Help me troubleshooting brightness issue

I am having isues with my laptops (i915, not NVIDIA ;-)) related to screen brightness:

  • When idling, the screen will be first dimmed (gnome-setting dim screen turned on).
  • Then, the display will go blank (screen blank setting turned on).
  • After some time, the display will light up again, displaying the lock screen and the message that the system will be suspended soon.
  • Again, after some time, the screen will go blank again.

Now, if I hit any key, the lock screen will reappear, but (unfortunately, for sake of reproducibility, not most of the time) come back with extreme low brightness (showing an opal-like effect).

Brightness can still be adjusted by keyboard and GUI. But even if I increase brightness to max level, the brightness stays extremely low.
(It looks like the display has been dimmed twice and after waking up the display, it was only un-dimmed once (if that makes any sense).)

The values of actual_brightness behave correctly and move up to their highest value.

[root@fedora ~]# grep . /sys/class/backlight/intel_backlight/*brightness

Same goes for setting brightness via dbus-send

dbus-send --session --type=method_call   --dest="org.gnome.SettingsDaemon.Power"   /org/gnome/SettingsDaemon/Power   org.freedesktop.DBus.Properties.Set   string:"org.gnome.SettingsDaemon.Power.Screen"   string:"Brightness"   variant:int32:100

There is no valuable information in journal during that time, either.

If I suspend the system and wake it up immediately, brightness behavior is back to normal.

Here’s more information for one of my laptops:
Graphics: Mesa Intel® HD Graphics 5500 (BDW GT2)

[root@fedora ~]# lspci|grep VGA
00:02.0 VGA compatible controller: Intel Corporation HD Graphics 5500 (rev 09)

(kernel switch i915.enable_psr=0 didn’t help)

I already checked similar topics here, but my case looks different.

At the moment, I suspect that this behavior is related to the screen locking, as the brightness issue is gone after having disabled automatic screen lock. (Having set automatic screen lock delay from “screen turns off” to 30 minutes seemed to decrease the probability for the brightness issue.)

Also filed a bug: Max brightness level stuck at dim setting intensity after inactivity before suspend (#661) · Issues · GNOME / gnome-settings-daemon · GitLab

Here are my questions:

  • is there any logging that I am missing or can I enable/increase logging to get more clues?
  • do you have any ideas what to restart on my system instead of suspending and waking the system up again?