ENGR00273073-1 arm: add cpu idle notification callback

Some modules may need to know cpu idle status and take
actions before and after cpu idle, so we can add
notification callback when enter/exit cpu idle, then
modules only need to register this notification callback,
everytime cpu enter/exit idle, the callback chain will be
executed.

Currently only cpufreq interactive governor use this
notification, as it wants to save power, the timers of
interactive governor are only enabled when cpu is not in idle.

Signed-off-by: Anson Huang <b20788@freescale.com>

1 files changed, 19 insertions, 0 deletions

diff --git a/kernel/cpu.c b/kernel/cpu.c
index 198a38883e64..6e995438287a 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -726,3 +726,22 @@ void init_cpu_online(const struct cpumask *src)
 {
 	cpumask_copy(to_cpumask(cpu_online_bits), src);
 }
+
+static ATOMIC_NOTIFIER_HEAD(idle_notifier);
+void idle_notifier_register(struct notifier_block *n)
+{
+	atomic_notifier_chain_register(&idle_notifier, n);
+}
+EXPORT_SYMBOL_GPL(idle_notifier_register);
+
+void idle_notifier_unregister(struct notifier_block *n)
+{
+	atomic_notifier_chain_unregister(&idle_notifier, n);
+}
+EXPORT_SYMBOL_GPL(idle_notifier_unregister);
+
+void idle_notifier_call_chain(unsigned long val)
+{
+	atomic_notifier_call_chain(&idle_notifier, val, NULL);
+}
+EXPORT_SYMBOL_GPL(idle_notifier_call_chain);