Re: [PATCH v2 1/4] devfreq: Register devfreq as a cooling device on demand

From: Chanwoo Choi <cwchoi00@gmail.com>
To: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: lukasz.luba@arm.com, linux-kernel@vger.kernel.org,
	linux-pm@vger.kernel.org, steven.price@arm.com,
	MyungJoo Ham <myungjoo.ham@samsung.com>,
	Kyungmin Park <kyungmin.park@samsung.com>,
	Chanwoo Choi <cw00.choi@samsung.com>
Subject: Re: [PATCH v2 1/4] devfreq: Register devfreq as a cooling device on demand
Date: Sat, 6 Mar 2021 09:39:20 +0900	[thread overview]
Message-ID: <7d51cdb7-e833-f267-1dca-e75a68b635ad@gmail.com> (raw)
In-Reply-To: <20210305170338.13647-1-daniel.lezcano@linaro.org>

Hi,

On 21. 3. 6. 오전 2:03, Daniel Lezcano wrote:
> Currently the default behavior is to manually having the devfreq
> backend to register themselves as a devfreq cooling device.
> 
> Instead of adding the code in the drivers for the thermal cooling
> device registering, let's provide a flag in the devfreq's profile to
> tell the common devfreq code to register the newly created devfreq as
> a cooling device.
> 
> Suggested-by: Chanwoo Choi <cwchoi00@gmail.com>
> Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
> ---
>   drivers/devfreq/devfreq.c | 11 +++++++++++
>   include/linux/devfreq.h   |  7 +++++++
>   2 files changed, 18 insertions(+)
> 
> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> index b6d63f02d293..5c0fdd3a48d2 100644
> --- a/drivers/devfreq/devfreq.c
> +++ b/drivers/devfreq/devfreq.c
> @@ -11,6 +11,7 @@
>   #include <linux/kmod.h>
>   #include <linux/sched.h>
>   #include <linux/debugfs.h>
> +#include <linux/devfreq_cooling.h>
>   #include <linux/errno.h>
>   #include <linux/err.h>
>   #include <linux/init.h>
> @@ -26,6 +27,7 @@
>   #include <linux/hrtimer.h>
>   #include <linux/of.h>
>   #include <linux/pm_qos.h>
> +#include <linux/thermal.h> >   #include <linux/units.h>

Acutally, current devfreq-next branch doesn't contain previous
your patch about units clean-up. So that when I applied it to next
branch, merge conflict happen because of '<linux/units.h>'.

Just send the patches again regardless of 'devfreq: Use HZ macros'.

>   #include "governor.h"
>   
> @@ -935,6 +937,13 @@ struct devfreq *devfreq_add_device(struct device *dev,
>   
>   	mutex_unlock(&devfreq_list_lock);
>   
> +	if (devfreq->profile->is_cooling_device) {
> +		devfreq->cdev = devfreq_cooling_em_register(devfreq, NULL);
> +		if (IS_ERR(devfreq->cdev))
> +			dev_info(dev, "Failed to register devfreq "
> +				 "cooling device\n");

Have to initialize devfreq->cdev by NULL when error happen.
Because of just returning from thermal_cooling_device_unregister
when cdev is not used.

> +	}
> +
>   	return devfreq;
>   
>   err_init:
> @@ -960,6 +969,8 @@ int devfreq_remove_device(struct devfreq *devfreq)
>   	if (!devfreq)
>   		return -EINVAL;
>   
> +	thermal_cooling_device_unregister(devfreq->cdev);
> +
>   	if (devfreq->governor) {
>   		devfreq->governor->event_handler(devfreq,
>   						 DEVFREQ_GOV_STOP, NULL);
> diff --git a/include/linux/devfreq.h b/include/linux/devfreq.h
> index 26ea0850be9b..554e7904b0c5 100644
> --- a/include/linux/devfreq.h
> +++ b/include/linux/devfreq.h
> @@ -98,11 +98,15 @@ struct devfreq_dev_status {
>    * @freq_table:		Optional list of frequencies to support statistics
>    *			and freq_table must be generated in ascending order.
>    * @max_state:		The size of freq_table.
> + *
> + * @is_cooling_device: A self-explanatory boolean giving the device a
> + *                     cooling effect property.
>    */
>   struct devfreq_dev_profile {
>   	unsigned long initial_freq;
>   	unsigned int polling_ms;
>   	enum devfreq_timer timer;
> +	bool is_cooling_device;
>   
>   	int (*target)(struct device *dev, unsigned long *freq, u32 flags);
>   	int (*get_dev_status)(struct device *dev,
> @@ -198,6 +202,9 @@ struct devfreq {
>   
>   	struct srcu_notifier_head transition_notifier_list;
>   
> +	/* Pointer to the cooling device if used for thermal mitigation */ > +	struct thermal_cooling_device *cdev;
> +
You need to the description of cdev instance to 'struct devfreq'.

>   	struct notifier_block nb_min;
>   	struct notifier_block nb_max;
>   };
> 

-- 
Best Regards,
Samsung Electronics
Chanwoo Choi