Dave Embedded Systems SBC AXEL, User Manual

Page: 128 / 139

S B C X U s e r ' s G u i d e v . 1 . 0 . 1
Parameter Description Default
exported directory
bootfile Path to the kernel binary
image on the tftp server xelk/uImage
fdtfile Path to the device tree
binary image on the tftp
server xelk/imx6q-sbcx.dtb
nfsargs
Kernel command line
with parameters for
loading the root file
system through NFS setenv bootargs root=/dev/nfs rw
nfsroot=${serverip}:${rootpath}
rootdelay=2
To run this configuration, just enter the command
run net_nfs
8.6 How can I change the CPU clock frequency?
A: The frequency of the CPU can be changed on the run using the
Cpufreq framework (please refer to the documentation included into the
Documentation/cpu-freq directory of the kernel source tree). The cpufreq
framework works in conjunction with the related driver & governor.
Cpufreq implementation controls the Linux OPP (Operating Performance
Points) adjusting the CPU core voltages and frequencies. CPUFreq is
enabled by default in the AXEL kernel configuration.
To view the available governors:
root@axel-lite:~# cat
/sys/devices/system/cpu/cpu0/cpufreq/scaling_available_governors
interactive conservative ondemand userspace powersave performance
To view the supported OPP's (frequency in KHz):
root@axel-lite:~# cat
/sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencie
s
396000 792000 996000
To change the OPP:
root@axel-lite:~# echo 396000 >
/sys/devices/system/cpu/cpu0/cpufreq/scaling_setspeed
Please note that OPP can be changed only using the userspace
governor. If governors like ondemand is used, OPP change happens
automatically based on the system load.
December, 2019
128/139