Bug 497167

Summary:	Unable to Switch Display Output to External Monitor in Display Configuration
Product:	[Plasma] plasmashell	Reporter:	Oleksii Zolotarevskyi <rockingcat>
Component:	Display Configuration widget and OSD	Assignee:	Plasma Bugs List <plasma-bugs-null>
Status:	RESOLVED FIXED
Severity:	normal	CC:	nate, xaver.hugl
Priority:	NOR	Keywords:	multiscreen
Version First Reported In:	6.2.4
Target Milestone:	1.0
Platform:	Manjaro
OS:	Linux
Latest Commit:		Version Fixed In:
Sentry Crash Report:
Attachments:	Output of drm_info when the monitor doesn't turn on

Description Oleksii Zolotarevskyi 2024-12-07 15:28:30 UTC

SUMMARY
Unable to switch from the laptop screen to an external monitor connected via DisplayPort, despite the external monitor being correctly displayed in the System Settings' Display Configuration.

Switching from the external monitor back to the laptop screen works without issues.

A workaround involves running the following xrandr command:
$ xrandr --output DP-2 --mode 2560x1440 --rate 164.83 --primary --output eDP-1-1 --off
Occasionally, this command must be run twice — once to wake the external monitor from sleep and again to fully activate it.

STEPS TO REPRODUCE
1. Connect an external monitor to a laptop via DisplayPort.
2. Activate only the laptop screen and deactivate the external monitor.
3. Select the "Switch to external screen" option in the System Tray's Display Configuration.

OBSERVED RESULT
The laptop screen turns off.
The external monitor remains in sleep mode and does not turn on.
It seems that Kscreen considers the switch successful, but the external monitor stays inactive. To recover, the external monitor must be turned off and on again, which restores the desktop to the laptop screen.

EXPECTED RESULT
The external monitor should wake from sleep and display the desktop as expected.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Manjaro KDE Stable
KDE Plasma Version: 6.2.4
KDE Frameworks Version: 6.8.0
Qt Version: 6.8.1

ADDITIONAL INFORMATION
Graphics Platform: X11
Graphics Adapter: Nvidia TU106M + Intel UHD Graphics 630, Nvidia set as primary GPU
Graphics Driver Version: 550.135

Comment 1 Oleksii Zolotarevskyi 2024-12-07 15:30:19 UTC

This issue resembles a previously reported bug (https://bugs.kde.org/show_bug.cgi?id=487811), but since that one is marked as resolved, I am reporting this as a new issue because the problem persists.

Comment 2 Nate Graham 2024-12-12 18:27:00 UTC

Does it also fail on Wayland, or only X11?

Comment 3 Oleksii Zolotarevskyi 2024-12-23 13:19:18 UTC

Seems like it also happens on Wayland. When switching to the external monitor, it doesn't turn on.

Comment 4 Zamundaaa 2025-01-10 14:14:03 UTC

Please attach the output of drm_info when the monitor doesn't turn on (you can get it with "sleep 10; drm_info", or over ssh)

Comment 5 Oleksii Zolotarevskyi 2025-01-10 15:24:12 UTC

Created attachment 177258 [details]
Output of drm_info when the monitor doesn't turn on

Comment 6 Bug Janitor Service 2025-01-25 03:47:11 UTC

🐛🧹 ⚠️ This bug has been in NEEDSINFO status with no change for at least 15 days. Please provide the requested information, then set the bug status to REPORTED. If there is no change for at least 30 days, it will be automatically closed as RESOLVED WORKSFORME.

For more information about our bug triaging procedures, please read https://community.kde.org/Guidelines_and_HOWTOs/Bug_triaging.

Thank you for helping us make KDE software even better for everyone!

Comment 7 Oleksii Zolotarevskyi 2025-01-25 11:05:24 UTC

The output of the drm_info is attached.

Comment 8 Nate Graham 2025-05-22 18:55:38 UTC

Does that help, Xaver?

Are you still experiencing this in Plasma 6.3.4 or later, Oleksii?

Comment 9 Oleksii Zolotarevskyi 2025-05-22 20:05:44 UTC

(In reply to Nate Graham from comment #8)
> Does that help, Xaver?
> 
> Are you still experiencing this in Plasma 6.3.4 or later, Oleksii?

Hi, thanks for the follow-up!

I'm currently on Plasma 6.3.5 and after several attempts I eventually could switch to external monitor, however the resolution has dropped from 2K to 640×480 and the dekstop appeared quite broken...

To be honest, with all the display issues using Nvidia 570 driver in X11, this particular one doesn't feel that critical anymore :)

Maybe it's best to just wait until Nvidia finally implements the display multiplexors in Wayland, then I hopefully can move from X11, unless I ditch Nvidia altogether before then.

I’ll go ahead and close this now, as I can’t reproduce the issue in its original form anymore.

Thanks again!

Comment 10 Nate Graham 2025-05-22 20:06:34 UTC

Great, thanks a lot!