drm/i915/dp: Explicitly disable symbol scrambling while training

The DP spec says training patterns 1 and 2 are to be sent non-scrambled,
and the GPU docs claim that happens (or at least, there's no explicit
scrambling control).  But the sink may be confused if we don't
explicitly tell it what we're doing, so play it safe.

Signed-off-by: Adam Jackson <ajax@redhat.com>
Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Keith Packard <keithp@keithp.com>

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 1c3a36feaf69de7834f5d59da4edef0013e6498e..8aecb072466b6cd34e16e8238ad634e5f5b2ec3f 100644 (file)
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -1370,7 +1370,8 @@ intel_dp_start_link_train(struct intel_dp *intel_dp)
                        reg = DP | DP_LINK_TRAIN_PAT_1;
 
                if (!intel_dp_set_link_train(intel_dp, reg,
-                                            DP_TRAINING_PATTERN_1))
+                                            DP_TRAINING_PATTERN_1 |
+                                            DP_LINK_SCRAMBLING_DISABLE))
                        break;
                /* Set training pattern 1 */
 
@@ -1445,7 +1446,8 @@ intel_dp_complete_link_train(struct intel_dp *intel_dp)
 
                /* channel eq pattern */
                if (!intel_dp_set_link_train(intel_dp, reg,
-                                            DP_TRAINING_PATTERN_2))
+                                            DP_TRAINING_PATTERN_2 |
+                                            DP_LINK_SCRAMBLING_DISABLE))
                        break;
 
                udelay(400);