[Intel-gfx] [PATCH 4/9] drm/i915: don't update GEN6_PMIMR when it's not needed

[Daniel Vetter]

On Wed, Aug 07, 2013 at 03:14:51PM +0100, Chris Wilson wrote:
> On Wed, Aug 07, 2013 at 10:34:11AM -0300, Paulo Zanoni wrote:
> > 2013/8/6 Chris Wilson <chris at chris-wilson.co.uk>:
> > > On Tue, Aug 06, 2013 at 06:57:14PM -0300, Paulo Zanoni wrote:
> > >> From: Paulo Zanoni <paulo.r.zanoni at intel.com>
> > >>
> > >> I did some brief tests and the "new_val = pmimr" condition usually
> > >> happens a few times after exiting games.
> > >>
> > >> Signed-off-by: Paulo Zanoni <paulo.r.zanoni at intel.com>
> > >
> > > I'm not sure of the value of this patch by itself. It did make me wonder
> > > what you were micro-optimising, and then I saw patch 5 and it made more
> > > sense.
> > 
> > Patches 4 and 5 are just micro optimizations and shouldn't be needed
> > for the PC8+, but I thought they would be useful. If you think they're
> > not worth it, we can discard them. I was trying to make the code
> > similar to the other IMR-changing functions.
> 
> Combined together, I think the micro-optimisation makes sense and would
> say it was less of a micro-optimisation than a consistent design to use
> the bookkeeping instead of touching registers. Just on its own this
> patch caused me to do a double-take and question what your motivation
> was.

I've added a small note to the commit message to (hopefully) capture this.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch