[Intel-gfx] [PATCH] PM / runtime: Add new helper for conditional usage count incrementation

[Ulf Hansson]

On 14 December 2015 at 23:22, Rafael J. Wysocki <rjw at rjwysocki.net> wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki at intel.com>
>
> Introduce a new runtime PM function, pm_runtime_get_if_in_use(),

As we already have pm_runtime_set_active() and pm_runtime_active(),
changing the new function name to "pm_runtime_get_if_active" may be
better!?

> 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 at intel.com>
> Acked-by: Imre Deak <imre.deak at intel.com>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki at intel.com>
> ---
>  Documentation/power/runtime_pm.txt |    5 +++++
>  drivers/base/power/runtime.c       |   21 +++++++++++++++++++++
>  include/linux/pm_runtime.h         |    5 +++++
>  3 files changed, 31 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 +966,27 @@ 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.
> + *
> + * Increment the device's runtime PM usage counter and return 'true' if its
> + * runtime PM status is RPM_ACTIVE and its usage counter is already different
> + * from zero at the same time.  Otherwise, return 'false'.
> + */
> +bool pm_runtime_get_if_in_use(struct device *dev)
> +{
> +       unsigned long flags;
> +       bool retval;
> +
> +       spin_lock_irqsave(&dev->power.lock, flags);
> +       retval = dev->power.runtime_status == RPM_ACTIVE
> +               && atomic_inc_not_zero(&dev->power.usage_count);

Don't we also need to check that runtime PM is enabled (&&
!dev->power.disable_depth), or the user of this function don't care
about that?

> +       spin_unlock_irqrestore(&dev->power.lock, flags);
> +       return retval;
> +}
> +EXPORT_SYMBOL_GPL(pm_runtime_get_if_in_use);
> +

[...]

Kind regards
Uffe