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

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Message-ID: <Pine.LNX.4.44L0.0911181045060.3036-100000@iolanthe.rowland.org>
Date:	Wed, 18 Nov 2009 10:51:15 -0500 (EST)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Simon Arlott <simon@...e.lp0.eu>
cc:	linux-usb@...r.kernel.org, <linux-kernel@...r.kernel.org>,
	<accessrunner-general@...ts.sourceforge.net>
Subject: Re: cxacru usb_bulk_msg() firmware upload 36x slower with OHCI vs.
 UHCI

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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