interface for changing clock frequency

ranchu

Guru 20755 points

Hello,

The interface for changing clock frequency for is done using sysfs (according to PSP):

cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies

Is it possible to change it using ioctl or other mechanism without sysfs/debugfs ?

Thanks,

Ran

over 9 years ago

0 Titusrathinaraj Stalin over 9 years ago

TI__Guru** 116100 points

Hi Ran,

Yes it is possible, some how you have to use the same stuffs that what SYSFS is doing.

You have to do all the PLL and clocking stuffs with lock mechanism.

Why don't you prefer this generic DVFS mechanism ?

It is very generic and useful interface & powerful too.

Do you have intense to use your own ioctl for clock change ?

0 ranchu over 9 years ago in reply to Titusrathinaraj Stalin

Guru 20755 points

Hi Titus,

Thanks for the quick response.
We disabled sysfs, debugfs from various SW reasons.
Can you please elaborate how we can alternatively do this access without sysfs ?

Thanks!
Ran

0 Titusrathinaraj Stalin over 9 years ago in reply to ranchu

TI__Guru** 116100 points

Hi Ran,

Please refer to the following kernel location and files then try to modify the frequency of processor.

arch/arm/mach-omap2/

opp.c

opp3xxx_data.c

pm33xx.c

0 ranchu over 9 years ago in reply to Titusrathinaraj Stalin

Guru 20755 points

Hi Titus,

Can you give some pointers as to the available methods to access the relevant variables so that we can modify frequency?

Thanks,

Ran

0 Titusrathinaraj Stalin over 9 years ago in reply to ranchu

TI__Guru** 116100 points

Hi Ran,

Typically linux don't have driver separately (apart DVFS thr SYSFS) for this but you have to write your own linux driver to accomplish this.

You have to understand the code which I gave already and try to use/implement in your module driver.

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interface for changing clock frequency