[RFC PATCH 2/5] thermal: cpu_cooling: Add notifications support for the clients

[Amit Daniel Kachhap <amit.daniel@samsung.com>]

This patch adds notification support for those clients of cpu_cooling
APIs which may want to do something interesting after receiving these
cpu_cooling events. The notifier structure passed is of both Set/Get type.
The notfications events can be of type,
1. CPU_COOLING_SET_STATE_PRE
2. CPU_COOLING_SET_STATE_POST
3. CPU_COOLING_GET_CUR_STATE
4. CPU_COOLING_GET_MAX_STATE

The advantages of these notfications is to differentiate between different
P states in the cpufreq table and the cooling states. The clients of these
events may group few P states into 1 cooling states. Also some more cooling
states can be enabled when the maximum of P state is reached. Post notifications
can be used for those cases.

Signed-off-by: Amit Daniel Kachhap <amit.daniel@samsung.com>
---
 drivers/thermal/cpu_cooling.c |   99 +++++++++++++++++++++++++++++++++++++++-
 include/linux/cpu_cooling.h   |   55 +++++++++++++++++++++++
 2 files changed, 151 insertions(+), 3 deletions(-)

diff --git a/drivers/thermal/cpu_cooling.c b/drivers/thermal/cpu_cooling.c
index 21f44d4..e2aeb36 100644
--- a/drivers/thermal/cpu_cooling.c
+++ b/drivers/thermal/cpu_cooling.c
@@ -50,6 +50,7 @@ struct cpufreq_cooling_device {
 	unsigned int cpufreq_state;
 	unsigned int cpufreq_val;
 	struct cpumask allowed_cpus;
+	struct cpufreq_cooling_status request_status;
 	struct list_head node;
 };
 static DEFINE_IDR(cpufreq_idr);
@@ -59,6 +60,8 @@ static DEFINE_MUTEX(cooling_cpufreq_lock);
 #define NOTIFY_INVALID NULL
 static struct cpufreq_cooling_device *notify_device;
 
+/* Notfier list to validates/updates the cpufreq cooling states */
+static BLOCKING_NOTIFIER_HEAD(cpufreq_cooling_state_notifier_list);
 /* A list to hold all the cpufreq cooling devices registered */
 static LIST_HEAD(cpufreq_cooling_list);
 
@@ -266,6 +269,21 @@ static unsigned int get_cpu_frequency(unsigned int cpu, unsigned long level)
 	return freq;
 }
 
+static int
+cpufreq_cooling_notify_states(struct cpufreq_cooling_status *request,
+			enum cpu_cooling_state_ops op)
+{
+	/* Invoke the notifiers which have registered for this state change */
+	if (op == CPU_COOLING_SET_STATE_PRE ||
+		op == CPU_COOLING_SET_STATE_POST ||
+		op == CPU_COOLING_GET_MAX_STATE ||
+		op == CPU_COOLING_GET_CUR_STATE) {
+		blocking_notifier_call_chain(
+			&cpufreq_cooling_state_notifier_list, op, request);
+	}
+	return 0;
+}
+
 /**
  * cpufreq_apply_cooling - function to apply frequency clipping.
  * @cpufreq_device: cpufreq_cooling_device pointer containing frequency
@@ -285,9 +303,18 @@ static int cpufreq_apply_cooling(struct cpufreq_cooling_device *cpufreq_device,
 	struct cpumask *mask = &cpufreq_device->allowed_cpus;
 	unsigned int cpu = cpumask_any(mask);
 
+	cpufreq_device->request_status.cur_state =
+						cpufreq_device->cpufreq_state;
+	cpufreq_device->request_status.new_state = cooling_state;
+
+	cpufreq_cooling_notify_states(&cpufreq_device->request_status,
+					CPU_COOLING_SET_STATE_PRE);
+
+	cooling_state = cpufreq_device->request_status.new_state;
 
 	/* Check if the old cooling action is same as new cooling action */
-	if (cpufreq_device->cpufreq_state == cooling_state)
+	if (cpufreq_device->cpufreq_state ==
+				cpufreq_device->request_status.new_state)
 		return 0;
 
 	clip_freq = get_cpu_frequency(cpu, cooling_state);
@@ -304,7 +331,8 @@ static int cpufreq_apply_cooling(struct cpufreq_cooling_device *cpufreq_device,
 	}
 
 	notify_device = NOTIFY_INVALID;
-
+	cpufreq_cooling_notify_states(&cpufreq_device->request_status,
+					CPU_COOLING_SET_STATE_POST);
 	return 0;
 }
 
@@ -383,6 +411,11 @@ static int cpufreq_get_max_state(struct thermal_cooling_device *cdev,
 	if (count > 0)
 		*state = count;
 
+	cpufreq_device->request_status.max_state = count;
+	cpufreq_cooling_notify_states(&cpufreq_device->request_status,
+					CPU_COOLING_GET_MAX_STATE);
+	*state = cpufreq_device->request_status.max_state;
+
 	return ret;
 }
 
@@ -410,8 +443,12 @@ static int cpufreq_get_cur_state(struct thermal_cooling_device *cdev,
 		/* Cooling device pointer not found */
 		return -EINVAL;
 	}
+	cpufreq_device->request_status.cur_state =
+						cpufreq_device->cpufreq_state;
+	cpufreq_cooling_notify_states(&cpufreq_device->request_status,
+					CPU_COOLING_GET_CUR_STATE);
 
