Linux CPUFreq

Linux CPUFreq is the frequency dynamically change lib.

1. the code is at linux/driver/cpufreq/

2. the sysfs user space interface is at /sys/devices/system/cpu/ . User could switch governor and set frequency range here.

3.each CPU has frequency policy structure object. CPU could share it. Policy contains frequency range setting.

4.frequency policy object connect to governor which is the real policy implementing unit.

5.governor 'ondemand' has a work queue, which calculate the CPU loading and then decide to change the frequency.

6.governor call cpufreq_driver->target() or target_index() to change the hardware clock setting.

7.voltage change is related to frequency change.