> This patch adds suspend and resume apis needed
> for devices which can idle. Suspend/resume apis
> are called from driver to suspend/resume devfreq
> load monitoring of that device.
>
> Signed-off-by: Rajagopal Venkat <rajagopal.venkat@linaro.org>

1. Some devfreq devices may need their own code to do suspend/resume; e.g.,
setting a specific frequency for suspend (especially with suspend-to-RAM). 

2. Are these new APIs (devfreq_suspend/resume_device()) intended to be
used by runtime_pm and pm(Suspend-to-RAM) callbacks of the parent devices?
If so, could you consider use the structure of runtime-pm (I don't have
an idea on how to do this for now)? For example, when a device is being
suspended, devfreq device's suspend is also called without calling it
explicitly at the device driver's suspend callback.

3. As in the patch 1/3, could you consider to integrate class-wide
features in devfreq.c, not in a governor?

Cheers!
MyungJoo

> ---
>  drivers/devfreq/devfreq.c                 | 30 ++++++++++++++++++++++++++++++
>  drivers/devfreq/governor_simpleondemand.c | 15 +++++++++++++++
>  include/linux/devfreq.h                   | 16 ++++++++++++++++
>  3 files changed, 61 insertions(+)
>
> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> index 5aa23a8..375b5aa1 100644
> --- a/drivers/devfreq/devfreq.c
> +++ b/drivers/devfreq/devfreq.c
> @@ -233,6 +233,36 @@ int devfreq_remove_device(struct devfreq *devfreq)
>  }
>  EXPORT_SYMBOL(devfreq_remove_device);
>
> +/**
> + * devfreq_suspend_device() - Suspend devfreq of a device.
> + * @devfreq  the devfreq instance to be suspended
> + */
> +int devfreq_suspend_device(struct devfreq *devfreq)
> +{
> +     if (!devfreq)
> +             return -EINVAL;
> +
> +     devfreq->governor->event_handler(devfreq, DEVFREQ_GOV_SUSPEND);
> +
> +     return 0;
> +}
> +EXPORT_SYMBOL(devfreq_suspend_device);
> +
> +/**
> + * devfreq_resume_device() - Resume devfreq of a device.
> + * @devfreq  the devfreq instance to be resumed
> + */
> +int devfreq_resume_device(struct devfreq *devfreq)
> +{
> +     if (!devfreq)
> +             return -EINVAL;
> +
> +     devfreq->governor->event_handler(devfreq, DEVFREQ_GOV_RESUME);
> +
> +     return 0;
> +}
> +EXPORT_SYMBOL(devfreq_resume_device);
> +
>  static ssize_t show_governor(struct device *dev,
>                            struct device_attribute *attr, char *buf)
>  {
> diff --git a/drivers/devfreq/governor_simpleondemand.c b/drivers/devfreq/governor_simpleondemand.c
> index 7c70c30..95e4db9 100644
> --- a/drivers/devfreq/governor_simpleondemand.c
> +++ b/drivers/devfreq/governor_simpleondemand.c
> @@ -221,6 +221,21 @@ static int devfreq_simple_ondemand_func(struct devfreq *df,
>               ondemand_exit(df);
>               break;
>
> +     case DEVFREQ_GOV_SUSPEND:
> +             if (delayed_work_pending(&data->work)) {
> +                     data->stop_queuing = true;
> +                     cancel_delayed_work_sync(&data->work);
> +             }
> +             break;
> +
> +     case DEVFREQ_GOV_RESUME:
> +             if (!delayed_work_pending(&data->work)) {
> +                     data->stop_queuing = false;
> +                     queue_delayed_work(devfreq_wq, &data->work,
> +                             msecs_to_jiffies(df->profile->polling_ms));
> +             }
> +             break;
> +
>       case DEVFREQ_GOV_LIMITS:
>               if (delayed_work_pending(&data->work)) {
>                       mutex_lock(&df->lock);
> diff --git a/include/linux/devfreq.h b/include/linux/devfreq.h
> index 600cc2e..7c6517f 100644
> --- a/include/linux/devfreq.h
> +++ b/include/linux/devfreq.h
> @@ -56,6 +56,8 @@ struct devfreq_dev_status {
>  #define DEVFREQ_GOV_START                    0x1
>  #define DEVFREQ_GOV_STOP                     0x2
>  #define DEVFREQ_GOV_LIMITS                   0x3
> +#define DEVFREQ_GOV_SUSPEND                  0x4
> +#define DEVFREQ_GOV_RESUME                   0x5
>
>  /**
>   * struct devfreq_dev_profile - Devfreq's user device profile
> @@ -155,6 +157,10 @@ extern struct devfreq *devfreq_add_device(struct device *dev,
>                                 void *data);
>  extern int devfreq_remove_device(struct devfreq *devfreq);
>
> +extern int devfreq_suspend_device(struct devfreq *devfreq);
> +
> +extern int devfreq_resume_device(struct devfreq *devfreq);
> +
>  /* Helper functions for devfreq user device driver with OPP. */
>  extern struct opp *devfreq_recommended_opp(struct device *dev,
>                                          unsigned long *freq, u32 flags);
> @@ -207,6 +213,16 @@ static int devfreq_remove_device(struct devfreq *devfreq)
>       return 0;
>  }
>
> +static int devfreq_suspend_device(struct devfreq *devfreq)
> +{
> +     return 0;
> +}
> +
> +extern int devfreq_resume_device(struct devfreq *devfreq)
> +{
> +     return 0;
> +}
> +
>  static struct opp *devfreq_recommended_opp(struct device *dev,
>                                          unsigned long *freq, u32 flags)
>  {
> --
> 1.7.11.3
>