Re: [PATCH] drm/i915: Avoid tweaking RPS before it is enabled

[Jesse Barnes <jbarnes@virtuousgeek.org>]

On Thu, 10 Oct 2013 21:58:50 +0100
Chris Wilson <chris@chris-wilson.co.uk> wrote:

> As we delay the initial RPS enabling (upon boot and after resume), there
> is a chance that we may start to render and trigger RPS boosts before we
> set up the punit. Any changes we make could result in inconsistent
> hardware state, with a danger of causing undefined behaviour. However,
> as the boosting is a optional tweak to RPS, we can simply ignore it
> whilst RPS is not yet enabled.
> 
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
> Cc: Jesse Barnes <jbarnes@virtuousgeek.org>
> ---
>  drivers/gpu/drm/i915/i915_drv.h |    1 +
>  drivers/gpu/drm/i915/intel_pm.c |   26 ++++++++++++++++----------
>  2 files changed, 17 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 640bff2..e0152e7 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -874,6 +874,7 @@ struct intel_gen6_power_mgmt {
>  	int last_adj;
>  	enum { LOW_POWER, BETWEEN, HIGH_POWER } power;
>  
> +	bool enabled;
>  	struct delayed_work delayed_resume_work;
>  
>  	/*
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index 6ffeb04..8070a07 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -3435,22 +3435,26 @@ void gen6_set_rps(struct drm_device *dev, u8 val)
>  void gen6_rps_idle(struct drm_i915_private *dev_priv)
>  {
>  	mutex_lock(&dev_priv->rps.hw_lock);
> -	if (dev_priv->info->is_valleyview)
> -		valleyview_set_rps(dev_priv->dev, dev_priv->rps.min_delay);
> -	else
> -		gen6_set_rps(dev_priv->dev, dev_priv->rps.min_delay);
> -	dev_priv->rps.last_adj = 0;
> +	if (dev_priv->rps.enabled) {
> +		if (dev_priv->info->is_valleyview)
> +			valleyview_set_rps(dev_priv->dev, dev_priv->rps.min_delay);
> +		else
> +			gen6_set_rps(dev_priv->dev, dev_priv->rps.min_delay);
> +		dev_priv->rps.last_adj = 0;
> +	}
>  	mutex_unlock(&dev_priv->rps.hw_lock);
>  }
>  
>  void gen6_rps_boost(struct drm_i915_private *dev_priv)
>  {
>  	mutex_lock(&dev_priv->rps.hw_lock);
> -	if (dev_priv->info->is_valleyview)
> -		valleyview_set_rps(dev_priv->dev, dev_priv->rps.max_delay);
> -	else
> -		gen6_set_rps(dev_priv->dev, dev_priv->rps.max_delay);
> -	dev_priv->rps.last_adj = 0;
> +	if (dev_priv->rps.enabled) {
> +		if (dev_priv->info->is_valleyview)
> +			valleyview_set_rps(dev_priv->dev, dev_priv->rps.max_delay);
> +		else
> +			gen6_set_rps(dev_priv->dev, dev_priv->rps.max_delay);
> +		dev_priv->rps.last_adj = 0;
> +	}
>  	mutex_unlock(&dev_priv->rps.hw_lock);
>  }
>  
> @@ -4657,6 +4661,7 @@ void intel_disable_gt_powersave(struct drm_device *dev)
>  			valleyview_disable_rps(dev);
>  		else
>  			gen6_disable_rps(dev);
> +		dev_priv->rps.enabled = false;
>  		mutex_unlock(&dev_priv->rps.hw_lock);
>  	}
>  }
> @@ -4676,6 +4681,7 @@ static void intel_gen6_powersave_work(struct work_struct *work)
>  		gen6_enable_rps(dev);
>  		gen6_update_ring_freq(dev);
>  	}
> +	dev_priv->rps.enabled = true;
>  	mutex_unlock(&dev_priv->rps.hw_lock);
>  }
>  

Yeah looks good.  Probably better than doing a sync on the delayed work
too, since that'll take over 1s.

Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>

-- 
Jesse Barnes, Intel Open Source Technology Center