/*
   *  linux/kernel/time/timekeeping.c
   *
   *  Kernel timekeeping code and accessor functions
   *
   *  This code was moved from linux/kernel/timer.c.
   *  Please see that file for copyright and history logs.
   *
   */

  #include <linux/timekeeper_internal.h>

  #include <linux/module.h>
  #include <linux/interrupt.h>
  #include <linux/percpu.h>
  #include <linux/init.h>
  #include <linux/mm.h>

  #include <linux/sched.h>

  #include <linux/syscore_ops.h>

  #include <linux/clocksource.h>
  #include <linux/jiffies.h>
  #include <linux/time.h>
  #include <linux/tick.h>

  #include <linux/stop_machine.h>

  #include <linux/pvclock_gtod.h>

  #include <linux/compiler.h>

  #include "tick-internal.h"

  #include "ntp_internal.h"

  #include "timekeeping_internal.h"

  #define TK_CLEAR_NTP		(1 << 0)
  #define TK_MIRROR		(1 << 1)

  #define TK_CLOCK_WAS_SET	(1 << 2)

  /*
   * The most important data for readout fits into a single 64 byte
   * cache line.
   */
  static struct {
  	seqcount_t		seq;
  	struct timekeeper	timekeeper;
  } tk_core ____cacheline_aligned;

  static DEFINE_RAW_SPINLOCK(timekeeper_lock);

  static struct timekeeper shadow_timekeeper;

  /**
   * struct tk_fast - NMI safe timekeeper
   * @seq:	Sequence counter for protecting updates. The lowest bit
   *		is the index for the tk_read_base array
   * @base:	tk_read_base array. Access is indexed by the lowest bit of
   *		@seq.
   *
   * See @update_fast_timekeeper() below.
   */
  struct tk_fast {
  	seqcount_t		seq;
  	struct tk_read_base	base[2];
  };
  
  static struct tk_fast tk_fast_mono ____cacheline_aligned;

  /* flag for if timekeeping is suspended */
  int __read_mostly timekeeping_suspended;

  /* Flag for if there is a persistent clock on this platform */
  bool __read_mostly persistent_clock_exist = false;

  static inline void tk_normalize_xtime(struct timekeeper *tk)
  {

  	while (tk->tkr.xtime_nsec >= ((u64)NSEC_PER_SEC << tk->tkr.shift)) {
  		tk->tkr.xtime_nsec -= (u64)NSEC_PER_SEC << tk->tkr.shift;

  		tk->xtime_sec++;
  	}
  }

  static inline struct timespec64 tk_xtime(struct timekeeper *tk)
  {
  	struct timespec64 ts;
  
  	ts.tv_sec = tk->xtime_sec;

  	ts.tv_nsec = (long)(tk->tkr.xtime_nsec >> tk->tkr.shift);

  	return ts;
  }

  static void tk_set_xtime(struct timekeeper *tk, const struct timespec64 *ts)

  {
  	tk->xtime_sec = ts->tv_sec;

  	tk->tkr.xtime_nsec = (u64)ts->tv_nsec << tk->tkr.shift;

  }

  static void tk_xtime_add(struct timekeeper *tk, const struct timespec64 *ts)

  {
  	tk->xtime_sec += ts->tv_sec;

  	tk->tkr.xtime_nsec += (u64)ts->tv_nsec << tk->tkr.shift;

  	tk_normalize_xtime(tk);

  }

  static void tk_set_wall_to_mono(struct timekeeper *tk, struct timespec64 wtm)

  {

  	struct timespec64 tmp;

  
  	/*
  	 * Verify consistency of: offset_real = -wall_to_monotonic
  	 * before modifying anything
  	 */

  	set_normalized_timespec64(&tmp, -tk->wall_to_monotonic.tv_sec,

  					-tk->wall_to_monotonic.tv_nsec);

  	WARN_ON_ONCE(tk->offs_real.tv64 != timespec64_to_ktime(tmp).tv64);

  	tk->wall_to_monotonic = wtm;

  	set_normalized_timespec64(&tmp, -wtm.tv_sec, -wtm.tv_nsec);
  	tk->offs_real = timespec64_to_ktime(tmp);

  	tk->offs_tai = ktime_add(tk->offs_real, ktime_set(tk->tai_offset, 0));

  }

  static inline void tk_update_sleep_time(struct timekeeper *tk, ktime_t delta)

  {

  	tk->offs_boot = ktime_add(tk->offs_boot, delta);

  }

  /**

   * tk_setup_internals - Set up internals to use clocksource clock.

   *

   * @tk:		The target timekeeper to setup.

   * @clock:		Pointer to clocksource.
   *
   * Calculates a fixed cycle/nsec interval for a given clocksource/adjustment
   * pair and interval request.
   *
   * Unless you're the timekeeping code, you should not be using this!
   */

  static void tk_setup_internals(struct timekeeper *tk, struct clocksource *clock)

  {
  	cycle_t interval;

  	u64 tmp, ntpinterval;

  	struct clocksource *old_clock;

  	old_clock = tk->tkr.clock;
  	tk->tkr.clock = clock;
  	tk->tkr.read = clock->read;
  	tk->tkr.mask = clock->mask;
  	tk->tkr.cycle_last = tk->tkr.read(clock);

  
  	/* Do the ns -> cycle conversion first, using original mult */
  	tmp = NTP_INTERVAL_LENGTH;
  	tmp <<= clock->shift;

  	ntpinterval = tmp;

  	tmp += clock->mult/2;
  	do_div(tmp, clock->mult);

  	if (tmp == 0)
  		tmp = 1;
  
  	interval = (cycle_t) tmp;

  	tk->cycle_interval = interval;

  
  	/* Go back from cycles -> shifted ns */

  	tk->xtime_interval = (u64) interval * clock->mult;
  	tk->xtime_remainder = ntpinterval - tk->xtime_interval;
  	tk->raw_interval =

  		((u64) interval * clock->mult) >> clock->shift;

  	 /* if changing clocks, convert xtime_nsec shift units */
  	if (old_clock) {
  		int shift_change = clock->shift - old_clock->shift;
  		if (shift_change < 0)

  			tk->tkr.xtime_nsec >>= -shift_change;

  		else

  			tk->tkr.xtime_nsec <<= shift_change;

  	}

  	tk->tkr.shift = clock->shift;

  	tk->ntp_error = 0;
  	tk->ntp_error_shift = NTP_SCALE_SHIFT - clock->shift;

  	tk->ntp_tick = ntpinterval << tk->ntp_error_shift;

  
  	/*
  	 * The timekeeper keeps its own mult values for the currently
  	 * active clocksource. These value will be adjusted via NTP
  	 * to counteract clock drifting.
  	 */

  	tk->tkr.mult = clock->mult;

  	tk->ntp_err_mult = 0;

