External monitor remains off in SDDM / KDE Plasma

Specialist · 2023-04-24 12:50:01

Hi there,

I run a Lenovo ThinkPad P1 Gen 5 (Intel i915 graphics) connected to an external monitor via a Lenovo Thunderbolt 4 Workstation Dock. When booting into SDDM / KDE Plasma on Xorg the external monitor shows up in xrandr as connected, but remains dark / off until turning it off and on again via xrandr.

Any ideas?

Thanks!

seth · 2023-04-24 13:27:41

shows up in xrandr as connected

"connected" doesn't mean active, what's the actual xrandr output in that situation?

https://wiki.archlinux.org/title/SDDM#L … ed_display
https://wiki.archlinux.org/title/KDE#Un … lution_set

Specialist · 2023-04-24 14:17:15

AFAICS the display is considered active (and there are actually windows located on the dark screen):

$ xrandr

Screen 0: minimum 320 x 200, current 7680 x 2470, maximum 16384 x 16384
eDP-1 connected 2560x1600+5120+870 (normal left inverted right x axis y axis) 344mm x 215mm
   2560x1600    165.00*+  60.00 +  59.99    59.97  
   2560x1440     59.99    59.99    59.96    59.95  
   2048x1536     85.00    75.00    60.00  
   1920x1440     85.00    75.00    60.00  
   1856x1392     75.00    60.01  
   1792x1344     75.00    60.01  
   2048x1152     59.99    59.98    59.90    59.91  
   1920x1200     59.88    59.95  
   1920x1080     60.01    59.97    59.96    59.93  
   1600x1200     85.00    75.00    70.00    65.00    60.00  
   1680x1050     59.95    59.88  
   1400x1050     74.76    59.98  
   1600x900      59.99    59.94    59.95    59.82  
   1280x1024     85.02    75.02    60.02  
   1400x900      59.96    59.88  
   1280x960      85.00    60.00  
   1440x810      60.00    59.97  
   1368x768      59.88    59.85  
   1280x800      59.99    59.97    59.81    59.91  
   1152x864      75.00  
   1280x720      60.00    59.99    59.86    59.74  
   1024x768      85.00    75.05    60.04    85.00    75.03    70.07    60.00  
   1024x768i     86.96  
   960x720       85.00    75.00    60.00  
   928x696       75.00    60.05  
   896x672       75.05    60.01  
   1024x576      59.95    59.96    59.90    59.82  
   960x600       59.93    60.00  
   832x624       74.55  
   960x540       59.96    59.99    59.63    59.82  
   800x600       85.00    75.00    70.00    65.00    60.00    85.14    72.19    75.00    60.32    56.25  
   840x525       60.01    59.88  
   864x486       59.92    59.57  
   700x525       74.76    59.98  
   800x450       59.95    59.82  
   640x512       85.02    75.02    60.02  
   700x450       59.96    59.88  
   640x480       85.09    60.00    85.01    72.81    75.00    59.94  
   720x405       59.51    58.99  
   720x400       85.04  
   684x384       59.88    59.85  
   640x400       59.88    59.98    85.08  
   576x432       75.00  
   640x360       59.86    59.83    59.84    59.32  
   640x350       85.08  
   512x384       85.00    75.03    70.07    60.00  
   512x384i      87.06  
   512x288       60.00    59.92  
   416x312       74.66  
   480x270       59.63    59.82  
   400x300       85.27    72.19    75.12    60.32    56.34  
   432x243       59.92    59.57  
   320x240       85.18    72.81    75.00    60.05  
   360x202       59.51    59.13  
   360x200       85.04  
   320x200       85.27  
   320x180       59.84    59.32  
   320x175       85.27  
HDMI-1 disconnected (normal left inverted right x axis y axis)
DP-1 disconnected (normal left inverted right x axis y axis)
DP-2 disconnected (normal left inverted right x axis y axis)
DP-3 disconnected (normal left inverted right x axis y axis)
DP-4 disconnected (normal left inverted right x axis y axis)
DP-1-1 disconnected (normal left inverted right x axis y axis)
DP-1-2 connected primary 5120x1440+0+0 (normal left inverted right x axis y axis) 1200mm x 340mm
   5120x1440     59.98*+  29.98  
   3840x1080     59.97 +
   2560x1080     60.00    59.94    59.98  
   1920x1080     60.00    60.00    50.00    59.94  
   1600x1200     60.00  
   1280x1024     75.02    60.02  
   1280x800      59.81  
   1152x864      75.00  
   1280x720      60.00    50.00    59.94  
   1024x768      75.03    60.00  
   800x600       75.00    60.32  
   720x576       50.00  
   720x480       60.00    59.94  
   640x480       75.00    60.00    59.94  
   720x400       70.08  
DP-1-3 disconnected (normal left inverted right x axis y axis)

