[mirror_ubuntu-zesty-kernel.git] / kernel / time / ntp.c

/*
 * NTP state machine interfaces and logic.
 *
 * This code was mainly moved from kernel/timer.c and kernel/time.c
 * Please see those files for relevant copyright info and historical
 * changelogs.
 */
#include <linux/capability.h>
#include <linux/clocksource.h>
#include <linux/workqueue.h>
#include <linux/hrtimer.h>
#include <linux/jiffies.h>
#include <linux/math64.h>
#include <linux/timex.h>
#include <linux/time.h>
#include <linux/mm.h>

/*
 * NTP timekeeping variables:
 */

/* USER_HZ period (usecs): */
unsigned long			tick_usec = TICK_USEC;

/* ACTHZ period (nsecs): */
unsigned long			tick_nsec;

u64				tick_length;
static u64			tick_length_base;

static struct hrtimer		leap_timer;

#define MAX_TICKADJ		500		/* usecs */
#define MAX_TICKADJ_SCALED \
  (((u64)(MAX_TICKADJ * NSEC_PER_USEC) << NTP_SCALE_SHIFT) / NTP_INTERVAL_FREQ)

/*
 * phase-lock loop variables
 */

/*
 * clock synchronization status
 *
 * (TIME_ERROR prevents overwriting the CMOS clock)
 */
static int			time_state = TIME_OK;

/* clock status bits:							*/
int				time_status = STA_UNSYNC;

/* TAI offset (secs):							*/
static long			time_tai;

/* time adjustment (nsecs):						*/
static s64			time_offset;

/* pll time constant:							*/
static long			time_constant = 2;

/* maximum error (usecs):						*/
long				time_maxerror = NTP_PHASE_LIMIT;

/* estimated error (usecs):						*/
long				time_esterror = NTP_PHASE_LIMIT;

/* frequency offset (scaled nsecs/secs):				*/
static s64			time_freq;

/* time at last adjustment (secs):					*/
static long			time_reftime;

long				time_adjust;

static long			ntp_tick_adj;

/*
 * NTP methods:
 */

static void ntp_update_frequency(void)
{
	u64 old_tick_length_base = tick_length_base;
	u64 second_length = (u64)(tick_usec * NSEC_PER_USEC * USER_HZ)
				<< NTP_SCALE_SHIFT;
	second_length += (s64)ntp_tick_adj << NTP_SCALE_SHIFT;
	second_length += time_freq;

	tick_length_base = second_length;

	tick_nsec = div_u64(second_length, HZ) >> NTP_SCALE_SHIFT;
	tick_length_base = div_u64(tick_length_base, NTP_INTERVAL_FREQ);

	/*
	 * Don't wait for the next second_overflow, apply
	 * the change to the tick length immediately
	 */
	tick_length += tick_length_base - old_tick_length_base;
}

static void ntp_update_offset(long offset)
{
	long mtemp;
	s64 freq_adj;

	if (!(time_status & STA_PLL))
		return;

	if (!(time_status & STA_NANO))
		offset *= NSEC_PER_USEC;

	/*
	 * Scale the phase adjustment and
	 * clamp to the operating range.
	 */
	offset = min(offset, MAXPHASE);
	offset = max(offset, -MAXPHASE);

	/*
	 * Select how the frequency is to be controlled
	 * and in which mode (PLL or FLL).
	 */
	if (time_status & STA_FREQHOLD || time_reftime == 0)
		time_reftime = xtime.tv_sec;
	mtemp = xtime.tv_sec - time_reftime;
	time_reftime = xtime.tv_sec;

	freq_adj = (s64)offset * mtemp;
	freq_adj <<= NTP_SCALE_SHIFT - 2 * (SHIFT_PLL + 2 + time_constant);
	time_status &= ~STA_MODE;
	if (mtemp >= MINSEC && (time_status & STA_FLL || mtemp > MAXSEC)) {
		freq_adj += div_s64((s64)offset << (NTP_SCALE_SHIFT - SHIFT_FLL),
				    mtemp);
		time_status |= STA_MODE;
	}
	freq_adj += time_freq;
	freq_adj = min(freq_adj, MAXFREQ_SCALED);
	time_freq = max(freq_adj, -MAXFREQ_SCALED);

	time_offset = div_s64((s64)offset << NTP_SCALE_SHIFT, NTP_INTERVAL_FREQ);
}

/**
 * ntp_clear - Clears the NTP state variables
 *
 * Must be called while holding a write on the xtime_lock
 */
void ntp_clear(void)
{
	time_adjust	= 0;		/* stop active adjtime() */
	time_status	|= STA_UNSYNC;
	time_maxerror	= NTP_PHASE_LIMIT;
	time_esterror	= NTP_PHASE_LIMIT;

	ntp_update_frequency();

