[Intel-gfx] [PATCH] drm/i915/gt: Disable manual rc6 for Braswell/Baytrail

[Chris Wilson]

Quoting Andi Shyti (2019-12-11 21:25:59)
> Hi Chris,
> 
> > The initial investigated showed that while the PCU on Braswell/Baytrail
> > controlled RC6 itself. setting the software RC6 request made no
> > difference. Further testing reveals though that it causes a delay in the
> > PCU on enabling RC6.
> > 
> > Closes: https://gitlab.freedesktop.org/drm/intel/issues/763
> > Fixes: 730eaeb52426 ("drm/i915/gt: Manual rc6 entry upon parking")
> > Testcase: igt/perf/rc6-disable
> > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > Cc: Andi Shyti <andi.shyti at intel.com>
> > Cc: Mika Kuoppala <mika.kuoppala at linux.intel.com>
> > Cc: Imre Deak <imre.deak at intel.com>
> > ---
> >  drivers/gpu/drm/i915/gt/intel_rc6.c | 3 +++
> >  1 file changed, 3 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/i915/gt/intel_rc6.c b/drivers/gpu/drm/i915/gt/intel_rc6.c
> > index 4dc82196b285..8ec2b7725141 100644
> > --- a/drivers/gpu/drm/i915/gt/intel_rc6.c
> > +++ b/drivers/gpu/drm/i915/gt/intel_rc6.c
> > @@ -612,6 +612,9 @@ void intel_rc6_park(struct intel_rc6 *rc6)
> >               return;
> >       }
> >  
> > +     if (!(rc6->ctl_enable & GEN6_RC_CTL_RC6_ENABLE))
> > +             return;
> > +
> 
> Huh? I didn't think this could be necessary! Nice catch!

Bah, CI takes all the credit. Stupid, stupid PCU.
-Chris