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>

1 files changed, 4 insertions, 2 deletions

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 1c3a36feaf69..8aecb072466b 100644
--- 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);