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Date:   Tue, 04 Dec 2018 14:36:11 +0900
From:   Chanwoo Choi <cw00.choi@samsung.com>
Organization: Samsung Electronics
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To:     Lukasz Luba <l.luba@partner.samsung.com>,
        linux-arm-kernel@lists.infradead.org,
        linux-samsung-soc@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-pm@vger.kernel.org, devicetree@vger.kernel.org
Cc:     tjakobi@math.uni-bielefeld.de, myungjoo.ham@samsung.com,
        kyungmin.park@samsung.com, rjw@rjwysocki.net, len.brown@intel.com,
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        anton@enomsg.org, ccross@android.com, tony.luck@intel.com,
        robh+dt@kernel.org, mark.rutland@arm.com, kgene@kernel.org,
        krzk@kernel.org, m.szyprowski@samsung.com, b.zolnierkie@samsung.com
Subject: Re: [PATCH v2 2/5] devfreq: add support for suspend/resume of a
 devfreq device
In-reply-to: <1543847475-7600-3-git-send-email-l.luba@partner.samsung.com>
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        <CGME20181203143131eucas1p217f22ac6d19682a54a57658a06980914@eucas1p2.samsung.com>
        <1543847475-7600-3-git-send-email-l.luba@partner.samsung.com>
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Hi Lukasz,

Looks good to me. But, I add the some comments.
If you will fix it, feel free to add my tag:
Reviewed-by: Chanwoo choi <cw00.choi@samsung.com>

On 2018년 12월 03일 23:31, Lukasz Luba wrote:
> The patch prepares devfreq device for handling suspend/resume
> functionality.  The new fields will store needed information during this

nitpick. Remove unneeded space. There are two spaces between '.' and 'The new'. 

> process.  Devfreq framework handles opp-suspend DT entry and there is no

ditto.

> need of modyfications in the drivers code.  It uses atomic variables to

ditto.

> make sure no race condition affects the process.
> 
> The patch is based on earlier work by Tobias Jakobi.

Please remove it from each patch description.

> 
> Suggested-by: Tobias Jakobi <tjakobi@math.uni-bielefeld.de>
> Suggested-by: Chanwoo Choi <cw00.choi@samsung.com>
> Signed-off-by: Lukasz Luba <l.luba@partner.samsung.com>
> ---
>  drivers/devfreq/devfreq.c | 51 +++++++++++++++++++++++++++++++++++++++--------
>  include/linux/devfreq.h   |  7 +++++++
>  2 files changed, 50 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> index a9fd61b..36bed24 100644
> --- a/drivers/devfreq/devfreq.c
> +++ b/drivers/devfreq/devfreq.c
> @@ -316,6 +316,10 @@ static int devfreq_set_target(struct devfreq *devfreq, unsigned long new_freq,
>  			"Couldn't update frequency transition information.\n");
>  
>  	devfreq->previous_freq = new_freq;
> +
> +	if (devfreq->suspend_freq)
> +		devfreq->resume_freq = cur_freq;
> +
>  	return err;
>  }
>  
> @@ -667,6 +671,9 @@ struct devfreq *devfreq_add_device(struct device *dev,
>  	}
>  	devfreq->max_freq = devfreq->scaling_max_freq;
>  
> +	devfreq->suspend_freq = dev_pm_opp_get_suspend_opp_freq(dev);
> +	atomic_set(&devfreq->suspend_count, 0);
> +
>  	dev_set_name(&devfreq->dev, "devfreq%d",
>  				atomic_inc_return(&devfreq_no));
>  	err = device_register(&devfreq->dev);
> @@ -867,14 +874,28 @@ EXPORT_SYMBOL(devm_devfreq_remove_device);
>   */
>  int devfreq_suspend_device(struct devfreq *devfreq)
>  {
> +	int ret;
> +
>  	if (!devfreq)
>  		return -EINVAL;
>  
> -	if (!devfreq->governor)
> -		return 0;
> +	if (devfreq->governor) {
> +		ret = devfreq->governor->event_handler(devfreq,
> +					DEVFREQ_GOV_SUSPEND, NULL);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	if (devfreq->suspend_freq) {
> +		if (atomic_inc_return(&devfreq->suspend_count) > 1)
> +			return 0;
> +
> +		ret = devfreq_set_target(devfreq, devfreq->suspend_freq, 0);
> +		if (ret)
> +			return ret;
> +	}
>  
> -	return devfreq->governor->event_handler(devfreq,
> -				DEVFREQ_GOV_SUSPEND, NULL);
> +	return 0;
>  }
>  EXPORT_SYMBOL(devfreq_suspend_device);
>  
> @@ -888,14 +909,28 @@ EXPORT_SYMBOL(devfreq_suspend_device);
>   */
>  int devfreq_resume_device(struct devfreq *devfreq)
>  {
> +	int ret;
> +
>  	if (!devfreq)
>  		return -EINVAL;
>  
> -	if (!devfreq->governor)
> -		return 0;
> +	if (devfreq->resume_freq) {
> +		if (atomic_dec_return(&devfreq->suspend_count) >= 1)
> +			return 0;
>  
> -	return devfreq->governor->event_handler(devfreq,
> -				DEVFREQ_GOV_RESUME, NULL);
> +		ret = devfreq_set_target(devfreq, devfreq->resume_freq, 0);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	if (devfreq->governor) {
> +		ret = devfreq->governor->event_handler(devfreq,
> +					DEVFREQ_GOV_RESUME, NULL);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	return 0;
>  }
>  EXPORT_SYMBOL(devfreq_resume_device);
>  
> diff --git a/include/linux/devfreq.h b/include/linux/devfreq.h
> index e4963b0..d985199 100644
> --- a/include/linux/devfreq.h
> +++ b/include/linux/devfreq.h
> @@ -131,6 +131,9 @@ struct devfreq_dev_profile {
>   * @scaling_min_freq:	Limit minimum frequency requested by OPP interface
>   * @scaling_max_freq:	Limit maximum frequency requested by OPP interface
>   * @stop_polling:	 devfreq polling status of a device.
> + * @suspend_freq:	 frequency of a device set during suspend phase.
> + * @resume_freq:	 frequency of a device set in resume phase.
> + * @suspend_count:	 suspend requests counter for a device.
>   * @total_trans:	Number of devfreq transitions
>   * @trans_table:	Statistics of devfreq transitions
>   * @time_in_state:	Statistics of devfreq states
> @@ -167,6 +170,10 @@ struct devfreq {
>  	unsigned long scaling_max_freq;
>  	bool stop_polling;
>  
> +	unsigned long suspend_freq;
> +	unsigned long resume_freq;
> +	atomic_t suspend_count;
> +
>  	/* information for device frequency transition */
>  	unsigned int total_trans;
>  	unsigned int *trans_table;
> 


-- 
Best Regards,
Chanwoo Choi
Samsung Electronics