Re: Athlon/AGP issue update

Val Henson
2002-01-25T18:35:20Z

On Wed, Jan 23, 2002 at 04:47:37PM +0100, benh@kernel.crashing.org wrote:
> >I don't think your PPC case needs the kernel mappings messed with.
> >I really doubt the PPC will speculatively fetch/store to a TLB
> >missing address.... unless you guys have large TLB mappings on
> >PPC too?
>
> Yes, we use BATs (sort of built-in fixed large TLBs) to map
> the lowmem (or entire RAM without CONFIG_HIGHMEM).

Looking at bat_mapin_ram, it looks like we only map the first 512MB of
RAM with BATs, so we actually map the 512MB - 768MB range with PTEs
(and highmem starts at 768MB). Two of the DBATs are used by I/O
mappings, so that only leaves two DBATs of 256MB each to map lowmem
anyway. Am I missing something?

By the way, does the "nobats" option currently work on PowerMac?

-VAL