/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>
#include <linux/module.h>

#include "tick-internal.h"


DEFINE_SPINLOCK(ntp_lock);


unsigned long			tick_usec = TICK_USEC;

unsigned long			tick_nsec;

static u64			tick_length;
static u64			tick_length_base;

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


static int			time_state = TIME_OK;

static int			time_status = STA_UNSYNC;

static long			time_tai;

static s64			time_offset;

static long			time_constant = 2;

static long			time_maxerror = NTP_PHASE_LIMIT;

static long			time_esterror = NTP_PHASE_LIMIT;

static s64			time_freq;

static long			time_reftime;

static long			time_adjust;

static s64			ntp_tick_adj;

#ifdef CONFIG_NTP_PPS

#define PPS_VALID	10	
#define PPS_POPCORN	4	
#define PPS_INTMIN	2	
#define PPS_INTMAX	8	
#define PPS_INTCOUNT	4	
#define PPS_MAXWANDER	100000	

static int pps_valid;		
static long pps_tf[3];		
static long pps_jitter;		
static struct timespec pps_fbase; 
static int pps_shift;		
static int pps_intcnt;		
static s64 pps_freq;		
static long pps_stabil;		

static long pps_calcnt;		
static long pps_jitcnt;		
static long pps_stbcnt;		
static long pps_errcnt;		


static inline s64 ntp_offset_chunk(s64 offset)
{
	if (time_status & STA_PPSTIME && time_status & STA_PPSSIGNAL)
		return offset;
	else
		return shift_right(offset, SHIFT_PLL + time_constant);
}

static inline void pps_reset_freq_interval(void)
{
	pps_shift = PPS_INTMIN;
	pps_intcnt = 0;
}

static inline void pps_clear(void)
{
	pps_reset_freq_interval();
	pps_tf[0] = 0;
	pps_tf[1] = 0;
	pps_tf[2] = 0;
	pps_fbase.tv_sec = pps_fbase.tv_nsec = 0;
	pps_freq = 0;
}

static inline void pps_dec_valid(void)
{
	if (pps_valid > 0)
		pps_valid--;
	else {
		time_status &= ~(STA_PPSSIGNAL | STA_PPSJITTER |
				 STA_PPSWANDER | STA_PPSERROR);
		pps_clear();
	}
}

static inline void pps_set_freq(s64 freq)
{
	pps_freq = freq;
}

static inline int is_error_status(int status)
{
	return (time_status & (STA_UNSYNC|STA_CLOCKERR))
		|| ((time_status & (STA_PPSFREQ|STA_PPSTIME))
			&& !(time_status & STA_PPSSIGNAL))
		|| ((time_status & (STA_PPSTIME|STA_PPSJITTER))
			== (STA_PPSTIME|STA_PPSJITTER))
		|| ((time_status & STA_PPSFREQ)
			&& (time_status & (STA_PPSWANDER|STA_PPSERROR)));
}

static inline void pps_fill_timex(struct timex *txc)
{
	txc->ppsfreq	   = shift_right((pps_freq >> PPM_SCALE_INV_SHIFT) *
					 PPM_SCALE_INV, NTP_SCALE_SHIFT);
	txc->jitter	   = pps_jitter;
	if (!(time_status & STA_NANO))
		txc->jitter /= NSEC_PER_USEC;
	txc->shift	   = pps_shift;
	txc->stabil	   = pps_stabil;
	txc->jitcnt	   = pps_jitcnt;
	txc->calcnt	   = pps_calcnt;
	txc->errcnt	   = pps_errcnt;
	txc->stbcnt	   = pps_stbcnt;
}

#else 

static inline s64 ntp_offset_chunk(s64 offset)
{
	return shift_right(offset, SHIFT_PLL + time_constant);
}

static inline void pps_reset_freq_interval(void) {}
static inline void pps_clear(void) {}
static inline void pps_dec_valid(void) {}
static inline void pps_set_freq(s64 freq) {}

static inline int is_error_status(int status)
{
	return status & (STA_UNSYNC|STA_CLOCKERR);
}

static inline void pps_fill_timex(struct timex *txc)
{
	
	txc->ppsfreq	   = 0;
	txc->jitter	   = 0;
	txc->shift	   = 0;
	txc->stabil	   = 0;
	txc->jitcnt	   = 0;
	txc->calcnt	   = 0;
	txc->errcnt	   = 0;
	txc->stbcnt	   = 0;
}

#endif 


static inline int ntp_synced(void)
{
	return !(time_status & STA_UNSYNC);
}



static void ntp_update_frequency(void)
{
	u64 second_length;
	u64 new_base;

	second_length		 = (u64)(tick_usec * NSEC_PER_USEC * USER_HZ)
						<< NTP_SCALE_SHIFT;

	second_length		+= ntp_tick_adj;
	second_length		+= time_freq;

