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

[Ulf Hansson]

On 14 March 2015 at 02:31, Rafael J. Wysocki <rjw at rjwysocki.net> wrote:
> 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.

I am happy to change, you don't happen to have a proposal? :-)

For genpd we already have these related APIs:

pm_genpd_poweron()
pm_genpd_name_poweron()
pm_genpd_poweroff_unused()

Theoretically we should be able to replace these with
dev_pm_domain_get|put() or whatever we decide to name them to.

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

I like that!

That also implies moving the calls to dev_pm_domain_attach|detach()
out of the buses and into the drivercore, since we need the PM domain
to be attached before calling dev_pm_domain_get|put(). I assume that's
what you also propose me to change, right?

Kind regards
Uffe