[Intel-gfx] [PATCH 2/10] drm/i915: Initialize DRRS delayed work

[Chris Wilson]

On Sat, Jan 10, 2015 at 02:25:57AM +0530, Vandana Kannan wrote:
> Add DRRS work function to trigger a switch to low refresh rate when activity
> is detected on screen.

Where is this function used? How can I judge that it does the right
thing?

> Signed-off-by: Vandana Kannan <vandana.kannan at intel.com>
> ---
>  drivers/gpu/drm/i915/intel_dp.c | 36 ++++++++++++++++++++++++++++--------
>  1 file changed, 28 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 778dcd0..30b3aa1 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -4814,20 +4814,38 @@ static void intel_dp_set_drrs_state(struct drm_device *dev, int refresh_rate)
>  		I915_WRITE(reg, val);
>  	}
>  
> +	dev_priv->drrs.refresh_rate_type = index;
> +
> +	DRM_DEBUG_KMS("eDP Refresh Rate set to : %dHz\n", refresh_rate);
> +}
> +
> +static void intel_edp_drrs_work(struct work_struct *work)

intel_edp_drrs_downclock_work() would be more self-descriptive

> +{
> +	struct drm_i915_private *dev_priv =
> +		container_of(work, typeof(*dev_priv), drrs.work.work);
> +	struct intel_dp *intel_dp = dev_priv->drrs.dp;
> +
> +	mutex_lock(&dev_priv->drrs.mutex);
> +
> +	if (!intel_dp)
> +		goto unlock;

Does dev_priv->drrs.mutex not also protect dev_priv->drrs.dp?

> +
>  	/*
> -	 * mutex taken to ensure that there is no race between differnt
> -	 * drrs calls trying to update refresh rate. This scenario may occur
> -	 * in future when idleness detection based DRRS in kernel and
> -	 * possible calls from user space to set differnt RR are made.
> +	 * The delayed work can race with an invalidate hence we need to
> +	 * recheck.
>  	 */

This comment no longer applies to all the other callers of
intel_dp_set_drrs_state()? Or did you miss adding the
lockdep_assert_held(&dev_priv->drrs.mutex)?

> -	mutex_lock(&dev_priv->drrs.mutex);
> +	if (dev_priv->drrs.busy_frontbuffer_bits)
> +		goto unlock;
>  
> -	dev_priv->drrs.refresh_rate_type = index;
> +	if (dev_priv->drrs.refresh_rate_type != DRRS_LOW_RR)
> +		intel_dp_set_drrs_state(dev_priv->dev,

Would it not be sensible for intel_dp_set_drrs_state() check for the
no-op itself?

> +			intel_dp->attached_connector->panel.
> +			downclock_mode->vrefresh);
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre