This is a note to let you know that I've just added the patch titled
drm/i915/dp: Revert "drm/i915/dp: fall back to 18 bpp when sink capability is unknown"
to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
drm-i915-dp-revert-drm-i915-dp-fall-back-to-18-bpp-when-sink-capability-is-unknown.patch
and it can be found in the queue-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 196f954e250943df414efd3d632254c29be38e59 Mon Sep 17 00:00:00 2001
From: Mario Kleiner <mario.kleiner.de@xxxxxxxxx>
Date: Wed, 6 Jul 2016 12:05:45 +0200
Subject: drm/i915/dp: Revert "drm/i915/dp: fall back to 18 bpp when sink capability is unknown"
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From: Mario Kleiner <mario.kleiner.de@xxxxxxxxx>
commit 196f954e250943df414efd3d632254c29be38e59 upstream.
This reverts commit 013dd9e03872
("drm/i915/dp: fall back to 18 bpp when sink capability is unknown")
This commit introduced a regression into stable kernels,
as it reduces output color depth to 6 bpc for any video
sink connected to a Displayport connector if that sink
doesn't report a specific color depth via EDID, or if
our EDID parser doesn't actually recognize the proper
bpc from EDID.
Affected are active DisplayPort->VGA converters and
active DisplayPort->DVI converters. Both should be
able to handle 8 bpc, but are degraded to 6 bpc with
this patch.
The reverted commit was meant to fix
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=105331
A followup patch implements a fix for that specific bug,
which is caused by a faulty EDID of the affected DP panel
by adding a new EDID quirk for that panel.
DP 18 bpp fallback handling and other improvements to
DP sink bpc detection will be handled for future
kernels in a separate series of patches.
Please backport to stable.
Signed-off-by: Mario Kleiner <mario.kleiner.de@xxxxxxxxx>
Acked-by: Jani Nikula <jani.nikula@xxxxxxxxx>
Cc: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
Signed-off-by: Dave Airlie <airlied@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/gpu/drm/i915/intel_display.c | 20 +++++---------------
1 file changed, 5 insertions(+), 15 deletions(-)
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -11952,21 +11952,11 @@ connected_sink_compute_bpp(struct intel_
pipe_config->pipe_bpp = connector->base.display_info.bpc*3;
}
- /* Clamp bpp to default limit on screens without EDID 1.4 */
- if (connector->base.display_info.bpc == 0) {
- int type = connector->base.connector_type;
- int clamp_bpp = 24;
-
- /* Fall back to 18 bpp when DP sink capability is unknown. */
- if (type == DRM_MODE_CONNECTOR_DisplayPort ||
- type == DRM_MODE_CONNECTOR_eDP)
- clamp_bpp = 18;
-
- if (bpp > clamp_bpp) {
- DRM_DEBUG_KMS("clamping display bpp (was %d) to default limit of %d\n",
- bpp, clamp_bpp);
- pipe_config->pipe_bpp = clamp_bpp;
- }
+ /* Clamp bpp to 8 on screens without EDID 1.4 */
+ if (connector->base.display_info.bpc == 0 && bpp > 24) {
+ DRM_DEBUG_KMS("clamping display bpp (was %d) to default limit of 24\n",
+ bpp);
+ pipe_config->pipe_bpp = 24;
}
}
Patches currently in stable-queue which might be from mario.kleiner.de@xxxxxxxxx are
queue-4.4/drm-edid-add-6-bpc-quirk-for-display-aeo-model-0.patch
queue-4.4/drm-i915-dp-revert-drm-i915-dp-fall-back-to-18-bpp-when-sink-capability-is-unknown.patch
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