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Date: Tue, 20 May 2008 17:35:56 -0500
From: Scott Wood <scottwood@freescale.com>
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To: Alan Cox <alan@lxorguk.ukuu.org.uk>
CC: benh@kernel.crashing.org, Trent Piepho <tpiepho@freescale.com>,
       linuxppc-dev@ozlabs.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] [POWERPC] Improve (in|out)_beXX() asm code
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Alan Cox wrote:
>> It looks like we rely on -fno-strict-aliasing to prevent reordering 
>> ordinary memory accesses (such as to DMA descriptors) past the I/O 
> 
> DMA descriptors in main memory are dependant on cache behaviour anyway
> and the dma_* operators should be the ones enforcing the needed behaviour.

What about memory obtained from dma_alloc_coherent()?  We still need a 
sync and a compiler barrier.  The current I/O accessors have the former, 
but not the latter.

-Scott