  }

  /* Timekeeper helper functions. */

  
  #ifdef CONFIG_ARCH_USES_GETTIMEOFFSET

  static u32 default_arch_gettimeoffset(void) { return 0; }
  u32 (*arch_gettimeoffset)(void) = default_arch_gettimeoffset;

  #else

  static inline u32 arch_gettimeoffset(void) { return 0; }

  #endif

  static inline s64 timekeeping_get_ns(struct tk_read_base *tkr)

  {

  	cycle_t cycle_now, delta;

  	s64 nsec;

  
  	/* read clocksource: */

  	cycle_now = tkr->read(tkr->clock);

  
  	/* calculate the delta since the last update_wall_time: */

  	delta = clocksource_delta(cycle_now, tkr->cycle_last, tkr->mask);

  	nsec = delta * tkr->mult + tkr->xtime_nsec;
  	nsec >>= tkr->shift;

  	/* If arch requires, add in get_arch_timeoffset() */

  	return nsec + arch_gettimeoffset();

  }

  static inline s64 timekeeping_get_ns_raw(struct timekeeper *tk)

  {

  	struct clocksource *clock = tk->tkr.clock;

  	cycle_t cycle_now, delta;

  	s64 nsec;

  
  	/* read clocksource: */

  	cycle_now = tk->tkr.read(clock);

  
  	/* calculate the delta since the last update_wall_time: */

  	delta = clocksource_delta(cycle_now, tk->tkr.cycle_last, tk->tkr.mask);

  	/* convert delta to nanoseconds. */

  	nsec = clocksource_cyc2ns(delta, clock->mult, clock->shift);

  	/* If arch requires, add in get_arch_timeoffset() */

  	return nsec + arch_gettimeoffset();

  }

  /**
   * update_fast_timekeeper - Update the fast and NMI safe monotonic timekeeper.
   * @tk:		The timekeeper from which we take the update
   * @tkf:	The fast timekeeper to update
   * @tbase:	The time base for the fast timekeeper (mono/raw)
   *
   * We want to use this from any context including NMI and tracing /
   * instrumenting the timekeeping code itself.
   *
   * So we handle this differently than the other timekeeping accessor
   * functions which retry when the sequence count has changed. The
   * update side does:
   *
   * smp_wmb();	<- Ensure that the last base[1] update is visible
   * tkf->seq++;
   * smp_wmb();	<- Ensure that the seqcount update is visible
   * update(tkf->base[0], tk);
   * smp_wmb();	<- Ensure that the base[0] update is visible
   * tkf->seq++;
   * smp_wmb();	<- Ensure that the seqcount update is visible
   * update(tkf->base[1], tk);
   *
   * The reader side does:
   *
   * do {
   *	seq = tkf->seq;
   *	smp_rmb();
   *	idx = seq & 0x01;
   *	now = now(tkf->base[idx]);
   *	smp_rmb();
   * } while (seq != tkf->seq)
   *
   * As long as we update base[0] readers are forced off to
   * base[1]. Once base[0] is updated readers are redirected to base[0]
   * and the base[1] update takes place.
   *
   * So if a NMI hits the update of base[0] then it will use base[1]
   * which is still consistent. In the worst case this can result is a
   * slightly wrong timestamp (a few nanoseconds). See
   * @ktime_get_mono_fast_ns.
   */
  static void update_fast_timekeeper(struct timekeeper *tk)
  {
  	struct tk_read_base *base = tk_fast_mono.base;
  
  	/* Force readers off to base[1] */
  	raw_write_seqcount_latch(&tk_fast_mono.seq);
  
  	/* Update base[0] */
  	memcpy(base, &tk->tkr, sizeof(*base));
  
  	/* Force readers back to base[0] */
  	raw_write_seqcount_latch(&tk_fast_mono.seq);
  
  	/* Update base[1] */
  	memcpy(base + 1, base, sizeof(*base));
  }
  
  /**
   * ktime_get_mono_fast_ns - Fast NMI safe access to clock monotonic
   *
   * This timestamp is not guaranteed to be monotonic across an update.
   * The timestamp is calculated by:
   *
   *	now = base_mono + clock_delta * slope
   *
   * So if the update lowers the slope, readers who are forced to the
   * not yet updated second array are still using the old steeper slope.
   *
   * tmono
   * ^
   * |    o  n
   * |   o n
   * |  u
   * | o
   * |o
   * |12345678---> reader order
   *
   * o = old slope
   * u = update
   * n = new slope
   *
   * So reader 6 will observe time going backwards versus reader 5.
   *
   * While other CPUs are likely to be able observe that, the only way
   * for a CPU local observation is when an NMI hits in the middle of
   * the update. Timestamps taken from that NMI context might be ahead
   * of the following timestamps. Callers need to be aware of that and
   * deal with it.
   */
  u64 notrace ktime_get_mono_fast_ns(void)
  {
  	struct tk_read_base *tkr;
  	unsigned int seq;
  	u64 now;
  
  	do {
  		seq = raw_read_seqcount(&tk_fast_mono.seq);
  		tkr = tk_fast_mono.base + (seq & 0x01);
  		now = ktime_to_ns(tkr->base_mono) + timekeeping_get_ns(tkr);
  
  	} while (read_seqcount_retry(&tk_fast_mono.seq, seq));
  	return now;
  }
  EXPORT_SYMBOL_GPL(ktime_get_mono_fast_ns);

  #ifdef CONFIG_GENERIC_TIME_VSYSCALL_OLD
  
  static inline void update_vsyscall(struct timekeeper *tk)
  {

  	struct timespec xt, wm;

  	xt = timespec64_to_timespec(tk_xtime(tk));

  	wm = timespec64_to_timespec(tk->wall_to_monotonic);
  	update_vsyscall_old(&xt, &wm, tk->tkr.clock, tk->tkr.mult,

  			    tk->tkr.cycle_last);

  }
  
  static inline void old_vsyscall_fixup(struct timekeeper *tk)
  {
  	s64 remainder;
  
  	/*
  	* Store only full nanoseconds into xtime_nsec after rounding
  	* it up and add the remainder to the error difference.
  	* XXX - This is necessary to avoid small 1ns inconsistnecies caused
  	* by truncating the remainder in vsyscalls. However, it causes
  	* additional work to be done in timekeeping_adjust(). Once
  	* the vsyscall implementations are converted to use xtime_nsec
  	* (shifted nanoseconds), and CONFIG_GENERIC_TIME_VSYSCALL_OLD
  	* users are removed, this can be killed.
  	*/

  	remainder = tk->tkr.xtime_nsec & ((1ULL << tk->tkr.shift) - 1);
  	tk->tkr.xtime_nsec -= remainder;
  	tk->tkr.xtime_nsec += 1ULL << tk->tkr.shift;

  	tk->ntp_error += remainder << tk->ntp_error_shift;

  	tk->ntp_error -= (1ULL << tk->tkr.shift) << tk->ntp_error_shift;

