[PATCH 1/9] PM / Domains: Add dev_pm_domain_get|put() APIs

[Rafael J. Wysocki]

On Friday, March 13, 2015 04:43:41 PM Ulf Hansson wrote:
> There may be more than one device in a PM domain which then will be
> probed at different points in time.
> 
> Depending on timing and runtime PM support, in for the device related
> driver/subsystem, a PM domain may be advised to power off after a
> successful probe sequence.
> 
> A general requirement for a device within a PM domain, is that the
> PM domain must stay powered during the probe sequence. To cope with
> such requirement, let's add the dev_pm_domain_get|put() APIs.
> 
> These APIs are intended to be invoked from subsystem-level code and the
> calls between get/put needs to be balanced.
> 
> dev_pm_domain_get(), tells the PM domain that it needs to increase a
> usage count and to keep supplying power. dev_pm_domain_put(), does the
> opposite.
> 
> For a PM domain to support this feature, it must implement the optional
> ->get|put() callbacks.
> 
> Signed-off-by: Ulf Hansson <ulf.hansson at linaro.org>
> ---
>  drivers/base/power/common.c | 40 ++++++++++++++++++++++++++++++++++++++++
>  include/linux/pm.h          |  2 ++
>  include/linux/pm_domain.h   |  4 ++++
>  3 files changed, 46 insertions(+)
> 
> diff --git a/drivers/base/power/common.c b/drivers/base/power/common.c
> index f32b802..99225af 100644
> --- a/drivers/base/power/common.c
> +++ b/drivers/base/power/common.c
> @@ -128,3 +128,43 @@ void dev_pm_domain_detach(struct device *dev, bool power_off)
>  		dev->pm_domain->detach(dev, power_off);
>  }
>  EXPORT_SYMBOL_GPL(dev_pm_domain_detach);
> +
> +/**
> + * dev_pm_domain_get - Increase usage count to keep a PM domain powered.
> + * @domain: The PM domain to operate on.
> + *
> + * This function will not by itself increase the usage count, that's up to each
> + * PM domain implementation to support. Typically it should be invoked from
> + * subsystem level code prior drivers starts probing.
> + *
> + * Do note, it's optional to implement the ->get() callback for a PM domain.
> + *
> + * Returns 0 on successfully increased usage count or negative error code.
> + */
> +int dev_pm_domain_get(struct dev_pm_domain *domain)
> +{
> +	int ret = 0;
> +
> +	if (domain && domain->get)
> +		ret = domain->get(domain);
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(dev_pm_domain_get);
> +
> +/**
> + * dev_pm_domain_put - Decrease usage count to allow a PM domain to power off.
> + * @domain: The PM domain to operate on.
> + *
> + * This function will not by itself decrease the usage count, that's up to each
> + * PM domain implementation to support. Typically it should be invoked from
> + * subsystem level code after drivers has finished probing.
> + *
> + * Do note, it's optional to implement the ->put() callback for a PM domain.
> + */
> +void dev_pm_domain_put(struct dev_pm_domain *domain)
> +{
> +	if (domain && domain->put)
> +		domain->put(domain);
> +}
> +EXPORT_SYMBOL_GPL(dev_pm_domain_put);
> diff --git a/include/linux/pm.h b/include/linux/pm.h
> index e2f1be6..e62330b 100644
> --- a/include/linux/pm.h
> +++ b/include/linux/pm.h
> @@ -607,6 +607,8 @@ extern void dev_pm_put_subsys_data(struct device *dev);
>  struct dev_pm_domain {
>  	struct dev_pm_ops	ops;
>  	void (*detach)(struct device *dev, bool power_off);
> +	int (*get)(struct dev_pm_domain *domain);
> +	void (*put)(struct dev_pm_domain *domain);

I don't like these names.  They suggest that it's always going to be about
reference counting which doesn't have to be the case in principle.

Also what about calling these from the driver core, ie. really_probe()?


-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.