Re: beaglebone: changing cpu frequency

[John Klos <john%ziaspace.com@localhost>]

> I finally debugged the code I added to allow the changing of the
> CPU frequency on the beaglebone (regardless of color).
>
> Use sysctl to change it:
>
> # sysctl -w machdep.frequency.current=1000
> cpu0: frequency changed from 550 MHz to 1000 MHz
> machdep.frequency.current: 550 -> 1000

It works, sorta. All frequencies work except 1 GHz:

cpu0: frequency changed from 550 MHz to 600 MHz
cpu0: frequency changed from 600 MHz to 650 MHz
cpu0: frequency changed from 650 MHz to 700 MHz
cpu0: frequency changed from 700 MHz to 720 MHz
cpu0: frequency changed from 720 MHz to 800 MHz
cpu0: frequency changed from 800 MHz to 900 MHz

When trying 1000 MHz, the BeagleBone Black locks up and isn't responsive 
either on the network or via serial.

On the other hand, the speed is actually being changed:

550 MHz, time ./primes
1000000, 15485863
      183.96 real       183.54 user         0.02 sys

900 MHz, time ./primes
1000000, 15485863
      112.29 real       112.11 user         0.01 sys

John