Display resolution 3840x2160@24rb stopped working after Upgrade from Stretch to Buster

[Jan Michael Greiner <jan0michael@yahoo.com>]

Dear all,

My laptop: Lenovo E520
Graphics: Intel HD Graphics 3000 (kernel module i915)

External display AOC U2879VF, 28 inch, connected by HDMI cable

With Debian Stretch (9.8) I had the display running with 3840x2160 resolution at 24Hz reduced blank.


I did this with something like:

export modename="3840x2160_24.00_rb"
xrandr --newmode $modename  209.75  3840 3888 3920 4000  2160 2163 2168 2185  +HSync -Vsync
xrandr --addmode HDMI-1 $modename
xrandr --output HDMI-1 --mode $modename
xrandr --output HDMI-1 --primary
xrandr --output LVDS-1 --off # switch laptop display off

After upgrade to Buster (Debian 10)

This does not work any more:
xxx@yyy:~$ xrandr --verbose
 Screen 0: minimum 320 x 200, current 1920 x 1080, maximum 8192 x 8192
XWAYLAND1 connected 1920x1080+0+0 (0x25) normal (normal left inverted right x axis y axis) 620mm x 340mm
    Identifier: 0x23
    Timestamp:  42126
    Subpixel:   unknown
    Gamma:      1.0:1.0:1.0
    Brightness: 0.0
    Clones:
    CRTC:       0
    CRTCs:      0
    Transform:  1.000000 0.000000 0.000000
                0.000000 1.000000 0.000000
                0.000000 0.000000 1.000000
               filter:
    non-desktop: 0
        supported: 0, 1
  1920x1080 (0x25) 173.000MHz -HSync +VSync *current +preferred
        h: width  1920 start 2048 end 2248 total 2576 skew    0 clock  67.16KHz
        v: height 1080 start 1083 end 1088 total 1120           clock  59.96Hz
 xxx@yyy:~$ export modename="3840x2160_24.00_rb"
xxx@yyy:~$ xrandr --newmode $modename  209.75  3840 3888 3920 4000  2160 2163 2168 2185  +HSync -Vsync
xxx@yyy:~$ xrandr --addmode XWAYLAND1 $modename
xxx@yyy:~$ xrandr --output XWAYLAND1 --mode $modename
xrandr: Configure crtc 0 failed
xxx@yyy:~$ xrandr --output XWAYLAND1 --mode $modename --verbose
screen 0: 3840x2160 1237x696 mm  78.83dpi
crtc 0: 3840x2160_24.00_rb  24.00 +0+0 "XWAYLAND1"
xrandr: Configure crtc 0 failed
crtc 0: disable
screen 0: revert
crtc 0: revert 


After searching the internet, and trying to understand the relationship between Wayland - graphics driver - graphics configuration - X etc. (which I was not successful at), I hope to get help here on this mailing list.

Best regards