[MTD/NAND] Blackfin NFC driver DMA bug ?

[Bryan Wu]

On Fri, Feb 22, 2008 at 4:54 PM, Ivan Djelic <ivan.djelic at parrot.com> wrote:
> 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).
>

Thanks a lot for the clarification.

If can be fixed in drivers or in MTD API, maybe MTD API is good place
to fix it completely as David mentioned.
I will found some way to fix it in my driver firstly.

Regards,
-Bryan Wu