I switched[1] to KDE 6.0 Beta 1 recently on a AMD laptop, on Wayland session the screen attached to external GPU cannot display properly on default, it cannot show any part of a window if I drag one to it from the internal display (internal display works normally), only random blurred/fuzzy screen or black screen.
GPU setup:
➜ ~ lspci | grep VGA
37:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Vega 20 [Radeon VII] (rev c1)
63:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Rembrandt (rev d8)
The eGPU Radeon VII is /dev/dri/card0 and the iGPU Radeon 680M (of a Ryzen 6800HS) is /dev/dri/card1.
Driver is the one in upstream kernel, tried kernel version 6.6.7-1-liquorix-amd64 and 6.5.0-1010-oem (of Ubuntu 22.04)
Other behaviors noticed:
- Mouse cursor can be displayed properly on the external screen (which seems strange?)
- Spectacle can capture all desktops correctly.
- No kernel/driver panic or warning in kernel message
- this phenomenon does not appear on Xorg session
- this phenomenon does not appear on KDE Plasma/KWin 5.27.x
- In accordance with this post ( Plasma breaks on Wayland with NVIDIA proprietary drivers eGPU ), the default setup seems equivalent to
export KWIN_DRM_DEVICES=/dev/dri/card1:/dev/dri/card0, and swapping them fixes it.
Current workaround: Use eGPU to render: add
export KWIN_DRM_DEVICES=/dev/dri/card0:/dev/dri/card1
to $KDE_PREFIX/usr/lib/x86_64-linux-gnu/libexec/plasma-dev-prefix.sh.
But the default case is strange, is there anything wrong with my setup, or should it considered a bug of KWin or Plasma or driver … ? How can I help to debug this ?
[1]: I choose to switch to KDE 6.0 from 5.27.10 because of a issue similar to Low fps and high CPU usage on external monitor connected to NVIDIA when default GPU is Intel