[Intel-gfx] [PATCH 3/6] drm/i915: Extend vlv/chv residency resolution

[Chris Wilson]

On Wed, Mar 15, 2017 at 05:43:01PM +0200, Mika Kuoppala wrote:
> Vlv and chv residency counters are 40 bits in width.
> With a control bit, we can choose between upper or lower
> 32 bit window into this counter.
> 
> Lets toggle this bit on and off on and read both parts.
> As a result we can push the wrap from 13 seconds to 54
> minutes.
> 
> v2: commit msg, loop readability, goto elimination (Chris)
> 
> Reported-by: Len Brown <len.brown at intel.com>

References: https://bugs.freedesktop.org/show_bug.cgi?id=94852

> Cc: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
> Signed-off-by: Mika Kuoppala <mika.kuoppala at intel.com>
> ---
>  u64 intel_rc6_residency_us(struct drm_i915_private *dev_priv,
>  			   const i915_reg_t reg)
>  {
> -	u64 raw_time; /* 32b value may overflow during fixed point math */
> -	u64 units = 128000ULL, div = 100000ULL;
> -	u64 ret;
> +	u64 time_hw, units, div, residency_us;
>  
>  	if (!intel_enable_rc6())
>  		return 0;
> @@ -8367,16 +8406,21 @@ u64 intel_rc6_residency_us(struct drm_i915_private *dev_priv,
>  		units = 1000;
>  		div = dev_priv->czclk_freq;
>  
> -		if (I915_READ(VLV_COUNTER_CONTROL) & VLV_COUNT_RANGE_HIGH)
> -			units <<= 8;
> +		time_hw = vlv_residency_raw(dev_priv, reg);
>  	} else if (IS_GEN9_LP(dev_priv)) {
>  		units = 1000;
>  		div = 1200;		/* 833.33ns */
> +
> +		time_hw = I915_READ(reg);
> +	} else {
> +		units = 128000; /* 1.28us */
> +		div = 100000;
> +
> +		time_hw = I915_READ(reg);
>  	}
>  
> -	raw_time = I915_READ(reg) * units;
> -	ret = DIV_ROUND_UP_ULL(raw_time, div);
> +	residency_us = DIV_ROUND_UP_ULL(time_hw * units, div);

This calc doesn't need to be inside the rpm, so just
>  
>  	intel_runtime_pm_put(dev_priv);
> -	return ret;
> +	return residency_us;

	return DIV_ROUND_UP_ULL(time_hw * units, div);

Either way,
Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre