1 files changed, 29 insertions, 22 deletions

diff --git a/drivers/gpu/drm/i915/intel_dp_link_training.c b/drivers/gpu/drm/i915/intel_dp_link_training.c
index 4da6e33c7fa1..30be0e39bd5f 100644
--- a/drivers/gpu/drm/i915/intel_dp_link_training.c
+++ b/drivers/gpu/drm/i915/intel_dp_link_training.c
@@ -129,7 +129,8 @@ static bool
 intel_dp_link_training_clock_recovery(struct intel_dp *intel_dp)
 {
 	uint8_t voltage;
-	int voltage_tries, max_vswing_tries;
+	int voltage_tries, cr_tries, max_cr_tries;
+	bool max_vswing_reached = false;
 	uint8_t link_config[2];
 	uint8_t link_bw, rate_select;
 
@@ -170,9 +171,21 @@ intel_dp_link_training_clock_recovery(struct intel_dp *intel_dp)
 		return false;
 	}
 
+	/*
+	 * The DP 1.4 spec defines the max clock recovery retries value
+	 * as 10 but for pre-DP 1.4 devices we set a very tolerant
+	 * retry limit of 80 (4 voltage levels x 4 preemphasis levels x
+	 * x 5 identical voltage retries). Since the previous specs didn't
+	 * define a limit and created the possibility of an infinite loop
+	 * we want to prevent any sync from triggering that corner case.
+	 */
+	if (intel_dp->dpcd[DP_DPCD_REV] >= DP_DPCD_REV_14)
+		max_cr_tries = 10;
+	else
+		max_cr_tries = 80;
+
 	voltage_tries = 1;
-	max_vswing_tries = 0;
-	for (;;) {
+	for (cr_tries = 0; cr_tries < max_cr_tries; ++cr_tries) {
 		uint8_t link_status[DP_LINK_STATUS_SIZE];
 
 		drm_dp_link_train_clock_recovery_delay(intel_dp->dpcd);
@@ -192,7 +205,7 @@ intel_dp_link_training_clock_recovery(struct intel_dp *intel_dp)
 			return false;
 		}
 
-		if (max_vswing_tries == 1) {
+		if (max_vswing_reached) {
 			DRM_DEBUG_KMS("Max Voltage Swing reached\n");
 			return false;
 		}
@@ -213,9 +226,11 @@ intel_dp_link_training_clock_recovery(struct intel_dp *intel_dp)
 			voltage_tries = 1;
 
 		if (intel_dp_link_max_vswing_reached(intel_dp))
-			++max_vswing_tries;
+			max_vswing_reached = true;
 
 	}
+	DRM_ERROR("Failed clock recovery %d times, giving up!\n", max_cr_tries);
+	return false;
 }
 
 /*
@@ -352,22 +367,14 @@ intel_dp_start_link_train(struct intel_dp *intel_dp)
 	return;
 
  failure_handling:
-	/* Dont fallback and prune modes if its eDP */
-	if (!intel_dp_is_edp(intel_dp)) {
-		DRM_DEBUG_KMS("[CONNECTOR:%d:%s] Link Training failed at link rate = %d, lane count = %d",
-			      intel_connector->base.base.id,
-			      intel_connector->base.name,
-			      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);
-	} else {
-		DRM_ERROR("[CONNECTOR:%d:%s] Link Training failed at link rate = %d, lane count = %d",
-			  intel_connector->base.base.id,
-			  intel_connector->base.name,
-			  intel_dp->link_rate, intel_dp->lane_count);
-	}
+	DRM_DEBUG_KMS("[CONNECTOR:%d:%s] Link Training failed at link rate = %d, lane count = %d",
+		      intel_connector->base.base.id,
+		      intel_connector->base.name,
+		      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;
 }