lib/posix/clock.c

/*
 * Copyright (c) 2018 Intel Corporation
 *
 * SPDX-License-Identifier: Apache-2.0
 */
#include <kernel.h>
#include <errno.h>
#include <posix/time.h>
#include <posix/sys/time.h>
#include <syscall_handler.h>
#include <spinlock.h>

/*
 * `k_uptime_get` returns a timestamp based on an always increasing
 * value from the system start.  To support the `CLOCK_REALTIME`
 * clock, this `rt_clock_base` records the time that the system was
 * started.  This can either be set via 'clock_settime', or could be
 * set from a real time clock, if such hardware is present.
 */
static struct timespec rt_clock_base;
static struct k_spinlock rt_clock_base_lock;

/**
 * @brief Get clock time specified by clock_id.
 *
 * See IEEE 1003.1
 */
int z_impl_clock_gettime(clockid_t clock_id, struct timespec *ts)
{
	struct timespec base;
	k_spinlock_key_t key;

	switch (clock_id) {
	case CLOCK_MONOTONIC:
		base.tv_sec = 0;
		base.tv_nsec = 0;
		break;

	case CLOCK_REALTIME:
		key = k_spin_lock(&rt_clock_base_lock);
		base = rt_clock_base;
		k_spin_unlock(&rt_clock_base_lock, key);
		break;

	default:
		errno = EINVAL;
		return -1;
	}

	uint64_t ticks = k_uptime_ticks();
	uint64_t elapsed_secs = k_ticks_to_ms_floor64(ticks) / MSEC_PER_SEC;
	uint64_t nremainder = ticks - k_ms_to_ticks_floor64(MSEC_PER_SEC * elapsed_secs);

	ts->tv_sec = (time_t) elapsed_secs;
	/* For ns 32 bit conversion can be used since its smaller than 1sec. */
	ts->tv_nsec = (int32_t) k_ticks_to_ns_floor32(nremainder);

	ts->tv_sec += base.tv_sec;
	ts->tv_nsec += base.tv_nsec;
	if (ts->tv_nsec >= NSEC_PER_SEC) {
		ts->tv_sec++;
		ts->tv_nsec -= NSEC_PER_SEC;
	}

	return 0;
}

#ifdef CONFIG_USERSPACE
int z_vrfy_clock_gettime(clockid_t clock_id, struct timespec *ts)
{
	Z_OOPS(Z_SYSCALL_MEMORY_WRITE(ts, sizeof(*ts)));
	return z_impl_clock_gettime(clock_id, ts);
}
#include <syscalls/clock_gettime_mrsh.c>
#endif

/**
 * @brief Set the time of the specified clock.
 *
 * See IEEE 1003.1.
 *
 * Note that only the `CLOCK_REALTIME` clock can be set using this
 * call.
 */
int clock_settime(clockid_t clock_id, const struct timespec *tp)
{
	struct timespec base;
	k_spinlock_key_t key;

	if (clock_id != CLOCK_REALTIME) {
		errno = EINVAL;
		return -1;
	}

	uint64_t elapsed_nsecs = k_ticks_to_ns_floor64(k_uptime_ticks());
	int64_t delta = (int64_t)NSEC_PER_SEC * tp->tv_sec + tp->tv_nsec
		- elapsed_nsecs;

	base.tv_sec = delta / NSEC_PER_SEC;
	base.tv_nsec = delta % NSEC_PER_SEC;

	key = k_spin_lock(&rt_clock_base_lock);
	rt_clock_base = base;
	k_spin_unlock(&rt_clock_base_lock, key);

	return 0;
}

/**
 * @brief Get current real time.
 *
 * See IEEE 1003.1
 */
int gettimeofday(struct timeval *tv, const void *tz)
{
	struct timespec ts;
	int res;

	/* As per POSIX, "if tzp is not a null pointer, the behavior
	 * is unspecified."  "tzp" is the "tz" parameter above. */
	ARG_UNUSED(tz);

	res = clock_gettime(CLOCK_REALTIME, &ts);
	tv->tv_sec = ts.tv_sec;
	tv->tv_usec = ts.tv_nsec / NSEC_PER_USEC;

	return res;
}