	tick_length	= tick_length_base;
	time_offset	= 0;
}

/*
 * Leap second processing. If in leap-insert state at the end of the
 * day, the system clock is set back one second; if in leap-delete
 * state, the system clock is set ahead one second.
 */
static enum hrtimer_restart ntp_leap_second(struct hrtimer *timer)
{
	enum hrtimer_restart res = HRTIMER_NORESTART;

	write_seqlock(&xtime_lock);

	switch (time_state) {
	case TIME_OK:
		break;
	case TIME_INS:
		xtime.tv_sec--;
		wall_to_monotonic.tv_sec++;
		time_state = TIME_OOP;
		printk(KERN_NOTICE
			"Clock: inserting leap second 23:59:60 UTC\n");
		hrtimer_add_expires_ns(&leap_timer, NSEC_PER_SEC);
		res = HRTIMER_RESTART;
		break;
	case TIME_DEL:
		xtime.tv_sec++;
		time_tai--;
		wall_to_monotonic.tv_sec--;
		time_state = TIME_WAIT;
		printk(KERN_NOTICE
			"Clock: deleting leap second 23:59:59 UTC\n");
		break;
	case TIME_OOP:
		time_tai++;
		time_state = TIME_WAIT;
		/* fall through */
	case TIME_WAIT:
		if (!(time_status & (STA_INS | STA_DEL)))
			time_state = TIME_OK;
		break;
	}
	update_vsyscall(&xtime, clock);

	write_sequnlock(&xtime_lock);

	return res;
}

/*
 * this routine handles the overflow of the microsecond field
 *
 * The tricky bits of code to handle the accurate clock support
 * were provided by Dave Mills (Mills@UDEL.EDU) of NTP fame.
 * They were originally developed for SUN and DEC kernels.
 * All the kudos should go to Dave for this stuff.
 */
void second_overflow(void)
{
	s64 time_adj;

	/* Bump the maxerror field */
	time_maxerror += MAXFREQ / NSEC_PER_USEC;
	if (time_maxerror > NTP_PHASE_LIMIT) {
		time_maxerror = NTP_PHASE_LIMIT;
		time_status |= STA_UNSYNC;
	}

	/*
	 * Compute the phase adjustment for the next second. The offset is
	 * reduced by a fixed factor times the time constant.
	 */
	tick_length	= tick_length_base;
	time_adj	= shift_right(time_offset, SHIFT_PLL + time_constant);
	time_offset	-= time_adj;
	tick_length	+= time_adj;

	if (unlikely(time_adjust)) {
		if (time_adjust > MAX_TICKADJ) {
			time_adjust -= MAX_TICKADJ;
			tick_length += MAX_TICKADJ_SCALED;
		} else if (time_adjust < -MAX_TICKADJ) {
			time_adjust += MAX_TICKADJ;
			tick_length -= MAX_TICKADJ_SCALED;
		} else {
			tick_length += (s64)(time_adjust * NSEC_PER_USEC /
					NTP_INTERVAL_FREQ) << NTP_SCALE_SHIFT;
			time_adjust = 0;
		}
	}
}

#ifdef CONFIG_GENERIC_CMOS_UPDATE

/* Disable the cmos update - used by virtualization and embedded */
int no_sync_cmos_clock  __read_mostly;

static void sync_cmos_clock(struct work_struct *work);

static DECLARE_DELAYED_WORK(sync_cmos_work, sync_cmos_clock);

static void sync_cmos_clock(struct work_struct *work)
{
	struct timespec now, next;
	int fail = 1;

	/*
	 * If we have an externally synchronized Linux clock, then update
	 * CMOS clock accordingly every ~11 minutes. Set_rtc_mmss() has to be
	 * called as close as possible to 500 ms before the new second starts.
	 * This code is run on a timer.  If the clock is set, that timer
	 * may not expire at the correct time.  Thus, we adjust...
	 */
	if (!ntp_synced()) {
		/*
		 * Not synced, exit, do not restart a timer (if one is
		 * running, let it run out).
		 */
		return;
	}

	getnstimeofday(&now);
	if (abs(now.tv_nsec - (NSEC_PER_SEC / 2)) <= tick_nsec / 2)
		fail = update_persistent_clock(now);

	next.tv_nsec = (NSEC_PER_SEC / 2) - now.tv_nsec - (TICK_NSEC / 2);
	if (next.tv_nsec <= 0)
		next.tv_nsec += NSEC_PER_SEC;

	if (!fail)
		next.tv_sec = 659;
	else
		next.tv_sec = 0;

	if (next.tv_nsec >= NSEC_PER_SEC) {
		next.tv_sec++;
		next.tv_nsec -= NSEC_PER_SEC;
	}
	schedule_delayed_work(&sync_cmos_work, timespec_to_jiffies(&next));
}

static void notify_cmos_timer(void)
{
	if (!no_sync_cmos_clock)
		schedule_delayed_work(&sync_cmos_work, 0);
}