This is when the external monitor (connected to DP-1-2) remains turned off. After fixing the issue through Settings, another xrandr run produces exactly the same output (character by character) - verified using diff.

Regarding ~/.local/share/kscreen/: I already removed that directory - without success.

seth · 2023-04-24 14:49:53

What happens if you only boot the multi-user.target (2nd link below), wait some seconds and then start the graphical.target?
(The handshake probably fails, likely due to the dock and this might be a race condition)

In doubt you can use the first link in #2 for a workaround.

Specialist · 2023-04-26 12:10:56

If I boot multi-user.target and then manually start graphical.target, everything works smoothly. The workaround from #2 does not help, though, i.e., the screen does not come up after directly booting graphical.target with the workaround active.

Sleeping before/after xrandr (in Xsetup) also doesn't change anything. What does work as a workaround, is to toggle the X session using Ctrl+Alt+F3, Ctrl+Alt+F2, but that's a bit ugly.

Last edited by Specialist (2023-04-26 12:14:35)

seth · 2023-04-26 12:20:10

What if you "systemctl edit sddm.service" and add

ExecStartPre=/usr/bin/sleep 2

?

Specialist · 2023-04-26 12:33:32

Unfortunately, that makes no difference.

What is your gut-feeling regarding the source of the problem? Probably i915/modesetting-related?

seth · 2023-04-26 12:50:59

My gut says it's the dock and has nothing to do w/ the local system.
Notably because of "What does work as a workaround, is to toggle the X session using Ctrl+Alt+F3, Ctrl+Alt+F2"

Extend the sleep (say, "30") to test whether your edit actually worked (and there's a significant delay before SDDM starts) and whether the timeout is relevant.

Specialist · 2023-04-27 07:06:27

With a 30 s sleep it works, i.e., the monitor comes up on login... I filed a bug for intel-drm: https://gitlab.freedesktop.org/drm/intel/-/issues/8402

seth · 2023-04-27 09:14:12

You can probably significantly reduce the timeout, also make sure to have i915 in the MODULES or kms in the HOOKS array in your mkinitcpio.conf

Specialist · 2023-04-27 16:42:09

It seems that a lower timeout does not reliably fix the issue. With 20 s it's still present.

i915 is already in the MODULES list, but kms is missing from the HOOKS list, but if I understand you correctly that's not required if i915 is in place.

seth · 2023-04-27 19:07:12

if I understand you correctly that's not required if i915 is in place

Correct.
20s is a looong time, is the issue at this delay infrequent or does it reliably not work?
If the latter, is the magic number maybe 26s?

Arch Linux

#1 2023-04-24 12:50:01

External monitor remains off in SDDM / KDE Plasma

#2 2023-04-24 13:27:41

Re: External monitor remains off in SDDM / KDE Plasma

#3 2023-04-24 14:17:15

Re: External monitor remains off in SDDM / KDE Plasma

#4 2023-04-24 14:49:53

Re: External monitor remains off in SDDM / KDE Plasma

#5 2023-04-26 12:10:56

Re: External monitor remains off in SDDM / KDE Plasma

#6 2023-04-26 12:20:10

Re: External monitor remains off in SDDM / KDE Plasma

#7 2023-04-26 12:33:32

Re: External monitor remains off in SDDM / KDE Plasma

#8 2023-04-26 12:50:59

Re: External monitor remains off in SDDM / KDE Plasma

#9 2023-04-27 07:06:27

Re: External monitor remains off in SDDM / KDE Plasma

#10 2023-04-27 09:14:12

Re: External monitor remains off in SDDM / KDE Plasma

#11 2023-04-27 16:42:09

Re: External monitor remains off in SDDM / KDE Plasma

#12 2023-04-27 19:07:12

Re: External monitor remains off in SDDM / KDE Plasma

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