  }
  #else
  #define old_vsyscall_fixup(tk)
  #endif

  static RAW_NOTIFIER_HEAD(pvclock_gtod_chain);

  static void update_pvclock_gtod(struct timekeeper *tk, bool was_set)

  {

  	raw_notifier_call_chain(&pvclock_gtod_chain, was_set, tk);

  }
  
  /**
   * pvclock_gtod_register_notifier - register a pvclock timedata update listener

   */
  int pvclock_gtod_register_notifier(struct notifier_block *nb)
  {

  	struct timekeeper *tk = &tk_core.timekeeper;

  	unsigned long flags;
  	int ret;

  	raw_spin_lock_irqsave(&timekeeper_lock, flags);

  	ret = raw_notifier_chain_register(&pvclock_gtod_chain, nb);

  	update_pvclock_gtod(tk, true);

  	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);

  
  	return ret;
  }
  EXPORT_SYMBOL_GPL(pvclock_gtod_register_notifier);
  
  /**
   * pvclock_gtod_unregister_notifier - unregister a pvclock
   * timedata update listener

   */
  int pvclock_gtod_unregister_notifier(struct notifier_block *nb)
  {

  	unsigned long flags;
  	int ret;

  	raw_spin_lock_irqsave(&timekeeper_lock, flags);

  	ret = raw_notifier_chain_unregister(&pvclock_gtod_chain, nb);

  	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);

  
  	return ret;
  }
  EXPORT_SYMBOL_GPL(pvclock_gtod_unregister_notifier);

  /*
   * Update the ktime_t based scalar nsec members of the timekeeper
   */
  static inline void tk_update_ktime_data(struct timekeeper *tk)
  {

  	u64 seconds;
  	u32 nsec;

  
  	/*
  	 * The xtime based monotonic readout is:
  	 *	nsec = (xtime_sec + wtm_sec) * 1e9 + wtm_nsec + now();
  	 * The ktime based monotonic readout is:
  	 *	nsec = base_mono + now();
  	 * ==> base_mono = (xtime_sec + wtm_sec) * 1e9 + wtm_nsec
  	 */

  	seconds = (u64)(tk->xtime_sec + tk->wall_to_monotonic.tv_sec);
  	nsec = (u32) tk->wall_to_monotonic.tv_nsec;
  	tk->tkr.base_mono = ns_to_ktime(seconds * NSEC_PER_SEC + nsec);

  
  	/* Update the monotonic raw base */
  	tk->base_raw = timespec64_to_ktime(tk->raw_time);

  
  	/*
  	 * The sum of the nanoseconds portions of xtime and
  	 * wall_to_monotonic can be greater/equal one second. Take
  	 * this into account before updating tk->ktime_sec.
  	 */
  	nsec += (u32)(tk->tkr.xtime_nsec >> tk->tkr.shift);
  	if (nsec >= NSEC_PER_SEC)
  		seconds++;
  	tk->ktime_sec = seconds;

  }

  /* must hold timekeeper_lock */

  static void timekeeping_update(struct timekeeper *tk, unsigned int action)

  {

  	if (action & TK_CLEAR_NTP) {

  		tk->ntp_error = 0;

  		ntp_clear();
  	}

  	tk_update_ktime_data(tk);

  	update_vsyscall(tk);
  	update_pvclock_gtod(tk, action & TK_CLOCK_WAS_SET);

  	if (action & TK_MIRROR)

  		memcpy(&shadow_timekeeper, &tk_core.timekeeper,
  		       sizeof(tk_core.timekeeper));

  
  	update_fast_timekeeper(tk);

  }

  /**

   * timekeeping_forward_now - update clock to the current time

   *

   * Forward the current clock to update its state since the last call to
   * update_wall_time(). This is useful before significant clock changes,
   * as it avoids having to deal with this time offset explicitly.

   */

  static void timekeeping_forward_now(struct timekeeper *tk)

  {

  	struct clocksource *clock = tk->tkr.clock;

  	cycle_t cycle_now, delta;

  	s64 nsec;

  	cycle_now = tk->tkr.read(clock);
  	delta = clocksource_delta(cycle_now, tk->tkr.cycle_last, tk->tkr.mask);
  	tk->tkr.cycle_last = cycle_now;

  	tk->tkr.xtime_nsec += delta * tk->tkr.mult;

  	/* If arch requires, add in get_arch_timeoffset() */

  	tk->tkr.xtime_nsec += (u64)arch_gettimeoffset() << tk->tkr.shift;

  	tk_normalize_xtime(tk);

  	nsec = clocksource_cyc2ns(delta, clock->mult, clock->shift);

  	timespec64_add_ns(&tk->raw_time, nsec);

  }
  
  /**

   * __getnstimeofday64 - Returns the time of day in a timespec64.

   * @ts:		pointer to the timespec to be set
   *

   * Updates the time of day in the timespec.
   * Returns 0 on success, or -ve when suspended (timespec will be undefined).

   */

  int __getnstimeofday64(struct timespec64 *ts)

  {

  	struct timekeeper *tk = &tk_core.timekeeper;

  	unsigned long seq;

  	s64 nsecs = 0;

  
  	do {

  		seq = read_seqcount_begin(&tk_core.seq);

  		ts->tv_sec = tk->xtime_sec;

  		nsecs = timekeeping_get_ns(&tk->tkr);

  	} while (read_seqcount_retry(&tk_core.seq, seq));

  	ts->tv_nsec = 0;

  	timespec64_add_ns(ts, nsecs);

  
  	/*
  	 * Do not bail out early, in case there were callers still using
  	 * the value, even in the face of the WARN_ON.
  	 */
  	if (unlikely(timekeeping_suspended))
  		return -EAGAIN;
  	return 0;
  }

  EXPORT_SYMBOL(__getnstimeofday64);

  
  /**

   * getnstimeofday64 - Returns the time of day in a timespec64.

   * @ts:		pointer to the timespec64 to be set

   *

   * Returns the time of day in a timespec64 (WARN if suspended).

