Monitor not going to sleep when going to powersave
This is a resubmit of #2668 (closed) focusing on the issues that were not covered by #2354 (closed).
Everything works fine, until the system sets the GPU in powersave mode (e.g. after 15 minutes of idle in GNOME). I would expect the screen to go black, the backlight go off and the screen go into powersave mode.
Instead, the following happened when using kernel 6.5.3:
- screen goes black and backlight goes off (as expected)
- after 12 seconds, the backlight goes back on (not expected) - consequently, the monitor doesn't go into powersaving mode
- when I press a key or move the mouse, all is normal (GNOME lock screen is displayed)
- so, this is not very good for powersaving, but usable.
All of this is 100% reproducible, simply by locking the screen from GNOME.
Also reported here: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1035075 https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/4773#note_1733210