timer_create() used hrtimer that is high res timer. When the board starts, BSP will pass hw timer to kernel that will be used by hrtimer.
kernel_imx/kernel/time/posix-timers.c
static int common_timer_create(struct k_itimer *new_timer)
{
hrtimer_init(&new_timer->it.real.timer, new_timer->it_clock, 0);
return 0;
}