Arch Linux

goldmund

Member

Registered: 2021-02-15

Posts: 73

[SOLVED] xrandr doesn't detect an external monitor

Hi!

I took another step towards Arch perfection and treated myself to a Thinkpad T420, but now I am having troubles as my external monitor through DisplayPort doesn't get detected.

$ xrandr
Screen 0: minimum 8 x 8, current 1600 x 900, maximum 32767 x 32767
LVDS1 connected primary 1600x900+0+0 (normal left inverted right x axis y axis) 310mm x 170mm
   1600x900      60.00*+
   1400x900      59.88  
   1368x768      60.00    59.88    59.85  
   1280x800      59.81    59.91  
   1280x720      59.86    60.00    59.74  
   1024x768      60.00  
   1024x576      60.00    59.90    59.82  
   960x540       60.00    59.63    59.82  
   800x600       60.32    56.25  
   864x486       60.00    59.92    59.57  
   800x450       60.00  
   640x480       59.94  
   720x405       59.51    60.00    58.99  
   640x360       59.84    59.32    60.00  
VGA1 disconnected (normal left inverted right x axis y axis)
VIRTUAL1 disconnected (normal left inverted right x axis y axis)

I find it strange that DisplayPort doesn't even get listed as "disconnected". I had to previously blacklist nouveau, because it was giving lots of errors (bus mmio read fault), but as nouveau was still running, DisplayPort did show up in xrandr.

Sorry, I have read up quite a lot on the ArchWiki, but I am still quite a newbie when it comes to drivers. Now I am going along the path of nvidia proprietary drivers with bumblebee. I am not even sure if I need bumblebee as I am not a gamer. I suppose I could just use Intel graphics, but at the same time it would be nice to make use of my GPU. I suppose I was also hoping that bumblebee could "magically" help solve my issue with the external monitor.

I have to modprobe the nvidia driver so that it gets loaded.

$ sudo modprobe nvidia
$ inxi -G
Graphics:  Device-1: Intel 2nd Generation Core Processor Family Integrated Graphics driver: i915 v: kernel 
           Device-2: NVIDIA GF119M [Quadro NVS 4200M] driver: nvidia v: 390.144 
           Device-3: Chicony integrated camera type: USB driver: uvcvideo 
           Display: server: X.Org 1.20.13 driver: loaded: intel unloaded: modesetting,vesa resolution: 1600x900~60Hz 
           OpenGL: renderer: Mesa DRI Intel HD Graphics 3000 (SNB GT2) v: 3.3 Mesa 21.1.6

$ nvidia-smi
Sat Aug  7 16:11:57 2021       
+-----------------------------------------------------------------------------+
| NVIDIA-SMI 390.144                Driver Version: 390.144                   |
|-------------------------------+----------------------+----------------------+
| GPU  Name        Persistence-M| Bus-Id        Disp.A | Volatile Uncorr. ECC |
| Fan  Temp  Perf  Pwr:Usage/Cap|         Memory-Usage | GPU-Util  Compute M. |
|===============================+======================+======================|
|   0  NVS 4200M           Off  | 00000000:01:00.0 N/A |                  N/A |
| N/A   40C    P0    N/A /  N/A |      0MiB /   964MiB |     N/A      Default |
+-------------------------------+----------------------+----------------------+                                           
+-----------------------------------------------------------------------------+
| Processes:                                                       GPU Memory |
|  GPU       PID   Type   Process name                             Usage      |
|=============================================================================|
|    0                    Not Supported                                       |
+-----------------------------------------------------------------------------+

And to add to my confusion:

$ nvidia-settings
ERROR: Unable to load info from any available system

I have installed the following:

mesa
xf86-video-intel
nvidia-390xx
nvidia-390xx-utils
nvidia-390xx-dkms
nvidia-settings
bbswitch-dkms
bumblebee (yes, I am in the bumblebee group)

Now I find myself going from one ArchWiki article to another one, already for many hours. I admit I am lost. Could someone please help? Thanks!

Last edited by goldmund (2021-08-07 16:49:47)

seth

Member

From: Won't reply 2 private help req

Registered: 2012-09-03

Posts: 77,365

Re: [SOLVED] xrandr doesn't detect an external monitor

You're running on the intel driver, but the output is wired to the nvidia chip
https://wiki.archlinux.org/title/NVIDIA_Optimus
https://wiki.archlinux.org/title/PRIME#Reverse_PRIME

Bumblebee isn't really the prime… ;-) choice anymore, but https://wiki.archlinux.org/title/Bumble … VIDIA_chip

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goldmund

Member

Registered: 2021-02-15

Posts: 73

Re: [SOLVED] xrandr doesn't detect an external monitor

Nice! I followed your links and although reverse PRIME didn't work (my GPU seems to be a little outdated), discrete card as primary GPU did work. Now I can see output on my external monitor. I also got rid of bumblebee.

Thank you, you've helped me yet again, seth! I really like that you always give me just a gentle nudge and you let me discover the rest myself. That's just what I need. :-)