Arch Linux

Dear arch devs,

I recently bought an i-tec USB-C 3.1 Dual 4K DP Video Adapter for my Lenovo ThinkPad L14 Gen 2 with Intel TigerLake-LP GT2 (Iris Xe). No nvidia involved (I've learned from my mistakes...). I'm using it to connect my two NEC MultiSync EA224Wmi LCD displays with a resolution of 1920x1080 using (I assume) the DisplayPort alternate mode.

Since upgrading to the Linux kernel to version 5.16.[0/1/2], the video adapter no longer works: the external screens remain blank, and are no longer shown as "connected" on the xrandr output. Downgrading to kernel 5.15.13 (without any other changes to the system) gets the video adapter back working.

Running through the kernel logs and the modules loaded, this is what I found out so far: With 5.16 the mei_pxp (Protected Xe Path) module has landed. This results in the following changes:

* typec_displayport module is no longer loaded by modprobe
* "ACPI: bus type drm_connector registered" now, instead of type PCI back in 5.15.13
* with 5.15.13: ucsi_acpi USBC000:00: UCSI_GET_PDOS returned 0 bytes. Now with 5.16: ucsi_acpi USBC000:00: PPM init failed (-110)

Xorg.0.log does not show any error messages, but never mentions the outputs DP-2-*

Blacklisting mei_pxp does not magically solve the issue. I checked with i-tec tech support, they state that no additional drivers are involved apart from the linux kernel.

As I'm not using extra/xf86-video-intel, but only kms, I assume this is a kernel bug. I posted the kernel logs of 5.15.13 and 5.16.1, as well as the Xorg logs can be found here: https://gist.github.com/mephinet/c38d2e858d179ff0b7c574046865cd4f

Any hint how to get USB-C DisplayPort alternate mode back working?
Thanks!