This is a note to let you know that I've just added the patch titled
drm/edid: Add 6 bpc quirk for display AEO model 0.
to the 4.7-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-edid-add-6-bpc-quirk-for-display-aeo-model-0.patch
and it can be found in the queue-4.7 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From e10aec652f31ec61d6a0b4d00d8ef8d2b66fa0fd Mon Sep 17 00:00:00 2001
From: Mario Kleiner <mario.kleiner.de@xxxxxxxxx>
Date: Wed, 6 Jul 2016 12:05:44 +0200
Subject: drm/edid: Add 6 bpc quirk for display AEO model 0.
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
From: Mario Kleiner <mario.kleiner.de@xxxxxxxxx>
commit e10aec652f31ec61d6a0b4d00d8ef8d2b66fa0fd upstream.
Bugzilla https://bugzilla.kernel.org/show_bug.cgi?id=105331
reports that the "AEO model 0" display is driven with 8 bpc
without dithering by default, which looks bad because that
panel is apparently a 6 bpc DP panel with faulty EDID.
A fix for this was made by commit 013dd9e03872
("drm/i915/dp: fall back to 18 bpp when sink capability is unknown").
That commit triggers new regressions in precision for DP->DVI and
DP->VGA displays. A patch is out to revert that commit, but it will
revert video output for the AEO model 0 panel to 8 bpc without
dithering.
The EDID 1.3 of that panel, as decoded from the xrandr output
attached to that bugzilla bug report, is somewhat faulty, and beyond
other problems also sets the "DFP 1.x compliant TMDS" bit, which
according to DFP spec means to drive the panel with 8 bpc and
no dithering in absence of other colorimetry information.
Try to make the original bug reporter happy despite the
faulty EDID by adding a quirk to mark that panel as 6 bpc,
so 6 bpc output with dithering creates a nice picture.
Tested by injecting the edid from the fdo bug into a DP connector
via drm_kms_helper.edid_firmware and verifying the 6 bpc + dithering
is selected.
This patch should be backported to stable.
Signed-off-by: Mario Kleiner <mario.kleiner.de@xxxxxxxxx>
Cc: 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/drm_edid.c | 8 ++++++++
1 file changed, 8 insertions(+)
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -74,6 +74,8 @@
#define EDID_QUIRK_FORCE_8BPC (1 << 8)
/* Force 12bpc */
#define EDID_QUIRK_FORCE_12BPC (1 << 9)
+/* Force 6bpc */
+#define EDID_QUIRK_FORCE_6BPC (1 << 10)
struct detailed_mode_closure {
struct drm_connector *connector;
@@ -100,6 +102,9 @@ static struct edid_quirk {
/* Unknown Acer */
{ "ACR", 2423, EDID_QUIRK_FIRST_DETAILED_PREFERRED },
+ /* AEO model 0 reports 8 bpc, but is a 6 bpc panel */
+ { "AEO", 0, EDID_QUIRK_FORCE_6BPC },
+
/* Belinea 10 15 55 */
{ "MAX", 1516, EDID_QUIRK_PREFER_LARGE_60 },
{ "MAX", 0x77e, EDID_QUIRK_PREFER_LARGE_60 },
@@ -4082,6 +4087,9 @@ int drm_add_edid_modes(struct drm_connec
drm_add_display_info(edid, &connector->display_info, connector);
+ if (quirks & EDID_QUIRK_FORCE_6BPC)
+ connector->display_info.bpc = 6;
+
if (quirks & EDID_QUIRK_FORCE_8BPC)
connector->display_info.bpc = 8;
Patches currently in stable-queue which might be from mario.kleiner.de@xxxxxxxxx are
queue-4.7/drm-edid-add-6-bpc-quirk-for-display-aeo-model-0.patch
--
To unsubscribe from this list: send the line "unsubscribe stable" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html