linux-kernel - Re: [PATCH][RFC] asm-generic:remove calling flush_write_buffers() in dma_sync_*_for

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Date:	Sun, 28 Jun 2009 15:34:35 +0000
From:	Arnd Bergmann <arnd@...db.de>
To:	tom.leiming@...il.com
Cc:	joerg.roedel@....com, fujita.tomonori@....ntt.co.jp,
	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org
Subject: Re: [PATCH][RFC] asm-generic:remove calling flush_write_buffers() in dma_sync_*_for_cpu

On Sunday 28 June 2009 14:39:19 tom.leiming@...il.com wrote:
> From: Ming Lei <tom.leiming@...il.com>
> 
> dma_sync_*_for_cpu() is introduced to make cpu access dma buffers safely when
> dma transfer is over, it seems there is nothing to do with cpu write buffer,
> so remove it.
> 
> Signed-off-by: Ming Lei <tom.leiming@...il.com>

Right, this looks correct. On a related note, flush_write_buffers is
architecture specific right now: only x86 and frv implement it at all,
though and with slightly different semantics.

Maybe it would be more consistent to change the dma_map_* and
dma_sync_*_for_device stuff there to wmb() to make it  portable
to other architectures.

	Arnd <><
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