How can I get the current CPU frequency of an ARM processor on Ubuntu?

Question

How can I get the current CPU frequency of an ARM processor on Ubuntu? Neither /proc/cpuinfo nor /sys/devices/system/cpu/cpu*/cpufreq helps.

In fact, there is no /sys/devices/system/cpu/cpu*/cpufreq directory on my Ubuntu system. And there is no CPU MHz information in /proc/cpuinfo either.

The platform specs are: NVIDIA® Jetson™ TX2, ubuntu16.04, linux 4.9.18.

Could anybody give some hints on acquiring the current CPU frequency of an ARM processor?

Is there any kernel configuration may inflence on getting current cpu frenqency?

Answer 1

• on a pi 4 with a recent kernel /sys/devices/system/cpu/cpufreq/ and it's children are present
• if you are lucky , your platform provides something like: /sys/devices/platform/soc/soc:firmware/raspberrypi-clk/raspberrypi-cpufreq
• you could try perfstat with : perf stat sleep 1 as stated in the comments here: https://stackoverflow.com/q/32474101/11993317
• there could be an interface in your SoC like here: https://superuser.com/questions/406141/how-to-get-an-arm-cpu-clock-speed-in-linux

Answer 2

According to kernel documentation:

3. How to change the CPU cpufreq policy and/or speed
====================================================

3.1 Preferred Interface: sysfs
------------------------------

The preferred interface is located in the sysfs filesystem. If you
mounted it at /sys, the cpufreq interface is located in a subdirectory
"cpufreq" within the cpu-device directory (e.g.
/sys/devices/system/cpu/cpu0/cpufreq/ for the first CPU).

<...snip>

cpuinfo_cur_freq :        Current frequency of the CPU as obtained from
              the hardware, in KHz. This is the frequency
              the CPU actually runs at.

I've tested this on a Raspberry Pi V4 and confirmed that cpuinfo_cur_freq is present. For me it does list the same speed as cpuinfo_max_freq but I can't claim to know if that's correct or not.

You may wish to read up on this interface and deliberately slow your CPU to prove that it's not running at max speed.

The interface should be located at:

/sys/devices/system/cpu/cpu0/cpufreq/

Answer 3

upgrade to kernel4.9 , get L4T and read below ...

From nVidia Documentation:

In kernel 4.9 and following, the common clock framework (CCF) is supported. As a result:

• All device drivers use the public CCF APIs include/linux/clk.h, and include/linux/clk-provider.h, including functions such as clk_get, clk_enable, devm_clk_get, clk_prepare_enable, clk_prepare_disable, clk_disable, and others, instead of platform-specific APIs.
• All clock drivers, including the Jetson custom clk driver, implement clk_ops.
• Clock sources and clocks required by devices are defined in the Device Tree.
• Clocks are controlled by an R5 called the Boot and Power Management Processor. It runs RTOS software from bpmp.bin. The Linux kernel running on CCPLEX requests this software for clock programming. The NVIDIA® Jetson™ Linux Driver Package (L4T) clock driver wrapper is available in the nvidia/drivers/clk/tegra/ directory.

To check clock status

Applies to: Jetson AGX Xavier series and Jetson TX2 series

• On the device, enter the following command to launch debugfs and check the clock:

sudo -s

cat /sys/kernel/debug/bpmp/debug/clk/clk_tree

---

there is also another good article on elinux wiki

Answer 4

The utility cpufreq-info should help.

1. Install it

   sudo apt install cpufrequtils
   

2. Run it

   $ cpufreq-info
   analyzing CPU 126:
     driver: cppc_cpufreq
     CPUs which run at the same hardware frequency: 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127
     CPUs which need to have their frequency coordinated by software: 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127
     maximum transition latency: 4294.55 ms.
     hardware limits: 200 MHz - 2.60 GHz
     available cpufreq governors: conservative, ondemand, userspace, powersave, performance, schedutil
     current policy: frequency should be within 400 MHz and 2.60 GHz.
                     The governor "ondemand" may decide which speed to use
                     within this range.
     current CPU frequency is 400 MHz.
   

Answer 5

All anyone can suggest to you with the information given is something like try command x.

With that in mind you can try: lscpu (though I expect it will pull back the same info as can be found in /proc/cpuinfo; worth a shot though)

To get a better answer the community would likely need additional information such as the kernel version of the system. Maybe the version of Ubuntu as well.

You can find the kernel version with: uname -r

You can find the OS version with: lsb_release -a

Please let us know what you find!