problem with USB disks on ALPHA3 w/ recent AMD chipset

Dear list,

I observe the following when I try to write to any USB drive:

Jun 17 22:02:35 manray kernel: (probe0:umass-sim0:0:0:0): INQUIRY.
CDB: 12 00 00 00 24 00
Jun 17 22:02:35 manray kernel: (probe0:umass-sim0:0:0:0): CAM status:
CCB request completed with an error
Jun 17 22:02:35 manray kernel: (probe0:umass-sim0:0:0:0): Retrying command
Jun 17 22:02:36 manray kernel: da0 at umass-sim0 bus 0 scbus2 target 0 lun 0
Jun 17 22:02:36 manray kernel: da0: <SanDisk Cruzer Blade 1.00>
Removable Direct Access SPC-4 SCSI device
Jun 17 22:02:36 manray kernel: da0: Serial Number 4C530001090427108375
Jun 17 22:02:36 manray kernel: da0: 40.000MB/s transfers
Jun 17 22:02:36 manray kernel: da0: 15264MB (31260672 512 byte sectors)
Jun 17 22:02:36 manray kernel: da0: quirks=0x2<NO_6_BYTE>
Jun 17 22:04:21 manray kernel: (da0:umass-sim0:0:0:0): WRITE(10). CDB:
2a 00 00 00 00 00 00 00 80 00
Jun 17 22:04:21 manray kernel: (da0:umass-sim0:0:0:0): CAM status: CCB
request completed with an error
Jun 17 22:04:21 manray kernel: (da0:umass-sim0:0:0:0): Retrying command
Jun 17 22:04:27 manray kernel: (da0:umass-sim0:0:0:0): WRITE(10). CDB:
2a 00 00 00 00 00 00 00 80 00
Jun 17 22:04:27 manray kernel: (da0:umass-sim0:0:0:0): CAM status: CCB
request completed with an error
Jun 17 22:04:27 manray kernel: (da0:umass-sim0:0:0:0): Retrying command
Jun 17 22:04:32 manray kernel: (da0:umass-sim0:0:0:0): WRITE(10). CDB:
2a 00 00 00 00 00 00 00 80 00
Jun 17 22:04:32 manray kernel: (da0:umass-sim0:0:0:0): CAM status: CCB
request completed with an error
Jun 17 22:04:32 manray kernel: (da0:umass-sim0:0:0:0): Retrying command
Jun 17 22:04:38 manray kernel: (da0:umass-sim0:0:0:0): WRITE(10). CDB:
2a 00 00 00 00 00 00 00 80 00
Jun 17 22:04:38 manray kernel: (da0:umass-sim0:0:0:0): CAM status: CCB
request completed with an error
Jun 17 22:04:38 manray kernel: (da0:umass-sim0:0:0:0): Retrying command
Jun 17 22:04:43 manray kernel: (da0:umass-sim0:0:0:0): WRITE(10). CDB:
2a 00 00 00 00 00 00 00 80 00
Jun 17 22:04:43 manray kernel: (da0:umass-sim0:0:0:0): CAM status: CCB
request completed with an error
Jun 17 22:04:43 manray kernel: (da0:umass-sim0:0:0:0): Error 5,
Retries exhausted
Jun 17 22:05:11 manray kernel: (da0:umass-sim0:0:0:0): got CAM status 0x44
Jun 17 22:05:11 manray kernel: (da0:umass-sim0:0:0:0): fatal error,
failed to attach to device
Jun 17 22:05:11 manray kernel: da0 at umass-sim0 bus 0 scbus2 target 0 lun 0
Jun 17 22:05:11 manray kernel: da0: <SanDisk Cruzer Blade 1.00> s/n
4C530001090427108375 detached
Jun 17 22:05:17 manray kernel: (da0:umass-sim0:0:0:0): Periph destroyed

I.e., when I dd, the dd exists prematurely with an error.

pciconf:

