[PATCH 1/5] pm: qos: add notifiers for CPU latency and wakeup latency QoS

[Yaxiong Tian]

Expose notifier registration for the system-wide CPU latency and
wakeup latency QoS constraints so listeners can react when the
aggregate target value changes.  pm_qos_update_target() already
invokes constraint notifiers when the effective value changes.

Signed-off-by: Yaxiong Tian <tianyaxiong@xxxxxxxxxx>
---
 include/linux/pm_qos.h | 23 +++++++++++++++++++
 kernel/power/qos.c     | 50 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 73 insertions(+)

diff --git a/include/linux/pm_qos.h b/include/linux/pm_qos.h
index 6cea4455f867..3759b453c6d6 100644
--- a/include/linux/pm_qos.h
+++ b/include/linux/pm_qos.h
@@ -149,6 +149,8 @@ bool cpu_latency_qos_request_active(struct pm_qos_request *req);
 void cpu_latency_qos_add_request(struct pm_qos_request *req, s32 value);
 void cpu_latency_qos_update_request(struct pm_qos_request *req, s32 new_value);
 void cpu_latency_qos_remove_request(struct pm_qos_request *req);
+int cpu_latency_qos_add_notifier(struct notifier_block *notifier);
+int cpu_latency_qos_remove_notifier(struct notifier_block *notifier);
 #else
 static inline s32 cpu_latency_qos_limit(void) { return INT_MAX; }
 static inline bool cpu_latency_qos_request_active(struct pm_qos_request *req)
@@ -160,15 +162,36 @@ static inline void cpu_latency_qos_add_request(struct pm_qos_request *req,
 static inline void cpu_latency_qos_update_request(struct pm_qos_request *req,
 						  s32 new_value) {}
 static inline void cpu_latency_qos_remove_request(struct pm_qos_request *req) {}
+static inline int cpu_latency_qos_add_notifier(struct notifier_block *notifier)
+{
+	return 0;
+}
+static inline int
+cpu_latency_qos_remove_notifier(struct notifier_block *notifier)
+{
+	return 0;
+}
 #endif
 
 #ifdef CONFIG_PM_QOS_CPU_SYSTEM_WAKEUP
 s32 cpu_wakeup_latency_qos_limit(void);
+int cpu_wakeup_latency_qos_add_notifier(struct notifier_block *notifier);
+int cpu_wakeup_latency_qos_remove_notifier(struct notifier_block *notifier);
 #else
 static inline s32 cpu_wakeup_latency_qos_limit(void)
 {
 	return PM_QOS_RESUME_LATENCY_NO_CONSTRAINT;
 }
+static inline int
+cpu_wakeup_latency_qos_add_notifier(struct notifier_block *notifier)
+{
+	return 0;
+}
+static inline int
+cpu_wakeup_latency_qos_remove_notifier(struct notifier_block *notifier)
+{
+	return 0;
+}
 #endif
 
 #ifdef CONFIG_PM
diff --git a/kernel/power/qos.c b/kernel/power/qos.c
index 1944dbeb0d4c..392ab3dbb923 100644
--- a/kernel/power/qos.c
+++ b/kernel/power/qos.c
@@ -212,12 +212,15 @@ bool pm_qos_update_flags(struct pm_qos_flags *pqf,
 #ifdef CONFIG_CPU_IDLE
 /* Definitions related to the CPU latency QoS. */
 
+static BLOCKING_NOTIFIER_HEAD(cpu_latency_qos_notifiers);
+
 static struct pm_qos_constraints cpu_latency_constraints = {
 	.list = PLIST_HEAD_INIT(cpu_latency_constraints.list),
 	.target_value = PM_QOS_CPU_LATENCY_DEFAULT_VALUE,
 	.default_value = PM_QOS_CPU_LATENCY_DEFAULT_VALUE,
 	.no_constraint_value = PM_QOS_CPU_LATENCY_DEFAULT_VALUE,
 	.type = PM_QOS_MIN,
+	.notifiers = &cpu_latency_qos_notifiers,
 };
 
 static inline bool cpu_latency_qos_value_invalid(s32 value)
@@ -335,6 +338,28 @@ void cpu_latency_qos_remove_request(struct pm_qos_request *req)
 }
 EXPORT_SYMBOL_GPL(cpu_latency_qos_remove_request);
 
+/**
+ * cpu_latency_qos_add_notifier - Add CPU latency QoS change notifier.
+ * @notifier: Notifier block managed by the caller.
+ */
+int cpu_latency_qos_add_notifier(struct notifier_block *notifier)
+{
+	return blocking_notifier_chain_register(&cpu_latency_qos_notifiers,
+						notifier);
+}
+EXPORT_SYMBOL_GPL(cpu_latency_qos_add_notifier);
+
+/**
+ * cpu_latency_qos_remove_notifier - Remove CPU latency QoS change notifier.
+ * @notifier: Notifier block previously registered.
+ */
+int cpu_latency_qos_remove_notifier(struct notifier_block *notifier)
+{
+	return blocking_notifier_chain_unregister(&cpu_latency_qos_notifiers,
+						  notifier);
+}
+EXPORT_SYMBOL_GPL(cpu_latency_qos_remove_notifier);
+
 /* User space interface to the CPU latency QoS via misc device. */
 
 static int cpu_latency_qos_open(struct inode *inode, struct file *filp)
@@ -417,12 +442,15 @@ static struct miscdevice cpu_latency_qos_miscdev = {
 
 #ifdef CONFIG_PM_QOS_CPU_SYSTEM_WAKEUP
 /* The CPU system wakeup latency QoS. */
+static BLOCKING_NOTIFIER_HEAD(cpu_wakeup_latency_qos_notifiers);
+
 static struct pm_qos_constraints cpu_wakeup_latency_constraints = {
 	.list = PLIST_HEAD_INIT(cpu_wakeup_latency_constraints.list),
 	.target_value = PM_QOS_RESUME_LATENCY_NO_CONSTRAINT,
 	.default_value = PM_QOS_RESUME_LATENCY_NO_CONSTRAINT,
 	.no_constraint_value = PM_QOS_RESUME_LATENCY_NO_CONSTRAINT,
 	.type = PM_QOS_MIN,
+	.notifiers = &cpu_wakeup_latency_qos_notifiers,
 };
 
 /**
@@ -436,6 +464,28 @@ s32 cpu_wakeup_latency_qos_limit(void)
 	return pm_qos_read_value(&cpu_wakeup_latency_constraints);
 }
 
+/**
+ * cpu_wakeup_latency_qos_add_notifier - Add wakeup latency QoS notifier.
+ * @notifier: Notifier block managed by the caller.
+ */
+int cpu_wakeup_latency_qos_add_notifier(struct notifier_block *notifier)
+{
+	return blocking_notifier_chain_register(&cpu_wakeup_latency_qos_notifiers,
+						notifier);
+}
+EXPORT_SYMBOL_GPL(cpu_wakeup_latency_qos_add_notifier);
+
+/**
+ * cpu_wakeup_latency_qos_remove_notifier - Remove wakeup latency QoS notifier.
+ * @notifier: Notifier block previously registered.
+ */
+int cpu_wakeup_latency_qos_remove_notifier(struct notifier_block *notifier)
+{
+	return blocking_notifier_chain_unregister(&cpu_wakeup_latency_qos_notifiers,
+						  notifier);
+}
+EXPORT_SYMBOL_GPL(cpu_wakeup_latency_qos_remove_notifier);
+
 static int cpu_wakeup_latency_qos_open(struct inode *inode, struct file *filp)
 {
 	struct pm_qos_request *req;
-- 
2.43.0