How to debug problem with multiple external monitors in docking station?

I have:

  • Lenovo laptop (T580) with Intel Corporation UHD Graphics 620 (rev 07)
  • LENOVO ThinkPad Ultra Dock (docking station)
  • 2x Dell UltraSharp 27 4K monitors (U2720Q)

Connecting a single monitor to the docking station at a time works just fine. Verified with both monitors and both DisplayPort connectors.

When I connect both monitors at the same time the Settings application i Gnome detects both correctly, but I am only able to get a picture on one, the other always stays black (not always the same though). Disabling the “built-in” monitor in the laptop changes nothing - one external monitor stays black.

Attaching both monitors directly to the laptop using USB-C actually allows me to use all three monitors (highest resolution) simultaneously without any problems.

I’ve also tried to attach the monitors to the 2x USB-C connectors in the docking station which does NOT work. The Settings application doesn’t even register the monitors, even though I do see some usb related stuff happening in dmesg.

How can I debug this (presumably docking station problem) further. I would prefer to make the monitors work with the docking station, but the second best thing is to be able to make a usable bug report.

Popular Topics: Docks, Docking Stations - Lenovo Support UU

Did you have a look there ?

This almost sounds like the laptop sees only one external monitor when attached to the docking station. When attached locally it actually sees and configures both.

Which monitor does it see in the docking station? The one attached first? The one attached second? Random if both attached when docked/booted?
We really need a bit more detail to fully identify the problem, such as laptop identification, docking station identification, etc.

The full output of “inxi -Fxx” when the laptop is not docked with both monitors attached, When it is docked with no monitors attached, and When it is docked with both monitors attached would help track down the issue.

You might also add the related dmesg output

Hi Jacob,

Welcome in ask fedora.
This could be a gnome issue
You should visit GNOME · GitLab to file a bug to gnome settings or control center. And ask your question there also.

qoute @computersavvy

This almost sounds like the laptop sees only one external monitor when attached to the docking station.

The configuration tool (Gnome Display Settings) sees both monitors (or rather all monitors because it also sees the built-in).

Output from inxi -Fxx | grep reso regardless of the monitors being attached to DP in dock or USB-C directly in laptop:

           resolution: 1: 3840x2160~60Hz 2: 3840x2160~60Hz 3: 1920x1080~60Hz s-dpi: 96

I’ve come a bit further though. The problem seems to be related to all three monitors having been enabled at the same time.

The following workaround will make the two external monitors work (when the built-in monitor is disabled). Do these steps synchronously on both external monitors at the same time:

  • Set “Resolution” to 1920x1080.
  • Set “Resolution” to 3840x2160 and “Refresh Rate” to 29.56Hz
  • Set “Refresh Rate” to 60Hz

I’ve experienced that a monitor sometimes would contain a 1/4 (top left) part of the picture. Sometimes even the build-in monitor that was supposed to disabled while the external monitor that was supposed to have the picture would be blank. But I can’t seem to reproduce this behavior consistently.

Every time I undock the laptop the configuration gets buggered and I need to do the above 3 steps again.

All three monitors works fine at the same time using the USB-C ports directly in the laptop.

qoute @ilikelinux

Did you have a look there ?

No I didn’t but I will now :slight_smile:

Good, have a look that you can upgrade your computers firmware and also the docking stations one.

Looks like the docking-station can not deal with the change of the “refresh rate” ?!