[Bug 261912] XHCI fails to attach to array on startup

From: <bugzilla-noreply_at_freebsd.org>
Date: Mon, 25 Apr 2022 14:34:49 UTC
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=261912

--- Comment #11 from Alexander Motin <mav@FreeBSD.org> ---
I can't say anything about USB devices detection side, but there are plenty of
interesting things going on PCI side here.  First, this port seems to be
Thunderbolt, not plain USB, so when you hot-plug the USB, system actually
detects PCI hot-plug of several levels of PCI hierarchy with XHCI controller at
the end.

 A pleasant surprise is that all resource allocation succeeds in case of
hot-plug, it seems BIOS through SMI or something else pre-allocated the
resources before OS touches it, so everything just works.

In case of boot with the USB devices already connected (contrary to what I
expect) resources below the top level bridge are not allocated by BIOS and I
see plenty of allocation errors.  Considering the XHCI controller is detected I
guess none of the errors are fatal, but I can only speculate that something may
still be not right there.

Sean, are there any BIOS options on the system like "fast boot" or something,
that could control resource allocation for "unnecesary" devices during boot?

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