PM / Domains: Introduce function to power off all unused PM domains

Add a new function pm_genpd_poweroff_unused() queuing up the
execution of pm_genpd_poweroff() for every initialized generic PM
domain.  Calling it will cause every generic PM domain without
devices in use to be powered off.
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Magnus Damm <damm@opensource.se>

drivers/base/power/domain.c

@@ -16,6 +16,9 @@
 #include <linux/sched.h>
 #include <linux/suspend.h>
 
+static LIST_HEAD(gpd_list);
+static DEFINE_MUTEX(gpd_list_lock);
+
 #ifdef CONFIG_PM
 
 static struct generic_pm_domain *dev_to_genpd(struct device *dev)
@@ -1241,4 +1244,22 @@ void pm_genpd_init(struct generic_pm_domain *genpd,
 	genpd->domain.ops.restore_noirq = pm_genpd_restore_noirq;
 	genpd->domain.ops.restore = pm_genpd_restore;
 	genpd->domain.ops.complete = pm_genpd_complete;
+	mutex_lock(&gpd_list_lock);
+	list_add(&genpd->gpd_list_node, &gpd_list);
+	mutex_unlock(&gpd_list_lock);
+}
+
+/**
+ * pm_genpd_poweroff_unused - Power off all PM domains with no devices in use.
+ */
+void pm_genpd_poweroff_unused(void)
+{
+	struct generic_pm_domain *genpd;
+
+	mutex_lock(&gpd_list_lock);
+
+	list_for_each_entry(genpd, &gpd_list, gpd_list_node)
+		genpd_queue_power_off_work(genpd);
+
+	mutex_unlock(&gpd_list_lock);
 }

include/linux/pm_domain.h

@@ -24,6 +24,7 @@ struct dev_power_governor {
 
 struct generic_pm_domain {
 	struct dev_pm_domain domain;	/* PM domain operations */
+	struct list_head gpd_list_node;	/* Node in the global PM domains list */
 	struct list_head sd_node;	/* Node in the parent's subdomain list */
 	struct generic_pm_domain *parent;	/* Parent PM domain */
 	struct list_head sd_list;	/* List of dubdomains */
@@ -71,6 +72,7 @@ extern int pm_genpd_remove_subdomain(struct generic_pm_domain *genpd,
 extern void pm_genpd_init(struct generic_pm_domain *genpd,
 			  struct dev_power_governor *gov, bool is_off);
 extern int pm_genpd_poweron(struct generic_pm_domain *genpd);
+extern void pm_genpd_poweroff_unused(void);
 #else
 static inline int pm_genpd_add_device(struct generic_pm_domain *genpd,
 				      struct device *dev)
@@ -98,6 +100,7 @@ static inline int pm_genpd_poweron(struct generic_pm_domain *genpd)
 {
 	return -ENOSYS;
 }
+static inline void pm_genpd_poweroff_unused(void) {}
 #endif
 
 #endif /* _LINUX_PM_DOMAIN_H */