#else
static inline void notify_cmos_timer(void) { }
#endif

/*
 * adjtimex mainly allows reading (and writing, if superuser) of
 * kernel time-keeping variables. used by xntpd.
 */
int do_adjtimex(struct timex *txc)
{
	struct timespec ts;
	int result;

	/* Validate the data before disabling interrupts */
	if (txc->modes & ADJ_ADJTIME) {
		/* singleshot must not be used with any other mode bits */
		if (!(txc->modes & ADJ_OFFSET_SINGLESHOT))
			return -EINVAL;
		if (!(txc->modes & ADJ_OFFSET_READONLY) &&
		    !capable(CAP_SYS_TIME))
			return -EPERM;
	} else {
		/* In order to modify anything, you gotta be super-user! */
		 if (txc->modes && !capable(CAP_SYS_TIME))
			return -EPERM;

		/*
		 * if the quartz is off by more than 10% then
		 * something is VERY wrong!
		 */
		if (txc->modes & ADJ_TICK &&
		    (txc->tick <  900000/USER_HZ ||
		     txc->tick > 1100000/USER_HZ))
				return -EINVAL;

		if (txc->modes & ADJ_STATUS && time_state != TIME_OK)
			hrtimer_cancel(&leap_timer);
	}

	getnstimeofday(&ts);

	write_seqlock_irq(&xtime_lock);

	/* If there are input parameters, then process them */
	if (txc->modes & ADJ_ADJTIME) {
		long save_adjust = time_adjust;

		if (!(txc->modes & ADJ_OFFSET_READONLY)) {
			/* adjtime() is independent from ntp_adjtime() */
			time_adjust = txc->offset;
			ntp_update_frequency();
		}
		txc->offset = save_adjust;
		goto adj_done;
	}
	if (txc->modes) {
		long sec;

		if (txc->modes & ADJ_STATUS) {
			if ((time_status & STA_PLL) &&
			    !(txc->status & STA_PLL)) {
				time_state = TIME_OK;
				time_status = STA_UNSYNC;
			}
			/* only set allowed bits */
			time_status &= STA_RONLY;
			time_status |= txc->status & ~STA_RONLY;

			switch (time_state) {
			case TIME_OK:
			start_timer:
				sec = ts.tv_sec;
				if (time_status & STA_INS) {
					time_state = TIME_INS;
					sec += 86400 - sec % 86400;
					hrtimer_start(&leap_timer, ktime_set(sec, 0), HRTIMER_MODE_ABS);
				} else if (time_status & STA_DEL) {
					time_state = TIME_DEL;
					sec += 86400 - (sec + 1) % 86400;
					hrtimer_start(&leap_timer, ktime_set(sec, 0), HRTIMER_MODE_ABS);
				}
				break;
			case TIME_INS:
			case TIME_DEL:
				time_state = TIME_OK;
				goto start_timer;
				break;
			case TIME_WAIT:
				if (!(time_status & (STA_INS | STA_DEL)))
					time_state = TIME_OK;
				break;
			case TIME_OOP:
				hrtimer_restart(&leap_timer);
				break;
			}
		}

		if (txc->modes & ADJ_NANO)
			time_status |= STA_NANO;
		if (txc->modes & ADJ_MICRO)
			time_status &= ~STA_NANO;

		if (txc->modes & ADJ_FREQUENCY) {
			time_freq = (s64)txc->freq * PPM_SCALE;
			time_freq = min(time_freq, MAXFREQ_SCALED);
			time_freq = max(time_freq, -MAXFREQ_SCALED);
		}

		if (txc->modes & ADJ_MAXERROR)
			time_maxerror = txc->maxerror;
		if (txc->modes & ADJ_ESTERROR)
			time_esterror = txc->esterror;

		if (txc->modes & ADJ_TIMECONST) {
			time_constant = txc->constant;
			if (!(time_status & STA_NANO))
				time_constant += 4;
			time_constant = min(time_constant, (long)MAXTC);
			time_constant = max(time_constant, 0l);
		}

		if (txc->modes & ADJ_TAI && txc->constant > 0)
			time_tai = txc->constant;

		if (txc->modes & ADJ_OFFSET)
			ntp_update_offset(txc->offset);
		if (txc->modes & ADJ_TICK)
			tick_usec = txc->tick;

		if (txc->modes & (ADJ_TICK|ADJ_FREQUENCY|ADJ_OFFSET))
			ntp_update_frequency();
	}

	txc->offset = shift_right(time_offset * NTP_INTERVAL_FREQ,
				  NTP_SCALE_SHIFT);
	if (!(time_status & STA_NANO))
		txc->offset /= NSEC_PER_USEC;

adj_done:
	result = time_state;	/* mostly `TIME_OK' */
	if (time_status & (STA_UNSYNC|STA_CLOCKERR))
		result = TIME_ERROR;

	txc->freq	   = shift_right((time_freq >> PPM_SCALE_INV_SHIFT) *
					 (s64)PPM_SCALE_INV, NTP_SCALE_SHIFT);
	txc->maxerror	   = time_maxerror;
	txc->esterror	   = time_esterror;
	txc->status	   = time_status;
	txc->constant	   = time_constant;
	txc->precision	   = 1;
	txc->tolerance	   = MAXFREQ_SCALED / PPM_SCALE;
	txc->tick	   = tick_usec;
	txc->tai	   = time_tai;

