Bug 204351

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@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@adyline.sk>
    Tested-by: Ivan Vlk <ari@adyline.sk>
    Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=108821
    Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
    Reviewed-by: Jani Nikula <jani.nikula@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