Re: [PATCH] drm/i915: Mask PM/RPS interrupt generation based on activity

[Deepak S <deepak.s@linux.intel.com>]

On Friday 28 March 2014 01:33 PM, Chris Wilson wrote:
> The speculation is that we can conserve more power by masking off
> the interrupts at source (PMINTRMSK) rather than filtering them by the
> up/down thresholds (RPINTLIM). We can select which events we know will
> be active based on the current frequency versus our imposed range, i.e.
> if at minimum, we know we will not want to generate any more
> down-interrupts and vice versa.
>
> v2: We only need the TIMEOUT when above min frequency.
> v3: Tweak VLV at the same time
>
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Deepak S <deepak.s@linux.intel.com>
> ---
> I see your point that I cannot remove PMINTRMSK from enable_interrupts
> without tweaking VLV at the same time. I did consider making this 4
> patches (factor out gen6_rps_pm_mask, tweak gen6+, tweak, vlv, remove it
> from enable_interrupts) but decided that was just being silly and
> squashed the two patches together instead.
> ---
>   drivers/gpu/drm/i915/intel_pm.c | 41 +++++++++++++++++++++++++----------------
>   1 file changed, 25 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index 154aa07d51a7..35a7b5b65883 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -3006,6 +3006,24 @@ static void gen6_set_rps_thresholds(struct drm_i915_private *dev_priv, u8 val)
>   	dev_priv->rps.last_adj = 0;
>   }
>   
> +static u32 gen6_rps_pm_mask(struct drm_i915_private *dev_priv, u8 val)
> +{
> +	u32 mask = 0;
> +
> +	if (val > dev_priv->rps.min_freq_softlimit)
> +		mask |= GEN6_PM_RP_DOWN_THRESHOLD | GEN6_PM_RP_DOWN_TIMEOUT;
> +	if (val < dev_priv->rps.max_freq_softlimit)
> +		mask |= GEN6_PM_RP_UP_THRESHOLD;
> +
> +	/* IVB and SNB hard hangs on looping batchbuffer
> +	 * if GEN6_PM_UP_EI_EXPIRED is masked.
> +	 */
> +	if (INTEL_INFO(dev_priv->dev)->gen <= 7 && !IS_HASWELL(dev_priv->dev))
> +		mask |= GEN6_PM_RP_UP_EI_EXPIRED;
> +
> +	return ~mask;
> +}
> +
>   /* gen6_set_rps is called to update the frequency request, but should also be
>    * called when the range (min_delay and max_delay) is modified so that we can
>    * update the GEN6_RP_INTERRUPT_LIMITS register accordingly. */
> @@ -3037,6 +3055,7 @@ void gen6_set_rps(struct drm_device *dev, u8 val)
>   	 * until we hit the minimum or maximum frequencies.
>   	 */
>   	I915_WRITE(GEN6_RP_INTERRUPT_LIMITS, gen6_rps_limits(dev_priv, val));
> +	I915_WRITE(GEN6_PMINTRMSK, gen6_rps_pm_mask(dev_priv, val));
>   
>   	POSTING_READ(GEN6_RPNSWREQ);
>   
> @@ -3089,6 +3108,9 @@ static void vlv_set_rps_idle(struct drm_i915_private *dev_priv)
>   	I915_WRITE(VLV_GTLC_SURVIVABILITY_REG,
>   		I915_READ(VLV_GTLC_SURVIVABILITY_REG) &
>   				~VLV_GFX_CLK_FORCE_ON_BIT);
> +
> +	I915_WRITE(GEN6_PMINTRMSK,
> +		   gen6_rps_pm_mask(dev_priv, dev_priv->rps.cur_freq));
>   }
>   
>   void gen6_rps_idle(struct drm_i915_private *dev_priv)
> @@ -3134,13 +3156,12 @@ void valleyview_set_rps(struct drm_device *dev, u8 val)
>   			 dev_priv->rps.cur_freq,
>   			 vlv_gpu_freq(dev_priv, val), val);
>   
> -	if (val == dev_priv->rps.cur_freq)
> -		return;
> +	if (val != dev_priv->rps.cur_freq)
> +		vlv_punit_write(dev_priv, PUNIT_REG_GPU_FREQ_REQ, val);
>   
> -	vlv_punit_write(dev_priv, PUNIT_REG_GPU_FREQ_REQ, val);
> +	I915_WRITE(GEN6_PMINTRMSK, val);
>   
>   	dev_priv->rps.cur_freq = val;
> -
>   	trace_intel_gpu_freq_change(vlv_gpu_freq(dev_priv, val));
>   }
>   
> @@ -3220,24 +3241,12 @@ int intel_enable_rc6(const struct drm_device *dev)
>   static void gen6_enable_rps_interrupts(struct drm_device *dev)
>   {
>   	struct drm_i915_private *dev_priv = dev->dev_private;
> -	u32 enabled_intrs;
>   
>   	spin_lock_irq(&dev_priv->irq_lock);
>   	WARN_ON(dev_priv->rps.pm_iir);
>   	snb_enable_pm_irq(dev_priv, dev_priv->pm_rps_events);
>   	I915_WRITE(GEN6_PMIIR, dev_priv->pm_rps_events);
>   	spin_unlock_irq(&dev_priv->irq_lock);
> -
> -	/* only unmask PM interrupts we need. Mask all others. */
> -	enabled_intrs = dev_priv->pm_rps_events;
> -
> -	/* IVB and SNB hard hangs on looping batchbuffer
> -	 * if GEN6_PM_UP_EI_EXPIRED is masked.
> -	 */
> -	if (INTEL_INFO(dev)->gen <= 7 && !IS_HASWELL(dev))
> -		enabled_intrs |= GEN6_PM_RP_UP_EI_EXPIRED;
> -
> -	I915_WRITE(GEN6_PMINTRMSK, ~enabled_intrs);
>   }
>   
>   static void gen8_enable_rps(struct drm_device *dev)

Reviewed-by:Deepak S <deepak.s@linux.intel.com>