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Subject: Re: [PATCH 07/11] PM / devfreq: check get_dev_status before start
 monitor
To:     Dong Aisheng <aisheng.dong@nxp.com>, linux-pm@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org
Cc:     dongas86@gmail.com, kernel@pengutronix.de, shawnguo@kernel.org,
        linux-imx@nxp.com, linux-kernel@vger.kernel.org,
        myungjoo.ham@samsung.com, kyungmin.park@samsung.com,
        cw00.choi@samsung.com, abel.vesa@nxp.com
References: <1615294733-22761-1-git-send-email-aisheng.dong@nxp.com>
 <1615294733-22761-8-git-send-email-aisheng.dong@nxp.com>
From:   Chanwoo Choi <cwchoi00@gmail.com>
Message-ID: <de25cd22-7f17-5902-21d3-881e3128dd31@gmail.com>
Date:   Wed, 10 Mar 2021 00:58:37 +0900
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On 21. 3. 9. 오후 9:58, Dong Aisheng wrote:
> The devfreq monitor depends on the device to provide load information
> by .get_dev_status() to calculate the next target freq.
> 
> And this will cause changing governor to simple ondemand fail
> if device can't support.
> 
> Signed-off-by: Dong Aisheng <aisheng.dong@nxp.com>
> ---
>   drivers/devfreq/devfreq.c                 | 10 +++++++---
>   drivers/devfreq/governor.h                |  2 +-
>   drivers/devfreq/governor_simpleondemand.c |  3 +--
>   3 files changed, 9 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> index 7231fe6862a2..d1787b6c7d7c 100644
> --- a/drivers/devfreq/devfreq.c
> +++ b/drivers/devfreq/devfreq.c
> @@ -482,10 +482,13 @@ static void devfreq_monitor(struct work_struct *work)
>    * to be called from governor in response to DEVFREQ_GOV_START
>    * event when device is added to devfreq framework.
>    */
> -void devfreq_monitor_start(struct devfreq *devfreq)
> +int devfreq_monitor_start(struct devfreq *devfreq)
>   {
>   	if (IS_SUPPORTED_FLAG(devfreq->governor->flags, IRQ_DRIVEN))
> -		return;
> +		return 0;
> +
> +	if (!devfreq->profile->get_dev_status)
> +		return -EINVAL;
>   
>   	switch (devfreq->profile->timer) {
>   	case DEVFREQ_TIMER_DEFERRABLE:
> @@ -495,12 +498,13 @@ void devfreq_monitor_start(struct devfreq *devfreq)
>   		INIT_DELAYED_WORK(&devfreq->work, devfreq_monitor);
>   		break;
>   	default:
> -		return;
> +		return -EINVAL;
>   	}
>   
>   	if (devfreq->profile->polling_ms)
>   		queue_delayed_work(devfreq_wq, &devfreq->work,
>   			msecs_to_jiffies(devfreq->profile->polling_ms));
> +	return 0;
>   }
>   EXPORT_SYMBOL(devfreq_monitor_start);
>   
> diff --git a/drivers/devfreq/governor.h b/drivers/devfreq/governor.h
> index 5cee3f64fe2b..31af6d072a10 100644
> --- a/drivers/devfreq/governor.h
> +++ b/drivers/devfreq/governor.h
> @@ -75,7 +75,7 @@ struct devfreq_governor {
>   				unsigned int event, void *data);
>   };
>   
> -void devfreq_monitor_start(struct devfreq *devfreq);
> +int devfreq_monitor_start(struct devfreq *devfreq);
>   void devfreq_monitor_stop(struct devfreq *devfreq);
>   void devfreq_monitor_suspend(struct devfreq *devfreq);
>   void devfreq_monitor_resume(struct devfreq *devfreq);
> diff --git a/drivers/devfreq/governor_simpleondemand.c b/drivers/devfreq/governor_simpleondemand.c
> index d57b82a2b570..ea287b57cbf3 100644
> --- a/drivers/devfreq/governor_simpleondemand.c
> +++ b/drivers/devfreq/governor_simpleondemand.c
> @@ -89,8 +89,7 @@ static int devfreq_simple_ondemand_handler(struct devfreq *devfreq,
>   {
>   	switch (event) {
>   	case DEVFREQ_GOV_START:
> -		devfreq_monitor_start(devfreq);
> -		break;
> +		return devfreq_monitor_start(devfreq);
>   
>   	case DEVFREQ_GOV_STOP:
>   		devfreq_monitor_stop(devfreq);
> 

Need to handle the all points of devfreq_monitor_start() usage.
please check the tegra30-devfreq.c for this update.

$ grep -rn "devfreq_monitor_start" drivers/
drivers/devfreq/governor_simpleondemand.c:92: 
devfreq_monitor_start(devfreq);
drivers/devfreq/tegra30-devfreq.c:744:		devfreq_monitor_start(devfreq);
......

-- 
Best Regards,
Samsung Electronics
Chanwoo Choi