hostb0_at_pci0:0:0:0: class=0x060000 card=0x15761022 chip=0x15761022
rev=0x00 hdr=0x00
vendor = 'Advanced Micro Devices, Inc. [AMD]'
class = bridge
subclass = HOST-PCI
none0_at_pci0:0:0:2: class=0x080600 card=0x15771022 chip=0x15771022
rev=0x00 hdr=0x00
vendor = 'Advanced Micro Devices, Inc. [AMD]'
class = base peripheral
subclass = IOMMU
vgapci0_at_pci0:0:1:0: class=0x030000 card=0x807e103c chip=0x98741002
rev=0xc4 hdr=0x00
vendor = 'Advanced Micro Devices, Inc. [AMD/ATI]'
device = 'Carrizo'
class = display
subclass = VGA
hdac0_at_pci0:0:1:1: class=0x040300 card=0x807e103c chip=0x98401002
rev=0x00 hdr=0x00
vendor = 'Advanced Micro Devices, Inc. [AMD/ATI]'
device = 'Kabini HDMI/DP Audio'
class = multimedia
subclass = HDA
hostb1_at_pci0:0:2:0: class=0x060000 card=0x00000000 chip=0x157b1022
rev=0x00 hdr=0x00
vendor = 'Advanced Micro Devices, Inc. [AMD]'
class = bridge
subclass = HOST-PCI
pcib1_at_pci0:0:2:1: class=0x060400 card=0x12341022 chip=0x157c1022
rev=0x00 hdr=0x01
vendor = 'Advanced Micro Devices, Inc. [AMD]'
class = bridge
subclass = PCI-PCI
pcib2_at_pci0:0:2:3: class=0x060400 card=0x12341022 chip=0x157c1022
rev=0x00 hdr=0x01
vendor = 'Advanced Micro Devices, Inc. [AMD]'
class = bridge
subclass = PCI-PCI
pcib3_at_pci0:0:2:5: class=0x060400 card=0x12341022 chip=0x157c1022
rev=0x00 hdr=0x01
vendor = 'Advanced Micro Devices, Inc. [AMD]'
class = bridge
subclass = PCI-PCI
hostb2_at_pci0:0:3:0: class=0x060000 card=0x00000000 chip=0x157b1022
rev=0x00 hdr=0x00
vendor = 'Advanced Micro Devices, Inc. [AMD]'
class = bridge
subclass = HOST-PCI
none1_at_pci0:0:8:0: class=0x108000 card=0x15781022 chip=0x15781022
rev=0x00 hdr=0x00
vendor = 'Advanced Micro Devices, Inc. [AMD]'
class = encrypt/decrypt
hostb3_at_pci0:0:9:0: class=0x060000 card=0x00000000 chip=0x157d1022
rev=0x00 hdr=0x00
vendor = 'Advanced Micro Devices, Inc. [AMD]'
class = bridge
subclass = HOST-PCI
hdac1_at_pci0:0:9:2: class=0x040300 card=0x807e103c chip=0x157a1022
rev=0x00 hdr=0x00
vendor = 'Advanced Micro Devices, Inc. [AMD]'
class = multimedia
subclass = HDA
xhci0_at_pci0:0:16:0: class=0x0c0330 card=0x807e103c chip=0x79141022
rev=0x20 hdr=0x00
vendor = 'Advanced Micro Devices, Inc. [AMD]'
device = 'FCH USB XHCI Controller'
class = serial bus
subclass = USB
ahci0_at_pci0:0:17:0: class=0x010601 card=0x807e103c chip=0x79011022
rev=0x49 hdr=0x00
vendor = 'Advanced Micro Devices, Inc. [AMD]'
device = 'FCH SATA Controller [AHCI mode]'
class = mass storage
subclass = SATA
ehci0_at_pci0:0:18:0: class=0x0c0320 card=0x807e103c chip=0x79081022
rev=0x49 hdr=0x00
vendor = 'Advanced Micro Devices, Inc. [AMD]'
device = 'FCH USB EHCI Controller'
class = serial bus
subclass = USB
none2_at_pci0:0:20:0: class=0x0c0500 card=0x807e103c chip=0x790b1022
rev=0x4a hdr=0x00
vendor = 'Advanced Micro Devices, Inc. [AMD]'
device = 'FCH SMBus Controller'
class = serial bus
subclass = SMBus
isab0_at_pci0:0:20:3: class=0x060100 card=0x807e103c chip=0x790e1022
rev=0x11 hdr=0x00
vendor = 'Advanced Micro Devices, Inc. [AMD]'
device = 'FCH LPC Bridge'
class = bridge
subclass = PCI-ISA
hostb4_at_pci0:0:24:0: class=0x060000 card=0x00000000 chip=0x15701022
rev=0x00 hdr=0x00
vendor = 'Advanced Micro Devices, Inc. [AMD]'
class = bridge
subclass = HOST-PCI
hostb5_at_pci0:0:24:1: class=0x060000 card=0x00000000 chip=0x15711022
rev=0x00 hdr=0x00
vendor = 'Advanced Micro Devices, Inc. [AMD]'
class = bridge
subclass = HOST-PCI
hostb6_at_pci0:0:24:2: class=0x060000 card=0x00000000 chip=0x15721022
rev=0x00 hdr=0x00
vendor = 'Advanced Micro Devices, Inc. [AMD]'
class = bridge
subclass = HOST-PCI
hostb7_at_pci0:0:24:3: class=0x060000 card=0x00000000 chip=0x15731022
rev=0x00 hdr=0x00
vendor = 'Advanced Micro Devices, Inc. [AMD]'
class = bridge
subclass = HOST-PCI
hostb8_at_pci0:0:24:4: class=0x060000 card=0x00000000 chip=0x15741022
rev=0x00 hdr=0x00
vendor = 'Advanced Micro Devices, Inc. [AMD]'
class = bridge
subclass = HOST-PCI
hostb9_at_pci0:0:24:5: class=0x060000 card=0x00000000 chip=0x15751022
rev=0x00 hdr=0x00
vendor = 'Advanced Micro Devices, Inc. [AMD]'
class = bridge
subclass = HOST-PCI
bge0_at_pci0:1:0:0: class=0x020000 card=0x807e103c chip=0x168714e4
rev=0x10 hdr=0x00
vendor = 'Broadcom Corporation'
device = 'NetXtreme BCM5762 Gigabit Ethernet PCIe'
class = network
subclass = ethernet
iwm0_at_pci0:2:0:0: class=0x028000 card=0x50108086 chip=0x095a8086
rev=0x61 hdr=0x00
vendor = 'Intel Corporation'
device = 'Wireless 7265'
class = network
none3_at_pci0:3:0:0: class=0xff0000 card=0x807e103c chip=0x522a10ec
rev=0x01 hdr=0x00
vendor = 'Realtek Semiconductor Co., Ltd.'
device = 'RTS522A PCI Express Card Reader'

This is on a recent CURRENT: r301970

All ideas most welcome!

Johannes