nRF connect SDK v3.1.0 changes behavior of clock_gettime()

[rlmediola]

When updating from nRF connect SDK v3.0.1 to v3.1.0 we noticed a change in the clock_gettime() function.

In the old version, the clock was not reset by a reboot.

The new version does reset the clock when rebooting.

Here is a simple example:

main.c:

#include <stdio.h>

#include <zephyr/kernel.h>

#include <zephyr/posix/time.h>

#include <zephyr/sys/reboot.h>

void print_time(void)

{

struct timespec clock_now;

if (0 != clock_gettime(CLOCK_MONOTONIC, &clock_now))

{

return;

}

printk("Time: %u\n", (uint32_t)(clock_now.tv_sec));

}

int main(void)

{

printk("Hello World! %s\n", CONFIG_BOARD_TARGET);

print_time();

k_msleep(10000);

print_time();

sys_reboot(SYS_REBOOT_COLD);

return 0;

}

prj.conf:

CONFIG_DATE_TIME=y
CONFIG_DATE_TIME_NTP=n
CONFIG_DATE_TIME_AUTO_UPDATE=n
CONFIG_REBOOT=y

Output with v3.0.1:

Hello World! nrf54l15dk/nrf54l15/cpuapp
Time: 0
Time: 10
Hello World! nrf54l15dk/nrf54l15/cpuapp
Time: 10

Output with v3.1.0:

Hello World! nrf54l15dk/nrf54l15/cpuapp
Time: 0
Time: 10
Hello World! nrf54l15dk/nrf54l15/cpuapp
Time: 0

I'm not sure if this is a bug or a fix, as I could not found where the change was made.

However, we relied on the counter not being reset after a reboot.

Is there a way to restore the old behavior?

Best regards,

Raphael Lamp

[Susheel Nuguru]

I think the new behavior is the expected behavior where this time should give the uptime from reboot. This is however debatable and we should not go into what is the right behavior or not.

You ask is why is this change happening.

The change is the effect of fixes done here The GRTC counter is not cleared at startup, therefore the `last_count` variable needs to be initialized accordingly

The exact change of code that influences this behavioral change is