	/* PPS is not implemented, so these are zero */
	txc->ppsfreq	   = 0;
	txc->jitter	   = 0;
	txc->shift	   = 0;
	txc->stabil	   = 0;
	txc->jitcnt	   = 0;
	txc->calcnt	   = 0;
	txc->errcnt	   = 0;
	txc->stbcnt	   = 0;
	write_sequnlock_irq(&xtime_lock);

	txc->time.tv_sec = ts.tv_sec;
	txc->time.tv_usec = ts.tv_nsec;
	if (!(time_status & STA_NANO))
		txc->time.tv_usec /= NSEC_PER_USEC;

	notify_cmos_timer();

	return result;
}

static int __init ntp_tick_adj_setup(char *str)
{
	ntp_tick_adj = simple_strtol(str, NULL, 0);
	return 1;
}

__setup("ntp_tick_adj=", ntp_tick_adj_setup);

void __init ntp_init(void)
{
	ntp_clear();
	hrtimer_init(&leap_timer, CLOCK_REALTIME, HRTIMER_MODE_ABS);
	leap_timer.function = ntp_leap_second;
}
Commit	Line	Data
4c7ee8de	1	/*
4c7ee8de JS	2	* NTP state machine interfaces and logic.
	3	*
	4	* This code was mainly moved from kernel/timer.c and kernel/time.c
	5	* Please see those files for relevant copyright info and historical
	6	* changelogs.
	7	*/
aa0ac365	8	#include <linux/capability.h>
7dffa3c6	9	#include <linux/clocksource.h>
eb3f938f	10	#include <linux/workqueue.h>
53bbfa9e IM	11	#include <linux/hrtimer.h>
	12	#include <linux/jiffies.h>
	13	#include <linux/math64.h>
	14	#include <linux/timex.h>
	15	#include <linux/time.h>
	16	#include <linux/mm.h>
4c7ee8de	17
b0ee7556	18	/*
53bbfa9e	19	* NTP timekeeping variables:
b0ee7556	20	*/
b0ee7556	21
53bbfa9e IM	22	/* USER_HZ period (usecs): */
	23	unsigned long tick_usec = TICK_USEC;
	24
	25	/* ACTHZ period (nsecs): */
	26	unsigned long tick_nsec;
7dffa3c6	27
53bbfa9e IM	28	u64 tick_length;
	29	static u64 tick_length_base;
	30
	31	static struct hrtimer leap_timer;
	32
	33	#define MAX_TICKADJ 500 /* usecs */
	34	#define MAX_TICKADJ_SCALED \
	35	(((u64)(MAX_TICKADJ * NSEC_PER_USEC) << NTP_SCALE_SHIFT) / NTP_INTERVAL_FREQ)
4c7ee8de JS	36
	37	/*
	38	* phase-lock loop variables
	39	*/
53bbfa9e IM	40
	41	/*
	42	* clock synchronization status
	43	*
	44	* (TIME_ERROR prevents overwriting the CMOS clock)
	45	*/
	46	static int time_state = TIME_OK;
	47
	48	/* clock status bits: */
	49	int time_status = STA_UNSYNC;
	50
	51	/* TAI offset (secs): */
	52	static long time_tai;
	53
	54	/* time adjustment (nsecs): */
	55	static s64 time_offset;
	56
	57	/* pll time constant: */
	58	static long time_constant = 2;
	59
	60	/* maximum error (usecs): */
	61	long time_maxerror = NTP_PHASE_LIMIT;
	62
	63	/* estimated error (usecs): */
	64	long time_esterror = NTP_PHASE_LIMIT;
	65
	66	/* frequency offset (scaled nsecs/secs): */
	67	static s64 time_freq;
	68
	69	/* time at last adjustment (secs): */
	70	static long time_reftime;
	71
	72	long time_adjust;
	73
	74	static long ntp_tick_adj;
	75
	76	/*
	77	* NTP methods:
	78	*/
4c7ee8de	79
70bc42f9 AB	80	static void ntp_update_frequency(void)
70bc42f9 AB	81	{
fdcedf7b	82	u64 old_tick_length_base = tick_length_base;
f4304ab2	83	u64 second_length = (u64)(tick_usec * NSEC_PER_USEC * USER_HZ)
7fc5c784 RZ	84	<< NTP_SCALE_SHIFT;
7fc5c784 RZ	85	second_length += (s64)ntp_tick_adj << NTP_SCALE_SHIFT;
074b3b87	86	second_length += time_freq;
70bc42f9	87
f4304ab2	88	tick_length_base = second_length;
70bc42f9	89
7fc5c784	90	tick_nsec = div_u64(second_length, HZ) >> NTP_SCALE_SHIFT;
71abb3af	91	tick_length_base = div_u64(tick_length_base, NTP_INTERVAL_FREQ);
