sched: ARM: arch_scale_freq_power

I work to link the cpu_power of ARM cores to their frequency by using arch_scale_freq_power. It's explained in the kernel that cpu_power is used to distribute load on cpus and a cpu with more cpu_power will pick up more load. The default value is SCHED_POWER_SCALE and I increase the value if I want a cpu to have more load than another one. Is there an advised range for cpu_power value as well as some time scale constraints for updating the cpu_power value ? I'm also wondering why this scheduler feature is currently disable by default ?

Regards, Vincent