PM: domains: Introduce dev_pm_domain_set_performance_state()

The generic PM domain is currently the only PM domain variant that supports
performance scaling. To allow performance scaling to be supported through a
common interface, let's add an optional callback ->set_performance_state(),
in the struct dev_pm_domain.

Moreover, let's add a function, dev_pm_domain_set_performance_state(), that
may be called by consumers to request a new performance state for a device
through its PM domain.

Note that, in most cases it's preferred that a consumer use the OPP library
to request a new performance state for its device. Although, this requires
some additional changes to be supported, which are being implemented from
subsequent changes.
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>

drivers/base/power/common.c

@@ -228,3 +228,24 @@ void dev_pm_domain_set(struct device *dev, struct dev_pm_domain *pd)
 	device_pm_check_callbacks(dev);
 }
 EXPORT_SYMBOL_GPL(dev_pm_domain_set);
+
+/**
+ * dev_pm_domain_set_performance_state - Request a new performance state.
+ * @dev: The device to make the request for.
+ * @state: Target performance state for the device.
+ *
+ * This function should be called when a new performance state needs to be
+ * requested for a device that is attached to a PM domain. Note that, the
+ * support for performance scaling for PM domains is optional.
+ *
+ * Returns 0 on success and when performance scaling isn't supported, negative
+ * error code on failure.
+ */
+int dev_pm_domain_set_performance_state(struct device *dev, unsigned int state)
+{
+	if (dev->pm_domain && dev->pm_domain->set_performance_state)
+		return dev->pm_domain->set_performance_state(dev, state);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(dev_pm_domain_set_performance_state);

include/linux/pm.h

@@ -719,6 +719,7 @@ extern void dev_pm_put_subsys_data(struct device *dev);
  * @activate: Called before executing probe routines for bus types and drivers.
  * @sync: Called after successful driver probe.
  * @dismiss: Called after unsuccessful driver probe and after driver removal.
+ * @set_performance_state: Called to request a new performance state.
  *
  * Power domains provide callbacks that are executed during system suspend,
  * hibernation, system resume and during runtime PM transitions instead of
@@ -731,6 +732,7 @@ struct dev_pm_domain {
 	int (*activate)(struct device *dev);
 	void (*sync)(struct device *dev);
 	void (*dismiss)(struct device *dev);
+	int (*set_performance_state)(struct device *dev, unsigned int state);
 };
 
 /*

include/linux/pm_domain.h

@@ -430,6 +430,7 @@ struct device *dev_pm_domain_attach_by_name(struct device *dev,
 void dev_pm_domain_detach(struct device *dev, bool power_off);
 int dev_pm_domain_start(struct device *dev);
 void dev_pm_domain_set(struct device *dev, struct dev_pm_domain *pd);
+int dev_pm_domain_set_performance_state(struct device *dev, unsigned int state);
 #else
 static inline int dev_pm_domain_attach(struct device *dev, bool power_on)
 {
@@ -452,6 +453,11 @@ static inline int dev_pm_domain_start(struct device *dev)
 }
 static inline void dev_pm_domain_set(struct device *dev,
 				     struct dev_pm_domain *pd) {}
+static inline int dev_pm_domain_set_performance_state(struct device *dev,
+						      unsigned int state)
+{
+	return 0;
+}
 #endif
 
 #endif /* _LINUX_PM_DOMAIN_H */