[PATCH 03/12] PM / Domains: Add notifier support for power domain transitions

[Amit Daniel Kachhap]

These power domain transition notifiers will assist in carrying
out some activity associated with domain power on/off such as
some registers which may lose its contents and need save/restore
across domain power off/on.

4 type of notifications are added,
GPD_OFF_PRE     - GPD state before power off
GPD_OFF_POST    - GPD state after power off
GPD_ON_PRE      - GPD state before power off
GPD_ON_POST     - GPD state after power off

3 notfication API's are exported.
1) int genpd_register_notifier(struct notifier_block *nb, char *pd_name);
2) int genpd_unregister_notifier(struct notifier_block *nb, char *pd_name);
3) void genpd_invoke_transition_notifier(struct generic_pm_domain *genpd,
			enum gpd_on_off_state state);

In this approach the notifiers are registered/unregistered with pd name.
The actual invoking of the notfiers will be done by the platform implementing
power domain enable/disable low level handlers according to the above
defined notification types. This approach will considerably reduce the
number of call to notifiers as compared to calling always from core
powerdomain subsystem.

Also the registered domain's will be managed inside a cache list and not
part of the genpd structure. This will help in registration of notifiers from
subsystems (such as clock) even when the PD subsystem is still not initialised.
This list also filters out the unregistered pd's requesting notification.

Cc: Rafael J. Wysocki <rafael.j.wysocki at intel.com>
Reviewed-by: Pankaj Dubey <pankaj.dubey at samsung.com>
Signed-off-by: Amit Daniel Kachhap <amit.daniel at samsung.com>
---
 drivers/base/power/domain.c |  112 ++++++++++++++++++++++++++++++++++++++++++-
 include/linux/pm_domain.h   |   31 ++++++++++++
 2 files changed, 142 insertions(+), 1 deletion(-)

diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
index 40bc2f4..e05045e 100644
--- a/drivers/base/power/domain.c
+++ b/drivers/base/power/domain.c
@@ -46,10 +46,19 @@
 	__retval;								\
 })
 
+struct cache_notify_domains {
+	char *name;
+	/* Node in the cache pm domain name list */
+	struct list_head cache_list_node;
+};
+
 static LIST_HEAD(gpd_list);
 static DEFINE_MUTEX(gpd_list_lock);
+static LIST_HEAD(domain_notify_list);
+static DEFINE_MUTEX(domain_notify_list_lock);
+static BLOCKING_NOTIFIER_HEAD(genpd_transition_notifier_list);
 
-static struct generic_pm_domain *pm_genpd_lookup_name(const char *domain_name)
+struct generic_pm_domain *pm_genpd_lookup_name(const char *domain_name)
 {
 	struct generic_pm_domain *genpd = NULL, *gpd;
 
@@ -66,6 +75,7 @@ static struct generic_pm_domain *pm_genpd_lookup_name(const char *domain_name)
 	mutex_unlock(&gpd_list_lock);
 	return genpd;
 }
+EXPORT_SYMBOL_GPL(pm_genpd_lookup_name);
 
 struct generic_pm_domain *dev_to_genpd(struct device *dev)
 {
@@ -1908,6 +1918,106 @@ void pm_genpd_init(struct generic_pm_domain *genpd,
 	mutex_unlock(&gpd_list_lock);
 }
 
