Turned off screens don't turn back on

0BADC0DE · 2024-11-21 10:33:58

I have setup my power management so that it should turn off and lock screens (1xHDMI + 1xDP over USB-C docking station) when idle.
It works indeed.
Only thing is that sometimes™ when I move the mouse, hit a SHIFT or NumLock key the DP screen doesn't turn on and keeps looping through its input ports (2xHDMI 1xDP).
The only way to get it back is to do CTRL-ALT-F3 to get a character console. After a few seconds the DP monitor turns back on.
When I hit ALT-F1 to get to the graphical displayport both are working.
It looks like the DP is not powered back on until I get to the character console.

This is not happening always and I have not been able to reproduce the problem.

My system is:

GPU : Intel Corporation TigerLake-LP GT2 
Kernel Version : 6.11.9.zen1-1
Plasma Version : 6.2.3-1
KDE Version : 24.08.3-1
Frameworks Version : 6.8.0-1
Qt5 Version : 5.15.15+kde+r141-1
Qt6 Version : 6.8.0-1
Wayland Version : 1.23.1-1
Plasma/Wayland Protocols Version : 1.14.0-1
XOrg/Wayland Version : 24.1.4-1
Mesa Version : 1:24.2.7-1
LibVA Version : 2.22.0-1
LIBVA_DRIVER_NAME=iHD
SDDM : extra/sddm 0.21.0-4

My docking station is a "Lenovo ThinkPad USB-C Dock Gen2" and monitors are "Samsung LU28R55" (DP) and "Samsung S24D300" (HDMI).

Any idea?

Last edited by 0BADC0DE (2024-11-21 10:35:57)

seth · 2024-11-21 15:18:24

The other output wakes up fine, it's only the one behind the USB dock?
USB autosuspend? Do other devices behind the dock still work?

You're probably relying on the mode switch to wake the output, you could instead try to change the resolution of refresh rate.
This is plasma on wayland? Have you ever experienced similar w/ X11?

And since the USB-C dock is involved, check the surrounding journal (from monitor when to sleep until it finally woke up) for relevant entries.

0BADC0DE · 2024-11-22 10:55:40

seth wrote:

The other output wakes up fine, it's only the one behind the USB dock?

Both are attached to the USB-C docking station, 1 on HDMI and 1 on DP.
(This is because one of the two displays has HDMI only.)
Actually everything is attached to the dock. I have a single USB3/USBC cable between the dock and the laptop, charging included.

seth wrote:

USB autosuspend?

No idea. How can I check?

seth wrote:

Do other devices behind the dock still work?

Keyboard and mouse are attached to the dock and both work.
Ethernet cable is attached to the dock RJ45 and works.
Only DP display "sometimes" doesn't wake up.
In the sense that the display cycles through all of its options and none is reported as active.

seth wrote:

You're probably relying on the mode switch to wake the output, you could instead try to change the resolution of refresh rate.

Not sure I get the point. Anyway, my primary display is the one that doesn't wake up.
I can try to switch the other one as primary and try to change resolution or refresh rate to wake the sleepy one up.

seth wrote:

This is plasma on wayland? Have you ever experienced similar w/ X11?

Yes, it is: see my earlier system report.
I don't have X11 since long now. And, as I am not able to reliably reproduce the problem this would require me to wait indefinitely until I get the issue.
Which makes the entire issue a "semi-decidable problem".

seth wrote:

And since the USB-C dock is involved, check the surrounding journal (from monitor when to sleep until it finally woke up) for relevant entries.

I can try this approach too.

Last edited by 0BADC0DE (2024-11-22 11:13:33)

seth · 2024-11-22 12:53:26

No idea. How can I check?

Disable it but since everything else behind the usb port still works, that's unlikely (ie. impossible)

Not sure I get the point. Anyway, my primary display is the one that doesn't wake up.

When you're handing over the output from wayland to the framebuffer console, there's a "resolution change" (even if you can't see it)
Reconfiguring the outputs (resolution or refresh rate change, maybe even just explicitly enabling the output) might mitigate this.

Also please post the output of "kscreendoctor" and "qdbus6 org.kde.KWin /KWin supportInformation" after losing the output.

Arch Linux

#1 2024-11-21 10:33:58

Turned off screens don't turn back on

#2 2024-11-21 15:18:24

Re: Turned off screens don't turn back on

#3 2024-11-22 10:55:40

Re: Turned off screens don't turn back on

#4 2024-11-22 12:53:26

Re: Turned off screens don't turn back on

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