[Intel-gfx] [PATCH] drm/i915: By default, enable RC6 on IVB and SNB when reasonable

[Daniel Vetter]

On Wed, Nov 23, 2011 at 03:43:05PM +0000, David Woodhouse wrote:
> On Wed, 2011-11-23 at 16:41 +0100, Daniel Vetter wrote:
> > Hm, that comment confuses me a bit. I've always thought that igfx_off only
> > instantiates a identity mapping and leaves the dmar unit on. Is that
> > wrong? 
> 
> It's completely off. If a DMAR unit has *only* graphics devices behind
> it (as the one for the built-in graphics does, because it's a whole
> boatload of speshul case for integration with the GTT), we just don't
> enable it at all. See the second for_each_drhd_unit() loop in
> init_no_remapping_devices().

That explanation confused me even more. So I've rechecked with
intel_iommu=igfx_off and already thought I've made a decent fool of
myself because I couldn't readily hang it. Turns out it's just much harder
to hang with that. So I think moving around the tlb flushing for other
dmar nodes to align with the idled igfx isn't a great solution, simply
because I can't reliably tell whether it fixes anything.
-Daniel
-- 
Daniel Vetter
Mail: daniel at ffwll.ch
Mobile: +41 (0)79 365 57 48