linux-kernel - Re: [PATCH 2/2] dma: tegra: fix residual calculation for cyclic case

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Message-ID: <1342149336.1726.5.camel@vkoul-udesk3>
Date:	Fri, 13 Jul 2012 08:45:36 +0530
From:	Vinod Koul <vinod.koul@...ux.intel.com>
To:	Stephen Warren <swarren@...dotorg.org>
Cc:	Laxman Dewangan <ldewangan@...dia.com>, dan.j.williams@...el.com,
	swarren@...dia.com, linux-kernel@...r.kernel.org,
	linux-tegra@...r.kernel.org
Subject: Re: [PATCH 2/2] dma: tegra: fix residual calculation for cyclic
 case

On Mon, 2012-07-02 at 10:02 -0600, Stephen Warren wrote:
> On 07/02/2012 02:22 AM, Laxman Dewangan wrote:
> > In cyclic mode of DMA, the byte transferred can be more
> > than the requested size and in this case, calculating
> > residuals based on the current position of DMA transfer to
> > bytes requested i.e. bytes required to transfer to reach
> > bytes requested from current DMA position.
> > 
> > Signed-off-by: Laxman Dewangan <ldewangan@...dia.com>
> 
> This makes sense to me, although I wonder if details like this aren't
> something that the dmaengine core should be handling.
No core doesn't know anything about the how much you are transferring
and where you are. That is the driver to calculate and provide.

-- 
~Vinod

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