[PATCH 5/5] drm/i915: Implement Link Rate fallback on Link training failure

[Manasi Navare <manasi.d.navare@intel.com>]

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.

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               | 63 ++++++++++++++++++++++++++-
 drivers/gpu/drm/i915/intel_dp_link_training.c | 28 +++++++++++-
 drivers/gpu/drm/i915/intel_drv.h              |  4 +-
 3 files changed, 90 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 4fb89e1..a56a34d 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -351,8 +351,14 @@ int intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp,
 		target_clock = fixed_mode->clock;
 	}
 
-	max_link_clock = intel_dp_max_link_rate(intel_dp);
-	max_lanes = intel_dp_max_lane_count(intel_dp);
+	/* Prune the modes using the fallback link rate/lane count */
+	if (connector->link_status == DRM_MODE_LINK_STATUS_BAD) {
+		max_link_clock = intel_dp->fallback_link_rate;
+		max_lanes = intel_dp->fallback_lane_count;
+	} else {
+		max_link_clock = intel_dp_max_link_rate(intel_dp);
+		max_lanes = intel_dp_max_lane_count(intel_dp);
+	}
 
 	max_rate = intel_dp_max_data_rate(max_link_clock, max_lanes);
 	mode_rate = intel_dp_link_required(target_clock, 18);
@@ -1588,6 +1594,7 @@ static int intel_dp_compute_bpp(struct intel_dp *intel_dp,
 	enum port port = dp_to_dig_port(intel_dp)->port;
 	struct intel_crtc *intel_crtc = to_intel_crtc(pipe_config->base.crtc);
 	struct intel_connector *intel_connector = intel_dp->attached_connector;
+	struct drm_connector *connector = &intel_connector->base;
 	int lane_count, clock;
 	int min_lane_count = 1;
 	int max_lane_count = intel_dp_max_lane_count(intel_dp);
@@ -1635,6 +1642,14 @@ static int intel_dp_compute_bpp(struct intel_dp *intel_dp,
 	if (adjusted_mode->flags & DRM_MODE_FLAG_DBLCLK)
 		return false;
 
+	/* Fall back to lower link rate in case of failure in previous modeset */
+	if (connector->link_status == DRM_MODE_LINK_STATUS_BAD) {
+		min_lane_count = max_lane_count = intel_dp->fallback_lane_count;
+		min_clock = max_clock = intel_dp_link_rate_index(intel_dp,
+								 common_rates,
+								 intel_dp->fallback_link_rate);
+	}
+
 	DRM_DEBUG_KMS("DP link computation with max lane count %i "
 		      "max bw %d pixel clock %iKHz\n",
 		      max_lane_count, common_rates[max_clock],
@@ -4415,6 +4430,10 @@ static bool intel_digital_port_connected(struct drm_i915_private *dev_priv,
 		intel_dp->compliance_test_active = 0;
 		intel_dp->compliance_test_type = 0;
 		intel_dp->compliance_test_data = 0;
+		intel_dp->fallback_link_rate = 0;
+		intel_dp->fallback_lane_count = 0;
+		drm_mode_connector_set_link_status_property(connector,
+							    DRM_MODE_LINK_STATUS_GOOD);
 
 		if (intel_dp->is_mst) {
 			DRM_DEBUG_KMS("MST device may have disappeared %d vs %d\n",
@@ -4506,6 +4525,11 @@ static bool intel_digital_port_connected(struct drm_i915_private *dev_priv,
 	DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n",
 		      connector->base.id, connector->name);
 
+	/* If this is a retry due to link trianing failure */
+	if (status == connector_status_connected &&
+	    connector->link_status == DRM_MODE_LINK_STATUS_BAD)
+		return status;
+
 	/* If full detect is not performed yet, do a full detect */
 	if (!intel_dp->detect_done)
 		status = intel_dp_long_pulse(intel_dp->attached_connector);
@@ -5671,6 +5695,37 @@ static bool intel_edp_init_connector(struct intel_dp *intel_dp,
 	return false;
 }
 
+static void intel_dp_modeset_retry_work_fn(struct work_struct *work)
+{
+	struct intel_connector *intel_connector;
+	struct drm_connector *connector;
+	struct drm_display_mode *mode;
+	bool verbose_prune = true;
+
+	intel_connector = container_of(work, typeof(*intel_connector),
+				       modeset_retry_work);
+	connector = &intel_connector->base;
+
+	/* Grab the locks before changing connector property*/
+	mutex_lock(&connector->dev->mode_config.mutex);
+	DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n", connector->base.id,
+		      connector->name);
+	list_for_each_entry(mode, &connector->modes, head) {
+		mode->status = intel_dp_mode_valid(connector,
+						   mode);
+	}
+	drm_mode_prune_invalid(connector->dev, &connector->modes,
+			       verbose_prune);
+	/* Set connector link status to BAD and send a Uevent to notify
+	 * userspace to do a modeset.
+	 */
+	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)
@@ -5683,6 +5738,10 @@ 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..cc243db 100644
--- a/drivers/gpu/drm/i915/intel_dp_link_training.c
+++ b/drivers/gpu/drm/i915/intel_dp_link_training.c
@@ -313,6 +313,30 @@ 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;
+	struct drm_connector *connector = &intel_connector->base;
+
+	if (!intel_dp_link_training_clock_recovery(intel_dp))
+		goto failure_handling;
+	if (!intel_dp_link_training_channel_equalization(intel_dp))
+		goto failure_handling;
+
+	/* Reset the Link Train Values */
+	DRM_DEBUG_KMS("Link Training Passed at Link Rate = %d, Lane count = %d",
+		      intel_dp->link_rate, intel_dp->lane_count);
+	intel_dp->fallback_link_rate = 0;
+	intel_dp->fallback_lane_count = 0;
+	drm_mode_connector_set_link_status_property(connector,
+						    DRM_MODE_LINK_STATUS_GOOD);
+	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 3f6b4c9..33be66f 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 {
@@ -889,7 +892,6 @@ struct intel_dp {
 	uint8_t lane_count;
 	int fallback_link_rate;
 	uint8_t fallback_lane_count;
-	bool link_train_failed;
 	uint8_t sink_count;
 	bool link_mst;
 	bool has_audio;
-- 
1.9.1

_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel