Message-ID: <4B5F4C76.4050100@codeaurora.org>
Date: Tue, 26 Jan 2010 12:11:34 -0800
From: Abhijeet Dharmapurikar <adharmap@codeaurora.org>
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To: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
CC: benh@kernel.crashing.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
Subject: Re: [RFC PATCH] dma: Add barrierless dma mapping/unmapping api
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FUJITA Tomonori wrote:
> On Tue, 26 Jan 2010 15:30:10 +1100
> Benjamin Herrenschmidt <benh@kernel.crashing.org> wrote:
> 
>> On Mon, 2010-01-25 at 18:35 -0800, adharmap@codeaurora.org wrote:
>>> From: Abhijeet Dharmapurikar <adharmap@quicinc.com>
>>>
  >
>> There are people nowadays putting AXI bridges and the whole ARM
>> paraphernalia of IP cores behind them on PowerPC cores for example and I
>> can see that happening with x86 as well.
>>
>> In your case, I believe your are fixing the wrong problem anyways. The
>> right approach would be instead to put all your buffer into an sglist
>> and use dma_map/unmap_sg().
> 
> Agreed again. That's exactly what I suggested before:
> 
> http://marc.info/?l=linux-kernel&m=126294076917753&w=2

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. I could change those calls to do a barrier 
  only after mapping the last buffer. This would be much more cleaner 
than introducing a .*_nobarrier API.

Thanks for all the replies.

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