https://bugs.kde.org/show_bug.cgi?id=527526
[email protected] changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |[email protected] --- Comment #6 from [email protected] --- After upgrading from Plasma/KWin 6.8.0 to 6.8.1, the external monitor driven by the NVIDIA GPU shows persistent flickering of UI elements (application launcher, panel, window frames/contents) when the mouse moves. The internal panel, driven by the AMD iGPU, is unaffected. The issue did not occur in 6.8.0. Hardware / Software OS: CachyOS Linux (Arch-based), kernel 7.2.11-1-cachyos KDE Plasma: 6.8.1 KDE Frameworks: 6.31.0 Qt: 6.12.0 KWin: 6.8.1 Mesa: 26.2.4 NVIDIA driver: 615.78.08 (proprietary) GPU 0 (display output): NVIDIA GeForce GTX 1650 Ti Mobile (TU117M), /dev/dri/card1 drives external HDMI-A-1 (2560x1440 @ 60, scale 1.5) GPU 1 (compositing): AMD Radeon Renoir (Radeon Vega), /dev/dri/card2 drives internal eDP-1 panel (disabled in this configuration) Compositor: KWin Wayland, OpenGL ES, renderer "AMD Radeon Graphics (radeonsi, renoir)" Steps to reproduce Boot into a Plasma 6.8.1 Wayland session on the above hybrid setup. Use the external monitor as the active display. Open the application launcher, move the mouse over the panel, or move the mouse over/inside application windows. Observe flickering of the affected UI elements. Static content is stable; flicker is triggered by mouse movement/input. Observed result Launcher, panel, and window frames/contents flicker on mouse movement. Cursor flickers only if KWIN_USE_BUFFER_AGE=0 is set (not in the default case). Whole screen is not black; only the affected elements on the NVIDIA-driven output. Expected result No flickering on either output during normal mouse movement. Workaround that fixes the issue Create ~/.config/plasma-workspace/env/kwin-flicker-workaround.sh (executable): #!/bin/sh export KWIN_DRM_DEVICES="/dev/dri/by-path/pci-0000\:05\:00.0-card:/dev/dri/by-path/pci-0000\:01\:00.0-card" export KWIN_DRM_FORCE_GL_FINISH_MGPU_COPY=1 export KWIN_DRM_FORCE_GL_FINISH_PRESENT=1 Relogin. Both monitors remain active and flicker is gone. Notes: KWIN_USE_BUFFER_AGE=0 alone did not help and introduced cursor flicker. KWIN_USE_OVERLAYS=0 alone did not help. KWIN_FORCE_SW_CURSOR=1 fixed cursor flicker but was not needed once buffer age was left at its default. KWIN_DRM_NO_AMS was not tested. Related bugs 527526 (same 6.8.1 multi-GPU regression, Intel/NVIDIA) 527251 (6.8.0 cross-GPU flicker, Intel/NVIDIA) 521668 (multi-GPU copy path, KWIN_DRM_FORCE_GL_FINISH_MGPU_COPY=1 fixes flicker) 527328 / 527421 (different trigger: non-atomic/legacy post-blend, fixed in 6.8.2) Additional context The fix in 6.8.2 for bug 527421 (disabling post-blend offloading on non-atomic drivers) does not apply here, since both GPUs report atomic mode setting support. The issue appears to be in the multi-GPU copy path introduced/changed in 6.8.1, resolved by forcing a glFinish before the cross-GPU copy/present. EOF echo "written" -- You are receiving this mail because: You are watching all bug changes.
