Re: [PATCH]: c-r4k.c 4/7 flush_cache_mm cleanup

[Ralf Baechle <ralf@linux-mips.org>]

On Fri, Mar 28, 2003 at 06:51:57PM +0100, Maciej W. Rozycki wrote:

> >     flush_cache_mm can use __flush_cache_all.
> 
>  Wrong, it should use r4k_flush_pcache_all() unconditionally, but I'm told
> such a setup triggers a bug somewhere, that needs to be tracked down
> before committing that change to the CVS.

Now that the problem is mentioned on the list lemme elaborate a bit.  The
problem mentioned only affects R4000SC and R4400SC processors.
Flush_cache_mm is only used when a mm is either copied on fork or when
it's finally destroyed.  Because the S-cache is is physically indexed
and the P-cache is refilled from the S-cache if data should be still in
there we don't need to flush the S-cache ever for any of the mm's
cacheflushing functions.  So the observation that things are only
working properly if we do flush the S-cache also suggest we're either
having a bug elsewhere in the cache code or we're hitting a hardware
problem.

  Ralf