Timeout with USB-C video adapter

[Andy Pont]

Hello,

I’m working on the coreboot port for a laptop which uses the N200 
(AlderLake-N).  The built in LCD and HDMI port are working correctly but 
I am having problems with driving an external display over USB.

The Linux kernel (6.5.0-27-generic in Ubuntu 23.10) gives a message that 
says:

i915 0000:00:02.0: [drm] *ERROR* Timeout waiting for DDI BUF D to get 
active

The timeout occurs in hsw_wait_for_power_well_enable().  I have put the 
full dmesg output of the drm_WARN_ON() messages on Pastebin[1].

I’m guessing something in the FSP isn’t being correctly configured but I 
don’t know whether it is graphics, USB, or power related.

Thanks in advance for any advice on where to look.

-Andy.

1. https://pastebin.com/p3JTYpTC