fdcedf7b JS	92
	93	/*
	94	* Don't wait for the next second_overflow, apply
	95	* the change to the tick length immediately
	96	*/
	97	tick_length += tick_length_base - old_tick_length_base;
70bc42f9 AB	98	}
70bc42f9 AB	99
ee9851b2 RZ	100	static void ntp_update_offset(long offset)
	101	{
	102	long mtemp;
	103	s64 freq_adj;
	104
	105	if (!(time_status & STA_PLL))
	106	return;
	107
eea83d89	108	if (!(time_status & STA_NANO))
9f14f669	109	offset *= NSEC_PER_USEC;
ee9851b2 RZ	110
	111	/*
	112	* Scale the phase adjustment and
	113	* clamp to the operating range.
	114	*/
9f14f669 RZ	115	offset = min(offset, MAXPHASE);
9f14f669 RZ	116	offset = max(offset, -MAXPHASE);
ee9851b2 RZ	117
	118	/*
	119	* Select how the frequency is to be controlled
	120	* and in which mode (PLL or FLL).
	121	*/
	122	if (time_status & STA_FREQHOLD \|\| time_reftime == 0)
	123	time_reftime = xtime.tv_sec;
	124	mtemp = xtime.tv_sec - time_reftime;
	125	time_reftime = xtime.tv_sec;
	126
9f14f669	127	freq_adj = (s64)offset * mtemp;
7fc5c784	128	freq_adj <<= NTP_SCALE_SHIFT - 2 * (SHIFT_PLL + 2 + time_constant);
eea83d89 RZ	129	time_status &= ~STA_MODE;
eea83d89 RZ	130	if (mtemp >= MINSEC && (time_status & STA_FLL \|\| mtemp > MAXSEC)) {
7fc5c784	131	freq_adj += div_s64((s64)offset << (NTP_SCALE_SHIFT - SHIFT_FLL),
074b3b87	132	mtemp);
eea83d89 RZ	133	time_status \|= STA_MODE;
eea83d89 RZ	134	}
ee9851b2	135	freq_adj += time_freq;
074b3b87 RZ	136	freq_adj = min(freq_adj, MAXFREQ_SCALED);
074b3b87 RZ	137	time_freq = max(freq_adj, -MAXFREQ_SCALED);
9f14f669	138
7fc5c784	139	time_offset = div_s64((s64)offset << NTP_SCALE_SHIFT, NTP_INTERVAL_FREQ);
ee9851b2 RZ	140	}
ee9851b2 RZ	141
b0ee7556 RZ	142	/**
	143	* ntp_clear - Clears the NTP state variables
	144	*
	145	* Must be called while holding a write on the xtime_lock
	146	*/
	147	void ntp_clear(void)
	148	{
53bbfa9e IM	149	time_adjust = 0; /* stop active adjtime() */
	150	time_status \|= STA_UNSYNC;
	151	time_maxerror = NTP_PHASE_LIMIT;
	152	time_esterror = NTP_PHASE_LIMIT;
b0ee7556 RZ	153
	154	ntp_update_frequency();
	155
53bbfa9e IM	156	tick_length = tick_length_base;
53bbfa9e IM	157	time_offset = 0;
b0ee7556 RZ	158	}
b0ee7556 RZ	159
4c7ee8de	160	/*
7dffa3c6 RZ	161	* Leap second processing. If in leap-insert state at the end of the
	162	* day, the system clock is set back one second; if in leap-delete
	163	* state, the system clock is set ahead one second.
4c7ee8de	164	*/
7dffa3c6	165	static enum hrtimer_restart ntp_leap_second(struct hrtimer *timer)
4c7ee8de	166	{
7dffa3c6	167	enum hrtimer_restart res = HRTIMER_NORESTART;
4c7ee8de	168
ca109491	169	write_seqlock(&xtime_lock);
4c7ee8de	170
4c7ee8de JS	171	switch (time_state) {
4c7ee8de JS	172	case TIME_OK:
4c7ee8de JS	173	break;
4c7ee8de JS	174	case TIME_INS:
7dffa3c6 RZ	175	xtime.tv_sec--;
	176	wall_to_monotonic.tv_sec++;
	177	time_state = TIME_OOP;
53bbfa9e IM	178	printk(KERN_NOTICE
53bbfa9e IM	179	"Clock: inserting leap second 23:59:60 UTC\n");
cc584b21	180	hrtimer_add_expires_ns(&leap_timer, NSEC_PER_SEC);
7dffa3c6	181	res = HRTIMER_RESTART;
4c7ee8de JS	182	break;
4c7ee8de JS	183	case TIME_DEL:
7dffa3c6 RZ	184	xtime.tv_sec++;
	185	time_tai--;
	186	wall_to_monotonic.tv_sec--;
	187	time_state = TIME_WAIT;