   */

  void getnstimeofday64(struct timespec64 *ts)

  {

  	WARN_ON(__getnstimeofday64(ts));

  }

  EXPORT_SYMBOL(getnstimeofday64);

  ktime_t ktime_get(void)
  {

  	struct timekeeper *tk = &tk_core.timekeeper;

  	unsigned int seq;

  	ktime_t base;
  	s64 nsecs;

  
  	WARN_ON(timekeeping_suspended);
  
  	do {

  		seq = read_seqcount_begin(&tk_core.seq);

  		base = tk->tkr.base_mono;

  		nsecs = timekeeping_get_ns(&tk->tkr);

  	} while (read_seqcount_retry(&tk_core.seq, seq));

  	return ktime_add_ns(base, nsecs);

  }
  EXPORT_SYMBOL_GPL(ktime_get);

  static ktime_t *offsets[TK_OFFS_MAX] = {
  	[TK_OFFS_REAL]	= &tk_core.timekeeper.offs_real,
  	[TK_OFFS_BOOT]	= &tk_core.timekeeper.offs_boot,
  	[TK_OFFS_TAI]	= &tk_core.timekeeper.offs_tai,
  };
  
  ktime_t ktime_get_with_offset(enum tk_offsets offs)
  {
  	struct timekeeper *tk = &tk_core.timekeeper;
  	unsigned int seq;
  	ktime_t base, *offset = offsets[offs];
  	s64 nsecs;
  
  	WARN_ON(timekeeping_suspended);
  
  	do {
  		seq = read_seqcount_begin(&tk_core.seq);

  		base = ktime_add(tk->tkr.base_mono, *offset);

  		nsecs = timekeeping_get_ns(&tk->tkr);

  
  	} while (read_seqcount_retry(&tk_core.seq, seq));
  
  	return ktime_add_ns(base, nsecs);
  
  }
  EXPORT_SYMBOL_GPL(ktime_get_with_offset);

  /**

   * ktime_mono_to_any() - convert mononotic time to any other time
   * @tmono:	time to convert.
   * @offs:	which offset to use
   */
  ktime_t ktime_mono_to_any(ktime_t tmono, enum tk_offsets offs)
  {
  	ktime_t *offset = offsets[offs];
  	unsigned long seq;
  	ktime_t tconv;
  
  	do {
  		seq = read_seqcount_begin(&tk_core.seq);
  		tconv = ktime_add(tmono, *offset);
  	} while (read_seqcount_retry(&tk_core.seq, seq));
  
  	return tconv;
  }
  EXPORT_SYMBOL_GPL(ktime_mono_to_any);
  
  /**

   * ktime_get_raw - Returns the raw monotonic time in ktime_t format
   */
  ktime_t ktime_get_raw(void)
  {
  	struct timekeeper *tk = &tk_core.timekeeper;
  	unsigned int seq;
  	ktime_t base;
  	s64 nsecs;
  
  	do {
  		seq = read_seqcount_begin(&tk_core.seq);
  		base = tk->base_raw;
  		nsecs = timekeeping_get_ns_raw(tk);
  
  	} while (read_seqcount_retry(&tk_core.seq, seq));
  
  	return ktime_add_ns(base, nsecs);
  }
  EXPORT_SYMBOL_GPL(ktime_get_raw);
  
  /**

   * ktime_get_ts64 - get the monotonic clock in timespec64 format

   * @ts:		pointer to timespec variable
   *
   * The function calculates the monotonic clock from the realtime
   * clock and the wall_to_monotonic offset and stores the result

   * in normalized timespec64 format in the variable pointed to by @ts.

   */

  void ktime_get_ts64(struct timespec64 *ts)

  {

  	struct timekeeper *tk = &tk_core.timekeeper;

  	struct timespec64 tomono;

  	s64 nsec;

  	unsigned int seq;

  
  	WARN_ON(timekeeping_suspended);
  
  	do {

  		seq = read_seqcount_begin(&tk_core.seq);

  		ts->tv_sec = tk->xtime_sec;

  		nsec = timekeeping_get_ns(&tk->tkr);

  		tomono = tk->wall_to_monotonic;

  	} while (read_seqcount_retry(&tk_core.seq, seq));

  	ts->tv_sec += tomono.tv_sec;
  	ts->tv_nsec = 0;
  	timespec64_add_ns(ts, nsec + tomono.tv_nsec);

  }

  EXPORT_SYMBOL_GPL(ktime_get_ts64);

  /**
   * ktime_get_seconds - Get the seconds portion of CLOCK_MONOTONIC
   *
   * Returns the seconds portion of CLOCK_MONOTONIC with a single non
   * serialized read. tk->ktime_sec is of type 'unsigned long' so this
   * works on both 32 and 64 bit systems. On 32 bit systems the readout
   * covers ~136 years of uptime which should be enough to prevent
   * premature wrap arounds.
   */
  time64_t ktime_get_seconds(void)
  {
  	struct timekeeper *tk = &tk_core.timekeeper;
  
  	WARN_ON(timekeeping_suspended);
  	return tk->ktime_sec;
  }
  EXPORT_SYMBOL_GPL(ktime_get_seconds);

  /**
   * ktime_get_real_seconds - Get the seconds portion of CLOCK_REALTIME
   *
   * Returns the wall clock seconds since 1970. This replaces the
   * get_seconds() interface which is not y2038 safe on 32bit systems.
   *
   * For 64bit systems the fast access to tk->xtime_sec is preserved. On
   * 32bit systems the access must be protected with the sequence
   * counter to provide "atomic" access to the 64bit tk->xtime_sec
   * value.
   */
  time64_t ktime_get_real_seconds(void)
  {
  	struct timekeeper *tk = &tk_core.timekeeper;
  	time64_t seconds;
  	unsigned int seq;
  
  	if (IS_ENABLED(CONFIG_64BIT))
  		return tk->xtime_sec;
  
  	do {
  		seq = read_seqcount_begin(&tk_core.seq);
  		seconds = tk->xtime_sec;
  
  	} while (read_seqcount_retry(&tk_core.seq, seq));
  
  	return seconds;
  }
  EXPORT_SYMBOL_GPL(ktime_get_real_seconds);

  #ifdef CONFIG_NTP_PPS
  
  /**
   * getnstime_raw_and_real - get day and raw monotonic time in timespec format
   * @ts_raw:	pointer to the timespec to be set to raw monotonic time
   * @ts_real:	pointer to the timespec to be set to the time of day
   *
   * This function reads both the time of day and raw monotonic time at the
   * same time atomically and stores the resulting timestamps in timespec
   * format.
   */
  void getnstime_raw_and_real(struct timespec *ts_raw, struct timespec *ts_real)
  {

  	struct timekeeper *tk = &tk_core.timekeeper;

  	unsigned long seq;
  	s64 nsecs_raw, nsecs_real;
  
  	WARN_ON_ONCE(timekeeping_suspended);
  
  	do {

  		seq = read_seqcount_begin(&tk_core.seq);

  		*ts_raw = timespec64_to_timespec(tk->raw_time);

  		ts_real->tv_sec = tk->xtime_sec;

  		ts_real->tv_nsec = 0;

  		nsecs_raw = timekeeping_get_ns_raw(tk);

  		nsecs_real = timekeeping_get_ns(&tk->tkr);

  	} while (read_seqcount_retry(&tk_core.seq, seq));

  
  	timespec_add_ns(ts_raw, nsecs_raw);
  	timespec_add_ns(ts_real, nsecs_real);
  }
  EXPORT_SYMBOL(getnstime_raw_and_real);
  
  #endif /* CONFIG_NTP_PPS */

  /**
   * do_gettimeofday - Returns the time of day in a timeval
   * @tv:		pointer to the timeval to be set
   *

   * NOTE: Users should be converted to using getnstimeofday()

