linux-kernel - Re: [PATCH v3 3/3] thermal: create a helper __thermal_cdev

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Message-ID: <3d08d5cf-9e3b-ae26-cfd5-bf9a40d11643@linaro.org>
Date:   Thu, 22 Apr 2021 09:58:43 +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 v3 3/3] thermal: create a helper __thermal_cdev_update()
 without a lock

On 21/04/2021 19:41, Lukasz Luba wrote:
> There is a need to have a helper function which updates cooling device
> state from the governors code. With this change governor can use
> lock and unlock while calling helper function. This avoid unnecessary
> second time lock/unlock which was in previous solution present in
> governor implementation. This new helper function must be called
> with mutex 'cdev->lock' hold.
> 
> The changed been discussed and part of code presented in thread:
> https://lore.kernel.org/linux-pm/20210419084536.25000-1-lukasz.luba@arm.com/
> 
> Co-developed-by: Daniel Lezcano <daniel.lezcano@...aro.org>
> Signed-off-by: Daniel Lezcano <daniel.lezcano@...aro.org>
> Signed-off-by: Lukasz Luba <lukasz.luba@....com>
> ---
>  drivers/thermal/gov_power_allocator.c |  5 +----
>  drivers/thermal/thermal_core.h        |  1 +
>  drivers/thermal/thermal_helpers.c     | 28 +++++++++++++++++----------

Why not add this patch first (without the ipa changes) and then replace
patch 2 by using the new function ? That will prevent to go back and forth.


>  3 files changed, 20 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/thermal/gov_power_allocator.c b/drivers/thermal/gov_power_allocator.c
> index f379f1aaa3b5..a6cdb2e892da 100644
> --- a/drivers/thermal/gov_power_allocator.c
> +++ b/drivers/thermal/gov_power_allocator.c
> @@ -595,12 +595,9 @@ static void allow_maximum_power(struct thermal_zone_device *tz, bool update)
>  		cdev->ops->get_requested_power(cdev, &req_power);
>  
>  		if (update)
> -			instance->cdev->updated = false;
> +			__thermal_cdev_update(instance->cdev);
>  
>  		mutex_unlock(&instance->cdev->lock);
> -
> -		if (update)
> -			thermal_cdev_update(instance->cdev);
>  	}
>  	mutex_unlock(&tz->lock);
>  }
> diff --git a/drivers/thermal/thermal_core.h b/drivers/thermal/thermal_core.h
> index 86b8cef7310e..726e327b4205 100644
> --- a/drivers/thermal/thermal_core.h
> +++ b/drivers/thermal/thermal_core.h
> @@ -66,6 +66,7 @@ static inline bool cdev_is_power_actor(struct thermal_cooling_device *cdev)
>  }
>  
>  void thermal_cdev_update(struct thermal_cooling_device *);
> +void __thermal_cdev_update(struct thermal_cooling_device *cdev);
>  
>  /**
>   * struct thermal_trip - representation of a point in temperature domain
> diff --git a/drivers/thermal/thermal_helpers.c b/drivers/thermal/thermal_helpers.c
> index 7f50f412e02a..3d7fd46104de 100644
> --- a/drivers/thermal/thermal_helpers.c
> +++ b/drivers/thermal/thermal_helpers.c
> @@ -192,18 +192,12 @@ static void thermal_cdev_set_cur_state(struct thermal_cooling_device *cdev,
>  	thermal_cooling_device_stats_update(cdev, target);
>  }
>  
> -void thermal_cdev_update(struct thermal_cooling_device *cdev)
> +
> +void __thermal_cdev_update(struct thermal_cooling_device *cdev)
>  {
>  	struct thermal_instance *instance;
>  	unsigned long target = 0;
>  
> -	mutex_lock(&cdev->lock);
> -	/* cooling device is updated*/
> -	if (cdev->updated) {
> -		mutex_unlock(&cdev->lock);
> -		return;
> -	}
> -
>  	/* Make sure cdev enters the deepest cooling state */
>  	list_for_each_entry(instance, &cdev->thermal_instances, cdev_node) {
>  		dev_dbg(&cdev->device, "zone%d->target=%lu\n",
> @@ -216,11 +210,25 @@ void thermal_cdev_update(struct thermal_cooling_device *cdev)
>  
>  	thermal_cdev_set_cur_state(cdev, target);
>  
> -	cdev->updated = true;
> -	mutex_unlock(&cdev->lock);
>  	trace_cdev_update(cdev, target);
>  	dev_dbg(&cdev->device, "set to state %lu\n", target);
>  }
> +
> +/**
> + * thermal_cdev_update - update cooling device state if needed
> + * @cdev:	pointer to struct thermal_cooling_device
> + *
> + * Update the cooling device state if there is a need.
> + */
> +void thermal_cdev_update(struct thermal_cooling_device *cdev)
> +{
> +	mutex_lock(&cdev->lock);
> +	if (!cdev->updated) {
> +		__thermal_cdev_update(cdev);
> +		cdev->updated = true;
> +	}
> +	mutex_unlock(&cdev->lock);
> +}
>  EXPORT_SYMBOL(thermal_cdev_update);
>  
>  /**
> 


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