[Intel-gfx] [PATCH 5/8] drm/i915: avoid waking up from PC8 on GMBUS operations

[Chris Wilson]

On Mon, Jul 29, 2013 at 05:48:24PM -0300, Paulo Zanoni wrote:
> From: Paulo Zanoni <paulo.r.zanoni at intel.com>
> 
> If we're already allowing PC8, just don't use the IRQs, so we won't
> need to wake from PC8. Waking up from PC8 is a slow thing, so avoid it
> when we can.

You would also need to explain that the GMBUS is outside of the display
power well.

Looks reasonable, the only bit is moving the read of forbid_count into
hsw_pc8_enabled() so that the gmbus code isn't poking around with
someone else's locks, and we can safely do an unlocked optimistic read
here.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre