Messages in this thread | | | Date | Sun, 22 Nov 2009 10:58:53 +0000 | From | Simon Arlott <> | Subject | Re: cxacru usb_bulk_msg() firmware upload 36x slower with OHCI vs. UHCI |
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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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