4k 30Hz only, when using 2nd 1080p monitor, HP EliteBook 850 G8, Lenovo Universal USB-C Dock (40AY)

[TMCJ]

Hello community,

I can't use 60Hz on my 4k monitor when connecting a 2nd 1080p monitor.

This is my setup which has the problems:

1. Monitor: Lenovo S28u-10 (DP), 4k doesn't switch to more than 30Hz

2. Monitor: Dell U2414H (HDMI), 1080p 60Hz

Dock: Lenovo Universal USB-C Dock (40AY) (firmware 3.0.92)

Notebook: HP EliteBook 850 G8, Ubuntu 22.04 LTS (firmware 01.15.02)

Those notebooks on the other hand do work with the docking station and show 4k 60Hz & 1080p 60Hz:

Dell Latitude 5420, Windows 10

Lenovo Y540, Ubuntu 22.04

Therefore I think it could be an issue with the HP notebook and I appreciate your help.

Best regards,

TMCJ

[Jupitero]

Hello.

Try selecting the "Enable High Resolution mode when connected to a USB-C DP alt mode dock" option in BIOS.

Please report back whether it helped or not.

[TMCJ]

Hello Jupitero,

Thanks for your reply.

I have tried this option. After setting it I had unfortunately no output at all. Both displays stayed dark.

Best regards,

TMCJ

[Jupitero]

Hello.

Not getting any output after setting this is odd. If your laptop has Nvidia discrete graphics option, try cycling between Hybrid, Discrete, Auto (or whatever options your model has) for troubleshooting purposes.

The Lenovo 40AY USB dock is a 10Gbps USB 3 Gen2 device. Can you check whether the dock and laptop have agreed on only 5Gbps Gen1 speed? You should be able to get this information under Linux with the help of this page. Try also disabling the Thunderbolt feature in BIOS if you are not using it, perhaps it is interfering with USB ?

If you are using nouveau drivers, try the NVidia official driver.