We've only computed whether we need to fall back to 6bpc due to dp link bandwidth constrains in mode_valid, but not mode_fixup. Under various circumstances X likes to create new modes which then lack proper 6bpc flags (if required), resulting in mode_fixup failures and ultimately black screens.
This is hopefully fixes the last regression fallout of the dp bandwidth fixes.
The likely culprit for this regression is
commit 3d794f87238f74d80e78a7611c7fbde8a54c85c2 Author: Keith Packard keithp@keithp.com Date: Wed Jan 25 08:16:25 2012 -0800
drm/i915: Force explicit bpp selection for intel_dp_link_required
Reported-and-tested-by: Brice Goglin Brice.Goglin@ens-lyon.org Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=48170 Cc: stable@kernel.org Signed-Off-by: Daniel Vetter daniel.vetter@ffwll.ch --- drivers/gpu/drm/i915/intel_dp.c | 49 +++++++++++++++++++++++++++----------- 1 files changed, 35 insertions(+), 14 deletions(-)
diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c index 110552f..065c26d 100644 --- a/drivers/gpu/drm/i915/intel_dp.c +++ b/drivers/gpu/drm/i915/intel_dp.c @@ -219,14 +219,38 @@ intel_dp_max_data_rate(int max_link_clock, int max_lanes) return (max_link_clock * max_lanes * 8) / 10; }
+static bool +intel_dp_adjust_dithering(struct intel_dp *intel_dp, + struct drm_display_mode *mode, + struct drm_display_mode *adjusted_mode) +{ + int max_link_clock = intel_dp_link_clock(intel_dp_max_link_bw(intel_dp)); + int max_lanes = intel_dp_max_lane_count(intel_dp); + int max_rate, mode_rate; + + mode_rate = intel_dp_link_required(mode->clock, 24); + max_rate = intel_dp_max_data_rate(max_link_clock, max_lanes); + + if (mode_rate > max_rate) { + mode_rate = intel_dp_link_required(mode->clock, 18); + if (mode_rate > max_rate) + return false; + + if (adjusted_mode) + adjusted_mode->private_flags + |= INTEL_MODE_DP_FORCE_6BPC; + + return true; + } + + return true; +} + static int intel_dp_mode_valid(struct drm_connector *connector, struct drm_display_mode *mode) { struct intel_dp *intel_dp = intel_attached_dp(connector); - int max_link_clock = intel_dp_link_clock(intel_dp_max_link_bw(intel_dp)); - int max_lanes = intel_dp_max_lane_count(intel_dp); - int max_rate, mode_rate;
if (is_edp(intel_dp) && intel_dp->panel_fixed_mode) { if (mode->hdisplay > intel_dp->panel_fixed_mode->hdisplay) @@ -236,16 +260,8 @@ intel_dp_mode_valid(struct drm_connector *connector, return MODE_PANEL; }
- mode_rate = intel_dp_link_required(mode->clock, 24); - max_rate = intel_dp_max_data_rate(max_link_clock, max_lanes); - - if (mode_rate > max_rate) { - mode_rate = intel_dp_link_required(mode->clock, 18); - if (mode_rate > max_rate) - return MODE_CLOCK_HIGH; - else - mode->private_flags |= INTEL_MODE_DP_FORCE_6BPC; - } + if (!intel_dp_adjust_dithering(intel_dp, mode, NULL)) + return MODE_CLOCK_HIGH;
if (mode->clock < 10000) return MODE_CLOCK_LOW; @@ -672,7 +688,7 @@ intel_dp_mode_fixup(struct drm_encoder *encoder, struct drm_display_mode *mode, int lane_count, clock; int max_lane_count = intel_dp_max_lane_count(intel_dp); int max_clock = intel_dp_max_link_bw(intel_dp) == DP_LINK_BW_2_7 ? 1 : 0; - int bpp = mode->private_flags & INTEL_MODE_DP_FORCE_6BPC ? 18 : 24; + int bpp; static int bws[2] = { DP_LINK_BW_1_62, DP_LINK_BW_2_7 };
if (is_edp(intel_dp) && intel_dp->panel_fixed_mode) { @@ -686,6 +702,11 @@ intel_dp_mode_fixup(struct drm_encoder *encoder, struct drm_display_mode *mode, mode->clock = intel_dp->panel_fixed_mode->clock; }
+ if (!intel_dp_adjust_dithering(intel_dp, mode, adjusted_mode)) + return false; + + bpp = adjusted_mode->private_flags & INTEL_MODE_DP_FORCE_6BPC ? 18 : 24; + for (lane_count = 1; lane_count <= max_lane_count; lane_count <<= 1) { for (clock = 0; clock <= max_clock; clock++) { int link_avail = intel_dp_max_data_rate(intel_dp_link_clock(bws[clock]), lane_count);