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#1 2017-10-07 19:38:11

werwas
Member
Registered: 2017-10-07
Posts: 4

Xorg not starting unless external monitor connected [SOLVED]

I'm not sure what topic this post falls under, so I'm posting on NC.
I am running arch on a Thinkpad T450. The other day, I plugged in an external monitor and started xorg, as I have done many times. It worked fine. I shutdown my computer, restarted it and now xorg will not start unless the external monitor is attached. It hangs. My guess is that it is trying to acquire a lock on the monitor and is failing since it is not attached.
The only thing that I did that was a bit out of the ordinary is doing an update while the external monitor was attached (which probably involved updating the linux kernel and xorg), but I'm not sure how that would cause this problem.

Does anyone have any ideas about what is happening and how I can fix it?

Last edited by werwas (2017-10-08 07:56:30)

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#2 2017-10-07 21:48:53

seth
Member
Registered: 2012-09-03
Posts: 49,983

Re: Xorg not starting unless external monitor connected [SOLVED]

How do you start X?
How do you know it "hangs"?
Did you try "DISPLAY=:0 xrandr -q" from another VT? (To see which outputs are used)

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#3 2017-10-08 06:54:50

werwas
Member
Registered: 2017-10-07
Posts: 4

Re: Xorg not starting unless external monitor connected [SOLVED]

I use startx. By "it hangs" I mean that the computer becomes unresponsive. I can't quit the process and I have to do a hard shutdown.

When the screen is connected "DISPLAY=:0 xrandr -q" displays both my laptop screen and the external monitor

Screen 0: minimum 320 x 200, current 2880 x 1024, maximum 8192 x 8192
eDP-1 connected primary 1600x900+0+0 (normal left inverted right x axis y axis) 309mm x 174mm
   1600x900      60.00*+
   1024x768      60.04    60.00  
   960x720       60.00  
   928x696       60.05  
   896x672       60.01  
   800x600       60.00    60.32    56.25  
   700x525       59.98  
   640x512       60.02  
   640x480       60.00    59.94  
   512x384       60.00  
   400x300       60.32    56.34  
   320x240       60.05  
DP-1 disconnected (normal left inverted right x axis y axis)
HDMI-1 disconnected (normal left inverted right x axis y axis)
DP-2 connected 1280x1024+1600+0 (normal left inverted right x axis y axis) 338mm x 270mm
   1280x1024     60.02*+  75.02  
   1152x864      75.00  
   1024x768      75.03    70.07    60.00  
   832x624       74.55  
   800x600       72.19    75.00    60.32    56.25  
   640x480       75.00    72.81    66.67    59.94  
   720x400       70.08  
HDMI-2 disconnected (normal left inverted right x axis y axis)

And without the external monitor connected:

Screen 0: minimum 320 x 200, current 2880 x 1024, maximum 8192 x 8192
eDP-1 connected primary 1600x900+0+0 (normal left inverted right x axis y axis) 309mm x 174mm
   1600x900      60.00*+
   1024x768      60.04    60.00  
   960x720       60.00  
   928x696       60.05  
   896x672       60.01  
   800x600       60.00    60.32    56.25  
   700x525       59.98  
   640x512       60.02  
   640x480       60.00    59.94  
   512x384       60.00  
   400x300       60.32    56.34  
   320x240       60.05  
DP-1 disconnected (normal left inverted right x axis y axis)
HDMI-1 disconnected (normal left inverted right x axis y axis)
DP-2 disconnected 1280x1024+1600+0 (normal left inverted right x axis y axis) 0mm x 0mm
HDMI-2 disconnected (normal left inverted right x axis y axis)
  1280x1024 (0x59) 108.000MHz +HSync +VSync
        h: width  1280 start 1328 end 1440 total 1688 skew    0 clock  63.98KHz
        v: height 1024 start 1025 end 1028 total 1066           clock  60.02Hz

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#4 2017-10-08 07:40:52

seth
Member
Registered: 2012-09-03
Posts: 49,983

Re: Xorg not starting unless external monitor connected [SOLVED]

Add "intel_iommu=off" to the kernel parameters (see pleathora of related posts)
If that doesn't help, please paste an Xorg log (from a success start)
Also ensure to have intel-ucode installed and enabled.

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#5 2017-10-08 07:54:57

werwas
Member
Registered: 2017-10-07
Posts: 4

Re: Xorg not starting unless external monitor connected [SOLVED]

Adding "intel_iommu=off" worked. Thanks.

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#6 2017-10-08 07:56:24

seth
Member
Registered: 2012-09-03
Posts: 49,983

Re: Xorg not starting unless external monitor connected [SOLVED]

Ok, one more "weird random problem caused by this" to note ...

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