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Date: Fri, 22 Feb 2008 09:54:03 +0100
From: Ivan Djelic <ivan.djelic@parrot.com>
To: Bryan Wu <cooloney@kernel.org>
Subject: Re: [MTD/NAND] Blackfin NFC driver DMA bug ?
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On Fri, Feb 22, 2008 at 09:45:33AM +0100, Ivan Djelic wrote:
> > Oh, I am not fully understand your concern.  The code is invalidating
> > or flushing buf before DMA operation.
> > And invalidate and flush operation is OK for buf which is not
> > cache-aligned on Blackfin arch. it also should be
> > OK for other arch.
> 
> Well, consider the following scenario, in which 'buf' is not cache-aligned:
> 
> 1) function bf5xx_nand_dma_rw() is called for reading data.
> 
> 2) dcache is partially invalidated on a range containing 'buf': this range is
> cache-aligned, of course.
> 
> 3) some variable residing nearby 'buf' (in the same cache line interval) is
> read (not modified), resulting in a cache line being fetched. Cache line is not
> dirty.

Also, the variable contents in 3) may also be corrupted because of the
invalidation in 2).