Bug 463625

Summary:	Blank screen is displayed across all monitors when DisplayPort monitor is enabled,
Product:	[Plasma] plasmashell	Reporter:	Bence Göblyös <goblyos.bence>
Component:	generic-multiscreen	Assignee:	Plasma Bugs List <plasma-bugs-null>
Status:	RESOLVED FIXED
Severity:	major	CC:	aleixpol, nate, notmart
Priority:	NOR
Version First Reported In:	5.26.4
Target Milestone:	1.0
Platform:	Fedora RPMs
OS:	Linux
Latest Commit:		Version Fixed In:	5.27
Sentry Crash Report:

Description Bence Göblyös 2022-12-30 17:23:11 UTC

SUMMARY

When the primary DisplayPort monitor is enabled, all screens go blank and display only a cursor. Moving the cursor to the top left corner will correctly display the window overview screen on all monitors.

Furthermore, after rebooting an installed system that has this issue, it will automatically disable the DP monitor and attempts to re-enable it will either be completely ignored (automatically resets after clicking off the tab in system settings) or in rare cases cause system settings to crash (cannot currently reproduce for crash dump). In the event it does work, it produces the above mentioned issue.

STEPS TO REPRODUCE
1. Run an up to date version (as of 2022-12-30) of Fedora KDE or the latest ISO (Fedora-KDE-Live-x86_64-37-1.7.iso or F37-KDE-x86_64-LIVE-20221215.iso) on a system with an RTX 2080 graphics card and one monitor attached with DisplayPort and another with HDMI.
2. Log into Plasma (either X11 or Wayland).
3. Enable DisplayPort monitor if it's disabled.

OBSERVED RESULT

Both screens are completely blank if DisplayPort monitor is enabled.

EXPECTED RESULT

Both screens display their respective desktops.

SOFTWARE/OS VERSIONS
Linux: 6.0.15-300.fc37.x86_64
KDE Plasma Version: 5.26.4
KDE Frameworks Version: 5.101.0
Qt Version: 5.15.7

ADDITIONAL INFORMATION

The issue is seemingly only reproducible with Fedora KDE, as neither Fedora Workstation nor KDE Neon exhibit this behavior. The issue occurs with both the proprietary NVIDIA drivers (installed through akmod-nvidia-525.60.11-1.fc37.x86_64, xorg-x11-drv-nvidia-525.60.11-1.fc37.x86_64 and xorg-x11-drv-nvidia-cuda-525.60.11-1.fc37.x86_64) and nouveau, as well as with a new DP cable. The issue first occurred after waking the computer from sleep, however I suspect it to be a coincidence, as the same happens on a live ISO as well.

Comment 1 Nate Graham 2023-01-06 21:05:13 UTC

This is finally fixed in Plasma 5.27, thank goodness.

Comment 2 Bence Göblyös 2023-01-10 19:21:30 UTC

(In reply to Nate Graham from comment #1)
> This is finally fixed in Plasma 5.27, thank goodness.

Is there a temporary fix while waiting for the patch?

Comment 3 Nate Graham 2023-01-10 19:23:37 UTC

You can try restarting Plasma with `plasmashell --replace`. Other than that, I'm afraid not.