Dpms not working?

2 monitor-setup on rpi4
dietpi: 8.16.2
mate desktop with mate-screensaver (need locking)

Have seen, that dpms was not working and found /etc/X11/xorg.conf.d/98-dietpi-disable_dpms.conf which seems to disable dpms and just uses screensaver.
Moved that file and rebootet.

Now dpms turns screen off after the given time, but turns it on again after just a few seconds.

What’s the problem with dpms here (why was there a need for 98-dietpi-disable_dpms.conf?) and is there any chance to get this working on my rpi4?

maybe @MichaIng could answer this question.

(short) update - did some research:

Have no autoselect hdmi source, but the problem occurs only with 2 monitors. If I only physically connect one device at a time it stays in standby. My (not confirmed) suspicion is, that both devices aren’t turned off at exactly same time and that some kind of resizing/moving primary-monitor/… kicks in.
Just don’t have an idea what could kick in, any idea?

Sorry for the late reply.

If I remember correctly, DPMS caused issues on RPi, especially with the legacy graphics driver and its APIs used, i.e. screen blanking during video playback.

With KMS indeed it might not be such a problem anymore, for Chromium kiosk mode we should be able to disable it separately via X server flags and/or make a dietpi-config video option for this.

I have also no idea why two screens might kick each others out of sleeping mode. gnome-power-manager is not installed in your case, is it?

dpkg -l gnome-power-manager

Did you check the power settings shipped with Mate?

KMS is enabled, right?

grep 'dtoverlay=vc4-' /boot/config.txt

Thanks for the reply!

dpkg -l gnome-power-manager

No not installed, only mate-power-manager.

Did you check the power settings shipped with Mate?

Looks fine in UI, is there some config-file I might check in console?

grep ‘dtoverlay=vc4-’ /boot/config.txt


Any further idea?