Wayland multi monitor disconnect issue on Plasma

alett · 2025-10-27 02:59:20

My desktop environment is KDE Plasma. I have two monitors connected to my laptop, one via thunderbolt (monitor 1), the other via HDMI (monitor 2). The difference is just due to what ports I've got where. I also don't know why, but if I change which is connected to what port, monitor 1 will still show up, 2 will not. This behavior carries across X11 and Wayland.

Everything works perfectly in X11, both monitors are recognized and work exactly as they should. Switch to Wayland, and things aren't so well behaved. Monitor 1 connected via thunderbolt works just fine, however 2 connected via HDMI regularly connects and disconnects every few seconds. I will get messages to the system tray about a display being detected and disconnected. Monitor 2 will light up saying signal lost periodically. I found a few other posts on different forums, some of which sound similar to what's happening for me. The best match is a Reddit thread which suggests turning off adaptive sync, however this setting doesn't seem to appear for me anywhere that I can tell. They also provide a link to the KDE forum which suggests making some changes to the plasma powerdevil. I made those changes, and they had no effect. This issue has persisted for months across multiple versions of Plasma. I have also attached logs generated when in a Wayland session which may or may not be relevant.

Not sure if this issue is better suited to a KDE forum or this one. We'll start here.

https://reddit.com/r/kde/comments/1i4gg … onnecting/
https://discuss.kde.org/t/plasma-waylan … pu/24357/6
Wayland logs: https://termbin.com/d507

Operating System: Arch Linux
KDE Plasma Version: 6.5.0
KDE Frameworks Version: 6.19.0
Qt Version: 6.10.0
Kernel Version: 6.17.4-arch2-1 (64-bit)
Graphics Platform: X11
Graphics Processor: Intel® Iris® Xe Graphics

Last edited by alett (2025-10-27 03:00:15)

seth · 2025-10-27 15:23:49

Please post your Xorg log, https://wiki.archlinux.org/title/Xorg#General
Also on a wayland session

qdbus6 org.kde.KWin /KWin supportInformation
kscreen-doctor

alett · 2025-10-28 02:06:25

Xorg log: https://termbin.com/sdy9
KS Doctor: https://termbin.com/lofp
KWin Support Information: https://termbin.com/8ptj
Note that the first display is the laptop screen, not shown in X11 logs because the lid can be closed in X11, it cannot be closed in Wayland with the displays dropping out every few seconds it will go to sleep.

seth · 2025-10-28 08:51:39

Single GPU, three outputs (the eDP very much shows up in the X11 log )
The eDP is congruent w/ the DP output, bot externals on 120Hz, the eDP 60Hz; no VRR, all scale 1.0

What if you run the external outputs at 60Hz?

 (--) modeset(0): HDMI max TMDS frequency 300000KHz
 (II) modeset(0): Printing probed modes for output HDMI-1
 (II) modeset(0): Modeline "1920x1080"x60.0  148.50  1920 2008 2052 2200  1080 1084 1089 1125 +hsync +vsync (67.5 kHz eP)
 (II) modeset(0): Modeline "1920x1080"x120.0  297.00  1920 2008 2052 2200  1080 1084 1089 1125 +hsync +vsync (135.0 kHz e)
 (II) modeset(0): Modeline "1920x1080"x119.9  296.70  1920 2008 2052 2200  1080 1084 1089 1125 +hsync +vsync (134.9 kHz e)
 (II) modeset(0): Modeline "1920x1080"x120.0  274.80  1920 1968 2000 2080  1080 1083 1088 1101 +hsync -vsync (132.1 kHz e)

 (II) modeset(0): Modeline "1920x1080"x120.0  297.00  1920 2008 2052 2200  1080 1084 1089 1125 +hsync +vsync (135.0 kHz e)
 (II) modeset(0): Modeline "1920x1080"x119.9  296.70  1920 2008 2052 2200  1080 1084 1089 1125 +hsync +vsync (134.9 kHz e)

are close to the 300MHz

What's the ougptut of "xrandr --verbose" on the working X11 session?

alett · 2025-11-02 16:36:57

Knocking refresh rate down to 60 Hz solved the problem.

seth · 2025-11-02 16:48:08

seth wrote:

What's the ougptut of "xrandr --verbose" on the working X11 session?

My guess is that X11 runs the 274.80 MHz modeline and wayland one of the ~297 MHz ones, but idk how to tell kwin_wayland to use a specific mode.
Do you have different options in the GUI?

Arch Linux

#1 2025-10-27 02:59:20

Wayland multi monitor disconnect issue on Plasma

#2 2025-10-27 15:23:49

Re: Wayland multi monitor disconnect issue on Plasma

#3 2025-10-28 02:06:25

Re: Wayland multi monitor disconnect issue on Plasma

#4 2025-10-28 08:51:39

Re: Wayland multi monitor disconnect issue on Plasma

#5 2025-11-02 16:36:57

Re: Wayland multi monitor disconnect issue on Plasma

#6 2025-11-02 16:48:08

Re: Wayland multi monitor disconnect issue on Plasma

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