[Bug 111452] New: Dull colors with kernel 5.2.0 on external monitors with intel-gfx

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=111452

            Bug ID: 111452
           Summary: Dull colors with kernel 5.2.0 on external monitors
                    with intel-gfx
           Product: DRI
           Version: XOrg git
          Hardware: x86-64 (AMD64)
                OS: Linux (All)
            Status: NEW
          Severity: normal
          Priority: medium
         Component: DRM/Intel
          Assignee: intel-gfx-bugs at lists.freedesktop.org
          Reporter: b.buschinski at googlemail.com
        QA Contact: intel-gfx-bugs at lists.freedesktop.org
                CC: intel-gfx-bugs at lists.freedesktop.org

With kernel 5.2.0 my colors on my external monitors are kind of dull.
Meaning the contrast seems lower and the gamma seems higher.
It worked fine with kernel 5.1.0.

It can be worked around with:

xrandr --output DP-1-1 --set 'Broadcast RGB' 'Full'
xrandr --output DP-1-2 --set 'Broadcast RGB' 'Full'

Only the external monitors (connected via laptop -> docking station -> display
port) are affected. The laptop display is fine.


I started bisecting it and result is:

37aa52bff2bcd4377c0f747f730f3d436f2fe58e is the first bad commit
commit 37aa52bff2bcd4377c0f747f730f3d436f2fe58e
Author: Ville Syrjälä <ville.syrjala at linux.intel.com>
Date:   Tue Mar 26 16:25:51 2019 +0200

    drm/i915: Add broadcast RGB property for DP MST

    Add the "Broadcast RGB" property to MST connectors, and implement
    the same logic for it as we have in the SST code.

    v2: Extract and reuse intel_dp_limited_color_range()

    Cc: Ivan Vlk <ari at adyline.sk>
    Tested-by: Ivan Vlk <ari at adyline.sk>
    Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=108821
    Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
    Reviewed-by: Jani Nikula <jani.nikula at intel.com> #v1
    Link:
https://patchwork.freedesktop.org/patch/msgid/20190326142556.21176-1-ville.syrjala@linux.intel.com

 drivers/gpu/drm/i915/intel_dp.c     | 39 ++++++++++++++++++++++++-------------
 drivers/gpu/drm/i915/intel_dp_mst.c | 15 ++++++++++++--
 drivers/gpu/drm/i915/intel_drv.h    |  2 ++
 3 files changed, 40 insertions(+), 16 deletions(-)



CPU: Intel(R) Core(TM) i5-6300U CPU @ 2.40GHz
Laptop: Dell Latitude E7470
Software:
- xorg-server-1.20.5
- mesa-19.1.3
- libdrm-2.4.99


Kernel Bugzilla Link: https://bugzilla.kernel.org/show_bug.cgi?id=204351

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