From mboxrd@z Thu Jan  1 00:00:00 1970
From: Tony Lindgren <tony@atomide.com>
Subject: Re: High CPU usage when video streaming on EHCI, 3.17.8 kernel with
 DMA enabled
Date: Mon, 18 May 2015 07:59:20 -0700
Message-ID: <20150518145919.GC10274@atomide.com>
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To: Matthieu CASTET <matthieu.castet@parrot.com>
Cc: Alan Stern <stern@rowland.harvard.edu>, Tom Mises <tommises@gmail.com>, linux-omap@vger.kernel.org, linux-usb@vger.kernel.org

* Matthieu CASTET <matthieu.castet@parrot.com> [150518 01:34]:
> Hi,
> 
> last time I checked uvc driver, it was doing memcpy of video buffer : see uvc_video_decode_data.
> 
> It your video resolution is big, this can eat lot's of cpu.
> 
> Doing a trace should help you.

For the memcpy part with DMA this patch should help too:

[PATCH] dmaengine: omap-dma: Add support for memcpy

Regards,

Tony