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

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

[Daniel Vetter]

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);
-- 
1.7.9.1

Re: [PATCH] drm/i915: properly compute dp dithering for user-created modes

[Chris Wilson]

On Tue, 10 Apr 2012 09:33:19 +0200, Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
> 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.

Based on my reading, this still leaves the issue of depth > 24 modes as
the upper bandwidth required is calculated on the presumption of
depth == 24, but the divider set to the fb depth in the normal case.
 
> 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);
Cut'n'paste bad whitespace.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre

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

[Daniel Vetter]

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.

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);
-- 
1.7.9.1

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

[Daniel Vetter]

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: 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..4b63791 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);
-- 
1.7.9.1

Re: [PATCH] drm/i915: properly compute dp dithering for user-created modes

[Adam Jackson]

On 4/10/12 4:42 AM, Daniel Vetter wrote:
> 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).

Certainly an improvement.

Reviewed-by: Adam Jackson <ajax@redhat.com>

- ajax

Re: [PATCH] drm/i915: properly compute dp dithering for user-created modes

[Daniel Vetter]

On Tue, Apr 10, 2012 at 09:46:53AM -0400, Adam Jackson wrote:
> On 4/10/12 4:42 AM, Daniel Vetter wrote:
> >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).
> 
> Certainly an improvement.
> 
> Reviewed-by: Adam Jackson <ajax@redhat.com>
I've picked this up for -fixes, thanks for the review.
-Daniel
-- 
Daniel Vetter
Mail: daniel@ffwll.ch
Mobile: +41 (0)79 365 57 48

Re: [Intel-gfx] [PATCH] drm/i915: properly compute dp dithering for user-created modes

[Keith Packard]

<#part sign=pgpmime>
On Tue, 10 Apr 2012 09:46:53 -0400, Adam Jackson <ajax@redhat.com> wrote:

> Certainly an improvement.
> 
> Reviewed-by: Adam Jackson <ajax@redhat.com>

I'd like to know if this actually helps someone before I stick it in
drm-intel-fixes...

-- 
keith.packard@intel.com