RPI 4B on UEFI: xhci0 disconnects under high load

[Robert Clausecker]

Good evening!

I have set up a FreeBSD system on a Raspberry Pi 4B as described
in bug #249520 (https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=249520).
After setting up the USB drive on a USB 2.0 port, the system boots.
However, when the system is under high I/O load (I tested this by
compiling a Go toolchain), the USB controller eventually hangs and
causes the system to effectively crash:

---
xhci_interrupt: host system error
xhci0: Resetting controller
uhub1: at usbus0, port 1, addr 1 (disconnected)
ugen0.2: <vendor 0x2109 USB2.0 Hub> at usbus0 (disconnected)
uhub2: at uhub1, port 1, addr 1 (disconnected)
ugen0.3: <ASIX Elec. Corp. AX88x72A> at usbus0 (disconnected)
axe0: at uhub2, port 2, addr 2 (disconnected)
ukphy0: detached
miibus0: detached
axe0: detached
ugen0.4: <VLI Manufacture String VLI Product String> at usbus0 (disconnected)
umass0: at uhub2, port 4, addr 3 (disconnected)
(da0:umass-sim0:0:0:0): WRITE(10). CDB: 2a 00 01 85 d9 0d 00 00 80 00 
(da0:umass-sim0:0:0:0): CAM status: CCB request completed with an error
(da0:umass-sim0:0:0:0): Retrying command, 3 more tries remain
da0 at umass-sim0 bus 0 scbus0 target 0 lun 0
da0: <WDC WDS2 40G2G0B-00EP UJ43>  s/n ABCDEFA74566 detached
Solaris: WARNING: Pool 'tau' has encountered an uncorrectable I/O failure and has been suspended.

Solaris: WARNING: Pool 'tau' has encountered an uncorrectable I/O failure and has been suspended.
---

This is despite having applied D25219 and the D26493--D26496 series
of patches which were supposed to address this sort of issue.  The same
issue does not seem to appear with an older kernel to which the
D26493--D26496 series of patches was not applied and which was not
compiled with -mcpu=cortex-a72.  The older kernel identifies itself as

    FreeBSD 13.0-CURRENT #2 ed6978a9a70-c271559(master)-dirty

It's the one I described in my earlier mails to this list.  So it seems
that in this case, pulling in patches meant to fix a bug seem to have
introduced in this first place.  Any idea what could have happened?

Yours sincerely,
Robert Clausecker

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