Re: [PATCH v2] PM / runtime: Add new helper for conditional usage count incrementation

[Ulf Hansson <ulf.hansson@linaro.org>]

On 17 December 2015 at 02:54, Rafael J. Wysocki <rjw@rjwysocki.net> wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
>
> Introduce a new runtime PM function, pm_runtime_get_if_in_use(),
> that will increment the device's runtime PM usage counter and
> return 'true' if its status is RPM_ACTIVE and its usage counter
> is greater than 0 at the same time ('false' will be returned
> otherwise).
>
> This is useful for things that should only be done if the device
> is active (from the runtime PM perspective) and used by somebody
> (as indicated by the usage counter) already and they are not worth
> bothering otherwise.
>
> Requested-by: Imre Deak <imre.deak@intel.com>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>

Kind regards
Uffe

> ---
>
> Changes from v1:
> - kerneldoc and runtime PM doc changes as suggested by Alan.
> - The new function returns an int now and -EINVAL is returned for devices
>   with runtime PM disabled.
>
> ---
>  Documentation/power/runtime_pm.txt |    6 ++++++
>  drivers/base/power/runtime.c       |   24 ++++++++++++++++++++++++
>  include/linux/pm_runtime.h         |    5 +++++
>  3 files changed, 35 insertions(+)
>
> Index: linux-pm/drivers/base/power/runtime.c
> ===================================================================
> --- linux-pm.orig/drivers/base/power/runtime.c
> +++ linux-pm/drivers/base/power/runtime.c
> @@ -966,6 +966,30 @@ int __pm_runtime_resume(struct device *d
>  EXPORT_SYMBOL_GPL(__pm_runtime_resume);
>
>  /**
> + * pm_runtime_get_if_in_use - Conditionally bump up the device's usage counter.
> + * @dev: Device to handle.
> + *
> + * Return -EINVAL if runtime PM is disabled for the device.
> + *
> + * If that's not the case and if the device's runtime PM status is RPM_ACTIVE
> + * and the runtime PM usage counter is nonzero, increment the counter and
> + * return 1.  Otherwise return 0 without changing the counter.
> + */
> +int pm_runtime_get_if_in_use(struct device *dev)
> +{
> +       unsigned long flags;
> +       int retval;
> +
> +       spin_lock_irqsave(&dev->power.lock, flags);
> +       retval = dev->power.disable_depth > 0 ? -EINVAL :
> +               dev->power.runtime_status == RPM_ACTIVE
> +                       && atomic_inc_not_zero(&dev->power.usage_count);
> +       spin_unlock_irqrestore(&dev->power.lock, flags);
> +       return retval;
> +}
> +EXPORT_SYMBOL_GPL(pm_runtime_get_if_in_use);
> +
> +/**
>   * __pm_runtime_set_status - Set runtime PM status of a device.
>   * @dev: Device to handle.
>   * @status: New runtime PM status of the device.
> Index: linux-pm/include/linux/pm_runtime.h
> ===================================================================
> --- linux-pm.orig/include/linux/pm_runtime.h
> +++ linux-pm/include/linux/pm_runtime.h
> @@ -39,6 +39,7 @@ extern int pm_runtime_force_resume(struc
>  extern int __pm_runtime_idle(struct device *dev, int rpmflags);
>  extern int __pm_runtime_suspend(struct device *dev, int rpmflags);
>  extern int __pm_runtime_resume(struct device *dev, int rpmflags);
> +extern int pm_runtime_get_if_in_use(struct device *dev);
>  extern int pm_schedule_suspend(struct device *dev, unsigned int delay);
>  extern int __pm_runtime_set_status(struct device *dev, unsigned int status);
>  extern int pm_runtime_barrier(struct device *dev);
> @@ -143,6 +144,10 @@ static inline int pm_schedule_suspend(st
>  {
>         return -ENOSYS;
>  }
> +static inline int pm_runtime_get_if_in_use(struct device *dev)
> +{
> +       return -EINVAL;
> +}
>  static inline int __pm_runtime_set_status(struct device *dev,
>                                             unsigned int status) { return 0; }
>  static inline int pm_runtime_barrier(struct device *dev) { return 0; }
> Index: linux-pm/Documentation/power/runtime_pm.txt
> ===================================================================
> --- linux-pm.orig/Documentation/power/runtime_pm.txt
> +++ linux-pm/Documentation/power/runtime_pm.txt
> @@ -371,6 +371,12 @@ drivers/base/power/runtime.c and include
>      - increment the device's usage counter, run pm_runtime_resume(dev) and
>        return its result
>
> +  int pm_runtime_get_if_in_use(struct device *dev);
> +    - return -EINVAL if 'power.disable_depth' is nonzero; otherwise, if the
> +      runtime PM status is RPM_ACTIVE and the runtime PM usage counter is
> +      nonzero, increment the counter and return 1; otherwise return 0 without
> +      changing the counter
> +
>    void pm_runtime_put_noidle(struct device *dev);
>      - decrement the device's usage counter
>
>