nvidia - external display unavailable after screen goes to sleep

I have seen the error in step 10 before. In my case it was caused by bug 1874207 in mutter so maybe wait for that to be fixed...

Also, next time the external display is "unavailable" please open a Terminal window and run 'xrandr'. Can you still see the external display there?

Daniel:

I have xrandr before and after and the monitor was detected in both cases. I ran:
xrandr > before.log #before locking the screen
xrandr > after.log #after locking the screen and the external monitor is no longer in use

diff before.log after.log which results in:
1,2c1,2
< Screen 0: minimum 8 x 8, current 3840 x 4320, maximum 32767 x 32767
< eDP-1-1 connected primary 3840x2160+0+2160 (normal left inverted right x axis y axis) 344mm x 194mm
---
> Screen 0: minimum 8 x 8, current 3840 x 2160, maximum 32767 x 32767
> eDP-1-1 connected primary 3840x2160+0+0 (normal left inverted right x axis y axis) 344mm x 194mm
64c64
< HDMI-1-2 connected 3840x2160+0+0 (normal left inverted right x axis y axis) 697mm x 392mm
---
> HDMI-1-2 connected (normal left inverted right x axis y axis)
66c66
< 3840x2160 30.00* 25.00 24.00 29.97 23.98
---
> 3840x2160 30.00 25.00 24.00 29.97 23.98

Thanks. Yes that shows the monitor is still connected but some bug in (gnome-control-center | mutter | nvidia driver) is preventing it from being configured properly.

As a first step please subscribe to bug 1874207 and wait until that has been declared "Fix Released" for focal. I expect an update around that time will fix a few little related issues.

Will do. Thanks Daniel

Daniel et al,

I wanted to provide an update based on the latest official mutter release as of today - 25.Mai.

The issue still exists. However, I provide the following in the event it helps to refine the underlying issue. Please let me know if there are logs that would be helpful to you or additional steps you would like me to take to help with the diagnosis.

From the desktop with dual monitors running:
1) Goto lock screen (win+l)
2) initial screen shows both monitors active
3) both screens go blac
4) external monitor goes into standby mode due to loss of signal
5) primary laptop displays turns on momentarily and a resolution change is observed based on the size of the mouse.
6) primary display goes black.
7) logging back in and going to display settings
8) system no longer uses external display and returns to single display

9) open gnome-control-center -> displays. Single Display is active

10) Attempt to select join displays

11) Error at the top of gnome-control-center: Changes cannot be applied - This could be due to hardware limitations

12) select mirror - click apply

13) a keep settings dialogue will pop-up briefly before the screen goes blank. When the screen comes back on, both screens come back on, with a new keep settings dialogue.

14) select keep settings. gnome-control-center now shows Joing Displays as being active. not/not mirror.
-------------------------------------------------

As an additional note. If instead of going to the lock screen I suspend the system, which includes both monitors going into sleep mode, the above issue is not observed.

Status changed to 'Confirmed' because the bug affects multiple users.

The same observed with NVIDIA 470.86 driver.