53bbfa9e IM	188	printk(KERN_NOTICE
53bbfa9e IM	189	"Clock: deleting leap second 23:59:59 UTC\n");
4c7ee8de JS	190	break;
4c7ee8de JS	191	case TIME_OOP:
153b5d05	192	time_tai++;
4c7ee8de	193	time_state = TIME_WAIT;
7dffa3c6	194	/* fall through */
4c7ee8de JS	195	case TIME_WAIT:
4c7ee8de JS	196	if (!(time_status & (STA_INS \| STA_DEL)))
ee9851b2	197	time_state = TIME_OK;
7dffa3c6 RZ	198	break;
	199	}
	200	update_vsyscall(&xtime, clock);
	201
ca109491	202	write_sequnlock(&xtime_lock);
7dffa3c6 RZ	203
	204	return res;
	205	}
	206
	207	/*
	208	* this routine handles the overflow of the microsecond field
	209	*
	210	* The tricky bits of code to handle the accurate clock support
	211	* were provided by Dave Mills (Mills@UDEL.EDU) of NTP fame.
	212	* They were originally developed for SUN and DEC kernels.
	213	* All the kudos should go to Dave for this stuff.
	214	*/
	215	void second_overflow(void)
	216	{
	217	s64 time_adj;
	218
	219	/* Bump the maxerror field */
	220	time_maxerror += MAXFREQ / NSEC_PER_USEC;
	221	if (time_maxerror > NTP_PHASE_LIMIT) {
	222	time_maxerror = NTP_PHASE_LIMIT;
	223	time_status \|= STA_UNSYNC;
4c7ee8de JS	224	}
	225
	226	/*
f1992393 RZ	227	* Compute the phase adjustment for the next second. The offset is
f1992393 RZ	228	* reduced by a fixed factor times the time constant.
4c7ee8de	229	*/
53bbfa9e IM	230	tick_length = tick_length_base;
	231	time_adj = shift_right(time_offset, SHIFT_PLL + time_constant);
	232	time_offset -= time_adj;
	233	tick_length += time_adj;
4c7ee8de	234
8f807f8d RZ	235	if (unlikely(time_adjust)) {
	236	if (time_adjust > MAX_TICKADJ) {
	237	time_adjust -= MAX_TICKADJ;
	238	tick_length += MAX_TICKADJ_SCALED;
	239	} else if (time_adjust < -MAX_TICKADJ) {
	240	time_adjust += MAX_TICKADJ;
	241	tick_length -= MAX_TICKADJ_SCALED;
	242	} else {
8f807f8d	243	tick_length += (s64)(time_adjust * NSEC_PER_USEC /
7fc5c784	244	NTP_INTERVAL_FREQ) << NTP_SCALE_SHIFT;
bb1d8605	245	time_adjust = 0;
8f807f8d	246	}
4c7ee8de JS	247	}
	248	}
	249
82644459	250	#ifdef CONFIG_GENERIC_CMOS_UPDATE
4c7ee8de	251
82644459 TG	252	/* Disable the cmos update - used by virtualization and embedded */
	253	int no_sync_cmos_clock __read_mostly;
	254
eb3f938f	255	static void sync_cmos_clock(struct work_struct *work);
82644459	256
eb3f938f	257	static DECLARE_DELAYED_WORK(sync_cmos_work, sync_cmos_clock);
82644459	258
eb3f938f	259	static void sync_cmos_clock(struct work_struct *work)
82644459 TG	260	{
	261	struct timespec now, next;
	262	int fail = 1;
	263
	264	/*
	265	* If we have an externally synchronized Linux clock, then update
	266	* CMOS clock accordingly every ~11 minutes. Set_rtc_mmss() has to be
	267	* called as close as possible to 500 ms before the new second starts.
	268	* This code is run on a timer. If the clock is set, that timer
	269	* may not expire at the correct time. Thus, we adjust...
	270	*/
53bbfa9e	271	if (!ntp_synced()) {
82644459 TG	272	/*
	273	* Not synced, exit, do not restart a timer (if one is
	274	* running, let it run out).
	275	*/
	276	return;
53bbfa9e	277	}
82644459 TG	278
82644459 TG	279	getnstimeofday(&now);
fa6a1a55	280	if (abs(now.tv_nsec - (NSEC_PER_SEC / 2)) <= tick_nsec / 2)
82644459 TG	281	fail = update_persistent_clock(now);
82644459 TG	282
