Re: [RFC][PATCH 2/2] drm/i915: Jump to at least RPe on VLV when increasing the GPU frequency

[Jesse Barnes <jbarnes@virtuousgeek.org>]

On Tue, 25 Jun 2013 21:38:11 +0300
ville.syrjala@linux.intel.com wrote:

> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> If the current GPU frquency is below RPe, and we're asked to increase
> it, just go directly to RPe. This should provide better performance
> faster than letting the frequency trickle up in response to the up
> threshold interrupts.
> 
> For now just do it for VLV, since that matches quite closely how VLV
> used to operate when the rps delayed timer kept things at RPe always.
> 
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
>  drivers/gpu/drm/i915/i915_irq.c | 12 ++++++++++--
>  1 file changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
> index 62f8b2d..d6bd0d7 100644
> --- a/drivers/gpu/drm/i915/i915_irq.c
> +++ b/drivers/gpu/drm/i915/i915_irq.c
> @@ -699,9 +699,17 @@ static void gen6_pm_rps_work(struct work_struct *work)
>  
>  	mutex_lock(&dev_priv->rps.hw_lock);
>  
> -	if (pm_iir & GEN6_PM_RP_UP_THRESHOLD)
> +	if (pm_iir & GEN6_PM_RP_UP_THRESHOLD) {
>  		new_delay = dev_priv->rps.cur_delay + 1;
> -	else
> +
> +		/*
> +		 * For better performance, jump directly
> +		 * to RPe if we're below it.
> +		 */
> +		if (IS_VALLEYVIEW(dev_priv->dev) &&
> +		    dev_priv->rps.cur_delay < dev_priv->rps.rpe_delay)
> +			new_delay = dev_priv->rps.rpe_delay;
> +	} else
>  		new_delay = dev_priv->rps.cur_delay - 1;
>  
>  	/* sysfs frequency interfaces may have snuck in while servicing the

Yeah, seems reasonable.  Going to RP1 on other platforms might be a
good approximation of this.

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

-- 
Jesse Barnes, Intel Open Source Technology Center
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