Arch Linux

Trix213

Member

From: Germany

Registered: 2020-03-26

Posts: 19

[SOLVED] 2nd monitor connected via DP not working anymore

Good evening everybody,

I am facing weird problems regarding my 2nd monitor, model being AOC G2460PF. After a shutdown of Arch without any changes to the system during the session and another start ~90 minutes later it cannot be detected anymore. I used to connect it via DP to my AMD Radeon RX 5700 XT. I tried turning the monitor off and on again, reattached the cables on both ends and checked that the monitor uses the right channel.

xrandr looks like this:

[daniel@Arch ~]$ sudo xrandr
[sudo] password for daniel: 
Screen 0: minimum 320 x 200, current 1920 x 1080, maximum 16384 x 16384
HDMI-A-0 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 597mm x 336mm
   1920x1080     60.00 + 165.00*  144.00   120.00   119.88   120.00    60.00    50.00    59.94  
   1680x1050     59.88  
   1280x1024     75.02    60.02  
   1440x900      59.90  
   1280x800      60.00  
   1280x720      60.00    50.00    59.94  
   1024x768      75.03    70.07    60.00  
   800x600       72.19    75.00    60.32    56.25  
   720x576       50.00  
   720x480       60.00    59.94  
   640x480       75.00    72.81    66.67    60.00    59.94  
DisplayPort-0 disconnected (normal left inverted right x axis y axis)
DisplayPort-1 disconnected (normal left inverted right x axis y axis)
DisplayPort-2 disconnected (normal left inverted right x axis y axis)
DisplayPort-3 disconnected (normal left inverted right x axis y axis)
HDMI-A-1 disconnected (normal left inverted right x axis y axis)

The monitor in question used to be registered as DisplayPort-0.

Any hints or ideas regarding my problem?

EDIT 1: I found this line when going through journalctl logs:

Apr 30 19:56:56 Arch kernel: [drm:retrieve_link_cap [amdgpu]] *ERROR* retrieve_link_cap: Read dpcd data failed.

Does this hint at a probable error source?

Thanks in advance
Daniel

Last edited by Trix213 (2020-05-01 08:09:10)

LukeLR

Member

Registered: 2016-03-18

Posts: 8

Re: [SOLVED] 2nd monitor connected via DP not working anymore

So you have definitely not done any system upgrades since the previous reboot? When my system is running for multiple days without restart (sleep / suspend mode) I tend to forget that there have been some system upgrades and I didn't reboot yet.

Trix213

Member

From: Germany

Registered: 2020-03-26

Posts: 19

Re: [SOLVED] 2nd monitor connected via DP not working anymore

Definitely not. I used my PC this noon, shut it down, turned it back on again and my monitor did not get detected anymore. No updates since before the session this noon.

seth

Member

From: Won't reply 2 private help req

Registered: 2012-09-03

Posts: 76,048

Re: [SOLVED] 2nd monitor connected via DP not working anymore

DPCD is the "DisplayPort Configuration Data", if that can't be read, you end up w/o a configured output.

a) is there also a backtrace?
b) try the LTS kernel (and or inspect the kernel lines in the older boot journals to see whether there might have been an update still or you just booted a different kernel by other means)
c) Is there any adapter involved or is this a direct DP/DP connection?
c) do you have more HW to test the behavior? (Other cable. Other cable! Other! Cable! Another system w/ a DP output. Other Monitor w/ a DP input.)

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Trix213

Member

From: Germany

Registered: 2020-03-26

Posts: 19

Re: [SOLVED] 2nd monitor connected via DP not working anymore

Thanks for your suggestions. I have no idea why or how this worked, but after trying an HDMI cable (the monitor proved to be functioning) the formerly dead DP connection worked again as well...
Closing this thread here.