[Intel-gfx] [PATCH] drm/i915: intel_dp_link_is_valid() should only return status of link

[Manasi Navare]

Intel_dp_link_is_valid() function reads the Link status registers
and returns a boolean to indicate link is valid or not.
If the link has lost lock and is not valid any more, it is
retrained outside the function else no previously trained link
is retained.

v2: Changed the function name from intel_dp_check_link_status()
to intel_dp_link_is_valid()  (Lukas Wunner)

Signed-off-by: Manasi Navare <manasi.d.navare at intel.com>
---
 drivers/gpu/drm/i915/intel_dp.c | 44 +++++++++++++++++++++++------------------
 1 file changed, 25 insertions(+), 19 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 0c5ba34..5b3e355 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -3862,36 +3862,34 @@ go_again:
 	return -EINVAL;
 }
 
-static void
-intel_dp_check_link_status(struct intel_dp *intel_dp)
+static bool
+intel_dp_link_is_valid(struct intel_dp *intel_dp)
 {
-	struct intel_encoder *intel_encoder = &dp_to_dig_port(intel_dp)->base;
 	struct drm_device *dev = intel_dp_to_dev(intel_dp);
 	u8 link_status[DP_LINK_STATUS_SIZE];
 
 	WARN_ON(!drm_modeset_is_locked(&dev->mode_config.connection_mutex));
 
 	if (!intel_dp_get_link_status(intel_dp, link_status)) {
-		DRM_ERROR("Failed to get link status\n");
-		return;
+		DRM_DEBUG_KMS("Failed to get link status\n");
+		return false;
 	}
 
-	if (!intel_encoder->base.crtc)
-		return;
+	/* Check if the link is valid by reading the bits of Link status
+	 * registers
+	 */
+	if (!drm_dp_channel_eq_ok(link_status, intel_dp->lane_count) ||
+	    !drm_dp_clock_recovery_ok(link_status, intel_dp->lane_count)) {
+		DRM_DEBUG_KMS("Channel EQ or CR not ok, need to retrain\n");
+		return false;
+	}
 
-	if (!to_intel_crtc(intel_encoder->base.crtc)->active)
-		return;
+	DRM_DEBUG_KMS("Link is good, no need to retrain\n");
+	return true;
 
-	/* if link training is requested we should perform it always */
-	if ((intel_dp->compliance_test_type == DP_TEST_LINK_TRAINING) ||
-	    (!drm_dp_channel_eq_ok(link_status, intel_dp->lane_count))) {
-		DRM_DEBUG_KMS("%s: channel EQ not ok, retraining\n",
-			      intel_encoder->base.name);
-		intel_dp_start_link_train(intel_dp);
-		intel_dp_stop_link_train(intel_dp);
-	}
 }
 
+
 /*
  * According to DP spec
  * 5.1.2:
@@ -3949,7 +3947,11 @@ intel_dp_short_pulse(struct intel_dp *intel_dp)
 	}
 
 	drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
-	intel_dp_check_link_status(intel_dp);
+	if (!intel_dp_link_is_valid(intel_dp) ||
+	    intel_dp->compliance_test_type == DP_TEST_LINK_TRAINING) {
+		intel_dp_start_link_train(intel_dp);
+		intel_dp_stop_link_train(intel_dp);
+	}
 	drm_modeset_unlock(&dev->mode_config.connection_mutex);
 
 	return true;
@@ -4270,7 +4272,11 @@ intel_dp_long_pulse(struct intel_connector *intel_connector)
 		 * link loss triggerring long pulse!!!!
 		 */
 		drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
-		intel_dp_check_link_status(intel_dp);
+		if (!intel_dp_link_is_valid(intel_dp) ||
+		    intel_dp->compliance_test_type == DP_TEST_LINK_TRAINING) {
+			intel_dp_start_link_train(intel_dp);
+			intel_dp_stop_link_train(intel_dp);
+		}
 		drm_modeset_unlock(&dev->mode_config.connection_mutex);
 		goto out;
 	}
-- 
1.9.1