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

[Chris Wilson]

On Fri, 23 Mar 2012 11:57:19 -0300, 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.
> 
> Note that while this exact patch does not has explicit tested-by's, the
> equivalent settings were fixed in 3.3 kernel by a smaller patch. And it
> has also received considerable testing through Canonical RC6 task-force
> testing at https://wiki.ubuntu.com/Kernel/PowerManagementRC6. Up to date,
> it looks like all the known issues are gone.
> 
> v2: improve description and reference a couple of open bugs related to
> RC6 which seem to be fixed with this change.
> 
> References: https://bugs.freedesktop.org/show_bug.cgi?id=41682
> References: https://bugs.freedesktop.org/show_bug.cgi?id=38567
> References: https://bugs.freedesktop.org/show_bug.cgi?id=44867
> Signed-off-by: Eugeni Dodonov <eugeni.dodonov at intel.com>
Acked-by: Chris Wilson <chris at chris-wilson.co.uk>
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre