[PATCH 1/9] PM / Domains: Add dev_pm_domain_get|put() APIs
Ulf Hansson
ulf.hansson at linaro.org
Wed Mar 18 06:41:47 PDT 2015
On 18 March 2015 at 02:09, Rafael J. Wysocki <rjw at rjwysocki.net> wrote:
> On Tuesday, March 17, 2015 03:40:47 PM Ulf Hansson wrote:
>> On 17 March 2015 at 15:45, Rafael J. Wysocki <rjw at rjwysocki.net> wrote:
>> > On Tuesday, March 17, 2015 10:27:03 AM Ulf Hansson wrote:
>> >> On 17 March 2015 at 04:01, Rafael J. Wysocki <rjw at rjwysocki.net> wrote:
>> >> > On Monday, March 16, 2015 10:26:46 AM Ulf Hansson wrote:
>> >> >> 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?
>> >> >
>> >> > Not really. I don't want to inflict the ACPI PM domain on every bus type
>> >> > that may not be prepared for using it or even may not want to use it (like
>> >> > PCI or PNP). That applies to genpd too to some extent.
>> >> >
>> >> > So bus types need to be able to opt in for using "default" PM domains, but
>> >> > at the same time if they do, the core is a better place to invoke the
>> >> > callbacks.
>> >>
>> >> Okay!
>> >>
>> >> >
>> >> > The patch below shows how that can be done. For the bus types using
>> >> > genpd or the ACPI PM domain today ->pm_domain_init and ->pm_domain_exit
>> >> > may point to the routines initializing/detaching those (which also will help
>> >> > to reduce code duplication somewhat) and that guarantees that the domains
>> >> > will be attached to devices before probing and the core can do the ->pre_probe
>> >> > and ->post_probe things for everybody.
>> >>
>> >> Overall, this seem like a very good idea!
>> >>
>> >> >
>> >> > Rafael
>> >> >
>> >> >
>> >> > ---
>> >> > drivers/base/bus.c | 12 +++++++++++-
>> >> > drivers/base/dd.c | 9 +++++++++
>> >> > include/linux/device.h | 3 +++
>> >> > include/linux/pm.h | 2 ++
>> >> > 4 files changed, 25 insertions(+), 1 deletion(-)
>> >> >
>> >> > Index: linux-pm/drivers/base/bus.c
>> >> > ===================================================================
>> >> > --- linux-pm.orig/drivers/base/bus.c
>> >> > +++ linux-pm/drivers/base/bus.c
>> >> > @@ -509,10 +509,15 @@ int bus_add_device(struct device *dev)
>> >> > int error = 0;
>> >> >
>> >> > if (bus) {
>> >> > + if (bus->pm_domain_init) {
>> >> > + error = bus->pm_domain_init(dev);
>> >> > + if (error)
>> >> > + goto out_put;
>> >> > + }
>> >> > pr_debug("bus: '%s': add device %s\n", bus->name, dev_name(dev));
>> >> > error = device_add_attrs(bus, dev);
>> >> > if (error)
>> >> > - goto out_put;
>> >> > + goto out_pm_domain;
>> >> > error = device_add_groups(dev, bus->dev_groups);
>> >> > if (error)
>> >> > goto out_groups;
>> >> > @@ -534,6 +539,9 @@ out_groups:
>> >> > device_remove_groups(dev, bus->dev_groups);
>> >> > out_id:
>> >> > device_remove_attrs(bus, dev);
>> >> > +out_pm_domain:
>> >> > + if (bus->pm_domain_exit)
>> >> > + bus->pm_domain_exit(dev);
>> >> > out_put:
>> >> > bus_put(dev->bus);
>> >> > return error;
>> >>
>> >> To make this work for bus_add_device(), we first need to change the
>> >> registration procedure for genpd DT providers. Currently that's done
>> >> when "PM domain drivers" invokes the __of_genpd_add_provider() API,
>> >> from SoC specific code and from different init levels.
>> >>
>> >> We need to have the available gendp DT providers registered when the
>> >> ->pm_domain_init() callback is invoked.
>> >>
>> >> Besides the changes above, genpd also needs to deal with attached
>> >> devices, but which don't have a corresponding driver bound. I believe
>> >> we have some corner cases to fix around this as well.
>> >>
>> >> As an intermediate step, how about adding the similar code as above
>> >> but into really_probe()? For the code in bus_remove_device() below, we
>> >> could add that into __device_release_driver()?
>> >
>> > Well, I wouldn't really like to add new callbacks to struct bus_type for
>> > intermediate steps, because that's guaranteed to lead to confusion.
>> >
>> > So I think the infrastructure is better added first and users may be
>> > switched over to it gradually.
>> >
>> > I don't see any particular problems with moving the ACPI PM domain
>> > attach/detach to bus_add/remove_device(), so that can be done as the first
>> > step. As for genpd, it can implement the ->post_probe thing first and do
>> > the rest in the bus type ->probe until the generic code is ready.
>>
>> Yes, that works.
>>
>> I will cook a new version of the patchset according to your suggestions.
>
> I'll send a cleaner version of my patch tomorrow (I actually would like to
> use different names for the new callbacks).
Okay, great!
>
> Also I can do the ACPI part of the work, please let me know if you want me to.
Appreciate your help! I wouldn't mind giving this a quick try. If I am
way off, just nack the patches and then please help out implement it.
Kind regards
Uffe
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