ARM: cpuidle: Document the code

Add kernel-doc format documentation in the code.
Signed-off-by: NDaniel Lezcano <daniel.lezcano@linaro.org>

arch/arm/kernel/cpuidle.c

@@ -21,6 +21,17 @@ static const struct of_cpuidle_method __cpuidle_method_of_table_sentinel
 
 static struct cpuidle_ops cpuidle_ops[NR_CPUS];
 
+/**
+ * arm_cpuidle_simple_enter() - a wrapper to cpu_do_idle()
+ * @dev: not used
+ * @drv: not used
+ * @index: not used
+ *
+ * A trivial wrapper to allow the cpu_do_idle function to be assigned as a
+ * cpuidle callback by matching the function signature.
+ *
+ * Returns the index passed as parameter
+ */
 int arm_cpuidle_simple_enter(struct cpuidle_device *dev,
 		struct cpuidle_driver *drv, int index)
 {
@@ -29,6 +40,16 @@ int arm_cpuidle_simple_enter(struct cpuidle_device *dev,
 	return index;
 }
 
+/**
+ * arm_cpuidle_suspend() - function to enter low power idle states
+ * @index: an integer used as an identifier for the low level PM callbacks
+ *
+ * This function calls the underlying arch specific low level PM code as
+ * registered at the init time.
+ *
+ * Returns -EOPNOTSUPP if no suspend callback is defined, the result of the
+ * callback otherwise.
+ */
 int arm_cpuidle_suspend(int index)
 {
 	int ret = -EOPNOTSUPP;
@@ -40,6 +61,15 @@ int arm_cpuidle_suspend(int index)
 	return ret;
 }
 
+/**
+ * arm_cpuidle_get_ops() - find a registered cpuidle_ops by name
+ * @method: the method name
+ *
+ * Search in the __cpuidle_method_of_table array the cpuidle ops matching the
+ * method name.
+ *
+ * Returns a struct cpuidle_ops pointer, NULL if not found.
+ */
 static struct cpuidle_ops *__init arm_cpuidle_get_ops(const char *method)
 {
 	struct of_cpuidle_method *m = __cpuidle_method_of_table;
@@ -51,6 +81,19 @@ static struct cpuidle_ops *__init arm_cpuidle_get_ops(const char *method)
 	return NULL;
 }
 
+/**
+ * arm_cpuidle_read_ops() - Initialize the cpuidle ops with the device tree
+ * @dn: a pointer to a struct device node corresponding to a cpu node
+ * @cpu: the cpu identifier
+ *
+ * Get the method name defined in the 'enable-method' property, retrieve the
+ * associated cpuidle_ops and do a struct copy. This copy is needed because all
+ * cpuidle_ops are tagged __initdata and will be unloaded after the init
+ * process.
+ *
+ * Return 0 on sucess, -ENOENT if no 'enable-method' is defined, -EOPNOTSUPP if
+ * no cpuidle_ops is registered for the 'enable-method'.
+ */
 static int __init arm_cpuidle_read_ops(struct device_node *dn, int cpu)
 {
 	const char *enable_method;
@@ -75,6 +118,22 @@ static int __init arm_cpuidle_read_ops(struct device_node *dn, int cpu)
 	return 0;
 }
 
+/**
+ * arm_cpuidle_init() - Initialize cpuidle_ops for a specific cpu
+ * @cpu: the cpu to be initialized
+ *
+ * Initialize the cpuidle ops with the device for the cpu and then call
+ * the cpu's idle initialization callback. This may fail if the underlying HW
+ * is not operational.
+ *
+ * Returns:
+ *  0 on success,
+ *  -ENODEV if it fails to find the cpu node in the device tree,
+ *  -EOPNOTSUPP if it does not find a registered cpuidle_ops for this cpu,
+ *  -ENOENT if it fails to find an 'enable-method' property,
+ *  -ENXIO if the HW reports a failure or a misconfiguration,
+ *  -ENOMEM if the HW report an memory allocation failure 
+ */
 int __init arm_cpuidle_init(int cpu)
 {
 	struct device_node *cpu_node = of_cpu_device_node_get(cpu);