Incorrect 64-bit Counter Behavior on nRF52840DK and nRF52833DK Devices Using counter_get_value_64()

[CienetmarkChen]

Hi Zephyr Community,

Describe the bug
We conducted hardware counter tests on the nRF52840DK[1] and nRF52833DK[2]. During testing, we found that calling counter_get_value_64() on these devices returns an incorrect counter value (it appears to remain static).

To Reproduce

1. Select an external clock device (e.g., timer, rtc) from the device tree file of the nRF52840DK or nRF52833DK.
2. In the test code, call counter_get_value_64() and pass the external clock device as the argument.
3. Build and flash the application to the board using the following commands:

west build -p -b nrf52840dk/nrf52840 <path/file>
west flash

4. Observe the output.

Expected behavior
The counter value of the external clock device should vary over time.

Impact
This issue could affect applications that rely on the 64-bit counter functionality.

Logs and console output
The following screenshot shows that the output value of the counter remains constant.

Environment:
OS: Linux
Toolchain: Zephyr SDK 0.16.8
Commit: 318b495

Additional context
[1] https://docs.nordicsemi.com/bundle/ps_nrf52840/page/keyfeatures_html5.html
[2] https://docs.nordicsemi.com/bundle/ps_nrf52833/page/keyfeatures_html5.html

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[nordicjm]

Where did you start the counter?

[CienetmarkChen]

Hi nordicjm,

Before calling the function counter_get_value_64, we ensured to start the counter by calling
counter_start once.

Further testing on the nrf52840dk board showed that calling counter_get_value_64 returns -ENOTSUP, as defined in counter.h, indicating unsupported functionality.

Here is our experimental code:
main.c:

#include <zephyr/kernel.h>
#include <zephyr/sys_clock.h>
#include <zephyr/drivers/counter.h>
#include <stdio.h>

static const struct device *external_sensor_clock = DEVICE_DT_GET(DT_CHOSEN(zephyr_sensor_clock));

int main(void)
{
	uint64_t cycles = 0;
	uint64_t delta_ns = 0;
	int err;
    
    	counter_start(external_sensor_clock);

	while (true) {
		k_sleep(K_MSEC(1000));

		err = sensor_clock_get_cycles(&cycles);
		if (err) {
			printf("Failed to get sensor clock cycles, error: %d\n", err);
		}

		printf("Cycles: %llu\n", cycles);

		delta_ns = sensor_clock_cycles_to_ns(cycles);

		printf("Nanoseconds: %llu\n", delta_ns);
	}

	return 0;
}

int sensor_clock_get_cycles(uint64_t *cycles)
{
	__ASSERT_NO_MSG(counter_is_counting_up(external_sensor_clock));

	int rc;
	rc = counter_get_value_64(external_sensor_clock, cycles);

	return rc;
}

uint64_t sensor_clock_cycles_to_ns(uint64_t cycles)
{
	uint32_t freq = counter_get_frequency(external_sensor_clock);

	if (freq == 0) {
		printf("Sensor clock %s has no fixed frequency\n", external_sensor_clock->name);
		return 0;
	}

	return (cycles * NSEC_PER_SEC) / freq;
}

nrf52840dk_nrf52840.overlay:

/ {
	chosen {
		zephyr,sensor-clock = &timer0;
	};
};

&timer0 {
	status = "okay";
};

&rtc0 {
	status = "okay";
};

prj.conf:

CONFIG_SENSOR=y
CONFIG_COUNTER=y
CONFIG_RTC=y

[nordicjm]

Then the function is not supported, this is not a bug

[CienetmarkChen]

Hi nordicjm,
Thank you for your reply.