[Intel-gfx] [PATCH] drm/i915/gt: Make the slice:unslice ratio request explicit for RPS

[Chris Wilson]

Quoting Chris Wilson (2020-04-21 14:50:51)
> Quoting Chris Wilson (2020-04-21 14:45:12)
> > In RPS, we have the option to only specify the unslice [ring] clock
> > ratio and for the pcu to derive the slice [gpu] clock ratio from its
> > magic table. We also have the option to tell the pcu to use our
> > requested gpu clock ratio, and for it to try and throttle the unslice
> > and slice ratios separately.
> > 
> > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > Cc: Mika Kuoppala <mika.kuoppala at linux.intel.com>
> > ---
> >  drivers/gpu/drm/i915/gt/intel_rps.c | 11 +++++++----
> >  1 file changed, 7 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/gt/intel_rps.c b/drivers/gpu/drm/i915/gt/intel_rps.c
> > index 4dcfae16a7ce..07321e1b22f6 100644
> > --- a/drivers/gpu/drm/i915/gt/intel_rps.c
> > +++ b/drivers/gpu/drm/i915/gt/intel_rps.c
> > @@ -662,14 +662,17 @@ static int gen6_rps_set(struct intel_rps *rps, u8 val)
> >         struct drm_i915_private *i915 = rps_to_i915(rps);
> >         u32 swreq;
> >  
> > -       if (INTEL_GEN(i915) >= 9)
> > -               swreq = GEN9_FREQUENCY(val);
> > -       else if (IS_HASWELL(i915) || IS_BROADWELL(i915))
> > +       if (INTEL_GEN(i915) >= 9) {
> > +               swreq = 0x2; /* only throttle slice, not unslice */
> 
> 0x0 == use implicit slice ratio
> 0x1 == use explicit slice ratio
> 0x2 == use separate throttling
> 
> Not sure if 0x2 actually was implemented in the end.

That being said, 0x2 seems to be doing better.
-Chris