Re: [PATCH 3/4] drm/i915: Simplify vlv/chv rc6 residency calculation

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

On Thu, 2015-09-24 at 23:29 +0300, ville.syrjala@linux.intel.com wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> We have the czclk freqeuency in dev_priv now, so let's just use it
                   ^frequency
> when converting the rc6 counters to milliseconds. This elimiantes
                                                        ^eliminates
> a bunch of hairy code that essentially tries to extract the czclk
> frequency using yet another method.
> 
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

Reviewed-by: Imre Deak <imre.deak@intel.com>

> ---
>  drivers/gpu/drm/i915/i915_sysfs.c | 31 +++----------------------------
>  1 file changed, 3 insertions(+), 28 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_sysfs.c b/drivers/gpu/drm/i915/i915_sysfs.c
> index 55bd04c..74086eb 100644
> --- a/drivers/gpu/drm/i915/i915_sysfs.c
> +++ b/drivers/gpu/drm/i915/i915_sysfs.c
> @@ -39,7 +39,7 @@ static u32 calc_residency(struct drm_device *dev, const u32 reg)
>  {
>  	struct drm_i915_private *dev_priv = dev->dev_private;
>  	u64 raw_time; /* 32b value may overflow during fixed point math */
> -	u64 units = 128ULL, div = 100000ULL, bias = 100ULL;
> +	u64 units = 128ULL, div = 100000ULL;
>  	u32 ret;
>  
>  	if (!intel_enable_rc6(dev))
> @@ -49,41 +49,16 @@ static u32 calc_residency(struct drm_device *dev, const u32 reg)
>  
>  	/* On VLV and CHV, residency time is in CZ units rather than 1.28us */
>  	if (IS_VALLEYVIEW(dev)) {
> -		u32 clk_reg, czcount_30ns;
> -
> -		if (IS_CHERRYVIEW(dev))
> -			clk_reg = CHV_CLK_CTL1;
> -		else
> -			clk_reg = VLV_CLK_CTL2;
> -
> -		czcount_30ns = I915_READ(clk_reg) >> CLK_CTL2_CZCOUNT_30NS_SHIFT;
> -
> -		if (!czcount_30ns) {
> -			WARN(!czcount_30ns, "bogus CZ count value");
> -			ret = 0;
> -			goto out;
> -		}
> -
> -		if (IS_CHERRYVIEW(dev) && czcount_30ns == 1) {
> -			/* Special case for 320Mhz */
> -			div = 10000000ULL;
> -			units = 3125ULL;
> -		} else {
> -			czcount_30ns += 1;
> -			div = 1000000ULL;
> -			units = DIV_ROUND_UP_ULL(30ULL * bias, czcount_30ns);
> -		}
> +		units = 1;
> +		div = dev_priv->czclk_freq;
>  
>  		if (I915_READ(VLV_COUNTER_CONTROL) & VLV_COUNT_RANGE_HIGH)
>  			units <<= 8;
> -
> -		div = div * bias;
>  	}
>  
>  	raw_time = I915_READ(reg) * units;
>  	ret = DIV_ROUND_UP_ULL(raw_time, div);
>  
> -out:
>  	intel_runtime_pm_put(dev_priv);
>  	return ret;
>  }


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