USB mass storage and ARM cache coherency

[Benjamin Herrenschmidt]

On Tue, 2010-03-02 at 21:11 +0900, FUJITA Tomonori wrote:
> 
> > Sorry to be a bit late to the party (on holiday), but I/D coherency
> is
> > supposed to be taken care of using flush_cache_page in the memory
> > mapping routines.
> 
> powerpc does that? To be exact, powerpc doesn't need
> flush_cache_page() and handles I/D coherency in the pte modification
> code. powerpc uses PG_arch_1 to avoid unnecessarily handling I/D
> coherency. Seems that IA64 does the same trick with PG_arch_1.

Right. We set PG_arch_1 to avoid doing it again of a given physical
page. We assume that it's always cleared when a page is recycled by the
page cache and we also clear it in flush_dcache_page() though the need
for that later thing is dubious...

Cheers,
Ben.