Re: High CPU usage when video streaming on EHCI, 3.17.8 kernel with DMA enabled

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* Tom Mises <tommises@xxxxxxxxx> [150701 11:24]:
> On Mon, May 18, 2015 at 8:59 AM, Tony Lindgren <tony@xxxxxxxxxxx> wrote:
> > For the memcpy part with DMA this patch should help too:
> >
> > [PATCH] dmaengine: omap-dma: Add support for memcpy
> 
> The patch should help, but not out of the box as far as I understand.
> My understanding is that to take advantage of this, it would be
> necessary to explicitly call the DMA API either by replacing memcpy()
> in uvc_video_decode_data() or by modyfying the memcpy()
> implementation. Is that correct?

Yes you should be able to configure the DMA to do memory-to-memory
copy where both source and destination address is looping over
the desired buffer size. Ideally you would move the data from camera
directly to the buffer without doing a memcpy inbetween.

Regards,

Tony
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