Score:1

External monitors via USB-C dock not recognized until I restart computer

sy flag
jth

I'm running Ubuntu 20.04.6 LTS on a Dell Latitude 3520 laptop, which is connected to two external monitors via a Dell USB-C dock. This works great, except when I suspend the laptop and disconnect the dock for the weekend, and then come back and re-connect the dock, the external monitors are no longer recognized, and neither is the ethernet cable (also connected to the dock), but my mouse and keyboard are recognized (also connected to the dock).

Reviewing the output of lsusb, I can see that the dock itself is recognized, but I don't see any change in the output when I disconnect the external monitors from the dock.

I see only the builtin display listed under Settings > Displays and in the output of xrandr.

The only fix that I've found is to restart my computer (logging out and in may also work, though I haven't tried that yet).

Is there a way to "reset" my connection with the USB-C dock and/or the ethernet cable and/or the external monitors, without restarting my computer?

us flag
Sometimes, Ubuntu does not recognize new devices after a kernel upgrade, unless the system is restarted. Just to ensure that it is not the case here, if you suspend, and resume immediately, does the issue occur?
jth avatar
sy flag
jth
@ArchismanPanigrahi I just tested this. If I suspend and resume immediately, without disconnecting the dock, the problem does not occur. However, if I suspend, disconnect the dock, reconnect the dock, and resume, then the problem does occur.
Ofiris avatar
mn flag
@jth, did you manage to solve it?
jth avatar
sy flag
jth
@Ofiris Yes, I posted an answer below.
Score:0
sy flag
jth

The problem seems to have been solved. I believe I flashed a firmware upgrade to the dock (from a different laptop running Pop!_OS) at some point recently, and I also upgraded my Dell laptop to Ubuntu 22.04.2 LTS. So either of those upgrades may have helped solve the issue.

Score:0
nz flag

I was having same issue on debian. Had to delete ~/.config/monitors.xml, then logout.

Now I can just plug my hub in anytime, and monitors work right away without issues. Hope this works for you too.

jth avatar
sy flag
jth
Awesome, thanks! I'll remember to try this if the issue re-appears.
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