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

	tick_length		+= new_base - tick_length_base;
	tick_length_base	 = new_base;
}

static inline s64 ntp_update_offset_fll(s64 offset64, long secs)
{
	time_status &= ~STA_MODE;

	if (secs < MINSEC)
		return 0;

	if (!(time_status & STA_FLL) && (secs <= MAXSEC))
		return 0;

	time_status |= STA_MODE;

	return div64_long(offset64 << (NTP_SCALE_SHIFT - SHIFT_FLL), secs);
}

static void ntp_update_offset(long offset)
{
	s64 freq_adj;
	s64 offset64;
	long secs;

	if (!(time_status & STA_PLL))
		return;

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

	offset = min(offset, MAXPHASE);
	offset = max(offset, -MAXPHASE);

	secs = get_seconds() - time_reftime;
	if (unlikely(time_status & STA_FREQHOLD))
		secs = 0;

	time_reftime = get_seconds();

	offset64    = offset;
	freq_adj    = ntp_update_offset_fll(offset64, secs);

	if (unlikely(secs > 1 << (SHIFT_PLL + 1 + time_constant)))
		secs = 1 << (SHIFT_PLL + 1 + time_constant);

	freq_adj    += (offset64 * secs) <<
			(NTP_SCALE_SHIFT - 2 * (SHIFT_PLL + 2 + time_constant));

	freq_adj    = min(freq_adj + time_freq, MAXFREQ_SCALED);

	time_freq   = max(freq_adj, -MAXFREQ_SCALED);

	time_offset = div_s64(offset64 << NTP_SCALE_SHIFT, NTP_INTERVAL_FREQ);
}

void ntp_clear(void)
{
	unsigned long flags;

	spin_lock_irqsave(&ntp_lock, flags);

	time_adjust	= 0;		
	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;

	
	pps_clear();
	spin_unlock_irqrestore(&ntp_lock, flags);

}


u64 ntp_tick_length(void)
{
	unsigned long flags;
	s64 ret;

	spin_lock_irqsave(&ntp_lock, flags);
	ret = tick_length;
	spin_unlock_irqrestore(&ntp_lock, flags);
	return ret;
}


int second_overflow(unsigned long secs)
{
	s64 delta;
	int leap = 0;
	unsigned long flags;

	spin_lock_irqsave(&ntp_lock, flags);

	switch (time_state) {
	case TIME_OK:
		if (time_status & STA_INS)
			time_state = TIME_INS;
		else if (time_status & STA_DEL)
			time_state = TIME_DEL;
		break;
	case TIME_INS:
		if (secs % 86400 == 0) {
			leap = -1;
			time_state = TIME_OOP;
			time_tai++;
			printk(KERN_NOTICE
				"Clock: inserting leap second 23:59:60 UTC\n");
		}
		break;
	case TIME_DEL:
		if ((secs + 1) % 86400 == 0) {
			leap = 1;
			time_tai--;
			time_state = TIME_WAIT;
			printk(KERN_NOTICE
				"Clock: deleting leap second 23:59:59 UTC\n");
		}
		break;
	case TIME_OOP:
		time_state = TIME_WAIT;
		break;

	case TIME_WAIT:
		if (!(time_status & (STA_INS | STA_DEL)))
			time_state = TIME_OK;
		break;
	}


	
	time_maxerror += MAXFREQ / NSEC_PER_USEC;
	if (time_maxerror > NTP_PHASE_LIMIT) {
		time_maxerror = NTP_PHASE_LIMIT;
		time_status |= STA_UNSYNC;
	}

	
	tick_length	 = tick_length_base;

	delta		 = ntp_offset_chunk(time_offset);
	time_offset	-= delta;
	tick_length	+= delta;

	
	pps_dec_valid();

	if (!time_adjust)
		goto out;

	if (time_adjust > MAX_TICKADJ) {
		time_adjust -= MAX_TICKADJ;
		tick_length += MAX_TICKADJ_SCALED;
		goto out;
	}

	if (time_adjust < -MAX_TICKADJ) {
		time_adjust += MAX_TICKADJ;
		tick_length -= MAX_TICKADJ_SCALED;
		goto out;
	}

	tick_length += (s64)(time_adjust * NSEC_PER_USEC / NTP_INTERVAL_FREQ)
							 << NTP_SCALE_SHIFT;
	time_adjust = 0;



out:
	spin_unlock_irqrestore(&ntp_lock, flags);

	return leap;
}

#ifdef CONFIG_GENERIC_CMOS_UPDATE

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 (!ntp_synced()) {
		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)
{
	schedule_delayed_work(&sync_cmos_work, 0);
}