4ff4b9e1	283	next.tv_nsec = (NSEC_PER_SEC / 2) - now.tv_nsec - (TICK_NSEC / 2);
82644459 TG	284	if (next.tv_nsec <= 0)
	285	next.tv_nsec += NSEC_PER_SEC;
	286
	287	if (!fail)
	288	next.tv_sec = 659;
	289	else
	290	next.tv_sec = 0;
	291
	292	if (next.tv_nsec >= NSEC_PER_SEC) {
	293	next.tv_sec++;
	294	next.tv_nsec -= NSEC_PER_SEC;
	295	}
eb3f938f	296	schedule_delayed_work(&sync_cmos_work, timespec_to_jiffies(&next));
82644459 TG	297	}
	298
	299	static void notify_cmos_timer(void)
4c7ee8de	300	{
298a5df4	301	if (!no_sync_cmos_clock)
eb3f938f	302	schedule_delayed_work(&sync_cmos_work, 0);
4c7ee8de JS	303	}
4c7ee8de JS	304
82644459 TG	305	#else
	306	static inline void notify_cmos_timer(void) { }
	307	#endif
	308
53bbfa9e IM	309	/*
53bbfa9e IM	310	* adjtimex mainly allows reading (and writing, if superuser) of
4c7ee8de JS	311	* kernel time-keeping variables. used by xntpd.
	312	*/
	313	int do_adjtimex(struct timex *txc)
	314	{
eea83d89	315	struct timespec ts;
4c7ee8de JS	316	int result;
4c7ee8de JS	317
916c7a85 RZ	318	/* Validate the data before disabling interrupts */
916c7a85 RZ	319	if (txc->modes & ADJ_ADJTIME) {
eea83d89	320	/* singleshot must not be used with any other mode bits */
916c7a85	321	if (!(txc->modes & ADJ_OFFSET_SINGLESHOT))
4c7ee8de	322	return -EINVAL;
916c7a85 RZ	323	if (!(txc->modes & ADJ_OFFSET_READONLY) &&
	324	!capable(CAP_SYS_TIME))
	325	return -EPERM;
	326	} else {
	327	/* In order to modify anything, you gotta be super-user! */
	328	if (txc->modes && !capable(CAP_SYS_TIME))
	329	return -EPERM;
	330
53bbfa9e IM	331	/*
	332	* if the quartz is off by more than 10% then
	333	* something is VERY wrong!
	334	*/
916c7a85 RZ	335	if (txc->modes & ADJ_TICK &&
	336	(txc->tick < 900000/USER_HZ \|\|
	337	txc->tick > 1100000/USER_HZ))
	338	return -EINVAL;
	339
	340	if (txc->modes & ADJ_STATUS && time_state != TIME_OK)
	341	hrtimer_cancel(&leap_timer);
52bfb360	342	}
4c7ee8de	343
7dffa3c6 RZ	344	getnstimeofday(&ts);
7dffa3c6 RZ	345
4c7ee8de	346	write_seqlock_irq(&xtime_lock);
4c7ee8de	347
4c7ee8de	348	/* If there are input parameters, then process them */
916c7a85 RZ	349	if (txc->modes & ADJ_ADJTIME) {
	350	long save_adjust = time_adjust;
	351
	352	if (!(txc->modes & ADJ_OFFSET_READONLY)) {
	353	/* adjtime() is independent from ntp_adjtime() */
	354	time_adjust = txc->offset;
	355	ntp_update_frequency();
	356	}
	357	txc->offset = save_adjust;
	358	goto adj_done;
	359	}
ee9851b2	360	if (txc->modes) {
916c7a85 RZ	361	long sec;
916c7a85 RZ	362
eea83d89 RZ	363	if (txc->modes & ADJ_STATUS) {
	364	if ((time_status & STA_PLL) &&
	365	!(txc->status & STA_PLL)) {
	366	time_state = TIME_OK;
	367	time_status = STA_UNSYNC;
	368	}
	369	/* only set allowed bits */
	370	time_status &= STA_RONLY;
	371	time_status \|= txc->status & ~STA_RONLY;
7dffa3c6 RZ	372
	373	switch (time_state) {
	374	case TIME_OK:
	375	start_timer:
	376	sec = ts.tv_sec;
	377	if (time_status & STA_INS) {
	378	time_state = TIME_INS;
	379	sec += 86400 - sec % 86400;
	380	hrtimer_start(&leap_timer, ktime_set(sec, 0), HRTIMER_MODE_ABS);
	381	} else if (time_status & STA_DEL) {
	382	time_state = TIME_DEL;
	383	sec += 86400 - (sec + 1) % 86400;
	384	hrtimer_start(&leap_timer, ktime_set(sec, 0), HRTIMER_MODE_ABS);
	385	}
	386	break;
	387	case TIME_INS:
	388	case TIME_DEL:
