[Intel-gfx] [PATCH] drm/i915/display/dp: 128/132b LT requirement

[Arun R Murthy]

For 128b/132b LT prior to LT DPTX should set power state, DP channel
coding and then link rate.

Signed-off-by: Arun R Murthy <arun.r.murthy at intel.com>
---
 .../drm/i915/display/intel_dp_link_training.c | 52 +++++++++++++------
 1 file changed, 35 insertions(+), 17 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 6aa4ae5e7ebe..83ea9ece0157 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_link_training.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_link_training.c
@@ -686,23 +686,41 @@ intel_dp_prepare_link_train(struct intel_dp *intel_dp,
 		drm_dbg_kms(&i915->drm,
 			    "[ENCODER:%d:%s] Using LINK_RATE_SET value %02x\n",
 			    encoder->base.base.id, encoder->base.name, rate_select);
-
-	/* Write the link configuration data */
-	link_config[0] = link_bw;
-	link_config[1] = crtc_state->lane_count;
-	if (drm_dp_enhanced_frame_cap(intel_dp->dpcd))
-		link_config[1] |= DP_LANE_COUNT_ENHANCED_FRAME_EN;
-	drm_dp_dpcd_write(&intel_dp->aux, DP_LINK_BW_SET, link_config, 2);
-
-	/* eDP 1.4 rate select method. */
-	if (!link_bw)
-		drm_dp_dpcd_write(&intel_dp->aux, DP_LINK_RATE_SET,
-				  &rate_select, 1);
-
-	link_config[0] = crtc_state->vrr.flipline ? DP_MSA_TIMING_PAR_IGNORE_EN : 0;
-	link_config[1] = intel_dp_is_uhbr(crtc_state) ?
-		DP_SET_ANSI_128B132B : DP_SET_ANSI_8B10B;
-	drm_dp_dpcd_write(&intel_dp->aux, DP_DOWNSPREAD_CTRL, link_config, 2);
+	if (intel_dp_is_uhbr(crtc_state)) {
+		/*
+		 * Spec DP2.1 Section 3.5.2.16
+		 * Prior to LT DPTX should set 128/132 DP Channel coding and then set link rate
+		 */
+		link_config[0] = crtc_state->vrr.enable ? DP_MSA_TIMING_PAR_IGNORE_EN : 0;
+		link_config[1] = intel_dp_is_uhbr(crtc_state) ?
+			DP_SET_ANSI_128B132B : DP_SET_ANSI_8B10B;
+		drm_dp_dpcd_write(&intel_dp->aux, DP_DOWNSPREAD_CTRL, link_config, 2);
+		/* Write the link configuration data */
+		link_config[0] = link_bw;
+		link_config[1] = crtc_state->lane_count;
+		if (drm_dp_enhanced_frame_cap(intel_dp->dpcd))
+			link_config[1] |= DP_LANE_COUNT_ENHANCED_FRAME_EN;
+		drm_dp_dpcd_write(&intel_dp->aux, DP_LINK_BW_SET, link_config, 2);
+		/* eDP 1.4 rate select method. */
+		if (!link_bw)
+			drm_dp_dpcd_write(&intel_dp->aux, DP_LINK_RATE_SET,
+					  &rate_select, 1);
+	} else {
+		/* Write the link configuration data */
+		link_config[0] = link_bw;
+		link_config[1] = crtc_state->lane_count;
+		if (drm_dp_enhanced_frame_cap(intel_dp->dpcd))
+			link_config[1] |= DP_LANE_COUNT_ENHANCED_FRAME_EN;
+		drm_dp_dpcd_write(&intel_dp->aux, DP_LINK_BW_SET, link_config, 2);
+		/* eDP 1.4 rate select method. */
+		if (!link_bw)
+			drm_dp_dpcd_write(&intel_dp->aux, DP_LINK_RATE_SET,
+					  &rate_select, 1);
+		link_config[0] = crtc_state->vrr.enable ? DP_MSA_TIMING_PAR_IGNORE_EN : 0;
+		link_config[1] = intel_dp_is_uhbr(crtc_state) ?
+			DP_SET_ANSI_128B132B : DP_SET_ANSI_8B10B;
+		drm_dp_dpcd_write(&intel_dp->aux, DP_DOWNSPREAD_CTRL, link_config, 2);
+	}
 
 	return true;
 }
-- 
2.25.1