Change cpu core speed without reboot

Jakob Justesen

Intellectual 400 points

Hi,

Is it possible in any way to change the cpu speed without a reboot?

Note, Halting and reloading usb modules ect. would be ok, we just want to avoid a reboot.

Hope anyone can help us.

over 8 years ago

0 Cvetolin Shulev-XID over 8 years ago

TI__Guru 65405 points

Hi Jakob,

If you are using a Linux kernel it is possible to change the cpu frequency without rebooting the system.
It is necessary to check all available frequencies supported by your processor by the command:
#cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequ

and the set one of the available values (300 MHz for example):
echo 300000 > /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_cur_freq

You can find more details in the linked article:
processors.wiki.ti.com/.../Sitara_Linux_Training:_Power_Management

BR
Tsvetolin Shulev

0 Jakob Justesen over 8 years ago in reply to Cvetolin Shulev-XID

Intellectual 400 points

Hi Tsvetolin,

Thank you very much for your answer.

My "/sys/devices/system/cpu/cpu0/" is empty.

I tried to do a menuconfigm, but the CPU Power Management fan only has a CPU idle PM support.

So how do get the cpufreq drivers working ?

Best regards

Jakob

0 Cvetolin Shulev-XID over 8 years ago in reply to Jakob Justesen

TI__Guru 65405 points

Jakob,

Could you specify what is your processor and what software you are using? Also could you post a link to the software release where can be downloaded?

BR
Tsvetolin Shulev

0 Jakob Justesen over 8 years ago in reply to Cvetolin Shulev-XID

Intellectual 400 points

Hi Tsvetolin,

We are using the DM368 processor.
And the ti-dvsdk_dm365-evm_4_02_00_06 which you can get here: www.ti.com/.../linuxdvsdk-dm36x
It uses the Linux kernel version 2.6.32-17

Best regards
Jakob

0 Jakob Justesen over 8 years ago in reply to Cvetolin Shulev-XID

Intellectual 400 points

Hi Tsvetolin,

I can't see my last reply, so I try again.

The processor is DM368.
The software is the TI-DVSDK: www.ti.com/.../linuxdvsdk-dm36x
Which includes linux kernel version 2.6.32-17

Best regards
Jakob

0 Cvetolin Shulev-XID over 8 years ago in reply to Jakob Justesen

TI__Guru 65405 points

Jakob,

This functionality is available for many of the DaVinci processors based on the ARM Cortex-A8 architecture but not available by default for DM368 which is based on the ARM9 architecture.

Could you check in the menuconfig whether the following options are set:

CPU Power Management --->
[*] CPU Frequency scaling
    <*> 'userspace' cpufreq policy governor
    Default CPUFreq governor (userspace) --->
      (X) usespace

Also check how to build multiple governor in the Dynamic Voltage and Frequency scaling users guide at:

BR
Tsvetolin Shulev

0 Jakob Justesen over 8 years ago in reply to Cvetolin Shulev-XID

Intellectual 400 points

Hi Tsvetolin,

The menuconfig option CPU Frequency scaling does not exist, I can only select CPU PM Idle.

CPU Power Management --->
[*] CPU Frequency scaling

Is there any way to enable CPU Frequency scaling ?

Best regards

Jakob

0 Cvetolin Shulev-XID over 8 years ago in reply to Jakob Justesen

TI__Guru 65405 points

Jakob,

It seems that this option is not available for your processor.

BR
Tsvetolin Shulev

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Change cpu core speed without reboot