	389	time_state = TIME_OK;
	390	goto start_timer;
	391	break;
	392	case TIME_WAIT:
	393	if (!(time_status & (STA_INS \| STA_DEL)))
	394	time_state = TIME_OK;
	395	break;
	396	case TIME_OOP:
	397	hrtimer_restart(&leap_timer);
	398	break;
	399	}
eea83d89 RZ	400	}
	401
	402	if (txc->modes & ADJ_NANO)
	403	time_status \|= STA_NANO;
	404	if (txc->modes & ADJ_MICRO)
	405	time_status &= ~STA_NANO;
ee9851b2 RZ	406
ee9851b2 RZ	407	if (txc->modes & ADJ_FREQUENCY) {
074b3b87 RZ	408	time_freq = (s64)txc->freq * PPM_SCALE;
	409	time_freq = min(time_freq, MAXFREQ_SCALED);
	410	time_freq = max(time_freq, -MAXFREQ_SCALED);
4c7ee8de	411	}
ee9851b2	412
eea83d89	413	if (txc->modes & ADJ_MAXERROR)
ee9851b2	414	time_maxerror = txc->maxerror;
eea83d89	415	if (txc->modes & ADJ_ESTERROR)
ee9851b2	416	time_esterror = txc->esterror;
4c7ee8de	417
ee9851b2	418	if (txc->modes & ADJ_TIMECONST) {
eea83d89 RZ	419	time_constant = txc->constant;
	420	if (!(time_status & STA_NANO))
	421	time_constant += 4;
	422	time_constant = min(time_constant, (long)MAXTC);
	423	time_constant = max(time_constant, 0l);
4c7ee8de	424	}
4c7ee8de	425
153b5d05 RZ	426	if (txc->modes & ADJ_TAI && txc->constant > 0)
	427	time_tai = txc->constant;
	428
916c7a85 RZ	429	if (txc->modes & ADJ_OFFSET)
916c7a85 RZ	430	ntp_update_offset(txc->offset);
ee9851b2 RZ	431	if (txc->modes & ADJ_TICK)
	432	tick_usec = txc->tick;
	433
	434	if (txc->modes & (ADJ_TICK\|ADJ_FREQUENCY\|ADJ_OFFSET))
	435	ntp_update_frequency();
	436	}
eea83d89	437
916c7a85 RZ	438	txc->offset = shift_right(time_offset * NTP_INTERVAL_FREQ,
	439	NTP_SCALE_SHIFT);
	440	if (!(time_status & STA_NANO))
	441	txc->offset /= NSEC_PER_USEC;
	442
	443	adj_done:
eea83d89	444	result = time_state; /* mostly `TIME_OK' */
ee9851b2	445	if (time_status & (STA_UNSYNC\|STA_CLOCKERR))
4c7ee8de JS	446	result = TIME_ERROR;
4c7ee8de JS	447
d40e944c RZ	448	txc->freq = shift_right((time_freq >> PPM_SCALE_INV_SHIFT) *
d40e944c RZ	449	(s64)PPM_SCALE_INV, NTP_SCALE_SHIFT);
4c7ee8de JS	450	txc->maxerror = time_maxerror;
	451	txc->esterror = time_esterror;
	452	txc->status = time_status;
	453	txc->constant = time_constant;
70bc42f9	454	txc->precision = 1;
074b3b87	455	txc->tolerance = MAXFREQ_SCALED / PPM_SCALE;
4c7ee8de	456	txc->tick = tick_usec;
153b5d05	457	txc->tai = time_tai;
4c7ee8de JS	458
	459	/* PPS is not implemented, so these are zero */
	460	txc->ppsfreq = 0;
	461	txc->jitter = 0;
	462	txc->shift = 0;
	463	txc->stabil = 0;
	464	txc->jitcnt = 0;
	465	txc->calcnt = 0;
	466	txc->errcnt = 0;
	467	txc->stbcnt = 0;
	468	write_sequnlock_irq(&xtime_lock);
ee9851b2	469
eea83d89 RZ	470	txc->time.tv_sec = ts.tv_sec;
	471	txc->time.tv_usec = ts.tv_nsec;
	472	if (!(time_status & STA_NANO))
	473	txc->time.tv_usec /= NSEC_PER_USEC;
ee9851b2	474
82644459	475	notify_cmos_timer();
ee9851b2 RZ	476
ee9851b2 RZ	477	return result;
4c7ee8de	478	}
10a398d0 RZ	479
	480	static int __init ntp_tick_adj_setup(char *str)
	481	{
	482	ntp_tick_adj = simple_strtol(str, NULL, 0);
	483	return 1;
	484	}
	485
	486	__setup("ntp_tick_adj=", ntp_tick_adj_setup);
7dffa3c6 RZ	487
	488	void __init ntp_init(void)
	489	{
	490	ntp_clear();
	491	hrtimer_init(&leap_timer, CLOCK_REALTIME, HRTIMER_MODE_ABS);
	492	leap_timer.function = ntp_leap_second;
	493	}