[Intel-gfx] [PATCH] drm/i915: Ajdust down threshold in intel_pm.

[Stéphane Marchesin]

On Mon, Jul 16, 2012 at 12:50 PM, Daniel Vetter <daniel at ffwll.ch> wrote:

> On Wed, Jul 04, 2012 at 09:52:11AM +0200, Daniel Vetter wrote:
> > On Tue, Jul 03, 2012 at 02:16:42PM -0700, Stéphane Marchesin wrote:
> > > The up and down thresholds are very asymetric, so it is possible
> > > to have a case where a spike of rendering increases the GPU clock to
> > > the max (because the up threshold is low) and then a simple blinking
> > > cursor is enough to keep the clock at the maximum speed forever
> > > (because the down threshold is high).
> > >
> > > Lowering the down threshold allows the GPU clock to go back down even
> > > when there is a blinking cursor on the screen.
> > >
> > > Signed-off-by: Stéphane Marchesin <marcheu at chromium.org>
> >
> > I've just merged Eugeni's hsw rc6 patches - those contain newly tuning
> > variables. Can you maybe try out whether these would have the same
> effect?
> > I'd prefer to simple enable these, presuming that the hw guys we've got
> > them from did some decent tuning ...
>
> Ping.
>
> 3.6 merge window is approach fast and I think I'd be good to get this in
> ... Or something similar, based on the hsw ratio between downclock and
> upclock limit, but with the slightly bigger thresholds used by ivb/snb for
> upclocks maybe?
>

So now that the dust settled, and that we better understand what's going
on, I am sure that those values are not adequate for us (neither the
default SNB/IVB, nor the Haswell ones).

For the record, here is what we set differently for Chrome OS to solve our
issues (we didn't see a performance regression, but we do get a major power
consumption reduction for lighter GPU loads like playing a video and that
blinking cursor):

GEN6_RP_DOWN_TIMEOUT 10000
GEN6_RP_UP_THRESHOLD 0x4000
GEN6_RP_DOWN_THRESHOLD 0x4000

Stéphane
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