Re: USB-related panic in 8.2_STABLE

[Taylor R Campbell <campbell+netbsd-tech-kern%mumble.net@localhost>]

> Date: Fri, 28 Apr 2023 11:32:44 +0200
> From: Edgar Fuß <ef%math.uni-bonn.de@localhost>
> 
> But we still don't know what led to the disconnect. Does the
> 	ohci0: 1 scheduling overruns
> give any clue?

Suggests a hardware problem to me.

According to the OHCI spec, this can happen if the driver has
committed too much bandwidth, and the driver is supposed to reduce the
bandwidth committed.  However, it is supposed to be a transient
problem that can be ignored a few times until it's happened for >=100
consecutive frames.

I suspect this is relevant when there's a lot of isochronous activity
(audio, video) and isn't supposed to happen otherwise.  And the NetBSD
ohci(4) driver doesn't do anything except print a message.  So if that
kind of activity wasn't happening, and if the device disconnected, it
might indicate a hardware fault.