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


static inline void process_adj_status(struct timex *txc, struct timespec *ts)
{
	if ((time_status & STA_PLL) && !(txc->status & STA_PLL)) {
		time_state = TIME_OK;
		time_status = STA_UNSYNC;
		
		pps_reset_freq_interval();
	}

	if (!(time_status & STA_PLL) && (txc->status & STA_PLL))
		time_reftime = get_seconds();

	
	time_status &= STA_RONLY;
	time_status |= txc->status & ~STA_RONLY;

}
static inline void process_adjtimex_modes(struct timex *txc, struct timespec *ts)
{
	if (txc->modes & ADJ_STATUS)
		process_adj_status(txc, ts);

	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 = txc->freq * PPM_SCALE;
		time_freq = min(time_freq, MAXFREQ_SCALED);
		time_freq = max(time_freq, -MAXFREQ_SCALED);
		
		pps_set_freq(time_freq);
	}

	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();
}

int do_adjtimex(struct timex *txc)
{
	struct timespec ts;
	int result;

	
	if (txc->modes & ADJ_ADJTIME) {
		
		if (!(txc->modes & ADJ_OFFSET_SINGLESHOT))
			return -EINVAL;
		if (!(txc->modes & ADJ_OFFSET_READONLY) &&
		    !capable(CAP_SYS_TIME))
			return -EPERM;
	} else {
		
		 if (txc->modes && !capable(CAP_SYS_TIME))
			return -EPERM;

		if (txc->modes & ADJ_TICK &&
		    (txc->tick <  900000/USER_HZ ||
		     txc->tick > 1100000/USER_HZ))
			return -EINVAL;
	}

	if (txc->modes & ADJ_SETOFFSET) {
		struct timespec delta;
		delta.tv_sec  = txc->time.tv_sec;
		delta.tv_nsec = txc->time.tv_usec;
		if (!capable(CAP_SYS_TIME))
			return -EPERM;
		if (!(txc->modes & ADJ_NANO))
			delta.tv_nsec *= 1000;
		result = timekeeping_inject_offset(&delta);
		if (result)
			return result;
	}

	getnstimeofday(&ts);

	spin_lock_irq(&ntp_lock);

	if (txc->modes & ADJ_ADJTIME) {
		long save_adjust = time_adjust;

		if (!(txc->modes & ADJ_OFFSET_READONLY)) {
			
			time_adjust = txc->offset;
			ntp_update_frequency();
		}
		txc->offset = save_adjust;
	} else {

		
		if (txc->modes)
			process_adjtimex_modes(txc, &ts);

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

	result = time_state;	
	
	if (is_error_status(time_status))
		result = TIME_ERROR;

	txc->freq	   = shift_right((time_freq >> PPM_SCALE_INV_SHIFT) *
					 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_fill_timex(txc);

	spin_unlock_irq(&ntp_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;
}

#ifdef	CONFIG_NTP_PPS

struct pps_normtime {
	__kernel_time_t	sec;	
	long		nsec;	
};

static inline struct pps_normtime pps_normalize_ts(struct timespec ts)
{
	struct pps_normtime norm = {
		.sec = ts.tv_sec,
		.nsec = ts.tv_nsec
	};

	if (norm.nsec > (NSEC_PER_SEC >> 1)) {
		norm.nsec -= NSEC_PER_SEC;
		norm.sec++;
	}

	return norm;
}

static inline long pps_phase_filter_get(long *jitter)
{
	*jitter = pps_tf[0] - pps_tf[1];
	if (*jitter < 0)
		*jitter = -*jitter;

	
	return pps_tf[0];
}

static inline void pps_phase_filter_add(long err)
{
	pps_tf[2] = pps_tf[1];
	pps_tf[1] = pps_tf[0];
	pps_tf[0] = err;
}

static inline void pps_dec_freq_interval(void)
{
	if (--pps_intcnt <= -PPS_INTCOUNT) {
		pps_intcnt = -PPS_INTCOUNT;
		if (pps_shift > PPS_INTMIN) {
			pps_shift--;
			pps_intcnt = 0;
		}
	}
}

static inline void pps_inc_freq_interval(void)
{
	if (++pps_intcnt >= PPS_INTCOUNT) {
		pps_intcnt = PPS_INTCOUNT;
		if (pps_shift < PPS_INTMAX) {
			pps_shift++;
			pps_intcnt = 0;
		}
	}
}

static long hardpps_update_freq(struct pps_normtime freq_norm)
{
	long delta, delta_mod;
	s64 ftemp;

