Low Power CPU operation

[A_Guyula]

Working with an IMX8m mini and I am looking for power saving operations. I noticed the low power boot mode of the processor. So, I am asking if there is there any way to set the ARM_A53_CLK_ROOT to less than 1Ghz values while linux is running? 

What about cores, can they be disabled. Say four cores reduced to 2 cores for different workloads?

[danielchen]

Hi

You can use below commands to enable/disable CPU.

echo 1 > /sys/devices/system/cpu/cpu1/online

echo 0 > /sys/devices/system/cpu/cpu1/online

Regards

Daniel

[A_Guyula]

This appears to function, thanks. 
Seems you MUST be root to execute these commands, just using sudo doesn't work. Guess I need to refresh on operating a root command as sudo vs actually being root.

Anything else you can help with ? Can the CPU clocks be reduced further than 1.2Ghz? 

A M

[danielchen]

Hi 

I would suggest you execute command " cpufreq-set -g powersave" to reduce the CPU frequency.  it can be reduced further than 1.2G hz

Regards

Daniel

[A_Guyula]

it can be reduced further than 1.2G hz

I am confused a little by the statement. Does powersave allow Linux to choose lower clock speed settings or are you saying that it can be done.

If it can be done, are there any examples? 

[danielchen · Accepted solution]

Hi @A_Guyula :

By default, current BSP support 3 frequencies for imx8mm EVK board.

danielchen_0-1747031852515.png

This is defined in device tree--imx8mm.dtsi

danielchen_1-1747031949803.png

If you need 1Ghz frequency, please add the relative node into the dts file

Regards

Daniel

[A_Guyula]

Assuming this works I label this a solution for now.

[A_Guyula]

Ah, my assumption was that these settings were selected by actual requirement, but this seems to lend some kind of arbitrary settings.

This look like a good thing to try then.

Thanks.