nuttx/sched/clock/clock_gettime.c

/****************************************************************************
 * sched/clock/clock_gettime.c
 *
 *   Copyright (C) 2007, 2009, 2011, 2014, 2016 Gregory Nutt.
 *   All rights reserved.
 *   Author: Gregory Nutt <gnutt@nuttx.org>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name NuttX nor the names of its contributors may be
 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <nuttx/config.h>

#include <stdint.h>
#include <time.h>
#include <assert.h>
#include <errno.h>
#include <debug.h>

#include <arch/irq.h>
#include <nuttx/arch.h>

#include "clock/clock.h"
#ifdef CONFIG_CLOCK_TIMEKEEPING
#  include "clock/clock_timekeeping.h"
#endif

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/****************************************************************************
 * Name: clock_gettime
 *
 * Description:
 *   Clock Functions based on POSIX APIs
 *
 ****************************************************************************/

int clock_gettime(clockid_t clock_id, struct timespec *tp)
{
  struct timespec ts;
  uint32_t carry;
  int ret = OK;

  sinfo("clock_id=%d\n", clock_id);
  DEBUGASSERT(tp != NULL);

#ifdef CONFIG_CLOCK_MONOTONIC
  /* CLOCK_MONOTONIC is an optional under POSIX: "If the Monotonic Clock
   * option is supported, all implementations shall support a clock_id
   * of CLOCK_MONOTONIC defined in <time.h>. This clock represents the
   * monotonic clock for the system. For this clock, the value returned
   * by clock_gettime() represents the amount of time (in seconds and
   * nanoseconds) since an unspecified point in the past (for example,
   * system start-up time, or the Epoch). This point does not change
   * after system start-up time. The value of the CLOCK_MONOTONIC clock
   * cannot be set via clock_settime(). This function shall fail if it
   * is invoked with a clock_id argument of CLOCK_MONOTONIC."
   */

  if (clock_id == CLOCK_MONOTONIC)
    {
      /* The the time elapsed since the timer was initialized at power on
       * reset.
       */

      ret = clock_systime_timespec(tp);
    }
  else
#endif

  /* CLOCK_REALTIME - POSIX demands this to be present.  CLOCK_REALTIME
   * represents the machine's best-guess as to the current wall-clock,
   * time-of-day time. This means that CLOCK_REALTIME can jump forward and
   * backward as the system time-of-day clock is changed.
   */

  if (clock_id == CLOCK_REALTIME)
    {
      /* Get the elapsed time since the time-of-day was last set.
       * clock_systime_timespec() provides the time since power was applied;
       * the bias value corresponds to the time when the time-of-day was
       * last set.
       */

#if defined(CONFIG_CLOCK_TIMEKEEPING)
      ret = clock_timekeeping_get_wall_time(tp);
#else
      ret = clock_systime_timespec(&ts);
      if (ret == OK)
        {
          irqstate_t flags;

          /* Add the base time to this.  The base time is the time-of-day
           * setting.  When added to the elapsed time since the time-of-day
           * was last set, this gives us the current time.
           */

          flags = spin_lock_irqsave();

          ts.tv_sec  += (uint32_t)g_basetime.tv_sec;
          ts.tv_nsec += (uint32_t)g_basetime.tv_nsec;

          spin_unlock_irqrestore(flags);

          /* Handle carry to seconds. */

          if (ts.tv_nsec >= NSEC_PER_SEC)
            {
              carry       = ts.tv_nsec / NSEC_PER_SEC;
              ts.tv_sec  += carry;
              ts.tv_nsec -= (carry * NSEC_PER_SEC);
            }

          /* And return the result to the caller. */

          tp->tv_sec  = ts.tv_sec;
          tp->tv_nsec = ts.tv_nsec;
        }
#endif /* CONFIG_CLOCK_TIMEKEEPING */
    }
  else
    {
      ret = -EINVAL;
    }

  /* Check for errors and set the errno value if necessary */

  if (ret < 0)
    {
      serr("Returning ERROR\n");

      set_errno(-ret);
      ret = ERROR;
    }
  else
    {
      sinfo("Returning tp=(%d,%d)\n", (int)tp->tv_sec, (int)tp->tv_nsec);
    }

  return ret;
}