How to call "clock_control_off(const struct device *dev, clock_control_subsys_t sys)" on LFCLK

[Ubaid_M]

Hi,

If i need to call zephyr driver API clock_control_off( ) present in zephyr\include\drivers\clock_control.h on LFCLK.
How can I do it,.?

As an example, to populate the argument '*dev' in 

clock_control_off(const struct device *dev, clock_control_subsys_t sys)

Do I Use something like:

	const struct device *clock;
	
	clock = device_get_binding("CLOCK");

Will this give me dev struct to LFCLK..?
And how do I populate for:

clock_control_subsys_t sys

for LFCLK.

Kindly suggest.

Thanks,

[Ubaid_M]

Should i declare a new device in project's zephyr.dts file for LFCLK label..?
As in:

		clock: clock@40000000 {
			compatible = "nordic,nrf-clock";
			reg = < 0x40000000 0x1000 >;
			interrupts = < 0x0 0x1 >;
			status = "okay";
			label = "LFCLK";
		};

What are the changes I need to consider to LFCLK device declaration as in above.?
And how do I set the argument "clock_control_subsys_t sys" for LFCLK.?

[Priyanka]

Hi,

The LFCLK is already on by default and this is done during startup for the Zephyr OS. If you need to do any changes, you could use the kconfig statements

CONFIG_CLOCK_CONTROL_NRF_ACCURACY

CONFIG_CLOCK_CONTROL_NRF_K32SRC_XTAL (=y by default)

CONFIG_CLOCK_CONTROL_NRF_K32SRC_RC

But the LFCLK is normally kept on since it is needed by the Zephyr Scheduler and bluetooth Stack. So if you plan to deselect the XTAL source, you need to enable RC oscillator, since you should select one LF clock source. You could try referring to LFCLK controller documentation for more details.

Generally, including the required kconfig statements in your prj.conf file should do the trick and you do not have to modify or set any code.

Kind Regards,

Priyanka

[Ubaid_M]

Hi,

Thanks for the info,
I am aware of the configurations, but my question was not that,
I rather want to know:

Ubaid_M said:

If i need to call zephyr driver API clock_control_off( ) present in zephyr\include\drivers\clock_control.h on LFCLK.
How can I do it,.?

as in

How do I populate the arguments '*dev' & 'sys' to call
"clock_control_off(const struct device *dev, clock_control_subsys_t sys)"

on LFCLK..?

 

[Priyanka]

Hi,

Could you specify as to what exactly you wish to implement this for? As I mentioned earlier, 

Priyanka said:

the LFCLK is normally kept on since it is needed by the Zephyr Scheduler and bluetooth Stack.

[Ubaid_M]

Hi Priyanka,

I want to understand which zephyr driver APIs can be used to control clocks, both HFCLK and LFCLK.
I understand the configurations and also that LFCLK is normally kept on.

I want to know if needed to to turn off/on, which zephyr APIs can be used.?
And How.? (how to populate and pass the arguments)

Ubaid_M said:

How do I populate the arguments '*dev' & 'sys' to call
"clock_control_off(const struct device *dev, clock_control_subsys_t sys)"

on LFCLK..?

[Priyanka]

Hi,

1. In order to turn the HFCLK on you could look into this code. I guess this thread could also prove helpful to your query. 

2. Regarding how to populate the clock_control_off(const struct device *dev, clock_control_subsys_t sys) , *dev is defined the same way as you had mentioned in the ticket. But clock_control_subsys_t is a type with which you can define a clock controller sub-system. You could take a look at this example to understand the format or method better. 

Moreover, stopping the LFCLK is not supported and doing the clock_control_off( )  on LFCLK will result in the error code -ENOTSUP.

I hope this was helpful

Kind Regards,

Priyanka

[Ubaid_M]

Hello Priyanka,

Thank you, this helps.
Please find as in the clock tree for my nRF board:

Now, moving ahead, suppose that if I want to use PCLK16M from HFCLK for a peripheral, how can I get that..?

Similarly, if I want to use PCLK32KI from LFCLK for a timer perhaps, how can I get that frequency..?

[Priyanka]

Hi,

It is possible like we mentioned earlier, to turn on the HFCLK or turn off the LFCLK (which is not recommended as it will result in an error), but you do not specify the frequency requirement. You can only specify or configure the source of your clock, i.e. external crystal, internal RC, etc.

Depending on your requirement, the system will automatically assign the required, based on your peripheral. 

The peripherals connected will automatically request the required clock type from the CLOCK peripheral based on the configuration of the peripheral. This can be seen mentioned in the CLOCK chapter. 

I hope this answers your doubts related to the ticket and in case of any different queries kindly open a new ticket.

Kind Regards,

Priyanka