Cannot detect external screen connected through docking station after kernel update

English Hardware
1

Hello All,

after having updated the kernel to 5.14.21.150400.24.11.default my external screen is no longer working.

My laptop is connected to a docking station via USB-C. When I start it, the external screen turns on and visualises some of the booting process, but it turns off once the graphic interface is reached. All the other peripherals connected to the docking station are reachable, and the screen works perfectly if I connect another laptop.

The only error I can spot on Xorg.0.log is:


(WW) Warning, couldn't open module intel
(EE) Failed to load module "intel" (module does not exist, 0)

This is happening because I have selected the NVIDIA card through prime-select.
The issue happens also if I switch to the intel graphics.

Should that be of any help, I have blacklisted the nouveau driver to avoid conflicts

Any suggestion?

2

EDIT:

Forgot to mention that connecting the screen directly to the laptop works.
Somehow the issue is linked to passing through the docking station

3

What do ls -l /sys/class/drm and inxi -Gaz report, both connected directly, and connected through docking station?

When connected through docking station, does the key sequence Ctrl-Alt-F3, Alt-F7 (or Alt-F1) change anything?

4

Try to boot with previous kernel.

Post

inxi -GSaz

Hint: not all USB-C ports are created equal…
You can attach external screen with another port(s).

5

Found an hardware workaround:
I have switched the external monitor connection to the docking station from USB-C to DVI, this has somewhat fixed the issue.
The laptop is still connected to the docking station via USB-C.

Thanks for all the suggestions