Ice Lake i7-1065G7 and Dell WD19TB TB dock: disconnect failures

Ice Lake i7-1065G7 and Dell WD19TB TB dock: disconnect failures

[grinko]

Hi,

there is an issue with the Thunderbolt driver for the Ice Lake CPU
i7-1065G7 (used for example in the Dell XPS 7390 2-in-1) and Thunderbolt
docks (Dell WD19TB).

Randomly after anywhere between a few minutes and a few hours of use,
the Thunderbolt dock will have a "disconnect event" in which all
peripherals disconnect briefly and all external monitors flicker and
lose signal. USB Mass Storage connected to the dock suffer IO errors,
and the monitors briefly regain signal only to then lose it for good.
The dock must be reconnected or the system rebooted to fix it for a time.

dmesg may or may not show the following line when it happens:

[ 4552.598580] i915 0000:00:02.0: [drm] *ERROR* CPU pipe B FIFO underrun

The issue was reported by multiple users to intel-drm here:

https://gitlab.freedesktop.org/drm/intel/-/issues/1453

But it seems to be related to Thunderbolt, not the i915 driver, as
non-Thunderbolt external screens work fine, and the failure sometimes
affects everything attached to the Thunderbolt dock, not just the
monitors (dmesg then shows USB reconnects and "xHCI host controller not
responding, assume dead"). So I'm sending this to the PCI mailing list
to which all Thunderbolt issues are being redirected.

The laptop and dock work flawlessly under Windows (ruling out
hardware/memory faults), and the issue persists ever since the 5.4
kernel all the way up to the most recent 5.7.4.

If you need any more information let me know.

Regards