Re: cxacru usb_bulk_msg() firmware upload 36x slower with OHCI vs. UHCI

[Simon Arlott <simon@fire.lp0.eu>]

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