kern/51395: USB Ethernet makes xhci hang

[bsiegert%NetBSD.org@localhost]

>Number:         51395
>Category:       kern
>Synopsis:       USB Ethernet makes xhci hang
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun Aug 07 09:35:00 +0000 2016
>Originator:     Benny Siegert
>Release:        NetBSD 7.99.34 (from 2016-07-30)
>Organization:
The NetBSD Foundation
>Environment:
NetBSD  7.99.34 NetBSD 7.99.34 (GENERIC) #0: Wed Aug  3 23:30:33 CEST 2016  root@:/usr/obj/sys/arch/amd64/compile/GENERIC amd64
>Description:
On an Intel NUC with USB 3.0, plugging in an Apple Ethernet adapter (axe driver) results in (what I think are) long timeouts when sending and receiving. "dhcpcd axe0" takes about 10 minutes to complete, and the USB keyboard becomes unresponsive during that time. I have seen keystrokes appear minutes later, though.

The USB is:

xhci0 at pci0 dev 20 function 0: vendor 8086 product a12f (rev. 0x31)
xhci0: interrupting at msi0 vec 0
xhci0: xHCI version 1.0
usb0 at xhci0: USB revision 3.0

The Ethernet adapter is:

axe0 at uhub0 port 2
axe0: Apple Computer Apple USB to Ethernet, rev 2.00/0.01, addr 4
ukphy0 at axe0 phy 16: OUI 0x007063, model 0x0006, rev. 1

When I run dhcpcd, I get a lease and a default route. Then things start to hang.
>How-To-Repeat:
Plug in USB Ethernet adapter
run dhcpcd axe0
>Fix:
?