Bug 513276

Summary:	Left and right monitors turn black for a few seconds after returning from having screens turned off
Product:	[Plasma] kwin	Reporter:	moichumoigaming
Component:	general	Assignee:	KWin default assignee <kwin-bugs-null>
Status:	CONFIRMED ---
Severity:	normal	CC:	archbtw123, kdedev, nate, serdarthtux
Priority:	NOR	Keywords:	multiscreen
Version First Reported In:	6.5.4
Target Milestone:	---
Platform:	Other
OS:	Linux
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:
Attachments:	drm_info drm_info after having turned off screens and resumed

Description moichumoigaming 2025-12-13 01:03:01 UTC

SUMMARY
After having returned from having the screens turned off via the kde feature "Turn screens off", in a triple monitor setup, left and right monitors (maybe more precisely non primary monitors, actually, no matter where they're put) turn black for a few seconds, then sometimes resume displaying output, sometimes don't.

STEPS TO REPRODUCE
Guaranteed way to have it happen :
1. Have firefox maximized on the center monitor.
2. Turn the screens off via the kde feature to turn them off.
3. Turn them back on (I move my mouse around and it wakes the computer up).
4. Wait a few seconds for all your monitors to properly turn on by themselves.
5. Using the window decoration, drag the firefox window to make it windowed.

Alternative way to trigger to bug:
1. Turn the screens off.
2. Turn them back on (I move my mouse around and it wakes the computer up).
3. Wait a while, or move your cursor to the left monitor and the black screen will trigger as soon as the cursor reaches the left screen.

OBSERVED RESULT
Left and right screens will turn off for a few seconds, then sometimes turn back on, sometimes not. If the bug happens whilst the cursor is on the middle screen, the cursor (and maybe whole system) will stutter. When display is not resumed, turning the screens off again, then back on again, can fix the issue.

EXPECTED RESULT
None of the above happening.

SOFTWARE/OS VERSIONS
Operating System: CachyOS Linux
KDE Plasma Version: 6.5.4
KDE Frameworks Version: 6.20.0
Qt Version: 6.10.1
Kernel Version: 6.18.0-3-cachyos (64-bit)
Graphics Platform: Wayland

GPU1 : AMD RX 9070 XT
GPU2 (headless, connected to a display, but not outputting by kwin): NVIDIA GeForce GTX 1080 Ti

My screen setup :
Left : 1080p 60hz, 150% scaling, 10 bit colors.
Middle : 2160p 240hz with DSC (display stream compression), 150% scaling, 10 bit colors.
Right : 1080p 60hz, 100% scaling, 10 bit colors.

ADDITIONAL INFORMATION
Appeared in kwin 6.5.4, and is still present after the fix for https://bugs.kde.org/show_bug.cgi?id=513151.

Comment 1 moichumoigaming 2025-12-13 01:46:18 UTC

After many screen off -> screen on cycles tests on the LTS kernel of my distro, 6.12.60-2-cachyos-lts, I haven't had this issue happen on the LTS kernel when doing the steps outlined in the "STEPS TO REPRODUCE" section of my original post.

Will update if this turns out to be incorrect.

Comment 2 Nate Graham 2025-12-16 22:16:52 UTC

Seems like it's a kernel driver regression, then? Thanks a lot for performing that debugging!

I'd recommend reporting this to the CachyOS folks.

Comment 3 moichumoigaming 2025-12-16 23:50:21 UTC

Hello, I would like to reopen this bug, as when testing for https://bugs.kde.org/show_bug.cgi?id=513277 on the latest kernel (6.18.1-2-cachyos), setting KWIN_DRM_NO_DIRECT_SCANOUT=1 fixes the bug reported in this report as well. No black screens after having turned off the screens and turned them back on when this env variable is set to 1.

Comment 4 TraceyC 2026-01-21 21:54:31 UTC

I'm sorry to hear you still have the black screen bug happening. Can you please attach the output of this command, as a file?

drm_info

Thanks.

Comment 5 moichumoigaming 2026-01-23 00:00:54 UTC

Created attachment 188794 [details]
drm_info

Here is the output of the drm_info command.

Comment 6 moichumoigaming 2026-01-23 00:14:25 UTC

Created attachment 188795 [details]
drm_info after having turned off screens and resumed

Here is the drm_info output after having turned off screens and turned them back on. The command was ran after the left and right monitors turned black, which is the bug reported.

The format of the framebuffers weirdly changed.

Comment 7 archbtw123 2026-01-26 23:05:19 UTC

I am also experiencing this problem. I can trigger it every time by:

1. Turning my monitor off and on.
2. Toggling Night Light suspend from the system tray.

And instead of toggling Night Light, I can also trigger it by opening a video in fullscreen in Firefox.