LayerscapeのトピックRe: Set CPU frequency not working

Set CPU frequency not working

noahw — Tue, 08 Apr 2025 01:55:16 GMT

I am following directions on this page (https://docs.nxp.com/bundle/GUID-39A0A446-70E5-4ED7-A580-E7508B61A5F1/page/GUID-40BE9AD5-DF6B-4D99-A3FB-5988A50DACA2.html) about switching CPU frequency by writing to a file in /sys.

When I try to run the command

echo 799999 > /sys/devices/system/cpu/cpu0/cpufreq/scaling_setspeed

I see the following error:

-bash: echo: write error: Invalid argument

What am I doing wrong? I tried other values like 300000, and I also tried putting the value in quotes, using the -n flag for echo, etc. I used chmod to add write permission to scaling_setspeed. Is there something else I need to do?

Re: Set CPU frequency not working

June_Lu — Tue, 08 Apr 2025 05:42:17 GMT

Please kindly share the MPU part number and SW version, thanks

Re: Set CPU frequency not working

noahw — Tue, 08 Apr 2025 16:34:01 GMT

@June_Lu This is the LS1028ARDB running LSDK 21.08, kernel 5.10.35.

Re: Set CPU frequency not working

June_Lu — Wed, 09 Apr 2025 09:49:35 GMT

In the default LSDK2108.

root@localhost:~# cd /sys/devices/system/cpu/cpu0/cpufreq

root@localhost:/sys/devices/system/cpu/cpu0/cpufreq# ls

affected_cpus cpuinfo_max_freq cpuinfo_transition_latency scaling_available_frequencies scaling_cur_freq scaling_governor scaling_min_freq stats

cpuinfo_cur_freq cpuinfo_min_freq related_cpus scaling_available_governors scaling_driver scaling_max_freq scaling_setspeed

root@localhost:/sys/devices/system/cpu/cpu0/cpufreq# cat scaling_available_governors

ondemand userspace performance

root@localhost:/sys/devices/system/cpu/cpu0/cpufreq# echo userspace > scaling_governor

root@localhost:/sys/devices/system/cpu/cpu0/cpufreq# cat scaling_cur_freq

600000

root@localhost:/sys/devices/system/cpu/cpu0/cpufreq# cat scaling_available_frequencies

1500000 1200000 750000 600000 375000 300000

root@localhost:/sys/devices/system/cpu/cpu0/cpufreq# echo 750000 > scaling_setspeed

root@localhost:/sys/devices/system/cpu/cpu0/cpufreq# cat scaling_cur_freq

750000