Re: [PATCH] drm/i915: make sure GPU freq drops to minimum after entering RC6

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Fri, Apr 19, 2013 at 10:22:45AM -0700, Jesse Barnes wrote:
> On VLV, the Punit doesn't automatically drop the GPU to it's minimum
> voltage level when entering RC6, so we arm a timer to do it for us from
> the RPS interrupt handler.  It'll generally only fire when we go idle
> (or if for some reason there's a long delay between RPS interrupts), but
> won't be re-armed again until the next RPS event, so shouldn't affect
> power consumption after we go idle and it triggers.
> 
> Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
> ---
>  drivers/gpu/drm/i915/i915_drv.h |    4 ++++
>  drivers/gpu/drm/i915/i915_irq.c |   11 +++++++++++
>  drivers/gpu/drm/i915/intel_pm.c |   32 ++++++++++++++++++++++++++++++++
>  3 files changed, 47 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 2557fc7..2900dd4 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -660,6 +660,7 @@ struct i915_suspend_saved_registers {
>  
>  struct intel_gen6_power_mgmt {
>  	struct work_struct work;
> +	struct work_struct vlv_work;
>  	u32 pm_iir;
>  	/* lock - irqsave spinlock that protectects the work_struct and
>  	 * pm_iir. */
> @@ -670,6 +671,7 @@ struct intel_gen6_power_mgmt {
>  	u8 cur_delay;
>  	u8 min_delay;
>  	u8 max_delay;
> +	u8 rpe_delay;
>  	u8 hw_max;
>  
>  	struct delayed_work delayed_resume_work;
> @@ -945,6 +947,8 @@ typedef struct drm_i915_private {
>  	} hpd_stats[HPD_NUM_PINS];
>  	struct timer_list hotplug_reenable_timer;
>  
> +	struct timer_list vlv_rps_timer;
> +
>  	int num_pch_pll;
>  	int num_plane;
>  
> diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
> index 932e7f8..99b2e1c 100644
> --- a/drivers/gpu/drm/i915/i915_irq.c
> +++ b/drivers/gpu/drm/i915/i915_irq.c
> @@ -488,6 +488,17 @@ static void gen6_pm_rps_work(struct work_struct *work)
>  			gen6_set_rps(dev_priv->dev, new_delay);
>  	}
>  
> +	if (IS_VALLEYVIEW(dev_priv->dev)) {
> +		/*
> +		 * On VLV, when we enter RC6 we may not be at the minimum
> +		 * voltage level, so arm a timer to check.  It should only
> +		 * fire when there's activity or once after we've entered
> +		 * RC6, and then won't be re-armed until the next RPS interrupt.
> +		 */
> +		mod_timer(&dev_priv->vlv_rps_timer, jiffies +
> +			  msecs_to_jiffies(100));
> +	}
> +
>  	mutex_unlock(&dev_priv->rps.hw_lock);
>  }
>  
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index 2557926..c1311c9 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -2545,6 +2545,9 @@ static void gen6_disable_rps(struct drm_device *dev)
>  	spin_unlock_irq(&dev_priv->rps.lock);
>  
>  	I915_WRITE(GEN6_PMIIR, I915_READ(GEN6_PMIIR));
> +
> +	if (IS_VALLEYVIEW(dev))
> +		del_timer_sync(&dev_priv->vlv_rps_timer);
>  }
>  
>  int intel_enable_rc6(const struct drm_device *dev)
> @@ -2822,6 +2825,30 @@ int valleyview_rps_min_freq(struct drm_i915_private *dev_priv)
>  	return val & 0xff;
>  }
>  
> +static void vlv_rps_timer_work(struct work_struct *work)
> +{
> +	drm_i915_private_t *dev_priv = container_of(work, drm_i915_private_t,
> +						    rps.vlv_work);
> +
> +	/*
> +	 * Timer fired, we must be idle.  Drop to min voltage state.
> +	 * Note: we use RPe here since it should match the
> +	 * Vmin we were shooting for.  That should give us better
> +	 * perf when we come back out of RC6 than if we used the
> +	 * min freq available.
> +	 */
> +	mutex_lock(&dev_priv->rps.hw_lock);
> +	valleyview_set_rps(dev_priv->dev, dev_priv->rps.rpe_delay);
> +	mutex_unlock(&dev_priv->rps.hw_lock);
> +}
> +
> +static void valleyview_rps_timer_func(unsigned long data)
> +{
> +	struct drm_i915_private *dev_priv = (struct drm_i915_private *)data;
> +
> +	queue_work(dev_priv->wq, &dev_priv->rps.vlv_work);
> +}

This looks somewhat like open coded delayed work to me. Would the
standard delayed work be OK for this, or was there some specific reason
you did it this way?

> +
>  static void valleyview_enable_rps(struct drm_device *dev)
>  {
>  	struct drm_i915_private *dev_priv = dev->dev_private;
> @@ -2886,6 +2913,7 @@ static void valleyview_enable_rps(struct drm_device *dev)
>  	rpe = valleyview_rps_rpe_freq(dev_priv);
>  	DRM_DEBUG_DRIVER("RPe GPU freq: %d\n",
>  			 vlv_gpu_freq(dev_priv->mem_freq, rpe));
> +	dev_priv->rps.rpe_delay = rpe;
>  
>  	val = valleyview_rps_min_freq(dev_priv);
>  	DRM_DEBUG_DRIVER("min GPU freq: %d\n", vlv_gpu_freq(dev_priv->mem_freq,
> @@ -2895,6 +2923,10 @@ static void valleyview_enable_rps(struct drm_device *dev)
>  	DRM_DEBUG_DRIVER("setting GPU freq to %d\n",
>  			 vlv_gpu_freq(dev_priv->mem_freq, rpe));
>  
> +	INIT_WORK(&dev_priv->rps.vlv_work, vlv_rps_timer_work);
> +	setup_timer(&dev_priv->vlv_rps_timer, valleyview_rps_timer_func,
> +		    (unsigned long)dev_priv);
> +
>  	valleyview_set_rps(dev_priv->dev, rpe);
>  
>  	/* requires MSI enabled */
> -- 
> 1.7.10.4
> 
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-- 
Ville Syrjälä
Intel OTC