   */
  void do_gettimeofday(struct timeval *tv)
  {

  	struct timespec64 now;

  	getnstimeofday64(&now);

  	tv->tv_sec = now.tv_sec;
  	tv->tv_usec = now.tv_nsec/1000;
  }

  EXPORT_SYMBOL(do_gettimeofday);

  /**

   * do_settimeofday64 - Sets the time of day.
   * @ts:     pointer to the timespec64 variable containing the new time

   *
   * Sets the time of day to the new time and update NTP and notify hrtimers
   */

  int do_settimeofday64(const struct timespec64 *ts)

  {

  	struct timekeeper *tk = &tk_core.timekeeper;

  	struct timespec64 ts_delta, xt;

  	unsigned long flags;

  	if (!timespec64_valid_strict(ts))

  		return -EINVAL;

  	raw_spin_lock_irqsave(&timekeeper_lock, flags);

  	write_seqcount_begin(&tk_core.seq);

  	timekeeping_forward_now(tk);

  	xt = tk_xtime(tk);

  	ts_delta.tv_sec = ts->tv_sec - xt.tv_sec;
  	ts_delta.tv_nsec = ts->tv_nsec - xt.tv_nsec;

  	tk_set_wall_to_mono(tk, timespec64_sub(tk->wall_to_monotonic, ts_delta));

  	tk_set_xtime(tk, ts);

  	timekeeping_update(tk, TK_CLEAR_NTP | TK_MIRROR | TK_CLOCK_WAS_SET);

  	write_seqcount_end(&tk_core.seq);

  	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);

  
  	/* signal hrtimers about time change */
  	clock_was_set();
  
  	return 0;
  }

  EXPORT_SYMBOL(do_settimeofday64);

  /**
   * timekeeping_inject_offset - Adds or subtracts from the current time.
   * @tv:		pointer to the timespec variable containing the offset
   *
   * Adds or subtracts an offset value from the current time.
   */
  int timekeeping_inject_offset(struct timespec *ts)
  {

  	struct timekeeper *tk = &tk_core.timekeeper;

  	unsigned long flags;

  	struct timespec64 ts64, tmp;

  	int ret = 0;

  
  	if ((unsigned long)ts->tv_nsec >= NSEC_PER_SEC)
  		return -EINVAL;

  	ts64 = timespec_to_timespec64(*ts);

  	raw_spin_lock_irqsave(&timekeeper_lock, flags);

  	write_seqcount_begin(&tk_core.seq);

  	timekeeping_forward_now(tk);

  	/* Make sure the proposed value is valid */

  	tmp = timespec64_add(tk_xtime(tk),  ts64);
  	if (!timespec64_valid_strict(&tmp)) {

  		ret = -EINVAL;
  		goto error;
  	}

  	tk_xtime_add(tk, &ts64);
  	tk_set_wall_to_mono(tk, timespec64_sub(tk->wall_to_monotonic, ts64));

  error: /* even if we error out, we forwarded the time, so call update */

  	timekeeping_update(tk, TK_CLEAR_NTP | TK_MIRROR | TK_CLOCK_WAS_SET);

  	write_seqcount_end(&tk_core.seq);

  	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);

  
  	/* signal hrtimers about time change */
  	clock_was_set();

  	return ret;

  }
  EXPORT_SYMBOL(timekeeping_inject_offset);

  
  /**
   * timekeeping_get_tai_offset - Returns current TAI offset from UTC
   *
   */
  s32 timekeeping_get_tai_offset(void)
  {

  	struct timekeeper *tk = &tk_core.timekeeper;

  	unsigned int seq;
  	s32 ret;
  
  	do {

  		seq = read_seqcount_begin(&tk_core.seq);

  		ret = tk->tai_offset;

  	} while (read_seqcount_retry(&tk_core.seq, seq));

  
  	return ret;
  }
  
  /**
   * __timekeeping_set_tai_offset - Lock free worker function
   *
   */

  static void __timekeeping_set_tai_offset(struct timekeeper *tk, s32 tai_offset)

  {
  	tk->tai_offset = tai_offset;

  	tk->offs_tai = ktime_add(tk->offs_real, ktime_set(tai_offset, 0));

  }
  
  /**
   * timekeeping_set_tai_offset - Sets the current TAI offset from UTC
   *
   */
  void timekeeping_set_tai_offset(s32 tai_offset)
  {

  	struct timekeeper *tk = &tk_core.timekeeper;

  	unsigned long flags;

  	raw_spin_lock_irqsave(&timekeeper_lock, flags);

  	write_seqcount_begin(&tk_core.seq);

  	__timekeeping_set_tai_offset(tk, tai_offset);

  	timekeeping_update(tk, TK_MIRROR | TK_CLOCK_WAS_SET);

  	write_seqcount_end(&tk_core.seq);

  	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);

  	clock_was_set();

  }

  /**
   * change_clocksource - Swaps clocksources if a new one is available
   *
   * Accumulates current time interval and initializes new clocksource
   */

  static int change_clocksource(void *data)

  {

  	struct timekeeper *tk = &tk_core.timekeeper;

  	struct clocksource *new, *old;

  	unsigned long flags;

  	new = (struct clocksource *) data;

  	raw_spin_lock_irqsave(&timekeeper_lock, flags);

  	write_seqcount_begin(&tk_core.seq);

  	timekeeping_forward_now(tk);

  	/*
  	 * If the cs is in module, get a module reference. Succeeds
  	 * for built-in code (owner == NULL) as well.
  	 */
  	if (try_module_get(new->owner)) {
  		if (!new->enable || new->enable(new) == 0) {

  			old = tk->tkr.clock;

  			tk_setup_internals(tk, new);
  			if (old->disable)
  				old->disable(old);
  			module_put(old->owner);
  		} else {
  			module_put(new->owner);
  		}

  	}

  	timekeeping_update(tk, TK_CLEAR_NTP | TK_MIRROR | TK_CLOCK_WAS_SET);

  	write_seqcount_end(&tk_core.seq);

  	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);

  	return 0;
  }

  /**
   * timekeeping_notify - Install a new clock source
   * @clock:		pointer to the clock source
   *
   * This function is called from clocksource.c after a new, better clock
   * source has been registered. The caller holds the clocksource_mutex.
   */

  int timekeeping_notify(struct clocksource *clock)

  {

  	struct timekeeper *tk = &tk_core.timekeeper;

  	if (tk->tkr.clock == clock)

  		return 0;

  	stop_machine(change_clocksource, clock, NULL);

  	tick_clock_notify();

  	return tk->tkr.clock == clock ? 0 : -1;

  }

  /**

   * getrawmonotonic64 - Returns the raw monotonic time in a timespec
   * @ts:		pointer to the timespec64 to be set

   *
   * Returns the raw monotonic time (completely un-modified by ntp)
   */

  void getrawmonotonic64(struct timespec64 *ts)

