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>

1 files changed, 21 insertions, 36 deletions

diff --git a/drivers/gpu/drm/i915/intel_dp_link_training.c b/drivers/gpu/drm/i915/intel_dp_link_training.c
index 80b932664743..c438b02184cb 100644
--- 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)