linux-kernel - Re: dma_unmap_single() lacking cache sync on some archs?

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Message-ID: <Pine.LNX.4.64.1109230005130.4190@axis700.grange>
Date:	Fri, 23 Sep 2011 00:06:51 +0200 (CEST)
From:	Guennadi Liakhovetski <g.liakhovetski@....de>
To:	Arvid Brodin <arvid.brodin@...a.com>
cc:	linux-kernel@...r.kernel.org
Subject: Re: dma_unmap_single() lacking cache sync on some archs?

On Thu, 22 Sep 2011, Arvid Brodin wrote:

> Hi,
> 
> I would expect cache synchronization for DMA_TO_DEVICE and DMA_BIDIRECTIONAL
> when dma_map_single() is called, and for DMA_FROM_DEVICE and DMA_BIDIRECTIONAL
> when dma_unmap_single() is called.
> 
> However, on some architechtures (at least avr32, blackfin, ...), cache
> synchronization only happens when dma_map_single() is called (and then
> irrespective of DMA direction). dma_unmap_single() is a no-op for these archs.
> 
> Isn't this a bug?

You'd get a better chance to reach your audience by cc'ing respective arch 
mailing lists and at least the linux-embedded@...r.kernel.org ML.

Thanks
Guennadi

> (Please CC me in responses.)
> 
> -- 
> Arvid Brodin
> Enea Services Stockholm AB

---
Guennadi Liakhovetski, Ph.D.
Freelance Open-Source Software Developer
http://www.open-technology.de/
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