linux-kernel - Re: dmaengine skip unmap (was: Re: [PATCH v4 5/6] dmaengine: Driver for the Synopsys DesignWare DMA controller)

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Date:	Fri, 4 Jul 2008 16:47:34 +0200
From:	Haavard Skinnemoen <haavard.skinnemoen@...el.com>
To:	Dan Williams <dan.j.williams@...el.com>
Cc:	Pierre Ossman <drzeus-list@...eus.cx>,
	linux-kernel@...r.kernel.org, linux-embedded@...r.kernel.org,
	kernel@...32linux.org,
	"Nelson, Shannon" <shannon.nelson@...el.com>,
	David Brownell <david-b@...bell.net>
Subject: Re: dmaengine skip unmap (was: Re: [PATCH v4 5/6] dmaengine: Driver
 for the Synopsys DesignWare DMA controller)

Dan Williams <dan.j.williams@...el.com> wrote:
> The one thing that stands out is that this driver does not unmap the
> source or destination buffers (and I now notice that fsldma is not doing
> this either, hmm...).  Yes, it is a no-op on avr32, for now, but the
> dma-mapping-api assumes that dma_map is always paired with dma_unmap.  I
> remember we discussed this earlier and that discussion inspired the
> patch below.  The end result is that dw_dmac can try to automatically
> dma_unmap the buffers unless an intelligent client, like the mmc driver,
> has disabled unmap.
> 
> Thoughts?

Looks reasonable. I'll update the dw_dmac driver and post a new version
in a few moments.

Haavard
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