drm/i915: Make DP link training channel equalization DP 1.2 Spec compliant

Fix the number of tries in channel euqalization link training sequence
according to DP 1.2 Spec. It returns a boolean depending on channel
equalization pass or failure.

Signed-off-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
Reviewed-by: Mika Kahola <mika.kahola@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

diff --git a/drivers/gpu/drm/i915/intel_dp_link_training.c b/drivers/gpu/drm/i915/intel_dp_link_training.c
index 80b9326..c438b02 100644 (file)
--- a/drivers/gpu/drm/i915/intel_dp_link_training.c
+++ b/drivers/gpu/drm/i915/intel_dp_link_training.c
@@ -244,12 +244,12 @@ static u32 intel_dp_training_pattern(struct intel_dp *intel_dp)
        return training_pattern;
 }
 
-static void
+static bool
 intel_dp_link_training_channel_equalization(struct intel_dp *intel_dp)
 {
-       bool channel_eq = false;
-       int tries, cr_tries;
+       int tries;
        u32 training_pattern;
+       uint8_t link_status[DP_LINK_STATUS_SIZE];
 
        training_pattern = intel_dp_training_pattern(intel_dp);
 
@@ -258,20 +258,11 @@ intel_dp_link_training_channel_equalization(struct intel_dp *intel_dp)
                                     training_pattern |
                                     DP_LINK_SCRAMBLING_DISABLE)) {
                DRM_ERROR("failed to start channel equalization\n");
-               return;
+               return false;
        }
 
-       tries = 0;
-       cr_tries = 0;
-       channel_eq = false;
-       for (;;) {
-               uint8_t link_status[DP_LINK_STATUS_SIZE];
-
-               if (cr_tries > 5) {
-                       DRM_ERROR("failed to train DP, aborting\n");
-                       intel_dp_dump_link_status(link_status);
-                       break;
-               }
+       intel_dp->channel_eq_status = false;
+       for (tries = 0; tries < 5; tries++) {
 
                drm_dp_link_train_channel_eq_delay(intel_dp->dpcd);
                if (!intel_dp_get_link_status(intel_dp, link_status)) {
@@ -282,44 +273,38 @@ intel_dp_link_training_channel_equalization(struct intel_dp *intel_dp)
                /* Make sure clock is still ok */
                if (!drm_dp_clock_recovery_ok(link_status,
                                              intel_dp->lane_count)) {
-                       intel_dp_link_training_clock_recovery(intel_dp);
-                       intel_dp_set_link_train(intel_dp,
-                                               training_pattern |
-                                               DP_LINK_SCRAMBLING_DISABLE);
-                       cr_tries++;
-                       continue;
+                       intel_dp_dump_link_status(link_status);
+                       DRM_DEBUG_KMS("Clock recovery check failed, cannot "
+                                     "continue channel equalization\n");
+                       break;
                }
 
                if (drm_dp_channel_eq_ok(link_status,
                                         intel_dp->lane_count)) {
-                       channel_eq = true;
+                       intel_dp->channel_eq_status = true;
+                       DRM_DEBUG_KMS("Channel EQ done. DP Training "
+                                     "successful\n");
                        break;
                }
 
-               /* Try 5 times, then try clock recovery if that fails */
-               if (tries > 5) {
-                       intel_dp_link_training_clock_recovery(intel_dp);
-                       intel_dp_set_link_train(intel_dp,
-                                               training_pattern |
-                                               DP_LINK_SCRAMBLING_DISABLE);
-                       tries = 0;
-                       cr_tries++;
-                       continue;
-               }
-
                /* Update training set as requested by target */
                intel_get_adjust_train(intel_dp, link_status);
                if (!intel_dp_update_link_train(intel_dp)) {
                        DRM_ERROR("failed to update link training\n");
                        break;
                }
-               ++tries;
+       }
+
+       /* Try 5 times, else fail and try at lower BW */
+       if (tries == 5) {
+               intel_dp_dump_link_status(link_status);
+               DRM_DEBUG_KMS("Channel equalization failed 5 times\n");
        }
 
        intel_dp_set_idle_link_train(intel_dp);
 
-       if (channel_eq)
-               DRM_DEBUG_KMS("Channel EQ done. DP Training successful\n");
+       return intel_dp->channel_eq_status;
+
 }
 
 void intel_dp_stop_link_train(struct intel_dp *intel_dp)

diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index 1bcf8ea..7700e32 100644 (file)
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -878,6 +878,7 @@ struct intel_dp {
        bool link_mst;
        bool has_audio;
        bool detect_done;
+       bool channel_eq_status;
        enum hdmi_force_audio force_audio;
        bool limited_color_range;
        bool color_range_auto;