Re: [PATCH 4/4] drm/i915: Use czclk_freq in vlv c0 residency calculations

[Imre Deak <imre.deak@intel.com>]

On Mon, 2015-09-28 at 23:47 +0300, Imre Deak wrote:
> On Thu, 2015-09-24 at 23:29 +0300, ville.syrjala@linux.intel.com wrote:
> > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > 
> > Replace the use of mem_freq/4 with czclk_freq in the vlv c0 residency
> > calculations.
> > 
> > Also deal with VLV_COUNT_RANGE_HIGH which affects all RCx residency
> > counters. We have just enough bits to do this without intermediate
> > divisions.
> > 
> > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > ---
> >  drivers/gpu/drm/i915/i915_irq.c | 8 ++++++--
> >  1 file changed, 6 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
> > index 07c87e0..d78ef64 100644
> > --- a/drivers/gpu/drm/i915/i915_irq.c
> > +++ b/drivers/gpu/drm/i915/i915_irq.c
> > @@ -998,12 +998,16 @@ static bool vlv_c0_above(struct drm_i915_private *dev_priv,
> >  			 int threshold)
> >  {
> >  	u64 time, c0;
> > +	unsigned int mul = 100;
> >  
> >  	if (old->cz_clock == 0)
> >  		return false;
> >  
> > +	if (I915_READ(VLV_COUNTER_CONTROL) & VLV_COUNT_RANGE_HIGH)
> > +		mul <<= 8;
> 
> Could've been a separate patch.
> 
> > +
> >  	time = now->cz_clock - old->cz_clock;
> > -	time *= threshold * dev_priv->mem_freq;
> > +	time *= threshold * dev_priv->czclk_freq;
> 
> Not introduced in this patch, but the above doesn't look correct to me.
> Time is cycles _divided_ by frequency, so imo the above should be either
> a division, or better we should calculate c0 (10ns) cycles here.
> 
> >  
> >  	/* Workload can be split between render + media, e.g. SwapBuffers
> >  	 * being blitted in X after being rendered in mesa. To account for
> > @@ -1011,7 +1015,7 @@ static bool vlv_c0_above(struct drm_i915_private *dev_priv,
> >  	 */
> >  	c0 = now->render_c0 - old->render_c0;
> >  	c0 += now->media_c0 - old->media_c0;
> > -	c0 *= 100 * VLV_CZ_CLOCK_TO_MILLI_SEC * 4 / 1000;
> > +	c0 *= mul * VLV_CZ_CLOCK_TO_MILLI_SEC;
> 
> Based on the above this would need to be fixed too.

Nvm the above, I realized now how it works:) I was confused seeing that
we scale by czclk freq and the 10ns freq the "opposite" time value.
Sorry for the noise.

> The above can be done as a follow-up if needed; this patch does what it
> says, so:
> Reviewed-by: Imre Deak <imre.deak@intel.com>
> 
> >  
> >  	return c0 >= time;
> >  }
> 
> 
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