[Intel-gfx] [PATCH] i915: fix ironlake edp panel setup (v4)

[Dave Airlie]

From: Dave Airlie <airlied at redhat.com>

The eDP spec claims a 20% overhead for the 8:10 encoding scheme used on the wire. Take this into account when picking the lane/clock speed for the panel.

v3: some panels are out of spec, try our best to deal with them, don't refuse modes on eDP panels, and try the largest allowed settings if all else fails on eDP.
v4: fix stupid typo, forgot to git add before amending.

Signed-off-by: Dave Airlie <airlied at redhat.com>
---
 drivers/gpu/drm/i915/intel_dp.c |   27 ++++++++++++++++++++++++---
 1 files changed, 24 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 6094e42..b4f0282 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -139,6 +139,12 @@ intel_dp_link_required(struct drm_device *dev,
 }
 
 static int
+intel_dp_max_data_rate(int max_link_clock, int max_lanes)
+{
+	return (max_link_clock * max_lanes * 8) / 10;
+}
+
+static int
 intel_dp_mode_valid(struct drm_connector *connector,
 		    struct drm_display_mode *mode)
 {
@@ -147,8 +153,11 @@ intel_dp_mode_valid(struct drm_connector *connector,
 	int max_link_clock = intel_dp_link_clock(intel_dp_max_link_bw(intel_encoder));
 	int max_lanes = intel_dp_max_lane_count(intel_encoder);
 
-	if (intel_dp_link_required(connector->dev, intel_encoder, mode->clock)
-			> max_link_clock * max_lanes)
+	/* only refuse the mode on non eDP since we have seen some wierd eDP panels
+	   which are outside spec tolerances but somehow work by magic */
+	if (!IS_eDP(intel_encoder) &&
+	    (intel_dp_link_required(connector->dev, intel_encoder, mode->clock)
+	     > intel_dp_max_data_rate(max_link_clock, max_lanes)))
 		return MODE_CLOCK_HIGH;
 
 	if (mode->clock < 10000)
@@ -509,7 +518,7 @@ intel_dp_mode_fixup(struct drm_encoder *encoder, struct drm_display_mode *mode,
 
 	for (lane_count = 1; lane_count <= max_lane_count; lane_count <<= 1) {
 		for (clock = 0; clock <= max_clock; clock++) {
-			int link_avail = intel_dp_link_clock(bws[clock]) * lane_count;
+			int link_avail = intel_dp_max_data_rate(intel_dp_link_clock(bws[clock]), lane_count);
 
 			if (intel_dp_link_required(encoder->dev, intel_encoder, mode->clock)
 					<= link_avail) {
@@ -524,6 +533,18 @@ intel_dp_mode_fixup(struct drm_encoder *encoder, struct drm_display_mode *mode,
 			}
 		}
 	}
+
+	if (IS_eDP(intel_encoder)) {
+		/* okay we failed just pick the highest */
+		dp_priv->lane_count = max_lane_count;
+		dp_priv->link_bw = bws[max_clock];
+		adjusted_mode->clock = intel_dp_link_clock(dp_priv->link_bw);
+		DRM_DEBUG_KMS("Force picking display port link bw %02x lane "
+			      "count %d clock %d\n",
+			      dp_priv->link_bw, dp_priv->lane_count,
+			      adjusted_mode->clock);
+		return true;
+	}
 	return false;
 }
 
-- 
1.7.1