Re: [PATCH 03/11] drm/i915: Rename and comment all the RPS *stuff*

Chris Wilson
2014-02-22T20:08:26Z

On Sat, Feb 22, 2014 at 11:40:43AM -0800, Ben Widawsky wrote:
> On Sat, Feb 22, 2014 at 07:37:04PM +0000, Chris Wilson wrote:
> > On Sat, Feb 22, 2014 at 11:34:16AM -0800, Ben Widawsky wrote:
> > > On Sat, Feb 22, 2014 at 01:37:16PM +0000, Chris Wilson wrote:
> > > > On Mon, Feb 17, 2014 at 07:01:44PM -0800, Ben Widawsky wrote:
> > > > > The names of the struct members for RPS are stupid. Every time I need to
> > > > > do anything in this code I have to spend a significant amount of time to
> > > > > remember what it all means. By renaming the variables (and adding the
> > > > > comments) I hope to clear up the situation. Indeed doing this make some
> > > > > upcoming patches more readable.
> > > > >
> > > > > I've avoided ILK because it's possible that the naming used for Ironlake
> > > > > matches what is in the docs. I believe the ILK power docs were never
> > > > > published, and I am too lazy to dig them up.
> > > > >
> > > > > While there may be mistakes, this patch was mostly done via sed. The
> > > > > renaming of "hw_max" required a bit of interactivity.
> > > >
> > > > It lost the distinction between RPe and RPn. I am in favour of keeping
> > > > RP0, RP1, RPe, RPn for the hardware/spec values and adding the set of
> > > > soft values used for actual interaction.
> > > > -Chris
> > > >
> > >
> > > And what is the difference between RPe, and RPn? I honestly have no clue
> > > what RPe is.
> >
> > It's a mythical beast on Valleyview for an inflection point in the
> > power/performance curve that the hardware designers recommend using.
> > -Chris
> >
>
> Isn't that exactly what RPn is supposed to be?

No, RPn is as low as they allow the hardware to drop the frequency. RPe
was a different beast for power-efficient rendering. As usual it comes
without a single piece of substantiating or verifiable piece of
evidence, nor even if it applies to Linux workloads. Yet it is lore that
we are expected to follow on faith.
-Chris

--
Chris Wilson, Intel Open Source Technology Centre