On 18/11/09 22:25, Alan Stern wrote:
> On Wed, 18 Nov 2009, Simon Arlott wrote:
>> > What happens with other sorts of devices, such as a USB flash drive?
>>
>> I can write a 10MB file to an USB flash drive over OHCI, and umount+sync
>> takes around 13 seconds.
>
> Yes, that's about right. It leads me to wonder if something funny is
> going on with the device, or least with the firmware-loading part of
> it. Odd that it works differently with UHCI and OHCI, though. There
> shouldn't be any differences visible to the device. You don't have
> anything else attached to the same bus, do you?
Yes, but not in use and I could disconnect everything to test it.
core/hcd.c has an interesting comment in usb_hcd_check_unlink_urb():
/* The USB 2.0 spec says 256 ms. This is close enough and won't
* exceed that limit if HZ is 100. The math is more clunky than
* maybe expected, this is to make sure that all timers for USB devices
* fire at the same time to give the CPU a break inbetween */
I'll try increasing the frequency of this timer too.
--
Simon Arlott
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