linux-kernel - Re: [PATCH 4/6] devfreq: add devfreq

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Date:   Thu, 22 Nov 2018 12:07:41 +0900
From:   Chanwoo Choi <cw00.choi@...sung.com>
To:     Lukasz Luba <l.luba@...tner.samsung.com>,
        linux-arm-kernel@...ts.infradead.org,
        linux-samsung-soc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org, devicetree@...r.kernel.org
Cc:     tjakobi@...h.uni-bielefeld.de, myungjoo.ham@...sung.com,
        kyungmin.park@...sung.com, rjw@...ysocki.net, len.brown@...el.com,
        pavel@....cz, gregkh@...uxfoundation.org, keescook@...omium.org,
        anton@...msg.org, ccross@...roid.com, tony.luck@...el.com,
        robh+dt@...nel.org, mark.rutland@....com, kgene@...nel.org,
        krzk@...nel.org, m.szyprowski@...sung.com, b.zolnierkie@...sung.com
Subject: Re: [PATCH 4/6] devfreq: add devfreq_suspend/resume() functions

Hi,

On 2018년 11월 22일 03:01, Lukasz Luba wrote:
> This patch adds implementation for global suspend/resume for
> devfreq framework. System suspend will next use these functions.
> 
> The patch draws on Tobias Jakobi's work posted ~2 years ago, who tried to
> solve issue with devfreq device's frequency during suspend/resume.
> During the discussion on LKML some corner cases and comments appeared
> related to the design. This patch address them keeping in mind suggestions
> from Chanwoo Choi.

Please remove the duplicate information about patch history.

> 
> Suggested-by: Tobias Jakobi <tjakobi@...h.uni-bielefeld.de>
> Suggested-by: Chanwoo Choi <cw00.choi@...sung.com>
> Signed-off-by: Lukasz Luba <l.luba@...tner.samsung.com>
> ---
>  drivers/devfreq/devfreq.c | 49 +++++++++++++++++++++++++++++++++++++++++++++++
>  include/linux/devfreq.h   |  7 +++++++
>  2 files changed, 56 insertions(+)
> 
> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> index 7e09de8..2f4391c 100644
> --- a/drivers/devfreq/devfreq.c
> +++ b/drivers/devfreq/devfreq.c
> @@ -44,6 +44,9 @@ static LIST_HEAD(devfreq_governor_list);
>  static LIST_HEAD(devfreq_list);
>  static DEFINE_MUTEX(devfreq_list_lock);
>  
> +/* Flag showing state of suspend/resume */
> +static bool devfreq_suspended;

Is it necessary? This patch just saves the 'true' or 'false' to this variable.
And there are no any point to check the value of this variable.
Please remove it.

> +
>  /**
>   * find_device_devfreq() - find devfreq struct using device pointer
>   * @dev:	device pointer used to lookup device devfreq.
> @@ -938,6 +941,52 @@ int devfreq_resume_device(struct devfreq *devfreq)
>  EXPORT_SYMBOL(devfreq_resume_device);
>  
>  /**
> + * devfreq_suspend() - Suspend devfreq governors and devices
> + *
> + * Called during system wide Suspend/Hibernate cycles for suspending governors
> + * and devices preserving the state for resume. On some platforms the devfreq
> + * device must have precise state (frequency) after resume in order to provide
> + * fully operating setup.
> + */
> +void devfreq_suspend(void)
> +{
> +	struct devfreq *devfreq;
> +	int ret;
> +
> +	mutex_lock(&devfreq_list_lock);
> +	list_for_each_entry(devfreq, &devfreq_list, node) {
> +		ret = devfreq_suspend_device(devfreq);
> +		if (ret)
> +			dev_warn(&devfreq->dev, "device suspend failed\n");
> +	}
> +	mutex_unlock(&devfreq_list_lock);
> +
> +	devfreq_suspended = true;

Remove it.

> +}
> +
> +/**
> + * devfreq_resume() - Resume devfreq governors and devices
> + *
> + * Called during system wide Suspend/Hibernate cycle for resuming governors and
> + * devices that are suspended with devfreq_suspend().
> + */
> +void devfreq_resume(void)
> +{
> +	struct devfreq *devfreq;
> +	int ret;
> +
> +	devfreq_suspended = false;

Remove it.

> +
> +	mutex_lock(&devfreq_list_lock);
> +	list_for_each_entry(devfreq, &devfreq_list, node) {
> +		ret = devfreq_resume_device(devfreq);
> +		if (ret)
> +			dev_warn(&devfreq->dev, "device resume failed\n");
> +	}
> +	mutex_unlock(&devfreq_list_lock);
> +}
> +
> +/**
>   * devfreq_add_governor() - Add devfreq governor
>   * @governor:	the devfreq governor to be added
>   */
> diff --git a/include/linux/devfreq.h b/include/linux/devfreq.h
> index 7fe96f9..4f0fea8 100644
> --- a/include/linux/devfreq.h
> +++ b/include/linux/devfreq.h
> @@ -202,6 +202,10 @@ extern void devm_devfreq_remove_device(struct device *dev,
>  extern int devfreq_suspend_device(struct devfreq *devfreq);
>  extern int devfreq_resume_device(struct devfreq *devfreq);
>  
> +

Remove the blank line.

> +extern void devfreq_suspend(void);
> +extern void devfreq_resume(void);
> +
>  /**
>   * update_devfreq() - Reevaluate the device and configure frequency
>   * @devfreq:	the devfreq device
> @@ -396,6 +400,9 @@ static inline int devfreq_update_stats(struct devfreq *df)
>  {
>  	return -EINVAL;
>  }
> +
> +static inline void devfreq_suspend(void) {}
> +static inline void devfreq_resume(void) {}

You better to move the inline definitions
under 'devfreq_resume_device' inline function.

>  #endif /* CONFIG_PM_DEVFREQ */
>  
>  #endif /* __LINUX_DEVFREQ_H__ */
> 


-- 
Best Regards,
Chanwoo Choi
Samsung Electronics