  {

  	struct timekeeper *tk = &tk_core.timekeeper;

  	struct timespec64 ts64;

  	unsigned long seq;
  	s64 nsecs;

  
  	do {

  		seq = read_seqcount_begin(&tk_core.seq);

  		nsecs = timekeeping_get_ns_raw(tk);

  		ts64 = tk->raw_time;

  	} while (read_seqcount_retry(&tk_core.seq, seq));

  	timespec64_add_ns(&ts64, nsecs);

  	*ts = ts64;

  }

  EXPORT_SYMBOL(getrawmonotonic64);

  /**

   * timekeeping_valid_for_hres - Check if timekeeping is suitable for hres

   */

  int timekeeping_valid_for_hres(void)

  {

  	struct timekeeper *tk = &tk_core.timekeeper;

  	unsigned long seq;
  	int ret;
  
  	do {

  		seq = read_seqcount_begin(&tk_core.seq);

  		ret = tk->tkr.clock->flags & CLOCK_SOURCE_VALID_FOR_HRES;

  	} while (read_seqcount_retry(&tk_core.seq, seq));

  
  	return ret;
  }
  
  /**

   * timekeeping_max_deferment - Returns max time the clocksource can be deferred

   */
  u64 timekeeping_max_deferment(void)
  {

  	struct timekeeper *tk = &tk_core.timekeeper;

  	unsigned long seq;
  	u64 ret;

  	do {

  		seq = read_seqcount_begin(&tk_core.seq);

  		ret = tk->tkr.clock->max_idle_ns;

  	} while (read_seqcount_retry(&tk_core.seq, seq));

  
  	return ret;

  }
  
  /**

   * read_persistent_clock -  Return time from the persistent clock.

   *
   * Weak dummy function for arches that do not yet support it.

   * Reads the time from the battery backed persistent clock.
   * Returns a timespec with tv_sec=0 and tv_nsec=0 if unsupported.

   *
   *  XXX - Do be sure to remove it once all arches implement it.
   */

  void __weak read_persistent_clock(struct timespec *ts)

  {

  	ts->tv_sec = 0;
  	ts->tv_nsec = 0;

  }

  /**
   * read_boot_clock -  Return time of the system start.
   *
   * Weak dummy function for arches that do not yet support it.
   * Function to read the exact time the system has been started.
   * Returns a timespec with tv_sec=0 and tv_nsec=0 if unsupported.
   *
   *  XXX - Do be sure to remove it once all arches implement it.
   */

  void __weak read_boot_clock(struct timespec *ts)

  {
  	ts->tv_sec = 0;
  	ts->tv_nsec = 0;
  }

  /*
   * timekeeping_init - Initializes the clocksource and common timekeeping values
   */
  void __init timekeeping_init(void)
  {

  	struct timekeeper *tk = &tk_core.timekeeper;

  	struct clocksource *clock;

  	unsigned long flags;

  	struct timespec64 now, boot, tmp;
  	struct timespec ts;

  	read_persistent_clock(&ts);
  	now = timespec_to_timespec64(ts);
  	if (!timespec64_valid_strict(&now)) {

  		pr_warn("WARNING: Persistent clock returned invalid value!
  "
  			"         Check your CMOS/BIOS settings.
  ");
  		now.tv_sec = 0;
  		now.tv_nsec = 0;

  	} else if (now.tv_sec || now.tv_nsec)
  		persistent_clock_exist = true;

  	read_boot_clock(&ts);
  	boot = timespec_to_timespec64(ts);
  	if (!timespec64_valid_strict(&boot)) {

  		pr_warn("WARNING: Boot clock returned invalid value!
  "
  			"         Check your CMOS/BIOS settings.
  ");
  		boot.tv_sec = 0;
  		boot.tv_nsec = 0;
  	}

  	raw_spin_lock_irqsave(&timekeeper_lock, flags);

  	write_seqcount_begin(&tk_core.seq);

  	ntp_init();

  	clock = clocksource_default_clock();

  	if (clock->enable)
  		clock->enable(clock);

  	tk_setup_internals(tk, clock);

  	tk_set_xtime(tk, &now);
  	tk->raw_time.tv_sec = 0;
  	tk->raw_time.tv_nsec = 0;

  	tk->base_raw.tv64 = 0;

  	if (boot.tv_sec == 0 && boot.tv_nsec == 0)

  		boot = tk_xtime(tk);

  	set_normalized_timespec64(&tmp, -boot.tv_sec, -boot.tv_nsec);

  	tk_set_wall_to_mono(tk, tmp);

  	timekeeping_update(tk, TK_MIRROR);

  	write_seqcount_end(&tk_core.seq);

  	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);

  }

  /* time in seconds when suspend began */

  static struct timespec64 timekeeping_suspend_time;

  
  /**

   * __timekeeping_inject_sleeptime - Internal function to add sleep interval
   * @delta: pointer to a timespec delta value
   *
   * Takes a timespec offset measuring a suspend interval and properly
   * adds the sleep offset to the timekeeping variables.
   */

  static void __timekeeping_inject_sleeptime(struct timekeeper *tk,

  					   struct timespec64 *delta)

  {

  	if (!timespec64_valid_strict(delta)) {

  		printk_deferred(KERN_WARNING
  				"__timekeeping_inject_sleeptime: Invalid "
  				"sleep delta value!
  ");

  		return;
  	}

  	tk_xtime_add(tk, delta);

  	tk_set_wall_to_mono(tk, timespec64_sub(tk->wall_to_monotonic, *delta));

  	tk_update_sleep_time(tk, timespec64_to_ktime(*delta));

  	tk_debug_account_sleep_time(delta);

  }

  /**

   * timekeeping_inject_sleeptime64 - Adds suspend interval to timeekeeping values
   * @delta: pointer to a timespec64 delta value

   *
   * This hook is for architectures that cannot support read_persistent_clock
   * because their RTC/persistent clock is only accessible when irqs are enabled.
   *
   * This function should only be called by rtc_resume(), and allows
   * a suspend offset to be injected into the timekeeping values.
   */

  void timekeeping_inject_sleeptime64(struct timespec64 *delta)

  {

  	struct timekeeper *tk = &tk_core.timekeeper;

  	unsigned long flags;

  	/*
  	 * Make sure we don't set the clock twice, as timekeeping_resume()
  	 * already did it
  	 */
  	if (has_persistent_clock())

  		return;

  	raw_spin_lock_irqsave(&timekeeper_lock, flags);

  	write_seqcount_begin(&tk_core.seq);

  	timekeeping_forward_now(tk);

  	__timekeeping_inject_sleeptime(tk, delta);

  	timekeeping_update(tk, TK_CLEAR_NTP | TK_MIRROR | TK_CLOCK_WAS_SET);

  	write_seqcount_end(&tk_core.seq);

  	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);

  
  	/* signal hrtimers about time change */
  	clock_was_set();
  }

  /**

   * timekeeping_resume - Resumes the generic timekeeping subsystem.

