drm/i915/dp: Reduce link params only after retrying with unchanged params

Try to maintain the current link parameters by retrying the link
training with unchanged link parameters before reducing these parameters
(sending an uevent to userspace to retrain the link instead).

Signed-off-by: Imre Deak <[email protected]>
Reviewed-by: Ville Syrjälä <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]

3 files changed, 14 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/display/intel_display_types.h b/drivers/gpu/drm/i915/display/intel_display_types.h
index 1af3d48a7b86..a50310f412dd 100644
--- a/drivers/gpu/drm/i915/display/intel_display_types.h
+++ b/drivers/gpu/drm/i915/display/intel_display_types.h
@@ -1771,6 +1771,8 @@ struct intel_dp {
 		int max_lane_count;
 		/* Max rate for the current link */
 		int max_rate;
+		/* Sequential link training failures after a passing LT */
+		int seq_train_failures;
 	} link;
 	bool reset_link_params;
 	int mso_link_count;
diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
index 0833302baabc..5f54b0a9f597 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -2961,6 +2961,7 @@ static void intel_dp_reset_link_params(struct intel_dp *intel_dp)
 {
 	intel_dp->link.max_lane_count = intel_dp_max_common_lane_count(intel_dp);
 	intel_dp->link.max_rate = intel_dp_max_common_rate(intel_dp);
+	intel_dp->link.seq_train_failures = 0;
 }
 
 /* Enable backlight PWM and backlight PP control. */
@@ -5075,6 +5076,9 @@ intel_dp_needs_link_retrain(struct intel_dp *intel_dp)
 					intel_dp->lane_count))
 		return false;
 
+	if (intel_dp->link.seq_train_failures)
+		return true;
+
 	/* Retrain if link not ok */
 	return !intel_dp_link_ok(intel_dp, link_status);
 }
diff --git a/drivers/gpu/drm/i915/display/intel_dp_link_training.c b/drivers/gpu/drm/i915/display/intel_dp_link_training.c
index 1164255cf5f2..8caf740e642f 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_link_training.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_link_training.c
@@ -1487,10 +1487,13 @@ void intel_dp_start_link_train(struct intel_dp *intel_dp,
 		passed = intel_dp_link_train_all_phys(intel_dp, crtc_state, lttpr_count);
 
 	if (passed) {
+		intel_dp->link.seq_train_failures = 0;
 		intel_encoder_link_check_queue_work(encoder, 2000);
 		return;
 	}
 
+	intel_dp->link.seq_train_failures++;
+
 	/*
 	 * Ignore the link failure in CI
 	 *
@@ -1508,6 +1511,11 @@ void intel_dp_start_link_train(struct intel_dp *intel_dp,
 		return;
 	}
 
+	if (intel_dp->link.seq_train_failures < 2) {
+		intel_encoder_link_check_queue_work(encoder, 0);
+		return;
+	}
+
 	intel_dp_schedule_fallback_link_training(intel_dp, crtc_state);
 }