[clug] Really slow USB after suspend to ram

[Carlo Hamalainen]

Hi,

My partner has an IBM Thinkpad X61 with Ubuntu 9.04, running the
2.6.28-16 kernel.

If I plug in a USB hard drive I see pretty good transfer rates:

$ sudo hdparm -t /dev/sdb

/dev/sdb:
 Timing buffered disk reads:   90 MB in  3.03 seconds =  29.68 MB/sec

But if I suspend to ram and then resume, the transfer rate drops dramatically:

/dev/sdb:  Timing buffered disk reads:    4 MB in  5.97 seconds = 685.70 kB/sec

That's slow enough to be unusable. Reloading USB modules doesn't seem
to help, and the kernel still seems to think that it's a high speed
device:

[ 1731.852126] usb 2-1: new high speed USB device using ehci_hcd and address 3
[ 1732.220267] usb 2-1: configuration #1 chosen from 1 choice
[ 1732.246405] scsi3 : SCSI emulation for USB Mass Storage devices

I tested the external drive on my laptop and it has no trouble before
or after suspending.

There are some long threads on *.ubuntu.com about this problem but I
can't find a definitive answer. Has anyone here dealt with this
problem?

-- 
Carlo Hamalainen
http://carlo-hamalainen.net