	
	if (freq_norm.sec > (2 << pps_shift)) {
		time_status |= STA_PPSERROR;
		pps_errcnt++;
		pps_dec_freq_interval();
		pr_err("hardpps: PPSERROR: interval too long - %ld s\n",
				freq_norm.sec);
		return 0;
	}

	ftemp = div_s64(((s64)(-freq_norm.nsec)) << NTP_SCALE_SHIFT,
			freq_norm.sec);
	delta = shift_right(ftemp - pps_freq, NTP_SCALE_SHIFT);
	pps_freq = ftemp;
	if (delta > PPS_MAXWANDER || delta < -PPS_MAXWANDER) {
		pr_warning("hardpps: PPSWANDER: change=%ld\n", delta);
		time_status |= STA_PPSWANDER;
		pps_stbcnt++;
		pps_dec_freq_interval();
	} else {	
		pps_inc_freq_interval();
	}

	delta_mod = delta;
	if (delta_mod < 0)
		delta_mod = -delta_mod;
	pps_stabil += (div_s64(((s64)delta_mod) <<
				(NTP_SCALE_SHIFT - SHIFT_USEC),
				NSEC_PER_USEC) - pps_stabil) >> PPS_INTMIN;

	
	if ((time_status & STA_PPSFREQ) != 0 &&
	    (time_status & STA_FREQHOLD) == 0) {
		time_freq = pps_freq;
		ntp_update_frequency();
	}

	return delta;
}

static void hardpps_update_phase(long error)
{
	long correction = -error;
	long jitter;

	
	pps_phase_filter_add(correction);
	correction = pps_phase_filter_get(&jitter);

	if (jitter > (pps_jitter << PPS_POPCORN)) {
		pr_warning("hardpps: PPSJITTER: jitter=%ld, limit=%ld\n",
		       jitter, (pps_jitter << PPS_POPCORN));
		time_status |= STA_PPSJITTER;
		pps_jitcnt++;
	} else if (time_status & STA_PPSTIME) {
		
		time_offset = div_s64(((s64)correction) << NTP_SCALE_SHIFT,
				NTP_INTERVAL_FREQ);
		
		time_adjust = 0;
	}
	
	pps_jitter += (jitter - pps_jitter) >> PPS_INTMIN;
}

/*
 * hardpps() - discipline CPU clock oscillator to external PPS signal
 *
 * This routine is called at each PPS signal arrival in order to
 * discipline the CPU clock oscillator to the PPS signal. It takes two
 * parameters: REALTIME and MONOTONIC_RAW clock timestamps. The former
 * is used to correct clock phase error and the latter is used to
 * correct the frequency.
 *
 * This code is based on David Mills's reference nanokernel
 * implementation. It was mostly rewritten but keeps the same idea.
 */
void hardpps(const struct timespec *phase_ts, const struct timespec *raw_ts)
{
	struct pps_normtime pts_norm, freq_norm;
	unsigned long flags;

	pts_norm = pps_normalize_ts(*phase_ts);

	spin_lock_irqsave(&ntp_lock, flags);

	
	time_status &= ~(STA_PPSJITTER | STA_PPSWANDER | STA_PPSERROR);

	
	time_status |= STA_PPSSIGNAL;
	pps_valid = PPS_VALID;

	if (unlikely(pps_fbase.tv_sec == 0)) {
		pps_fbase = *raw_ts;
		spin_unlock_irqrestore(&ntp_lock, flags);
		return;
	}

	
	freq_norm = pps_normalize_ts(timespec_sub(*raw_ts, pps_fbase));

	if ((freq_norm.sec == 0) ||
			(freq_norm.nsec > MAXFREQ * freq_norm.sec) ||
			(freq_norm.nsec < -MAXFREQ * freq_norm.sec)) {
		time_status |= STA_PPSJITTER;
		
		pps_fbase = *raw_ts;
		spin_unlock_irqrestore(&ntp_lock, flags);
		pr_err("hardpps: PPSJITTER: bad pulse\n");
		return;
	}

	

	
	if (freq_norm.sec >= (1 << pps_shift)) {
		pps_calcnt++;
		
		pps_fbase = *raw_ts;
		hardpps_update_freq(freq_norm);
	}

	hardpps_update_phase(pts_norm.nsec);

	spin_unlock_irqrestore(&ntp_lock, flags);
}
EXPORT_SYMBOL(hardpps);

#endif	

static int __init ntp_tick_adj_setup(char *str)
{
	ntp_tick_adj = simple_strtol(str, NULL, 0);
	ntp_tick_adj <<= NTP_SCALE_SHIFT;

	return 1;
}

__setup("ntp_tick_adj=", ntp_tick_adj_setup);

void __init ntp_init(void)
{
	ntp_clear();
}