AM6 CPU freq and num of cores
CPU cores
There are two ways to disable/enable CPU cores:
1. Add 'maxcpus=n' (n being the number of cores you wish to activate), to the kernel command line (the bootargs from U-Boot).
E.g. Assuming you are using our latest U-Boot, stop at the U-Boot command line and enter:
=> setenv kernelargs maxcpus=2
2. To disable/enable cores at kernel runtime:
Disable core X:
# echo 0 > /sys/devices/system/cpu/cpuX/online
Enable core X:
# echo 1 > /sys/devices/system/cpu/cpuX/online
X being the core number you want to enable/disable, and can range from '1' to '(number of actual CPU cores)-1' (cpu0 is always enabled).
To see the active cores, run:
# cat /proc/cpuinfo
CPU frequencies
Governors:
There are several frequency governors which determine the frequency policy.
The default frequency governor is "ondemand", which sets the CPU frequency depending on the current system load.
(Note: the default governor is selected in the kernel defconfig. You can choose a different default governor using menuconfig before building the kernel - to reach this setting, go to: CPU Power Management -> CPU Frequency scaling -> Default CPUFreq governor)
To list all available governors:
# cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_governors
To read about the different governors, see the following page from the Linux documentation:
https://github.com/varigit/linux-imx/blob/5.4-2.1.x-imx_var01/Documentation/admin-guide/pm/cpufreq.rst
To set the current governor:
# echo GOVERNOR > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
(GOVERNOR being one of the available governors)
Useful commands:
To see the available CPU frequencies:
# cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies
To see the current CPU frequency:
# cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq
Common scenarios:
1. Use the default "ondemand" governor and limit the maximum allowed CPU freq. using the following commands:
To see the current maximum allowed CPU frequency:
# cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq
To set the maximum allowed CPU frequency:
# echo FREQ > /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq
(FREQ being one of the available CPU frequencies)
2. Use the "userspace" governor and set the CPU to a specific frequency using the following command:
# echo FREQ > /sys/devices/system/cpu/cpu0/cpufreq/scaling_setspeed
(FREQ being one of the available CPU frequencies)