[PATCH 3/9] drm/i915/dp: Clear DPCD training pattern before transmitting the idle pattern

[Ville Syrjala <ville.syrjala@linux.intel.com>]

From: Ville Syrjälä <ville.syrjala@linux.intel.com>

We are supposed to switch off the training pattern in DPCD before
we start transmitting the idle pattern. For LTTPRs we do that
correctly, but for the sink DPRX we only do this correctly
for some platforms.

On pre-HSW (where we don't implement the .set_idle_link_train()
hook), we directly switch from transmitting the training pattern
to normal pixel transmission (the hardware should guarantee that
the minimum number of required idle patters will be transmitted
during this transition).

For HSW+ we start transmitting the idle pattern earlier, and only
switch off the DPCD training pattern after we switch from the idle
pattern to normal pixel transmission. Adjust the code to disable
the DPCD training pattern before we start transmitting the idle
patter.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
---
 drivers/gpu/drm/i915/display/intel_dp_link_training.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_dp_link_training.c b/drivers/gpu/drm/i915/display/intel_dp_link_training.c
index 11953b03bb6a..b2fb641e4e96 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_link_training.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_link_training.c
@@ -1125,7 +1125,9 @@ void intel_dp_stop_link_train(struct intel_dp *intel_dp,
 {
 	intel_dp->link_trained = true;
 
-	intel_dp_disable_dpcd_training_pattern(intel_dp, DP_PHY_DPRX);
+	if (!intel_dp->set_idle_link_train)
+		intel_dp_disable_dpcd_training_pattern(intel_dp, DP_PHY_DPRX);
+
 	intel_dp_program_link_training_pattern(intel_dp, crtc_state, DP_PHY_DPRX,
 					       DP_TRAINING_PATTERN_DISABLE);
 
@@ -1357,8 +1359,10 @@ intel_dp_link_train_all_phys(struct intel_dp *intel_dp,
 	if (ret)
 		ret = intel_dp_link_train_phy(intel_dp, crtc_state, DP_PHY_DPRX);
 
-	if (intel_dp->set_idle_link_train)
+	if (intel_dp->set_idle_link_train) {
+		intel_dp_disable_dpcd_training_pattern(intel_dp, DP_PHY_DPRX);
 		intel_dp->set_idle_link_train(intel_dp, crtc_state);
+	}
 
 	return ret;
 }
-- 
2.45.3