   *
   * This is for the generic clocksource timekeeping.
   * xtime/wall_to_monotonic/jiffies/etc are
   * still managed by arch specific suspend/resume code.
   */

  static void timekeeping_resume(void)

  {

  	struct timekeeper *tk = &tk_core.timekeeper;

  	struct clocksource *clock = tk->tkr.clock;

  	unsigned long flags;

  	struct timespec64 ts_new, ts_delta;
  	struct timespec tmp;

  	cycle_t cycle_now, cycle_delta;
  	bool suspendtime_found = false;

  	read_persistent_clock(&tmp);
  	ts_new = timespec_to_timespec64(tmp);

  	clockevents_resume();

  	clocksource_resume();

  	raw_spin_lock_irqsave(&timekeeper_lock, flags);

  	write_seqcount_begin(&tk_core.seq);

  	/*
  	 * After system resumes, we need to calculate the suspended time and
  	 * compensate it for the OS time. There are 3 sources that could be
  	 * used: Nonstop clocksource during suspend, persistent clock and rtc
  	 * device.
  	 *
  	 * One specific platform may have 1 or 2 or all of them, and the
  	 * preference will be:
  	 *	suspend-nonstop clocksource -> persistent clock -> rtc
  	 * The less preferred source will only be tried if there is no better
  	 * usable source. The rtc part is handled separately in rtc core code.
  	 */

  	cycle_now = tk->tkr.read(clock);

  	if ((clock->flags & CLOCK_SOURCE_SUSPEND_NONSTOP) &&

  		cycle_now > tk->tkr.cycle_last) {

  		u64 num, max = ULLONG_MAX;
  		u32 mult = clock->mult;
  		u32 shift = clock->shift;
  		s64 nsec = 0;

  		cycle_delta = clocksource_delta(cycle_now, tk->tkr.cycle_last,
  						tk->tkr.mask);

  
  		/*
  		 * "cycle_delta * mutl" may cause 64 bits overflow, if the
  		 * suspended time is too long. In that case we need do the
  		 * 64 bits math carefully
  		 */
  		do_div(max, mult);
  		if (cycle_delta > max) {
  			num = div64_u64(cycle_delta, max);
  			nsec = (((u64) max * mult) >> shift) * num;
  			cycle_delta -= num * max;
  		}
  		nsec += ((u64) cycle_delta * mult) >> shift;

  		ts_delta = ns_to_timespec64(nsec);

  		suspendtime_found = true;

  	} else if (timespec64_compare(&ts_new, &timekeeping_suspend_time) > 0) {
  		ts_delta = timespec64_sub(ts_new, timekeeping_suspend_time);

  		suspendtime_found = true;

  	}

  
  	if (suspendtime_found)
  		__timekeeping_inject_sleeptime(tk, &ts_delta);
  
  	/* Re-base the last cycle value */

  	tk->tkr.cycle_last = cycle_now;

  	tk->ntp_error = 0;

  	timekeeping_suspended = 0;

  	timekeeping_update(tk, TK_MIRROR | TK_CLOCK_WAS_SET);

  	write_seqcount_end(&tk_core.seq);

  	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);

  
  	touch_softlockup_watchdog();
  
  	clockevents_notify(CLOCK_EVT_NOTIFY_RESUME, NULL);
  
  	/* Resume hrtimers */

  	hrtimers_resume();

  }

  static int timekeeping_suspend(void)

  {

  	struct timekeeper *tk = &tk_core.timekeeper;

  	unsigned long flags;

  	struct timespec64		delta, delta_delta;
  	static struct timespec64	old_delta;
  	struct timespec tmp;

  	read_persistent_clock(&tmp);
  	timekeeping_suspend_time = timespec_to_timespec64(tmp);

  	/*
  	 * On some systems the persistent_clock can not be detected at
  	 * timekeeping_init by its return value, so if we see a valid
  	 * value returned, update the persistent_clock_exists flag.
  	 */
  	if (timekeeping_suspend_time.tv_sec || timekeeping_suspend_time.tv_nsec)
  		persistent_clock_exist = true;

  	raw_spin_lock_irqsave(&timekeeper_lock, flags);

  	write_seqcount_begin(&tk_core.seq);

  	timekeeping_forward_now(tk);

  	timekeeping_suspended = 1;

  
  	/*
  	 * To avoid drift caused by repeated suspend/resumes,
  	 * which each can add ~1 second drift error,
  	 * try to compensate so the difference in system time
  	 * and persistent_clock time stays close to constant.
  	 */

  	delta = timespec64_sub(tk_xtime(tk), timekeeping_suspend_time);
  	delta_delta = timespec64_sub(delta, old_delta);

  	if (abs(delta_delta.tv_sec)  >= 2) {
  		/*
  		 * if delta_delta is too large, assume time correction
  		 * has occured and set old_delta to the current delta.
  		 */
  		old_delta = delta;
  	} else {
  		/* Otherwise try to adjust old_system to compensate */
  		timekeeping_suspend_time =

  			timespec64_add(timekeeping_suspend_time, delta_delta);

  	}

  
  	timekeeping_update(tk, TK_MIRROR);

  	write_seqcount_end(&tk_core.seq);

  	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);

  
  	clockevents_notify(CLOCK_EVT_NOTIFY_SUSPEND, NULL);

  	clocksource_suspend();

  	clockevents_suspend();

  
  	return 0;
  }
  
  /* sysfs resume/suspend bits for timekeeping */

  static struct syscore_ops timekeeping_syscore_ops = {

  	.resume		= timekeeping_resume,
  	.suspend	= timekeeping_suspend,

  };

  static int __init timekeeping_init_ops(void)

  {

  	register_syscore_ops(&timekeeping_syscore_ops);
  	return 0;

  }

  device_initcall(timekeeping_init_ops);

  
  /*

   * Apply a multiplier adjustment to the timekeeper

   */

  static __always_inline void timekeeping_apply_adjustment(struct timekeeper *tk,
  							 s64 offset,
  							 bool negative,
  							 int adj_scale)

  {

  	s64 interval = tk->cycle_interval;
  	s32 mult_adj = 1;

  	if (negative) {
  		mult_adj = -mult_adj;
  		interval = -interval;
  		offset  = -offset;

  	}

  	mult_adj <<= adj_scale;
  	interval <<= adj_scale;
  	offset <<= adj_scale;

  	/*
  	 * So the following can be confusing.
  	 *

  	 * To keep things simple, lets assume mult_adj == 1 for now.

