OS: 9front (9front.org)
Release: “Do not install” (10522) and nightly 10852
Laptop: AMD 7040 series DIY edition 13 inches
The bootloader and kernel boot fine but when it reaches the bootargs prompt the USB stick is not detected. There is no port-presence in the PORTSC registers from the rootports. I can confirm that the ports have 5V power at least. The kernel does not see anything connected through the expansion cards, there is no port status transition at all.
It is likely that 9front xHCI driver does not support this chipset.
If you happen to have an old USB 2.0 flash drive, it should use EHCI instead and that might work.
I talked with one of the 9front kernel programmers through their IRC channel, specifically with the person who wrote the XHCI controller driver, who said that the driver exists and supports XHCI while the documentation found in the FQA is outdated and it’s going to be updated in future.
Is the chip expected to not conform to the standard XHCI specification? If so, are the divergences documented anywhere?
No. It is not expected to not conform.
I see how you got to this question based on what I said and what additional insider knowledge you had, however.