https://bugs.kde.org/show_bug.cgi?id=524476
Bug ID: 524476
Summary: Intermittent RA24 amdgpu format / atomic modeset
failure on RDNA4 at KWin Wayland login, correlated
with SDDM login timing
Classification: Plasma
Product: kwin
Version First master
Reported In:
Platform: Other
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: compositing
Assignee: [email protected]
Reporter: [email protected]
Target Milestone: ---
Created attachment 195291
--> https://bugs.kde.org/attachment.cgi?id=195291&action=edit
KWin Wayland: intermittent RA24 amdgpu modeset failure on RDNA4 at login
DESCRIPTION
On some logins, the primary monitor (DisplayPort, G-Sync capable, connected to
an AMD RX 9070 XT / RDNA4) freezes/micro-freezes for a few seconds right at
session startup. Kernel logs show repeated "Unsupported screen format RA24"
errors from amdgpu, immediately followed by KWin failing to apply the output
configuration and the atomic modeset commit failing with "Invalid argument".
Severity varies: sometimes it's a brief ~1s burst that resolves on its own,
other times it loops continuously for longer and the screen stays frozen until
I switch to a TTY and back.
STEPS TO REPRODUCE
1. Boot the system, reach the SDDM login screen
2. Log in immediately as soon as the login screen appears
3. Observe the primary monitor during/right after KWin starts
OBSERVED RESULT
Primary monitor freezes for a few seconds (sometimes longer, requiring a TTY
switch to recover). Kernel log shows repeated:
"amdgpu 0000:08:00.0: [drm] *ERROR* Unsupported screen format RA24
little-endian (0x34324152)"
followed by:
"kwin_core: Applying output configuration failed!"
"kwin_wayland_drm: Atomic modeset commit failed! Invalid argument"
EXPECTED RESULT
Clean session startup with no output configuration failures, regardless of
login timing.
SOFTWARE/OS VERSIONS
Operating System: PikaOS 4 (Debian SID base)
KDE Plasma Version: 6.7.4
KDE Frameworks Version: 6.28.0
Qt Version: 6.10.2
Kernel Version: 7.1.8-pikaos (64-bit)
Graphics Platform: Wayland
ADDITIONAL INFORMATION
CPU: AMD Ryzen 7 5700X 8-Core Processor
GPU: AMD Radeon RX 9070 XT (Navi 48, RDNA4)
RAM: 32 GiB
Monitors: Primary Acer (DisplayPort, G-Sync capable, 1920x1080@144Hz) +
secondary HP (HDMI, 1366x768)
I've noticed a consistent correlation with login timing relative to the SDDM
screen appearing:
- Logging in immediately when SDDM appears → reliably triggers the RA24 errors
- Waiting a few seconds on the login screen before entering credentials → clean
boot every time
This has been tested repeatedly in both directions with the same result,
including back-to-back boots with identical configuration. This suggests a
startup race condition (GPU/monitor detection not fully settled before KWin's
first modeset attempt) rather than a static misconfiguration.
Things I've ruled out (issue persisted after each):
- Disabling Adaptive Sync/VRR on the primary monitor
- Disabling a third-party GPU control daemon (LACT) autostart
- Forcing 8-bit color depth (instead of "Automatic 10-bit") on both monitors
Happy to attach full journalctl boot logs (clean + affected) if useful.
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