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

From: Alan Stern
Date: Wed Nov 18 2009 - 10:51:22 EST


On Wed, 18 Nov 2009, Simon Arlott wrote:

> Can anyone explain this speed difference I'm seeing with usb_bulk_msg()?
>
> Increasing the size of the data doesn't improve the speed at all. This
> makes firmware loading take significantly longer with OHCI.
>
> I've tested this with two UHCI controllers, two OHCI controllers, and
> two different versions of the device. Even on the same system with the
> same device the speed difference occurs between OHCI and UHCI.
>
> I've added a debug line to drivers/usb/atm/cxacru.c in cxacru_fw(),
> which uploads the firmware in PAGE_SIZE chunks:
> + printk(KERN_INFO "cxacru: sending fw %#x size %#x to %#x", fw, offb, offd);
> ret = usb_bulk_msg(usb_dev, usb_sndbulkpipe(usb_dev, CXACRU_EP_CMD),
>
>
> With OHCI and PAGE_SIZE chunks (4KB):
> [2567188.504299] cxacru: sending fw 0x3 size 0x1000 to 0xe00
> [2567188.760293] cxacru: sending fw 0x3 size 0x1000 to 0x1c00
> [2567189.016258] cxacru: sending fw 0x3 size 0x1000 to 0x2a00
> [2567189.272235] cxacru: sending fw 0x3 size 0x1000 to 0x3800
> [2567189.528210] cxacru: sending fw 0x3 size 0x1000 to 0x4600
> [2567189.784488] cxacru: sending fw 0x3 size 0x1000 to 0x5400
> ...
> [2567233.044134] cxacru: sending fw 0x3 size 0x2c0 to 0x98668

...

> With OHCI and PAGE_SIZE*8 chunks (32KB):
> [ 4731.826738] cxacru: sending fw 0x3 size 0x8000 to 0x7000
> [ 4733.874628] cxacru: sending fw 0x3 size 0x8000 to 0xe000
> [ 4735.922353] cxacru: sending fw 0x3 size 0x8000 to 0x15000
> [ 4737.970153] cxacru: sending fw 0x3 size 0x8000 to 0x1c000
> [ 4740.017937] cxacru: sending fw 0x3 size 0x8000 to 0x23000
> [ 4742.065814] cxacru: sending fw 0x3 size 0x8000 to 0x2a000
> ...
> [ 4774.830569] cxacru: sending fw 0x3 size 0x62c0 to #98668

Each OHCI transfer requires about 256 ms per 4-KB page. There's no
obvious reason for this to take so long. I'd guess it was caused by a
hardware problem except that you say the same thing happened with two
different controllers. Were they both on the same computer?

You may have to do a bisection search to find the answer.

Alan Stern

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