No image via KVM switch. USB-C->dual DisplayPort->KVM

Submitted by Stuart

Assigned to Intel GFX Bugs mailing list

Link to original bug (#109829)

Description

Created attachment 143523
dmesg

Hi all,

I have a NUC7i7BNH with the latest BIOS (0062) running Ubuntu 18.04 (uname -r = 4.18.0-15-generic). I have the NUC connected via USB-C to a dual DisplayPort adapter, to an Avocent SV340D KVM. Also tried kernel v5.0-rc7.

If I have the KVM on the switch for the NUC, everything works great. If I switch the KVM to another channel, and then switch back to the NUC, I only get black screens. The only solution is to hard reboot the NUC.

This relates to a bug I raised on https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1816269.

Specifically [ 135.089830] [drm:intel_cpu_fifo_underrun_irq_handler [i915]] ERROR CPU pipe A FIFO underrun followed by a lot of thunderblot hotplug messages.

Attachment 143523, "dmesg":
dmesg.txt