How to enable USB ports on the Raspberry Pi Compute Module 4 (CM4)?

[dmlz76]

Hello,

For my project I'm trying to use the RP CM4 due to the small form factor and the ability to use custom base boards (currently I'm using this board CM4-IO-BASE-C for prototyping, but long term I'm planning to make a custom one for my project).
I'm able to boot Chromium OS successfully, however the USB keyboard and mouse are not detected.
This is a known hurdle for CM4, since by default CM4 has the USB controller disabled to save on power.
For Raspi OS they work around this by adding this to the boot config.txt:
dtoverlay=dwc2, dr_mode=host

If I understand correctly this switches to a different USB driver (dwc2) which presumably knows how to enable the USB controller.

Is it possible to do something similar on Chromium OS?

I also tried FydeOS and openFyde and they all run into the same issue, so I suspect this is something in the base Chromium OS setup ...
I'm trying to get my setup so I can build from source, so even if the solution requires code changes that would work for me ... I'm just not very knowledgeable in the Chromium/Linux driver tree setup, so any help or pointers will be greatly appreciated.
Thank you!