
>
>> ---
>>  drivers/gpu/drm/i915/intel_dp.c  | 38 ++++++++++++++++++++++++++++++++++++++
>>  drivers/gpu/drm/i915/intel_drv.h |  2 ++
>>  2 files changed, 40 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
>> index 434dc7d..1b5e0d0 100644
>> --- a/drivers/gpu/drm/i915/intel_dp.c
>> +++ b/drivers/gpu/drm/i915/intel_dp.c
>> @@ -278,6 +278,44 @@ 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;
>> +}
>> +
>> +int 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 link_rate_index;
>> +
>> +	link_rate_index = intel_dp_link_rate_index(intel_dp,
>> +						   common_rates,
>> +						   link_rate);
>> +	if (link_rate_index > 0) {
>> +		intel_dp->max_sink_link_bw = drm_dp_link_rate_to_bw_code(common_rates[link_rate_index - 1]);
>> +		intel_dp->max_sink_lane_count = lane_count;
>> +	} else if (lane_count > 1) {
>> +		intel_dp->max_sink_link_bw = intel_dp_max_link_bw(intel_dp);
>> +		intel_dp->max_sink_lane_count = lane_count >> 1;
>> +	} else {
>> +		DRM_ERROR("Link Training Unsuccessful\n");
>> +		return -1;
>> +	}
>> +
>> +	return 0;
>> +}
>> +
>>  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 377693e..0a20422 100644
>> --- a/drivers/gpu/drm/i915/intel_drv.h
>> +++ b/drivers/gpu/drm/i915/intel_drv.h
>> @@ -1400,6 +1400,8 @@ bool intel_dp_init_connector(struct intel_digital_port *intel_dig_port,
>>  void intel_dp_set_link_params(struct intel_dp *intel_dp,
>>  			      int link_rate, uint8_t lane_count,
>>  			      bool link_mst);
>> +int 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);

-- 
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