linux-kernel - Re: [PATCH 1/2] thermal: power_allocator: maintain the device statistics from going stale

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Date:   Fri, 2 Apr 2021 17:54:26 +0200
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     Lukasz Luba <lukasz.luba@....com>, linux-kernel@...r.kernel.org
Cc:     linux-pm@...r.kernel.org, amitk@...nel.org, rui.zhang@...el.com
Subject: Re: [PATCH 1/2] thermal: power_allocator: maintain the device
 statistics from going stale

On 31/03/2021 18:33, Lukasz Luba wrote:
> When the temperature is below the first activation trip point the cooling
> devices are not checked, so they cannot maintain fresh statistics. It
> leads into the situation, when temperature crosses first trip point, the
> statistics are stale and show state for very long period. 

Can you elaborate the statistics you are referring to ?

I can understand the pid controller needs temperature but I don't
understand the statistics with the cooling device.


> This has impact
> on IPA algorithm calculation and wrong decisions. Thus, check the cooling
> devices even when the temperature is low, to refresh these statistics.
> 
> Signed-off-by: Lukasz Luba <lukasz.luba@....com>
> ---
>  drivers/thermal/gov_power_allocator.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/drivers/thermal/gov_power_allocator.c b/drivers/thermal/gov_power_allocator.c
> index 2802a0e13c88..0cbd10cab193 100644
> --- a/drivers/thermal/gov_power_allocator.c
> +++ b/drivers/thermal/gov_power_allocator.c
> @@ -575,15 +575,27 @@ static void allow_maximum_power(struct thermal_zone_device *tz)
>  {
>  	struct thermal_instance *instance;
>  	struct power_allocator_params *params = tz->governor_data;
> +	u32 req_power;
>  
>  	mutex_lock(&tz->lock);
>  	list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
> +		struct thermal_cooling_device *cdev = instance->cdev;
> +
>  		if ((instance->trip != params->trip_max_desired_temperature) ||
>  		    (!cdev_is_power_actor(instance->cdev)))
>  			continue;
>  
>  		instance->target = 0;
>  		mutex_lock(&instance->cdev->lock);
> +		/*
> +		 * Call for updating the cooling devices local stats and avoid
> +		 * periods of dozen of seconds when those have not been
> +		 * maintained. The long period would come into the first check
> +		 * when lower threshold is crossed. Thus, limit it to single
> +		 * one longer polling period.
> +		 */
> +		cdev->ops->get_requested_power(cdev, &req_power);
> +
>  		instance->cdev->updated = false;
>  		mutex_unlock(&instance->cdev->lock);
>  		thermal_cdev_update(instance->cdev);
> 


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