+/**
+ * genpd_register_notifier - Register a PM domain for future notification.
+ * @nb: notification block containing notification handle.
+ * @pd_name: PM domain name.
+ */
+int genpd_register_notifier(struct notifier_block *nb, char *pd_name)
+{
+	int ret;
+	struct cache_notify_domains *entry;
+
+	if (!pd_name)
+		return -EINVAL;
+
+	/* Search if the pd is already registered */
+	mutex_lock(&domain_notify_list_lock);
+	list_for_each_entry(entry, &domain_notify_list, cache_list_node) {
+		if (!strcmp(entry->name, pd_name))
+			break;
+	}
+	mutex_unlock(&domain_notify_list_lock);
+
+	if (entry) {
+		pr_err("%s: pd already exists\n", __func__);
+		return -EINVAL;
+	}
+
+	entry = kzalloc(sizeof(*entry), GFP_KERNEL);
+	if (!entry)
+		return -ENOMEM;
+
+	entry->name = pd_name;
+
+	mutex_lock(&domain_notify_list_lock);
+	list_add(&entry->cache_list_node, &domain_notify_list);
+	mutex_unlock(&domain_notify_list_lock);
+	ret = blocking_notifier_chain_register(
+				&genpd_transition_notifier_list, nb);
+	return ret;
+}
+
+/**
+ * genpd_unregister_notifier - Un-register a PM domain for future notification.
+ * @nb: notification block containing notification handle.
+ * @pd_name: PM domain name.
+ */
+int genpd_unregister_notifier(struct notifier_block *nb, char *pd_name)
+{
+	int ret;
+	struct cache_notify_domains *entry;
+
+	mutex_lock(&domain_notify_list_lock);
+	list_for_each_entry(entry, &domain_notify_list, cache_list_node) {
+		if (!strcmp(entry->name, pd_name))
+			break;
+	}
+	if (!entry) {
+		mutex_unlock(&domain_notify_list_lock);
+		pr_err("%s: Invalid pd name\n", __func__);
+		return -EINVAL;
+	}
+	list_del(&entry->cache_list_node);
+	mutex_unlock(&domain_notify_list_lock);
+	ret = blocking_notifier_chain_unregister(
+				&genpd_transition_notifier_list, nb);
+	return ret;
+}
+
+/**
+ * genpd_invoke_transition_notifier - Calls the matching notification handler.
+ * @genpd: generic power domain structure.
+ * @state: can be of type - GPD_OFF_PRE/GPD_OFF_POST/GPD_ON_PRE/GPD_ON_POST.
+ */
+void genpd_invoke_transition_notifier(struct generic_pm_domain *genpd,
+			enum gpd_on_off_state state)
+{
+	struct cache_notify_domains *entry;
+
+	if (!genpd) {
+		pr_err("Invalid genpd parameter\n");
+		return;
+	}
+
+	if (state != GPD_OFF_PRE || state != GPD_OFF_POST
+			|| state != GPD_ON_PRE || state != GPD_ON_POST) {
+		pr_err("Invalid state parameter\n");
+		return;
+	}
+
+	mutex_lock(&domain_notify_list_lock);
+	list_for_each_entry(entry, &domain_notify_list, cache_list_node) {
+		if (!strcmp(entry->name, genpd->name))
+			break;
+	}
+	mutex_unlock(&domain_notify_list_lock);
+	if (!entry) /* Simply ignore */
+		return;
+
+	blocking_notifier_call_chain(&genpd_transition_notifier_list, state,
+				genpd);
+}
 #ifdef CONFIG_PM_GENERIC_DOMAINS_OF
 /*
  * Device Tree based PM domain providers.
diff --git a/include/linux/pm_domain.h b/include/linux/pm_domain.h
index 73e938b..659997f 100644
--- a/include/linux/pm_domain.h
+++ b/include/linux/pm_domain.h
@@ -25,6 +25,13 @@ enum gpd_status {
 	GPD_STATE_POWER_OFF,	/* PM domain is off */
 };
 
+enum gpd_on_off_state {
+	GPD_OFF_PRE = 0,	/* GPD state before power off */
+	GPD_OFF_POST,		/* GPD state after power off */
+	GPD_ON_PRE,		/* GPD state before power on */
+	GPD_ON_POST,		/* GPD state after power on */
+};
+
 struct dev_power_governor {
 	bool (*power_down_ok)(struct dev_pm_domain *domain);
 	bool (*stop_ok)(struct device *dev);
@@ -148,6 +155,12 @@ extern int pm_genpd_name_poweron(const char *domain_name);
 
 extern struct dev_power_governor simple_qos_governor;
 extern struct dev_power_governor pm_domain_always_on_gov;
+
+struct generic_pm_domain *pm_genpd_lookup_name(const char *domain_name);
+int genpd_register_notifier(struct notifier_block *nb, char *pd_name);
+int genpd_unregister_notifier(struct notifier_block *nb, char *pd_name);
+void genpd_invoke_transition_notifier(struct generic_pm_domain *genpd,
+			enum gpd_on_off_state state);
 #else
 
 static inline struct generic_pm_domain_data *dev_gpd_data(struct device *dev)
@@ -219,6 +232,24 @@ static inline int pm_genpd_name_poweron(const char *domain_name)
 {
 	return -ENOSYS;
 }
+static inline struct
+generic_pm_domain *pm_genpd_lookup_name(const char *domain_name)
+{
+	return NULL;
+}
+static inline int
+genpd_register_notifier(struct notifier_block *nb, char *pd_name)
+{
+	return 0;
+}
+static inline int
+genpd_unregister_notifier(struct notifier_block *nb, char *pd_name)
+{
+	return 0;
+}
+static inline void
+genpd_invoke_transition_notifier(struct generic_pm_domain *genpd,
+			enum gpd_on_off_state state) { }
 #define simple_qos_governor NULL
 #define pm_domain_always_on_gov NULL
 #endif
-- 
1.7.9.5