https://bugs.kde.org/show_bug.cgi?id=512155
Bug ID: 512155
Summary: Laptop screen does not turn on after turning off
external monitor
Classification: Plasma
Product: kwin
Version First unspecified
Reported In:
Platform: Other
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: multi-screen
Assignee: [email protected]
Reporter: [email protected]
Target Milestone: ---
SUMMARY
On a setup where a laptop screen is off and an external monitor is on, turning
the external monitor off while the laptop is awake does not switch to the
built-in screen; likewise, putting the computer to sleep, then waking it when
no longer connected to the external monitor does not turn on the built-in
screen (which necessitates a reboot).
STEPS TO REPRODUCE
1. Connect to the external monitor and set the display configuration to "Switch
to external screen".
Either:
2. Turn off or unplug the external monitor from the laptop.
or
2. Put the laptop to sleep and unplug turn off or unplug the external monitor
from the laptop.
3. Wake the laptop.
OBSERVED RESULT
The laptop's built-in screen does not turn on.
EXPECTED RESULT
The laptop's built-in screen should turn on.
SOFTWARE/OS VERSIONS
Operating System: Kubuntu 25.10
KDE Plasma Version: 6.4.5
KDE Frameworks Version: 6.17.0
Qt Version: 6.9.2
Kernel Version: 6.17.0-6-generic (64-bit)
Graphics Platform: Wayland
Processors: 12 × 12th Gen Intel® Core™ i5-1235U
Memory: 48 GiB of RAM (46.8 GiB usable)
Graphics Processor: Intel® Iris® Xe Graphics
Manufacturer: LENOVO
Product Name: 21AHCTO1WW
System Version: ThinkPad T14 Gen 3
External monitor: Dell S2722DC (attached to the laptop via USB-C
ADDITIONAL INFORMATION
The biggest problem with this bug is that it does not always happen. After a
reboot things work as they should, but will, eventually, fail. Repeatedly (at
least a dozen times) turning on and off the monitor does not trigger it, but
then after a half-day or day the system no longer switches to the built-in
monitor.
After the bug occurs once, the laptop screen will never turn on unless "Switch
to laptop screen" is manually selected in the Display configuration selection,
and "Switch to external screen" must then manually selected to switch back to
the external monitor.
This poses a significant problem when I put the laptop to sleep, then unplug it
while asleep as there is no way to interact with the computer. As far as I can
tell the keyboard is useless as well: I can't log in and, say use krunner to
restart the computer while the built-in screen is off (key presses do not seem
to be recognized). The computer definitely wakes up though (the laptop's LED,
which blinks when asleep, becomes solid). The only solutions are to reattach
the external monitor (which shows nothing, but if the laptop lid is closed and
reopened then shows a picture on wake-up) or (if not next to the monitor) force
a shutdown of the machine by holding the power button down.
There was never issue like this in previous versions of Kubuntu, in 25.04 and
before (so in Plasma 6.3 and earlier). However, I was using X11, and now am
using Wayland (since the X11 session was removed upon upgrading).
I tried to compare system logs when it successfully switches to the laptop
screen and not, and did notice a ton of "kwin_wayland_drm: Atomic modeset test
failed! Invalid argument" errors when it fails. And I will gladly provide any
other necessary information.
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