how2: frequency scalink at i.MX 27/51/53 under Linux?

[LiborG]

can you advise how can be changed core-clock freq. and how to control it under Linux?

//Imagine for example typical power-saving scenarios with 3 power modes and sequentially/dynamically adjusted core-clocking.

can you imagine that for example video-de/compression will work also during frequency scaling without interruption??

Thx, Libor

[MarianoGoluboff]

Hi Libor,

take a look at the document mx53_linux.pdf that is in the downloadable Linux docs bundle.

Chapter 6 has details on the frequency scaling driver. From that document:

To view what values the CPU frequency can be changed to in KHz (The values in the first column are thefrequency values) use this command:

cat /sys/devices/system/cpu/cpu0/cpufreq/stats/time_in_state

To change the CPU frequency to a value that is given by using the command above (for example, to 160MHz) use this command:

echo 160000 > /sys/devices/system/cpu/cpu0/cpufreq/scaling_setspeed

The frequency 160000 is in KHz, which is 160 MHz.

The maximum frequency can be checked using this command:

cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq

Use the following command to view the current CPU frequency in KHz:

cat /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_cur_freq