InBuilt RTC Implementation for nrf54l15 nordic MCU

[Naveen Krishna Yadav Malyala]

My task is to implement inbuilt RTC for nordic MCU nrf54l15 series.

When i use the below API nrfx_grtc_init, it is throwing a error and returning a error code which is saying Zephyr already initialized GRTC internally.

is it true ? if not, how i can use the API for initialising the RTC , any other API we need to use?
provide inputs in going forward.

//Initialize GRTC
// nrfx_err_t err = nrfx_grtc_init(GRTC_IRQ_PRIORITY);
// if (err != NRFX_SUCCESS)
// {
// printk("nrfx_grtc_init() failed with code: %d\n", err);
// // prints NRFX_ERROR_ALREADY =195887116 error code
// // Zephyr already initialized GRTC internally
// return;
// }

[Naveen Krishna Yadav Malyala]

Also, i am using the below IRQ handler for nrf54l15, is it the correct one to use ? suggest if any ?

void GRTC_2_IRQHandler(void)
{
//nrfx_grtc_irq_handler(); // Handles internal NRFX logic
printk(">>> GRTC IRQ Handler called <<<\n");

// Check and clear Compare0 event
if (nrf_grtc_event_check(NRF_GRTC, NRF_GRTC_EVENT_COMPARE_0))
{
nrf_grtc_event_clear(NRF_GRTC, NRF_GRTC_EVENT_COMPARE_0);
printk("Compare0 event occurred!\n");
gpio_pin_toggle_dt(&led);
printk("LED toggled!\n");

// Schedule next compare event (every 5 seconds)
uint64_t next_ticks = nrf_grtc_sys_counter_get(NRF_GRTC) + (TOGGLE_INTERVAL_SEC * ticks_per_sec);
//set_grtc_compare(0, next_ticks);

printk("Rescheduling next compare at ticks: %llu\n", next_ticks);

nrf_grtc_sys_counter_cc_set(NRF_GRTC, 0, next_ticks);
//nrf_grtc_event_clear(NRF_GRTC, NRF_GRTC_EVENT_COMPARE_0);
nrf_grtc_int_enable(NRF_GRTC, NRF_GRTC_INT_COMPARE0_MASK);
}
}

[Naveen Krishna Yadav Malyala]

I am using the below lines of code for RTC_init() and making toggle a LED every 5 seconds as per the RTC frequency ?
are the below API's being correctly used for nrf54l15 ?
Can i get the correct HIGH clock frequency being used for nrf54l15 MCU ? 
provide inputs on the above 2 questions as well.

void GRTC_Init(void)
{
printk("Starting GRTC LED toggle example on nRF54L15...\n");

if (!device_is_ready(led.port))
{
printk("LED GPIO not ready!\n");
return;
}

gpio_pin_configure_dt(&led, GPIO_OUTPUT_INACTIVE);

//Initialize GRTC
// nrfx_err_t err = nrfx_grtc_init(GRTC_IRQ_PRIORITY);
// if (err != NRFX_SUCCESS)
// {
// printk("nrfx_grtc_init() failed with code: %d\n", err);
// // prints NRFX_ERROR_ALREADY =195887116 error code
// // Zephyr already initialized GRTC internally
// return;
// }

// Measure actual GRTC frequency dynamically
measure_grtc_frequency();

/* Configure NVIC manually (no Zephyr IRQ macros) */
NVIC_SetPriority(GRTC_2_IRQn, GRTC_IRQ_PRIORITY);
NVIC_EnableIRQ(GRTC_2_IRQn);
printk("NVIC IRQ enabled for GRTC_2_IRQn: %d\n", NVIC_GetEnableIRQ(GRTC_2_IRQn));

// Schedule first compare event after 5 seconds
// Converts seconds to ticks accurately based on actual GRTC frequency (~15.8 MHz on nRF54L15).
uint64_t ticks = nrf_grtc_sys_counter_get(NRF_GRTC) + (TOGGLE_INTERVAL_SEC * ticks_per_sec);
nrf_grtc_sys_counter_cc_set(NRF_GRTC, 0, ticks); //set_grtc_compare(0, ticks);

// No nrfx_grtc_init() because Zephyr already initialized GRTC
// Just enable interrupt for channel 0
nrf_grtc_int_enable(NRF_GRTC, NRF_GRTC_INT_COMPARE0_MASK);

printk("LED will toggle every 5 seconds.\n");
}