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