Re: [PATCH] drm/i915: By default, enable RC6 on IVB and SNB whenreasonable

From: David Woodhouse
Date: Wed Nov 23 2011 - 09:02:07 EST


On Wed, 2011-11-23 at 11:26 +0100, Daniel Vetter wrote:
> On Tue, Nov 22, 2011 at 07:31:34PM -0800, Keith Packard wrote:
> > On Tue, 22 Nov 2011 20:15:31 +0000, Matthew Garrett <mjg@xxxxxxxxxx> wrote:
> >
> > > So the user has to choose between 5W of power saving or having dmar? And
> > > we default to giving them dmar? I think that's going to come as a
> > > surprise to people.
> >
> > You'd have to go into the BIOS to turn this on for most machines at
> > least?
> >
> > But, yeah, it seems like we should be turning DMAR off unless explicitly
> > requested; I can't understand how you'd ever need this running native on
> > the hardware. Not exactly an area I care about deeply; I've always
> > worked hard to make sure all virtualization garbage is disabled on every
> > machine I use.
>
> Problem is that we need to disable dmar on the entire box, afaics. And I
> assume that a bunch of people abusing desktop boards as servers will call
> "regression" on that.

Hm, do you really have to disable it for the entire box, or just the
graphics?

Do we have a coherent erratum from Intel for the issues mentioned above
with DMAR+gfx+RC6?

Keith, do you know if a sighting has been filed and the hardware folks
are working on it?

Rajesh, are you familiar with this issue?

--
dwmw2

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