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From: Tony Lindgren <tony-4v6yS6AI5VpBDgjK7y7TUQ@public.gmane.org>
To: Tom Mises <tommises-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Cc: Ash Charles <ashcharles-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
	Matthieu CASTET
	<matthieu.castet-ITF29qwbsa/QT0dZR+AlfA@public.gmane.org>,
	Alan Stern
	<stern-nwvwT67g6+6dFdvTe/nMLpVzexx5G7lz@public.gmane.org>,
	"linux-omap-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
	<linux-omap-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	linux-usb-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	linux-uvc-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org
Subject: Re: High CPU usage when video streaming on EHCI, 3.17.8 kernel with DMA enabled
Date: Wed, 1 Jul 2015 23:22:35 -0700	[thread overview]
Message-ID: <20150702062234.GZ4156@atomide.com> (raw)
In-Reply-To: <CALmG-ARrzJ=kRH-958F20WPH+=VCpjrgMuyn9MWv4uj2dnSRpw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>

* Tom Mises <tommises-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> [150701 11:24]:
> On Mon, May 18, 2015 at 8:59 AM, Tony Lindgren <tony-4v6yS6AI5VpBDgjK7y7TUQ@public.gmane.org> 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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      parent reply	other threads:[~2015-07-02  6:22 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-05-17  6:45 High CPU usage when video streaming on EHCI, 3.17.8 kernel with DMA enabled Tom Mises
     [not found] ` <CALmG-ASRge4g6euyUEaxrLryvNR_tFSRexFSDZ5HNuzx_W4AyA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2015-05-17 14:06   ` Alan Stern
2015-05-18  8:27     ` Matthieu CASTET
2015-05-18 14:59       ` Tony Lindgren
     [not found]         ` <20150518145919.GC10274-4v6yS6AI5VpBDgjK7y7TUQ@public.gmane.org>
2015-05-21 21:20           ` Ash Charles
     [not found]             ` <CAK8F28mdedXgL660SqTLeNZ7hVHOmRR7YwuTdkyY3XmnZ97_Zw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2015-07-01 18:22               ` Tom Mises
     [not found]                 ` <CALmG-ARrzJ=kRH-958F20WPH+=VCpjrgMuyn9MWv4uj2dnSRpw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2015-07-02  6:22                   ` Tony Lindgren [this message]

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