-	*state = cpufreq_device->cpufreq_state;
+	*state = cpufreq_device->request_status.cur_state;
 
 	return 0;
 }
@@ -520,6 +557,7 @@ __cpufreq_cooling_register(struct device_node *np,
 	}
 	cpufreq_dev->cool_dev = cool_dev;
 	cpufreq_dev->cpufreq_state = 0;
+	cpufreq_dev->request_status.devdata = devdata;
 	mutex_lock(&cooling_cpufreq_lock);
 
 	/* Register the notifier for first cpufreq cooling device */
@@ -614,3 +652,58 @@ void cpufreq_cooling_unregister(struct thermal_cooling_device *cdev)
 	kfree(cpufreq_dev);
 }
 EXPORT_SYMBOL_GPL(cpufreq_cooling_unregister);
+
+/**
+ * cpufreq_cooling_register_notifier - register a driver with cpufreq cooling.
+ * @nb:	notifier function to register.
+ * @list: CPU_COOLING_STATE_NOTIFIER type.
+ *
+ * Add a driver to receive cpufreq cooling notifications like current state,
+ * max state and set state. The drivers after reading the events can perform
+ * some mapping between the P states and cooling states like grouping some P
+ * states into 1 cooling state.
+ *
+ * Return: 0 (success)
+ */
+int cpufreq_cooling_register_notifier(struct notifier_block *nb,
+					unsigned int list)
+{
+	int ret = 0;
+	switch (list) {
+	case CPU_COOLING_STATE_NOTIFIER:
+		ret = blocking_notifier_chain_register(
+				&cpufreq_cooling_state_notifier_list, nb);
+		break;
+	default:
+		ret = -EINVAL;
+	}
+	return ret;
+}
+EXPORT_SYMBOL_GPL(cpufreq_cooling_register_notifier);
+
+/**
+ * cpufreq_cooling_unregister_notifier - unregisters a driver with cpufreq
+ * cooling.
+ * @nb:	notifier function to unregister.
+ * @list: CPU_COOLING_STATE_NOTIFIER type.
+ *
+ * Removes a driver to receive further cpufreq cooling notifications.
+ *
+ * Return: 0 (success)
+ */
+int cpufreq_cooling_unregister_notifier(struct notifier_block *nb,
+					unsigned int list)
+{
+	int ret = 0;
+	switch (list) {
+	case CPU_COOLING_STATE_NOTIFIER:
+		ret = blocking_notifier_chain_unregister(
+				&cpufreq_cooling_state_notifier_list, nb);
+		break;
+	default:
+		ret = -EINVAL;
+	}
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(cpufreq_cooling_unregister_notifier);
diff --git a/include/linux/cpu_cooling.h b/include/linux/cpu_cooling.h
index aaef7d8..f786935 100644
--- a/include/linux/cpu_cooling.h
+++ b/include/linux/cpu_cooling.h
@@ -28,6 +28,22 @@
 #include <linux/thermal.h>
 #include <linux/cpumask.h>
 
+#define CPU_COOLING_STATE_NOTIFIER	(0)
+
+enum cpu_cooling_state_ops {
+	CPU_COOLING_SET_STATE_PRE,
+	CPU_COOLING_SET_STATE_POST,
+	CPU_COOLING_GET_CUR_STATE,
+	CPU_COOLING_GET_MAX_STATE,
+};
+
+struct cpufreq_cooling_status {
+	unsigned long cur_state;
+	unsigned long new_state;
+	unsigned long max_state;
+	void *devdata;
+};
+
 #ifdef CONFIG_CPU_THERMAL
 /**
  * cpufreq_cooling_register - function to create cpufreq cooling device.
@@ -62,6 +78,34 @@ of_cpufreq_cooling_register(struct device_node *np,
 void cpufreq_cooling_unregister(struct thermal_cooling_device *cdev);
 
 unsigned long cpufreq_cooling_get_level(unsigned int cpu, unsigned int freq);
+
+/**
+ * cpufreq_cooling_register_notifier - register a driver with cpufreq cooling.
+ * @nb:	notifier function to register.
+ * @list: CPU_COOLING_STATE_NOTIFIER type.
+ *
+ * Add a driver to receive cpufreq cooling notifications like current state,
+ * max state and set state. The drivers after reading the events can perform
+ * some mapping between the P states and cooling states like grouping some P
+ * states into 1 cooling state.
+ *
+ * Return: 0 (success)
+ */
+int cpufreq_cooling_register_notifier(struct notifier_block *nb,
+					unsigned int list);
+
+/**
+ * cpufreq_cooling_unregister_notifier - unregisters a driver with cpufreq
+ * cooling.
+ * @nb:	notifier function to unregister.
+ * @list: CPU_COOLING_STATE_NOTIFIER type.
+ *
+ * Removes a driver to receive further cpufreq cooling notifications.
+ *
+ * Return: 0 (success)
+ */
+int cpufreq_cooling_unregister_notifier(struct notifier_block *nb,
+					unsigned int list);
 #else /* !CONFIG_CPU_THERMAL */
 static inline struct thermal_cooling_device *
 cpufreq_cooling_register(const struct cpumask *clip_cpus, void *devdata)
@@ -84,6 +128,17 @@ unsigned long cpufreq_cooling_get_level(unsigned int cpu, unsigned int freq)
 {
 	return THERMAL_CSTATE_INVALID;
 }
+static inline int
+cpufreq_cooling_register_notifier(struct notifier_block *nb, unsigned int list)
+{
+	return 0;
+}
+static inline int
+cpufreq_cooling_unregister_notifier(struct notifier_block *nb,
+					unsigned int list)
+{
+	return 0;
+}
 #endif	/* CONFIG_CPU_THERMAL */
 
 #endif /* __CPU_COOLING_H__ */
-- 
1.7.1