Created attachment 182482 [details] Recording of screen flickering SUMMARY I got access to a gaming HDR display (Dell G2724D) and am trying it out. What I noticed is that when I watch YouTube videos and set the in fullscreen it was flickering. This didn't happen if I opened PIP window of the video (in Firefox) and maximised this PIP window. Also it appears it is only happening when HDR is enabled and when Colour Accuracy setting is set to Prefer Efficiency. If set to Prefer Color Accuracy there is no flickering. Also no flickering if I disable HDR mode. STEPS TO REPRODUCE 1. Enable HDR 2. Set Color Accuracy to Prefer Efficiency 3. Open Youtube Video in Firefox 4. Play it fullscreen (e.g. via pressing F key) OBSERVED RESULT Screen flickers as if some short clear white frames were shown in the middle of the video (see attached video) EXPECTED RESULT Screen should not flicker and should play as in SDR or Prefer Color Accuracy mode SOFTWARE/OS VERSIONS Operating System: openSUSE Tumbleweed 20250618 KDE Plasma Version: 6.4.0 KDE Frameworks Version: 6.15.0 Qt Version: 6.9.1 Kernel Version: 6.15.2-1-default (64-bit) Graphics Platform: Wayland Processors: 16 × AMD Ryzen 7 7840HS w/ Radeon 780M Graphics Memory: 32 GiB of RAM (30.7 GiB usable) Graphics Processor: AMD Radeon 780M Manufacturer: SLIMBOOK Product Name: EXCALIBUR-16-AMD7 ADDITIONAL INFORMATION Firefox version: 139.0.4 Mesa: 25.1.3
I can reproduce this issue with that combination of settings on the HDR-capable TV connected to my HTPC. No issue seen when not using HDR, or when using "Prefer color accuracy".
This is almost certainly a driver bug. Most likely we'll just have to disable DEGAMMA_LUT on AMD... just like we already did for Intel and NVidia :/ To make sure, does the flicker go away if you put KWIN_DRM_NO_DIRECT_SCANOUT=1 into /etc/environment, reboot and test again?
Yes, with KWIN_DRM_NO_DIRECT_SCANOUT=1 the flicker goes away. So I guess I should report this bug to amdgpu? Any additional info I should also include when doing so?
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Changed status to REPORTED (see comment #3 ), also already opened an issue in AMD GPU issue tracker: https://gitlab.freedesktop.org/drm/amd/-/issues/4429
Plasma 6.4.4 will have degamma lut disabled, so this should be gone then