kern/52931: Kernel panics with Atheros usb wireless interface.

[trebol4444%gmx.com@localhost]

>Number:         52931
>Category:       kern
>Synopsis:       Kernel panics with Atheros usb wireless interface.
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Wed Jan 17 17:25:00 +0000 2018
>Originator:     trebol
>Release:        NetBSD current 8.99.12
>Organization:
>Environment:
NetBSD nor 8.99.12 NetBSD 8.99.12 (SUNXI_UFS) #0: Tue Jan 16 06:12:46 UTC 2018  trebol@nor:/data/netbsd/src/sys/arch/evbarm/compile/obj/SUNXI_UFS evbarm
>Description:
This happen randomly with an Atheros usb wireless card.

panic: kernel diagnostic assertion "j < exfer->ex_nsqtd" failed: file "/usr/src/sys/dev/usb/ehci.c", line 2980 j=1
nsqtd=1
cpu0: Begin traceback...
0x99e6192c: netbsd:db_panic+0xc
0x99e61944: netbsd:vpanic+0x1a4
0x99e6195c: netbsd:__udivmoddi4
0x99e619fc: netbsd:ehci_reset_sqtd_chain.isra.2+0x4f4
0x99e61a44: netbsd:ehci_device_bulk_start+0xb8
0x99e61a6c: netbsd:usbd_transfer+0xb4
0x99e61adc: netbsd:athn_usb_start+0x1f8
0x99e61b04: netbsd:if_transmit+0x108
0x99e61b44: netbsd:ether_output+0x464
0x99e61b6c: netbsd:ip_if_output+0x60
0x99e61c5c: netbsd:ip_output+0x114c
0x99e61d34: netbsd:tcp_output+0x1b48
0x99e61e9c: netbsd:tcp_input+0x11f8
0x99e61f64: netbsd:ipintr+0xa10
0x99e61fac: netbsd:softint_dispatch+0xd4
Bad frame pointer: 0x807cdf6c
cpu0: End traceback...

# usbdevs -v | grep ATHEROS
  port 3 addr 5: high speed, power 500 mA, config 1, UB93(0x3327), ATHEROS(0x13d3), rev 1.08(0x0108), serial 12345
>How-To-Repeat:
It happens randomly, almost allways when a big chunk of data is being transmitted.
>Fix: