1. CPUidle framework provides the capability to sleep to the different low power modes.
2. idle thread will call cpu_startup_entry()->cpu_idle_loop()->cpuidle_idle_call() to use cpuidle framework.
3. in cpuidle_idle_call(), cpuidle_select() ,cpuidle_enter() and cpuidle_reflect() are called. They are the governor API for the cpuidle framework.
4. governor 'menu' will calculate which low power mode to enter. The calculation is based on cpu loading, iowaiters and exit latency.
5. low power modes are defined in cpuidle_driver. cpuidle_register() registers cpuidle_driver.