Re: [PATCH 2/5] [POWERPC] 8xx: generic 8xx code arch/powerpc port

On Nov 17, 2006, at 3:00 AM, Christoph Hellwig wrote:

this is used by arch/ppc/fec.c to set mapping uncachable, which
seems rather odd to me.

I thought arch/ppc/fec.c is dead in favor of the
"generic" version in the drivers/net directory?

We use the va_to_pte() functions to find
the mappings to create "coherent" cache areas
by changing the cache attributes of the vmalloc()
space.  We can't use virt_to_phys() or similar
associated functions because they simply do the
kernel virtual arithmetic and don't return the
proper PTEs for for changing these attributes.

I believe this is also used on the 4xx, but I
could be mistaken.

.....  For now we'll have to keep it I think, but
it might make sense to move the implementation to fec.c.

I don't know what version of fec.c you are looking
at, but it should use the dma_alloc_coherent() functions
and be stashing both the physical and virtual addresses.
I made this change long ago and I hope it hasn't
been lost.

The coherent dma functions will in turn use
the va_to_pte() (or associated functions) mentioned
above.

Thanks.


	-- Dan