I don't need to disable compositing myself. Just putting mpv in fullscreen when playing a video is sufficient to get a garbled screen on other virtual desktops. Not sure, if mpv is forcing compositing off by itself.

Looks like a bug in xf86-video-amdgpu, cause with modesetting driver everything works fine.

Please attach the corresponding Xorg log file, preferably captured after the problem occurred.

Created attachment 125982 [details]
Xorg.0.log

Xorg.0.log when screen distortions started. Looks pretty normal to me. Are there any debug options I need to enable?

I've noticed now, that with modesetting the flickering happens too. Again it's happening when putting a video into fullscreen and switching to another virtual desktop of KDE. It's not as heavy as with amdgpu, so I didn't noticed this before.

Since it happens with modesetting as well, it's more likely a Mesa issue.

I wonder if this might be a duplicate of bug 97029. Maybe try if setting the environment variable R600_DEBUG=nodma for the kwin process avoids the problem.

Actually, it's better to set the environment variable for the Xorg process as well, since that might perform the corrupted rendering.

(In reply to Michel Dänzer from comment #5)
> Since it happens with modesetting as well, it's more likely a Mesa issue.
> 
> I wonder if this might be a duplicate of bug 97029. Maybe try if setting the
> environment variable R600_DEBUG=nodma for the kwin process avoids the
> problem.

Yes, seems this fixes the distortions as well as the flickering. I've set R600_DEBUG globally, so kwin and Xorg are affected both.

*** This bug has been marked as a duplicate of bug 97029 ***

Reopening for tracking flickering separately from 97029.

Flickering is happening mostly with amdgpu driver. Sometimes I've observed this with modesetting too, but I can't trigger it reliable with this driver.

With amdgpu I can trigger this easily by starting a video with mpv and putting it into fullscreen. Ending the video or the fullscreen mode causes the flickering around newly created windows. I'll add a screencast how this look like.

The flickering can be stopped by starting again a video in fullscreen. As long as the video is on one virtual desktop, everything works like expected. It doesn't matter if xv, opengl, vdpau or vaapi output is used.

Created attachment 126033 [details]
screencast with flickering

It seems the flickering is related to the repaint rate of the screen. With video playback it's more heavy than by typing some text. The faster the typing is, the heavier the flickering becomes.

The video resembles kwin bug: https://bugs.kde.org/show_bug.cgi?id=361154 which was fixed in plasma 5.7.4.

(In reply to network723 from comment #12)
> The video resembles kwin bug: https://bugs.kde.org/show_bug.cgi?id=361154
> which was fixed in plasma 5.7.4.

I'm running plasma 5.7.4 here and still have the problem. Additionally it's only affecting amdgpu systems like Carrizo. I don't see this on a Sumo system (radeon/r600). Tomorrow I can try if I can trigger this on Kabini too.

Which 'Tearing prevention ("vsync")' mode are you using in the kwin compositor settings? Maybe attach a screenshot of that settings page.

(In reply to Michel Dänzer from comment #14)
> Which 'Tearing prevention ("vsync")' mode are you using in the kwin
> compositor settings? Maybe attach a screenshot of that settings page.

Was "Automatic" , but test with "Never" shows the same behavior. I've suspected glamor to be related here, but a test on Sumo with AccelMethod glamor doesn't reproduce the error.

I've seen similar flickering with kwin 5.7.4 from archlinux:
https://www.youtube.com/watch?v=EnzI7dmjihI

With latest kwin git it does not happen anymore. So if anyone wants to try it an confirm whether kwin git fixes it: you only need kwayland git, the rest of kde plasma can stay on the latest release version.

Flickering seems to be gone for me too, but I didn't update kwin or related. The parts I've updated last weekend:

llvm
drm
mesa
xf86-video-amdgpu

I have some distortions in the top frame of the window (screenshot of chromium appended). I will test an update of kwin, if it will fix this.

Created attachment 126230 [details]
distortion in window after leaving fullscreen in mpv

Discard that. It still happens with kwin git.

(In reply to Johannes Hirte from comment #17)
> Flickering seems to be gone for me too, but I didn't update kwin or related.
> The parts I've updated last weekend:
>

No it isn't. The one time I've thought it was gone, it was restricted to the title bar, where the distortions happened. After reboot it's back as before.

I've tested on a Kabini system, cause I thought it's using amdgpu too. But I was wrong, it's only using radeonsi from mesa. On kernel and ddx side it's still the radeon driver. I will update everything to current git and re-test with amdgpu.

This also happens with intel gpu, but no flickering, black areas stand still, until something causes update of that part of the screen.

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