View source for CPU freq and num of cores

{{PageHeader|Set the CPU freq. and number of active cores}}
{{DocImage|category1=Yocto|category2=VAR-SOM-MX6}}[[Category:DART-6UL]] [[Category:VAR-SOM-MX7]][[Category:DART-MX8M]][[Category:DART-MX8M-MINI]]

{{Note|If your motivation is to simulate a weaker SOC model (for example, simulate an i.MX6Solo using an i.MX6Quad),<br>
note that there are a few other differences between some of the i.MX SOC models, like RAM bus width (32bit on the Solo, 64bit on the Quad) and some graphics acceleration features.<br>
See all the differences in the comparison table here:<br>
http://www.nxp.com/docs/en/brochure/FLYRIMXPRDCMPR.pdf}}

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= CPU cores =
There are two ways to disable/enable CPU cores:<br>
<br>
1. Add 'maxcpus=n' (n being the number of cores you wish to activate), to the kernel command line (the bootargs from U-Boot).<br>
E.g. Assuming you are using our latest U-Boot, stop at the U-Boot command line and enter:
 => setenv kernelargs maxcpus=2
<br>
2. To disable/enable cores at kernel runtime:<br>
Disbale core X:<br>
 # echo 0 > /sys/devices/system/cpu/cpuX/online
Enable core X:<br>
 # 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).<br>
<br>
To see the active cores, run:<br>
 # cat /proc/cpuinfo

= CPU frequencies =
'''Governors''':<br>
There are several frequency governors which determine the frequency policy.<br>
The default frequency governor is "ondemand", which sets the CPU frequency depending on the current system load.<br>
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:<br>
https://github.com/varigit/linux-imx/blob/imx_4.9.88_2.0.0_ga-var01/Documentation/cpu-freq/governors.txt<br>
<br>
To set the current governor:
 # echo GOVERNOR > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
(GOVERNOR being one of the available governors)<br>
<br>
'''Useful commands''':<br>
To see the available CPU frequencies:<br>
 # cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies
<br>
To see the current CPU frequency:<br>
 # cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq
<br>
Common scenarios:<br>
1. Use the default "ondemand" governor and limit the maximum allowed CPU freq. using the following commands:<br>
<br>
To see the current maximum allowed CPU frequency:<br>
 # cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq
<br>
To set the maximum allowed CPU frequency:<br>
 # echo FREQ > /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq
(FREQ being one of the available CPU frequencies)<br>
<br>
2. Use the "userspace" governor and set the CPU to a specific frequency using the following command:<br>

 # echo FREQ > /sys/devices/system/cpu/cpu0/cpufreq/scaling_setspeed
(FREQ being one of the available CPU frequencies)<br>