https://bugs.kde.org/show_bug.cgi?id=509100
Bug ID: 509100
Summary: PowerDevil periodically pokes DPMS while the screen is
off
Classification: Plasma
Product: plasmashell
Version First 6.3.6
Reported In:
Platform: Debian stable
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: Power management & brightness
Assignee: [email protected]
Reporter: [email protected]
Target Milestone: 1.0
SUMMARY
PowerDevil periodically pokes DPMS while the screen is off, causing USB hub
devices to briefly wake, even when no user activity occurs. This bothers me
because I have connected a back light (and my mouse) to the usb hub of my
monitor, so powering it on causes blips in the backlight.
STEPS TO REPRODUCE
1 Login to Plasma 6 on X11 or Wayland.
2 Lock the screen with Ctrl–Alt–L.
3 Let the monitor enter DPMS-off state.
4 Wait ~25 seconds — the monitor briefly wakes (1–2 s), and the USB hub
devices power on.
5 Start audio playback (e.g., Audacious); the blips stop immediately.
6 Stop audio playback; blips resume.
OBSERVED RESULT
DPMS briefly toggled every ~25 s when no audio is playing.
USB hub devices wake during these short DPMS pulses.
No logging appears in journalctl --user or via dbus-monitor.
EXPECTED RESULT
Once the screen is off via DPMS, it should remain off until user activity.
PowerDevil should not trigger brief wake pulses that affect USB hubs.
SOFTWARE/OS VERSIONS
Debian Trixie
Linux/KDE Plasma: 4:6.3.6
KDE Plasma Version: 4:6.3.6
ADDITIONAL INFORMATION
I did see this kind of blibs on Plasma5 (Debian Bookworm), but not nearly
as often. Maybe a few times in an hour.
Editing ~/.config/powermanagementprofilesrc to set [AC][DimDisplay]
idleTime=0 stops the blips.
The blips are suppressed while audio is playing, suggesting the DPMS timer
is internally inhibited by active audio streams.
No D-Bus or external signals trigger these DPMS pokes; it seems to occur
entirely inside PowerDevil’s timers.
This happens on my BenQ PD3200U monitor
Suggestions:
The internal PowerDevil idle timer should not touch DPMS when the screen is
already off.
Consider separating “monitor off” checks from periodic timers that can wake
USB devices unnecessarily.
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