[Intel-gfx] ironlake rc6 + iommu = hangage

[Daniel Vetter]

On Sun, Aug 26, 2012 at 02:53:50PM +1000, Dave Airlie wrote:
> It appears that running with iommu=on and ILK rc6 enabled on drm-next
> my machine hangs somewhere randomly between gdm starting, logging in,
> and gnome-shell starting.
> 
> Setting iommu=igfx_off or off works around it.

Since the same rc6+iommu combination is known to not work on snb, too,
I'll just disable rc6 if the iommu is on. Since we've never figured out
what's broken with rc6 on ilk (and all the old reporters disappeared)
thanks a lot for hitting this ;-)

> btw I don't know if I'm seeing any power saving with ILK rc6 enabled,
> will do a  bit more checking.

Little afaik. Since the gpu is on a separate die in the package there's
much less to switch off - all the inter-die coordination happens manually
on ilk and hence all that stuff needs to be kept on.

Thanks, Daniel
-- 
Daniel Vetter
Mail: daniel at ffwll.ch
Mobile: +41 (0)79 365 57 48