linux-kernel - Re: [PATCH v9 16/19] PM / devfreq: Add new interrupt

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Message-ID: <e6308af7-97c8-3d1d-5072-a8ec3c478e6e@samsung.com>
Date:   Tue, 5 Nov 2019 13:01:50 +0900
From:   Chanwoo Choi <cw00.choi@...sung.com>
To:     Dmitry Osipenko <digetx@...il.com>,
        Thierry Reding <thierry.reding@...il.com>,
        MyungJoo Ham <myungjoo.ham@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Tomeu Vizoso <tomeu.vizoso@...labora.com>,
        Peter Geis <pgwipeout@...il.com>,
        Michał Mirosław <mirq-linux@...e.qmqm.pl>
Cc:     linux-pm@...r.kernel.org, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v9 16/19] PM / devfreq: Add new interrupt_driven flag
 for governors

Hi Dmitry,

On 19. 11. 5. 오전 6:56, Dmitry Osipenko wrote:
> Currently interrupt-driven governors (like NVIDIA Tegra30 ACTMON governor)
> are used to set polling_ms=0 in order to avoid periodic polling of device
> status by devfreq core. This means that polling interval can't be changed
> by userspace for such governors.
> 
> The new governor flag allows interrupt-driven governors to convey that
> devfreq core shouldn't perform polling of device status and thus generic
> devfreq polling interval could be supported by these governors now.
> 
> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
> ---
>  drivers/devfreq/devfreq.c  | 17 +++++++++++++++++
>  drivers/devfreq/governor.h |  3 +++
>  2 files changed, 20 insertions(+)
> 
> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> index b905963cea7d..4eff37e8bb07 100644
> --- a/drivers/devfreq/devfreq.c
> +++ b/drivers/devfreq/devfreq.c
> @@ -409,6 +409,9 @@ static void devfreq_monitor(struct work_struct *work)
>   */
>  void devfreq_monitor_start(struct devfreq *devfreq)
>  {
> +	if (devfreq->governor->interrupt_driven)
> +		return;
> +
>  	INIT_DEFERRABLE_WORK(&devfreq->work, devfreq_monitor);
>  	if (devfreq->profile->polling_ms)
>  		queue_delayed_work(devfreq_wq, &devfreq->work,
> @@ -426,6 +429,9 @@ EXPORT_SYMBOL(devfreq_monitor_start);
>   */
>  void devfreq_monitor_stop(struct devfreq *devfreq)
>  {
> +	if (devfreq->governor->interrupt_driven)
> +		return;
> +
>  	cancel_delayed_work_sync(&devfreq->work);
>  }
>  EXPORT_SYMBOL(devfreq_monitor_stop);
> @@ -453,6 +459,10 @@ void devfreq_monitor_suspend(struct devfreq *devfreq)
>  	devfreq_update_status(devfreq, devfreq->previous_freq);
>  	devfreq->stop_polling = true;
>  	mutex_unlock(&devfreq->lock);
> +
> +	if (devfreq->governor->interrupt_driven)
> +		return;
> +
>  	cancel_delayed_work_sync(&devfreq->work);
>  }
>  EXPORT_SYMBOL(devfreq_monitor_suspend);
> @@ -473,11 +483,15 @@ void devfreq_monitor_resume(struct devfreq *devfreq)
>  	if (!devfreq->stop_polling)
>  		goto out;
>  
> +	if (devfreq->governor->interrupt_driven)
> +		goto out_update;
> +
>  	if (!delayed_work_pending(&devfreq->work) &&
>  			devfreq->profile->polling_ms)
>  		queue_delayed_work(devfreq_wq, &devfreq->work,
>  			msecs_to_jiffies(devfreq->profile->polling_ms));
>  
> +out_update:
>  	devfreq->last_stat_updated = jiffies;
>  	devfreq->stop_polling = false;
>  
> @@ -509,6 +523,9 @@ void devfreq_interval_update(struct devfreq *devfreq, unsigned int *delay)
>  	if (devfreq->stop_polling)
>  		goto out;
>  
> +	if (devfreq->governor->interrupt_driven)
> +		goto out;
> +
>  	/* if new delay is zero, stop polling */
>  	if (!new_delay) {
>  		mutex_unlock(&devfreq->lock);
> diff --git a/drivers/devfreq/governor.h b/drivers/devfreq/governor.h
> index bbe5ff9fcecf..dc7533ccc3db 100644
> --- a/drivers/devfreq/governor.h
> +++ b/drivers/devfreq/governor.h
> @@ -31,6 +31,8 @@
>   * @name:		Governor's name
>   * @immutable:		Immutable flag for governor. If the value is 1,
>   *			this govenror is never changeable to other governor.
> + * @interrupt_driven:	Devfreq core won't schedule polling work for this
> + *			governor if value is set to 1.
>   * @get_target_freq:	Returns desired operating frequency for the device.
>   *			Basically, get_target_freq will run
>   *			devfreq_dev_profile.get_dev_status() to get the
> @@ -49,6 +51,7 @@ struct devfreq_governor {
>  
>  	const char name[DEVFREQ_NAME_LEN];
>  	const unsigned int immutable;
> +	const unsigned int interrupt_driven;
>  	int (*get_target_freq)(struct devfreq *this, unsigned long *freq);
>  	int (*event_handler)(struct devfreq *devfreq,
>  				unsigned int event, void *data);
> 

Reviewed-by: Chanwoo Choi <cw00.choi@...sung.com>

-- 
Best Regards,
Chanwoo Choi
Samsung Electronics