[Intel-gfx] [PATCH 2/2] drm/i915: enable plain RC6 on Sandy Bridge by default

Eugeni Dodonov eugeni at dodonov.net
Sat Feb 11 20:24:16 CET 2012

On Sat, Feb 11, 2012 at 10:59, Chris Wilson <chris at chris-wilson.co.uk>wrote:

> On Sat, 11 Feb 2012 10:34:15 -0200, Eugeni Dodonov <
> eugeni.dodonov at intel.com> wrote:
> > This is yet another chapter in the ongoing saga of bringing RC6 to Sandy
> > Bridge machines by default.
> >
> > Now that we have discovered that RC6 issues are triggered by RC6+ state,
> > let's try to disable it by default. Plain RC6 is the one responsible for
> > most energy savings, and so far it haven't given any problems - at least,
> > none we are aware of.
> >
> > So with this, when i915_enable_rc6=-1 (e.g., the default value), we'll
> > attempt to enable plain RC6 only on SNB. For Ivy Bridge, the behavior
> > stays the same as always - we enable both RC6 and deep RC6.
> We appear to be lacking a bunch of tested-bys for what we proclaim to
> have been tested.

So far I had 2 reports saying that RC6 solved the problems which were
present with RC6+RC6p (previous default) on SNB.

I'll wait a bit more and send a v2 version of this patch with all the
Tested-by's. Indeed, it makes sense to have those on this patch before
picking it into any kernel tree. Meanwhile, if there are any other
volunteers who were affected by SNB RC6 voodoo in the past and are willing
to give these patches a try, please, do so!

(Not that it wouldn't prevent all the possible issues, but it would certify
that it is not a placebo effect at least for someone...)

Eugeni Dodonov
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