Commit c4867936 authored by Daniel Vetter's avatar Daniel Vetter
Browse files

drm/i915: properly compute dp dithering for user-created modes 



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.

Chris Wilson pointed out that we still get things wrong for bpp > 24,
but that should be fixed in another patch (and it'll be easier because
this patch consolidates the logic).

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

v2: Fix indentation and tune down the too bold claim that this should
fix the world. Both noticed by Chris Wilson.

v3: Try to really git add things.

Reported-and-tested-by: default avatarBrice Goglin <Brice.Goglin@ens-lyon.org>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=48170


Cc: stable@kernel.org
Reviewed-by: default avatarAdam Jackson <ajax@redhat.com>
Signed-Off-by: default avatarDaniel Vetter <daniel.vetter@ffwll.ch>
parent 14667a4b

drivers/gpu/drm/i915/intel_dp.c

+35 −14
Original line number Diff line number Diff line
@@ -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)

	if (!intel_dp_adjust_dithering(intel_dp, mode, NULL))

		return MODE_CLOCK_HIGH;

			else

				mode->private_flags |= INTEL_MODE_DP_FORCE_6BPC;

	}



	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);

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