Link Training regression on USB-C to VGA adapter
This is a regression from 4.19.146 -> 5.15.35 kernel. It happens on Lenovo laptop with i5-8265U CPU on a specific Lenovo model USB-C to VGA adapter (however, there is another model of Lenovo adapters where the issue does not seem to happen - so seems USB dongle model specific).
The issue happens on boot, when the BIOS uses the VGA display as it's main boot up display (lid closed during early boot). And the BIOS initializes and displays it's logo on the VGA. (I haven't been able to reproduce the issue so far if lid is open, and BIOS uses the internal display for it's gfx). The glitch is also intermittent, it happens about 50-80% times of the boots.
The main problem being link training failing for the external display, resulting in wrong resolution selected (as the preferred resolution is rejected due to too high clock).
Additional testing and comments for kernels: 5.15.65 issue as described, see attached dmesg logs 5.15.35 issue as described 5.13.19 seems to end up with VGA screen black (no signal) 5.12.19 randomly ok, wrong resolution, or black screen (no signal) 5.11.22 often ok, but seen black screen and few times wrong resolution; see attached dmesg logs 5.10.141 was not able to reproduce any problems with 20 reboots 4.19.146 no problem ever