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.

  • StritOP
    1•8 months ago

    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.

    • @Zamundaaa@discuss.tchncs.de
      4•8 months ago

      Okay, sounds like a bandwidth related issue. Could you try putting KWIN_DRM_PREFER_COLOR_DEPTH=24 into /etc/environment and rebooting?

      • StritOP
        1•8 months ago

        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?

        • @Zamundaaa@discuss.tchncs.de
          4•8 months ago

          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

          • StritOP
            1•8 months ago

            That’s awesome. Thank you for all your work!