https://bugs.kde.org/show_bug.cgi?id=422455
Bug ID: 422455
Summary: Monitor power saving won't work when using DisplayPort
cable
Product: Powerdevil
Version: 5.18.5
Platform: Other
OS: Linux
Status: REPORTED
Severity: major
Priority: NOR
Component: general
Assignee: plasma-b...@kde.org
Reporter: sonichedgehog_hyperblas...@yahoo.com
Target Milestone: ---
I recently bought an 1080p / 144 Hz Viewsonic monitor which I run on my AMD
Radeon (amdgpu) card:
https://www.viewsonic.com/us/products/shop/monitors/vx2458-c-mhd.html
I noticed that when using a DisplayPort cable rather than a HDMI one, the
monitor refuses to go or stay into standby making it impossible to use this
essential power saving feature. I was convinced this is a Kernel or driver
issue and discussed it on generic Linux forums. Someone then suggested I try
putting the monitor in standby in an IceWM session, which to my surprise works
perfectly, revealing the bug lies with KDE most likely its PowerDevil module.
Here's a list of the exact results I get with each session:
- IceWM: Tested with 'xset dpms force standby'. Monitor properly goes into
standby, resumes only once a key is pressed or the mouse is moved.
- Plasma (X11): Tested with 'xset dpms force standby'. Monitor goes into
standby but only stays there for about 3 seconds, powering on afterward despite
not moving the mouse or pressing any key.
- Plasma (Wayland): Tested with a 1 minute timeout from System Settings due to
lack of alternative to xset for triggering standby on demand. Monitor goes
powers down for roughly 3 seconds, after which it powers back on and reveals
the login screen (the session crashes, see bug #420160 for this aspect).
It should be reiterated that my monitor properly handles energy saving on both
the X11 and Wayland Plasma sessions when using a HDMI cable, this only happens
over DisplayPort. I have to use DP due to HDMI only supporting up to 120 Hz of
the 144 Hz allowed by the monitor. Currently I have to trade the ability to put
the screen in standby, which results in extra electricity consumption as well
as wearing the monitor out more rapidly. As my above test indicates the issue
is KDE related, I hope we can find out what it is and have it fixed for the
next Plasma release if possible.
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