Arch Linux

odin

Member

Registered: 2025-05-13

Posts: 2

Problem with resolution detection on boot/sddm on multimonitor setup

Hello

I have a 4-monitor setup:

    Ultra-wide monitor (DisplayPort-0) — central

    Full HD monitor (DisplayPort-1) — pivot on the left

    Full HD monitor (DisplayPort-2) — pivot on the right

    Full HD monitor (HDMI-A-0) — horizontal on top

After the initial installation, everything worked fine. It continued to work well for some time. However, one day after booting my PC, I encountered an issue: the SDDM login screen was displayed at a low resolution (800x600) on all monitors (duplicate screen like), and my left pivot monitor (DisplayPort-1) was not working at all.

After some quick Googling, I found a potential solution. It involved creating a script to add a custom resolution using xrandr and appending a command to the GRUB boot parameters (I believe it was on the line that ends with quiet, to prevent boot logs from flooding the screen). However, this approach didn’t work for me.

To be honest, while I found some similar problems online (on Reddit and forums), none of them were exactly the same as mine. I tried several suggested fixes and configurations, none of them worked (maybe I was implementing them wrong or they just don't work for me - I don't know).

At this point, I have no idea what to do. As a last resort, I'm asking here. Maybe some log-jedi-master here can spot something useful in my /var/log/Xorg.0.log file from when the issue occurred.

One workaround I found that temporarily resolves the problem is this:

    Unplug the DisplayPort cable from the affected monitor.

    Reboot the PC — all other monitors display at the correct resolution.

    Plug the DisplayPort cable back in — the PC detects the monitor correctly as Full HD.

This solution seems to work for a while (I've tested rebooting several times), but usually, the issue returns the next day after a fresh boot.

My xorg.0.log https://pastebin.com/QDvx0ZnX
My xrandr output https://pastebin.com/0UbsnyHq

I can see there DisplayPort-1 have no full-hd resolution detected but that's it.
I don't know what can I do about it.

System monitor looks like this:

Resolution have list:
800x600
720x576
720x480
720x400
640x460

But I can't grab screen with combo-box open >_<!

Last edited by odin (2025-05-13 16:34:46)

odin

Member

Registered: 2025-05-13

Posts: 2

Re: Problem with resolution detection on boot/sddm on multimonitor setup

Ok I found something which cause issue and solution (more workaround).

The problem is one of my monitors is TV like. It wont turn on from idle like normal monitor.
I need to turn it on then it switch-like from TV mode to PC mode and set resolution.
Long story short. If I turn on tv-like monitor BEFORE I turn PC, wait a sec for it to switch to PC source and setup resolution problem not occure.