[coreboot] MTRR setup strategy

[Corey Osgood]

On Tue, Jan 27, 2009 at 9:30 PM, Eric W. Biederman <ebiederm at xmission.com>wrote:

> Carl-Daniel Hailfinger <c-d.hailfinger.devel.2006 at gmx.net> writes:
>
> > Assuming you don't have anything you want to cache near 4 GB (like
> flash):
> > Both strategies are equally efficient if the contiguous cacheable area
> > has a size of 2^n+2^(n-1).
> > The additive strategy is more efficient if the size is 2^n+2^(n-k) and
> k>1.
> > The subtractive strategy is more efficient if the size is 2^n-2^(n-k)
> > and k>1.
> >
> > I hope that you accept this without a detailed mathematical proof. ;-)
> >
> >> I wonder... the subtractive strategy you subscribe is mentioned in
> >> mtrr.c too and the comment claims it is implemented. But it very much
> >> seems it is not.
> >>
> >
> > Ouch.
>
> When did it break?
>
> I remember the subtractive mtrr setup working correctly.
> At least most of the time.


???
I'm not seeing any code in v2 capable of calculating subtractive mtrrs, is
it possibly in v1?  Am I missing something? I'm only looking in mtrr.c.

Thanks,
Corey
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