  	 *

  	 * When mult_adj != 1, remember that the interval and offset values

  	 * have been appropriately scaled so the math is the same.
  	 *
  	 * The basic idea here is that we're increasing the multiplier
  	 * by one, this causes the xtime_interval to be incremented by
  	 * one cycle_interval. This is because:
  	 *	xtime_interval = cycle_interval * mult
  	 * So if mult is being incremented by one:
  	 *	xtime_interval = cycle_interval * (mult + 1)
  	 * Its the same as:
  	 *	xtime_interval = (cycle_interval * mult) + cycle_interval
  	 * Which can be shortened to:
  	 *	xtime_interval += cycle_interval
  	 *
  	 * So offset stores the non-accumulated cycles. Thus the current
  	 * time (in shifted nanoseconds) is:
  	 *	now = (offset * adj) + xtime_nsec
  	 * Now, even though we're adjusting the clock frequency, we have
  	 * to keep time consistent. In other words, we can't jump back
  	 * in time, and we also want to avoid jumping forward in time.
  	 *
  	 * So given the same offset value, we need the time to be the same
  	 * both before and after the freq adjustment.
  	 *	now = (offset * adj_1) + xtime_nsec_1
  	 *	now = (offset * adj_2) + xtime_nsec_2
  	 * So:
  	 *	(offset * adj_1) + xtime_nsec_1 =
  	 *		(offset * adj_2) + xtime_nsec_2
  	 * And we know:
  	 *	adj_2 = adj_1 + 1
  	 * So:
  	 *	(offset * adj_1) + xtime_nsec_1 =
  	 *		(offset * (adj_1+1)) + xtime_nsec_2
  	 *	(offset * adj_1) + xtime_nsec_1 =
  	 *		(offset * adj_1) + offset + xtime_nsec_2
  	 * Canceling the sides:
  	 *	xtime_nsec_1 = offset + xtime_nsec_2
  	 * Which gives us:
  	 *	xtime_nsec_2 = xtime_nsec_1 - offset
  	 * Which simplfies to:
  	 *	xtime_nsec -= offset
  	 *
  	 * XXX - TODO: Doc ntp_error calculation.
  	 */

  	if ((mult_adj > 0) && (tk->tkr.mult + mult_adj < mult_adj)) {

  		/* NTP adjustment caused clocksource mult overflow */
  		WARN_ON_ONCE(1);
  		return;
  	}

  	tk->tkr.mult += mult_adj;

  	tk->xtime_interval += interval;

  	tk->tkr.xtime_nsec -= offset;

  	tk->ntp_error -= (interval - offset) << tk->ntp_error_shift;

  }
  
  /*
   * Calculate the multiplier adjustment needed to match the frequency
   * specified by NTP
   */
  static __always_inline void timekeeping_freqadjust(struct timekeeper *tk,
  							s64 offset)
  {
  	s64 interval = tk->cycle_interval;
  	s64 xinterval = tk->xtime_interval;
  	s64 tick_error;
  	bool negative;
  	u32 adj;
  
  	/* Remove any current error adj from freq calculation */
  	if (tk->ntp_err_mult)
  		xinterval -= tk->cycle_interval;

  	tk->ntp_tick = ntp_tick_length();

  	/* Calculate current error per tick */
  	tick_error = ntp_tick_length() >> tk->ntp_error_shift;
  	tick_error -= (xinterval + tk->xtime_remainder);
  
  	/* Don't worry about correcting it if its small */
  	if (likely((tick_error >= 0) && (tick_error <= interval)))
  		return;
  
  	/* preserve the direction of correction */
  	negative = (tick_error < 0);
  
  	/* Sort out the magnitude of the correction */
  	tick_error = abs(tick_error);
  	for (adj = 0; tick_error > interval; adj++)
  		tick_error >>= 1;
  
  	/* scale the corrections */
  	timekeeping_apply_adjustment(tk, offset, negative, adj);
  }
  
  /*
   * Adjust the timekeeper's multiplier to the correct frequency
   * and also to reduce the accumulated error value.
   */
  static void timekeeping_adjust(struct timekeeper *tk, s64 offset)
  {
  	/* Correct for the current frequency error */
  	timekeeping_freqadjust(tk, offset);
  
  	/* Next make a small adjustment to fix any cumulative error */
  	if (!tk->ntp_err_mult && (tk->ntp_error > 0)) {
  		tk->ntp_err_mult = 1;
  		timekeeping_apply_adjustment(tk, offset, 0, 0);
  	} else if (tk->ntp_err_mult && (tk->ntp_error <= 0)) {
  		/* Undo any existing error adjustment */
  		timekeeping_apply_adjustment(tk, offset, 1, 0);
  		tk->ntp_err_mult = 0;
  	}
  
  	if (unlikely(tk->tkr.clock->maxadj &&

  		(abs(tk->tkr.mult - tk->tkr.clock->mult)
  			> tk->tkr.clock->maxadj))) {

  		printk_once(KERN_WARNING
  			"Adjusting %s more than 11%% (%ld vs %ld)
  ",
  			tk->tkr.clock->name, (long)tk->tkr.mult,
  			(long)tk->tkr.clock->mult + tk->tkr.clock->maxadj);
  	}

  
  	/*
  	 * It may be possible that when we entered this function, xtime_nsec
  	 * was very small.  Further, if we're slightly speeding the clocksource
  	 * in the code above, its possible the required corrective factor to
  	 * xtime_nsec could cause it to underflow.
  	 *
  	 * Now, since we already accumulated the second, cannot simply roll
  	 * the accumulated second back, since the NTP subsystem has been
  	 * notified via second_overflow. So instead we push xtime_nsec forward
  	 * by the amount we underflowed, and add that amount into the error.
  	 *
  	 * We'll correct this error next time through this function, when
  	 * xtime_nsec is not as small.
  	 */

  	if (unlikely((s64)tk->tkr.xtime_nsec < 0)) {
  		s64 neg = -(s64)tk->tkr.xtime_nsec;
  		tk->tkr.xtime_nsec = 0;

  		tk->ntp_error += neg << tk->ntp_error_shift;

  	}

  }
  
  /**

   * accumulate_nsecs_to_secs - Accumulates nsecs into secs
   *
   * Helper function that accumulates a the nsecs greater then a second
   * from the xtime_nsec field to the xtime_secs field.
   * It also calls into the NTP code to handle leapsecond processing.
   *
   */

  static inline unsigned int accumulate_nsecs_to_secs(struct timekeeper *tk)

  {

  	u64 nsecps = (u64)NSEC_PER_SEC << tk->tkr.shift;

  	unsigned int clock_set = 0;

  	while (tk->tkr.xtime_nsec >= nsecps) {

  		int leap;

  		tk->tkr.xtime_nsec -= nsecps;

  		tk->xtime_sec++;
  
  		/* Figure out if its a leap sec and apply if needed */
  		leap = second_overflow(tk->xtime_sec);

  		if (unlikely(leap)) {

  			struct timespec64 ts;

  
  			tk->xtime_sec += leap;

  			ts.tv_sec = leap;
  			ts.tv_nsec = 0;
  			tk_set_wall_to_mono(tk,

  				timespec64_sub(tk->wall_to_monotonic, ts));

  			__timekeeping_set_tai_offset(tk, tk->tai_offset - leap);

  			clock_set = TK_CLOCK_WAS_SET;