MPC8260 cache patch

[Jonathan Larmour]

Gary Thomas wrote:
> 
> Technically, this should not matter.  The only time this would make any
> difference would be if the FLASH functions modified data that was already
> within the data cache.  If the lines were left valid and then the cache
> disabled, when the cache was re-enabled, the lines in the cache could
> override the changes in memory, leading to an inconsistent state.  So,
> for safety's sake, we should leave the invalidate calls in there.  BTW,
> as far as I can see the only time this could cause a problem would be
> on the "inquire" function - the one that computes the size and shape of
> the FLASH.  If that data were already in the cache, then things could
> go awry.  The only other routines only write to the FLASH and should not
> be touching memory anyway.

I think this only applies to the simplest of operations. It only takes a 
  read/write/read operation to risk problems. You could provoke this by 
just cksumming an area of flash before doing a write to it, and then 
cksumming it again, for example[1]. Unlikely, but, users given a CLI can 
do whatever they want :-).

More troublesome would be flash file systems of course, and they rely on 
the underlying drivers doing the right thing.

Jifl
[1] Talking of which, I'm I the only one still showing a mismatch between 
RedBoot cksum and Linux cksum? I thought all these issues were worked out 
not all that long ago.
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