kern/52911: xhci: panic while plugging in USB device

[jmcneill%invisible.ca@localhost]

>Number:         52911
>Category:       kern
>Synopsis:       xhci: panic while plugging in USB device
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun Jan 07 22:45:00 +0000 2018
>Originator:     Jared McNeill
>Release:        8.99.11
>Organization:
>Environment:
NetBSD 8.99.11 (TEGRA) #0: Fri Jan  5 10:04:13 UTC 2018
        mkrepro%mkrepro.NetBSD.org@localhost:/usr/src/sys/arch/evbarm/compile/TEGRA

>Description:
tx1# panic: kernel diagnostic assertion "bus->ub_devices[usb_addr2dindex(dev->ud_addr)] == NULL" failed: file "/usr/src/sys/dev/usb/xhci.c", line 2357 addr 1 already allocated
Stopped in pid 0.48 (system) at netbsd:cpu_Debugger+0x4:        bx      r14
db{0}> tr                          
0x9c1bfe04: netbsd:vpanic+0x14
0x9c1bfe1c: netbsd:__udivmoddi4
0x9c1bfeb4: netbsd:xhci_new_device+0x6c0
0x9c1bff0c: netbsd:usbd_new_device+0x44
0x9c1bff64: netbsd:uhub_explore+0x2f0
0x9c1bff8c: netbsd:usb_discover.isra.2+0x7c
0x9c1bffac: netbsd:usb_event_thread+0x88


usb0 at xhci0: USB revision 3.0
uhub0 at usb0: vendor 0000 (0000) xHCI Root Hub (0000), class 9/0, rev 3.00/1.00, addr 0
usb1 at xhci0: USB revision 2.0
uhub1 at usb1: vendor 0000 (0000) xHCI Root Hub (0000), class 9/0, rev 2.00/1.00, addr 0


tx1# usbdevs -v
Controller /dev/usb0:
addr 0: super speed, self powered, config 1, xHCI Root Hub(0x0000), vendor 0000(0x0000), rev 1.00(0x0100)
 port 1 addr 1: super speed, power 64 mA, config 2, USB 10/100/1000 LAN(0x09ff), Nvidia(0x0955), rev 30.00(0x3000), serial 000001000000
 port 2 disabled
 port 3 disabled
 port 4 disabled
Controller /dev/usb1:
addr 0: high speed, self powered, config 1, xHCI Root Hub(0x0000), vendor 0000(0x0000), rev 1.00(0x0100)
 port 1 powered
 port 2 powered
 port 3 powered
 port 4 powered
 port 5 powered

>How-To-Repeat:
Plug a USB3 memory stick in to a Jetson TX1 board.
>Fix: