https://bugs.kde.org/show_bug.cgi?id=527564
Bug ID: 527564
Summary: Black screen with visible cursor on iGPU (Vega 11)
output in RX 6800 + iGPU setup; fixed by
KWIN_DRM_USE_MODIFIERS=0
Classification: Plasma
Product: kwin
Version First 6.8.0
Reported In:
Platform: Other
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: multi-screen
Assignee: [email protected]
Reporter: [email protected]
Target Milestone: ---
Created attachment 197486
--> https://bugs.kde.org/attachment.cgi?id=197486&action=edit
kscreen-doctor -o output and kernel/kwin journal excerpts (with and without
KWIN_DRM_USE_MODIFIERS=0)
Setup: openSUSE Tumbleweed 20261017, Plasma 6.8.0, KWin 6.8.0,
KDE Frameworks 6.31.0, Qt 6.11.2, kernel 7.2.11, Wayland.
Mesa 26.2.5-1699.2.pm.1 (appears to come from the Packman repository).
GPUs: AMD Radeon RX 6800 (03:00.0, card1) and Ryzen 5 3400G Vega 11 /
Picasso (09:00.0, card0, 1024M VRAM carve-out). Monitor 1 is on the RX 6800
(HDMI-A-1, 1920x1080 landscape), monitor 2 is on the motherboard HDMI
(Vega 11, HDMI-A-3, 1920x1080 in portrait, rotation 270).
Steps to reproduce:
1. Boot with both monitors connected, one on each GPU.
2. Log into a Plasma Wayland session.
Actual result: the monitor on the Vega 11 does not show the desktop.
After a system update with kernel 7.1.2 it showed a half-black,
half-green image; with kernel 7.2.11 it is fully black, but the cursor
is visible and moves. kwin_wayland logs:
"Failed to create framebuffer: Invalid argument"
Expected result: the desktop is shown on both monitors, as before the update.
Workaround: adding "export KWIN_DRM_USE_MODIFIERS=0" to a script in
~/.config/plasma-workspace/env/ fixes it. With it, both monitors work,
including the portrait one.
Other notes:
- Both monitors display the SDDM login screen correctly.
- Screen rotation is not the cause: setting the Vega output to normal
rotation did not change anything.
- amdgpu.sg_display=0 and raising the iGPU VRAM from 64M to 1024M in the
BIOS did not fix it without the workaround.
- Probably the RX 6800 and the Vega 11 do not share a buffer modifier
that works for scanout/import, but I have not verified that.
- A single attached file (kwin-report.txt) contains the kscreen-doctor -o
output and two journal excerpts: one from a boot WITH the
KWIN_DRM_USE_MODIFIERS=0 workaround, and one from a boot WITHOUT it,
which shows the "Failed to create framebuffer: Invalid argument" error.
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