Re: [PATCH] drm/i915: Kick the rps worker when changing the boost frequency

[Mika Kuoppala <mika.kuoppala@linux.intel.com>]

Chris Wilson <chris@chris-wilson.co.uk> writes:

> The boost frequency is only applied from the RPS worker while someone is
> waiting on a request and requested a boost. As such, when the user
> wishes to change the frequency, we have to kick the worker in order to
> re-evaluate whether to apply the boost frequency.
>
> Fixes: 29ecd78d3b79 ("drm/i915: Define a separate variable and control for RPS waitboost frequency")
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Mika Kuoppala <mika.kuoppala@intel.com>
> ---
>  drivers/gpu/drm/i915/i915_sysfs.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_sysfs.c b/drivers/gpu/drm/i915/i915_sysfs.c
> index b33d2158c234..d97463bb69ad 100644
> --- a/drivers/gpu/drm/i915/i915_sysfs.c
> +++ b/drivers/gpu/drm/i915/i915_sysfs.c
> @@ -304,8 +304,9 @@ static ssize_t gt_boost_freq_mhz_store(struct device *kdev,
>  {
>  	struct drm_i915_private *dev_priv = kdev_minor_to_i915(kdev);
>  	struct intel_rps *rps = &dev_priv->gt_pm.rps;
> -	u32 val;
> +	bool boost = false;
>  	ssize_t ret;
> +	u32 val;
>  
>  	ret = kstrtou32(buf, 0, &val);
>  	if (ret)
> @@ -317,8 +318,13 @@ static ssize_t gt_boost_freq_mhz_store(struct device *kdev,
>  		return -EINVAL;
>  
>  	mutex_lock(&dev_priv->pcu_lock);
> -	rps->boost_freq = val;
> +	if (val != rps->boost_freq) {
> +		rps->boost_freq = val;
> +		boost = true;
> +	}
>  	mutex_unlock(&dev_priv->pcu_lock);
> +	if (boost)
> +		schedule_work(&rps->work);
>

Can the rps work handler handle a situation
where the powers are off? It bails out if we dont
have iir nor boost, which might be enough of a
safeguard.

If it can, why not just kick the rps work
unconditionally?

Further, on all other freq store entries in sysfs
update val and schedule unconditionally?

Then the handler would be the single entry to
re-evaluation and setting the hardware.

-Mika

>  	return count;
>  }
> -- 
> 2.16.2
>
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