How to change the CPU core clock speed (in general how to reduce power consumption)?

nlbutts · ‎2019-07-01

I noticed cpufrequtils are installed in the default image. But when you run cpufreq-info you get a message that indicates it is not supported.

root@stm32mp1:~# cpufreq-info
cpufrequtils 008: cpufreq-info (C) Dominik Brodowski 2004-2009
Report errors and bugs to cpufreq@vger.kernel.org, please.
analyzing CPU 0:
  no or unknown cpufreq driver is active on this CPU
analyzing CPU 1:
  no or unknown cpufreq driver is active on this CPU

I then updated the kernel to include the cpu frequency scaling code, but I get the same error.

I'm trying to reduce the power consumption of the target platform. So I have done the following:

1) Unplugged the LCD

2) Switched Ethernet to 10/100 instead of Gigabit Ethernet, this drops the power by 200 mW.

3) Trying to reduce core clocks and turn off peripherals.

Does anyone have any other suggestions to reduce power?

Bernard PUEL · ‎2019-07-04

stm32mp1 does not support today dynamic frequency scaling, so cpufreq cannot be used. If you want to change cpu frequency, you need to use the clock tree (better use CubeMx for the graphical interface).

For power, an application note is available: https://www.st.com/resource/en/application_note/dm00449434.pdf or directly in the wiki ("power") to get overview and fast how-to.