From mboxrd@z Thu Jan  1 00:00:00 1970
From: Matthew Garrett <mjg59@srcf.ucam.org>
Subject: Re: [PATCH] drm/i915: By default, enable RC6 on IVB and SNB when
 reasonable
Date: Tue, 22 Nov 2011 20:51:45 +0000
Message-ID: <20111122205145.GA7206@srcf.ucam.org>
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To: Eugeni Dodonov <eugeni@dodonov.net>
Cc: Keith Packard <keithp@keithp.com>, intel-gfx@lists.freedesktop.org, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org
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On Tue, Nov 22, 2011 at 06:46:21PM -0200, Eugeni Dodonov wrote:
> On Tue, Nov 22, 2011 at 18:15, Matthew Garrett <mjg@redhat.com> wrote:
> 
> > On Fri, Nov 18, 2011 at 10:41:29PM -0800, Keith Packard wrote:
> >
> > > +     /*
> > > +      * Only enable RC6 if all dma remapping is disabled, or if
> > > +      * there's no iommu present in the machine.
> > > +      */
> > > +     if (INTEL_INFO(dev)->gen == 6)
> > > +             return no_iommu || dmar_disabled;
> >
> > So the user has to choose between 5W of power saving or having dmar? And
> > we default to giving them dmar?
> 
> 
> From the latest investigations, it is either this, or random gpu hangs and
> crashes when both are enabled :(.

So blacklist dmar on sandybridge. The power saving is going to be more 
important for most users.

-- 
Matthew Garrett | mjg59@srcf.ucam.org