5.1 USB panic on second removal of memory stick

[Bob Lee <glee%force10networks.com@localhost>]

        I'm working on a PowerPC system, and have a problem when I remove the
usb memory stick the second time.  That is insert memory stick, remove
memory stick, insert memory stick, and remove memory stick.
        At this point the system panics, with 'ehci_rem_qh: ED not found'.
        Anyone else seen anything like this?

Back trace:

db> tr
0xd99a4d00: at panic+0x210
0xd99a4d50: at ehci_rem_qh+0xb8
0xd99a4d70: at ehci_close_pipe+0x50
0xd99a4da0: at usbd_close_pipe+0xb8
0xd99a4dc0: at umass_disco+0x50
0xd99a4de0: at umass_detach+0x12c
0xd99a4e10: at config_detach+0x1a0
0xd99a4e50: at usb_disconnect_port+0xd4
0xd99a4e90: at uhub_explore+0x250
0xd99a4ee0: at usb_discover+0x98
0xd99a4f00: at usb_event_thread+0xf8
0xd99a4f30: at setfunc_trampoline+0x8
0xd99a4fe8: at 0xfffffffc

Dmesg:
        ...
ohci0: interrupting at gpp 31
ohci0: OHCI version 1.0
usb0 at ohci0: USB revision 1.0
BCM vendor = 1131, dev = 1562, pa_function 1ehci0 at pci0 dev 6 function 1: vend
or 0x1131 product 0x1562 (rev. 0x30)
ehci0: interrupting at gpp 31
ehci0: EHCI version 1.0
ehci0: companion controller, 2 ports each: ohci0
usb1 at ehci0: USB revision 2.0
pcmcia0 at pcic0 controller 0 socket 0
pcmcia1 at pcic0 controller 0 socket 1
gtpci1 at gt0 unit 1gtpci_attach:reprogramming the localbus number of interface 
1
gtpci1: pci1 error interrupts at irqs pci 1
pci1 at gtpci1 bus 1: id 1PCI - Wrote to c88 size - 0x1ffff000
pci1: i/o space, memory space enabled, rd/line, rd/mult, wr/inv ok
obio0 at gt0 unit 0: addr 0xf0000000-0xffffff, big-endian
obio1 at gt0 unit 1: addr 0xf3600000-0xfffff, big-endian
obio2 at gt0 unit 2: addr 0xe0000000-0x7ffffff, big-endian
obio3 at gt0 unit 3: addr 0xff000000-0x2ffff, big-endian
obio4 at gt0 unit 4: addr 0xfff00000-0x1ffff, big-endian
gtcntmr1 at gt0 unit 1: offset 854
i2c0 at gt0 unit 0
biomask c00.50.0.0 netmask c00.50.0.0 ttymask c00.50.0.0
timecounter: Timecounter "clockinterrupt" frequency 100 Hz quality 0
timecounter: Timecounter "mftb" frequency 33333333 Hz quality 100
gfe0: deferred init  ether_input, gfe0  mac 00:01:e8:00:00:6e
gfe1: deferred init  mac 00:01:e8:00:00:14 f10_input,promisc,gfe1
gfe2: deferred init starting the UST poll/delay facility on 1
uhub0 at usb1: vendor 0x1131 EHCI root hub, class 9/0, rev 2.00/1.00, addr 1
uhub0: 2 ports with 2 removable, self powered
uhub1 at usb0: vendor 0x1131 OHCI root hub, class 9/0, rev 1.00/1.00, addr 1
uhub1: 2 ports with 2 removable, self powered
 mac 00:01:e8:85:40:80 f10_input,gfe2
wdc0 at pcmcia0 function 0: <Netlist, Flash v1.0>
pcic0: port 0x400-0x40f
wdc0: i/o mapped mode
atabus0 at wdc0 channel 0
wd0 at atabus0 drive 0: <Netlist Flash v1.0>
wd0: drive supports 1-sector PIO transfers, LBA addressing
wd0: 3919 MB, 7964 cyl, 16 head, 63 sec, 512 bytes/sect x 8027712 sectors
wdc1 at pcmcia1 function 0: <Netlist, Flash v1.0>
pcic0: port 0x410-0x41f
wdc1: i/o mapped mode
umass0 at uhub0 port 1 configuration 1 interface 0
umass0: A-DATA A-DATA USB Flash Drive, rev 2.00/1.00, addr 2
umass0: using SCSI over Bulk-Only
scsibus0 at umass0: 2 targets, 1 lun per target
atabus1 at wdc1 channel 0
wd1 at atabus1 drive 0
sd0 at scsibus0 target 0 lun 0
: <A-DATA, USB Flash Drive, 0 .00> disk removable
: <Netlist Flash v1.0>
wd1: drive supports 1-sector PIO transfers, LBA addressing
wd1: 3919 MB, 7964 cyl, 16 head, 63 sec, 512 bytes/sect x 8027712 sectors
sd0: 7701 MB, 500 cyl, 8 head, 32 sec, 512 bytes/sect x 15771759 sectors
md0: internal 16384 KB image area
mountroot: trying ffs...
root file system type: ffs
sd0: no disk label
sd0(umass0:0:0:0): generic HBA error
sd0: detached
scsibus0: detached
umass0: detached
umass0: at uhub0 port 1 (addr 2) disconnected
umass0 at uhub0 port 1 configuration 1 interface 0
umass0: CHIPSBNK v3.3.8.1, rev 2.00/1.00, addr 2
umass0: using SCSI over Bulk-Only
scsibus0 at umass0: 2 targets, 1 lun per target
sd0 at scsibus0 target 0 lun 0: <CHIPSBNK, v3.3.8.1, 5.00> disk removable
sd0: fabricating a geometry
sd0: 954 MB, 954 cyl, 64 head, 32 sec, 512 bytes/sect x 1953792 sectors
sd0: detached
scsibus0: detached
panic: ehci_rem_qh: ED not found