Subject: Re: [PATCH 3/16] powerpc/4xx: Extended DCR support v2

From: Josh Boyer <[email-masked]>
Date: Wed, 17 Dec 2008 12:33:29 -0500

On Mon, Dec 15, 2008 at 04:44:17PM +1100, Benjamin Herrenschmidt wrote:
>This adds supports to the "extended" DCR addressing via
>the indirect mfdcrx/mtdcrx instructions supported by some
>4xx cores (440H6 and later)
>
>I enabled the feature for now only on AMCC 460 chips
>
>Signed-off-by: Benjamin Herrenschmidt <[email-masked]>

Acked-by: Josh Boyer <[email-masked]>

I actually ran some tests on this patch on a Bamboo board that
lacks the new instructions.  While tbench might not be great here,
it's the thing I had handy and it does drive some DCR access given
that every interrupt uses DCR instructions to handle the UIC bits
(and some of the MAL stuff I'm assuming).

The results with and without the patch were pretty close.
Differences were in the noise range.  I wanted to test on
Canyonlands, which does have the new instructions, but mine
appears to be DOA.

So in summary, it doesn't make things worse :).

josh