Second display sometimes not being recognized.

Decker · 2022-06-11 03:46:02

Hey there!

My setup involves two displays:
- Display 1: LG UltraGear connected via DP; quite new model.
- Display 2: BenQ GL2450H connected via HDMI; roughly 8 years old.

Booting my system results in both displays being detected in 99% of all times.

However, in the remaining 1%, it occurs that Display 2 is not being recognized at all.
It doesn't light up when the display manager (SDDM) starts and running 'xrandr --listmonitors' or 'xrandr | grep ' connected' only list Display 1.

I suspect, that Display 2 sometimes needs more time to "wake up and react" to probing signals sent, since it's quite old and has been a budget solution anyway.

Does anybody know how to solve this issue?
I hope there are solutions independent of the display server since I am planning to set myself up with a pure "wayland" system in the near future.

Thanks in advance!

--- Some extra information:

Software used:
[table]
[tr]
[th]Software[/th]
[th]Name[/th]
[/tr]
[tr]
[td]Bootloader[/td]
[td]systemd-boot[/td]
[/tr]
[tr]
[td]GPU-Driver[/td]
[td]amdgpu[/td]
[/tr]
[tr]
[td]Window Manager[/td]
[td]KDE Plasma (X11)[/td]
[/tr]
[/table]

- The display "layout" has been manually specified in the files "40-monitors.conf":

Section "Monitor"
	Identifier	"DP-1"
EndSection

Section "Monitor"
	Identifier	"HDMI-1"
	Option		"LeftOf" "DP-1"
EndSection

Despite this KDE seldom arranges them wrong. Perhaps this issue is related?

- Unplugging and plugging in the HDMI cable worked at least once to solve this issue. I am not sure if this worked every time.

EDIT:

- This issue never happened on Windows. Let's hope this is not a driver issue.

Last edited by Decker (2022-06-11 03:58:48)

seth · 2022-06-11 06:08:35

There's no [table] in bbcode, maybe clean up the post itr.

1. https://wiki.archlinux.org/title/Kernel … _KMS_start
2. Delay the graphical.target (SDDM)
3. check the system journal for amdgpu errors

Is the output active in the earlier booting phase?
There's also a chance that the hyper-fragile HDMI handshake fails because the signal is weak (cable/interference) and system is too busy to correct that "in time" (again: hyper-fragile…) during the boot.

Arch Linux

#1 2022-06-11 03:46:02

Second display sometimes not being recognized.

#2 2022-06-11 06:08:35

Re: Second display sometimes not being recognized.

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