Hi all.
Happy KDE Plasma user for a long time and I generally love the desktop experience. But I do have one small issue.
At work, I have 2x 4K displays. connected through a Dock. But in Plasma it’s only able to give me around 1080p resolution on both of them. In contrast, the display manager SDDM and TTY displays 4k on each fine.
So am I missing a trick to get the max resolution in Plasma? My install is Arch Linux, kernel 6.4.12, Plasma 5.27, Wayland session.
I did install the displaylink AUR package, as I thought it might be the dock limiting the video output, but it isn’t as TTY and SDDM seems to display it correctly.
Happy to hear any thoughts and any ideas. :)
EDIT: The screens turn on and work fine with 4K resolutions in a Plasma X11 session.
around 1080p resolution
What do you mean by that? Is the biggest resolution you can select in the display settings 1080p, or do things look as big as you’d expect from a 1080p monitor?
I can select up to 2160p in the settings, but the screens just turn black until the settings reset, if I do. The highest resolution where the displays both turn on is 1080p. If I set them to 1440p only 1 of them turns on.
Okay, sounds like a bandwidth related issue. Could you try putting KWIN_DRM_PREFER_COLOR_DEPTH=24 into /etc/environment and rebooting?
This worked for me. Thank you very much. I’m now running 2x 4K screens on Plasma wayland.
What is the default color depth set to? 32?
The default is 30. Drivers are supposed to limit the bit depth automatically to make the display work, but DisplayLink is quite shitty so I guess I should not be too surprised. I think I’ll just make KWin force it to 24 for DisplayLink by default to get rid of the problem for everyone
Edit: heh, I already effectively did. It should not happen in Plasma 6 anymore
That’s awesome. Thank you for all your work!
So, a small update here.
Switching to Xorg, seems to get both monitors capable of running in 2160p mode. So it seems to be a Plasma Wayland limitation.
