Subject: Re: [RFC PATCH] dma: Add barrierless dma mapping/unmapping api
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: adharmap@codeaurora.org, linux-kernel@vger.kernel.org,
       linux-arm-msm@vger.kernel.org, dwalker@codeaurora.org, arnd@arndb.de,
       akpm@linux-foundation.org, mingo@elte.hu, joerg.roedel@amd.com,
       maciej.sosnowski@intel.com, dan.j.williams@intel.com,
       beckyb@kernel.crashing.org, yanghy@cn.fujitsu.com,
       linux-arch@vger.kernel.org, adharmap@quicinc.com
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Date: Wed, 27 Jan 2010 17:49:47 +1100
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On Wed, 2010-01-27 at 14:19 +0900, FUJITA Tomonori wrote:
> > I somehow missed your post, my apologies. Agreed that
> dma_map/unmap_sg 
> > would be the correct api to use here, however they still call the 
> > dmac_.*_range to map buffers.
> 
> Hmm, sounds like arm's implementation issue. dma_map_sg API doesn't
> require such. dma_map_sg API gives what you want, do a sync only after
> mapping the last buffer.

dmac_* appears to be ARM's low-level ops for cache flushing on
non-coherent DMA, so it's really down to arch stuff here and how ARM
implements dma_[un]map_sg() and we keep a sane global driver API.

Cheers,
Ben.


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