Hi everyone,

I have some trouble with my Dell XPS 13 9300 and the WD19TB thunderbolt dock.

At the time I bought the notebook there was no developer editon available here in Germany so
I installed Ubuntu 20.04 myself with dual boot. The notebook itself works like a charm. But the WD19TB keeps troubling me:

- The external monitors work only if they are connected at boot time. Later connecting thunderbolt to the running system does not give me a signal on the external monitors.

- Even if the dock is connected at boot time the external monitors often lose the signal, went black and never come back. Connected USB devices like keyboard and mouse will come back and can be used after some seconds. I need to reboot the system to get my external monitors to work again.

On some days I can use the external monitors for hours without problem, on others I can barley use them at all.

If the monitors disconnect the following message is found in the system log:[drm:intel_cpu_fifo_underrun_irq_handler [i915]] *ERROR* CPU pipe B FIFO underrun

I tried the following: Disable Monitor Sleep, Disabling CPU sleep modes, Newer Kernels (5.4.x up to the newest 5.6.x), even other linux distros via live USB. All had the same problem. I also tried a different WD19TB and using the other thunderbolt port on the XPS.

Under Windows there are no such problems, everything works like a charm. But I can't do my work there.

Bios and WD19TB Firmware are the lastest versions available from Dell

 

Thanks for reading, any help appreciated