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

[Dan Ritter <dsr@randomstring.org>]

Jan Michael Greiner wrote: 
> 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.

Your problem is likely to be Wayland, which is trying to replace
X. Switching back will probably solve your issue.

-dsr-