Problem using USB thumbdrive using 5.3-BETA6.

Hello,

With three working FreeBSD systems running RELENG_5_2 (5.2.1-RELEASE-p10
at this time), i can use, without any problem, a 64MB USB thumbdrive for
months now.

But since i test the upcoming 5.3-RELEASE (RELENG_5 branch), it seems
impossible to have it to even be detect when i plug it in.


* Info. under a RELENG_5_2 system (_working_ installation):
# usbdevs -v
Controller /dev/usb0:
addr 1: full speed, self powered, config 1, UHCI root hub(0x0000), \
  VIA(0x0000), rev 1.00
 port 1 addr 2: full speed, power 100 mA, config 1, USB Mass Storage \
  Device(0x1060), vendor 0x0c45(0x0c45), rev 1.00
 port 2 powered

# dmesg
[...]
umass0: vendor 0x0c45 USB Mass Storage Device, rev 1.10/1.00, addr 2
GEOM: create disk da0 dp=0xc495a850
da0 at umass-sim0 bus 0 target 0 lun 0
da0: <USB NAND FLASH DISK 0.20> Removable Direct Access SCSI-2 device
da0: 1.000MB/s transfers
da0: 62MB (128000 512 byte sectors: 64H 32S/T 62C)

# camcontrol devlist -v
scbus0 on ata0 bus 0:
<  >                               at scbus0 target -1 lun -1 ()
scbus1 on ata1 bus 0:
<PLEXTOR DVDR   PX-712A 1.01>      at scbus1 target 0 lun 0 (pass0,cd0)
<PLEXTOR CD-R   PX-W4012A 1.02>    at scbus1 target 1 lun 0 (pass1,cd1)
<  >                               at scbus1 target -1 lun -1 ()
scbus2 on umass-sim0 bus 0:
<USB NAND FLASH DISK 0.20>         at scbus2 target 0 lun 0 (da0,pass2)
scbus-1 on xpt0 bus 0:
<  >                               at scbus-1 target -1 lun -1 (xpt0)


* Info. under a RELENG_5 system (_broken_ installation):
# usbdevs -v
Controller /dev/usb0:
addr 1: full speed, self powered, config 1, UHCI root hub(0x0000), \
  VIA(0x0000), rev 1.00
 port 1 addr 0 should never happen!
 port 2 powered

# dmesg
[...]
uhub0: device problem, disabling port 1


Worse, if i boot when the USB thumbdrive is plugged, the system hangs
printing the following message (during boot kernel message sequence)
after few minutes of waiting:
 umass0: BBB reset failed, TIMEOUT
 umass0: BBB bulk-in clear stall failed, TIMEOUT
 umass0: BBB bulk-out clear stall failed, TIMEOUT
 umass0: BBB reset failed, TIMEOUT
[...]
Then, i unplugged the device and the system panic instantaneously.

Any clue, advice or answer to this particular problem?
-- 
-jpeg.