RE: PATCH: support for Arctic/Beech/Ebony

Eugene Surovegin
2003-01-30T17:41:45Z

At 03:23 AM 1/30/2003, you wrote:
> > Joakim,
> >
> > At 01:46 PM 1/29/2003, you wrote:
> > > - You don't need mb() since ioremap will add the
> > > GUARDED attribute to the mapping.
> >
> > Well, this is not quite correct.
> >
> > GUARDED attribute does _NOT_ prevent reordering of loads and stores on PPC
> > (on 4xx at least).
> >
> > See comments in asm-ppc/system.h and also IBM app note "Software
> > consideration when migrating to the PowerPC 440GP from 405GP"
> >
>
>hmm, maybe it's specific to the 8xx family. 860 and 862 does not do
>speculative accesses on GUARDED memory.

It does! But speculative accesses and access reordering are not the same
thing :)

There is a subtle difference.

>Me wounders what GUARDED is good for if it doesn't prevent reordering.

I think it's a FAQ for PPC devel list :)

Eugene.