[deliverable/linux.git] / include / linux / timex.h

/*****************************************************************************
 *                                                                           *
 * Copyright (c) David L. Mills 1993                                         *
 *                                                                           *
 * Permission to use, copy, modify, and distribute this software and its     *
 * documentation for any purpose and without fee is hereby granted, provided *
 * that the above copyright notice appears in all copies and that both the   *
 * copyright notice and this permission notice appear in supporting          *
 * documentation, and that the name University of Delaware not be used in    *
 * advertising or publicity pertaining to distribution of the software       *
 * without specific, written prior permission.  The University of Delaware   *
 * makes no representations about the suitability this software for any      *
 * purpose.  It is provided "as is" without express or implied warranty.     *
 *                                                                           *
 *****************************************************************************/

/*
 * Modification history timex.h
 *
 * 29 Dec 97	Russell King
 *	Moved CLOCK_TICK_RATE, CLOCK_TICK_FACTOR and FINETUNE to asm/timex.h
 *	for ARM machines
 *
 *  9 Jan 97    Adrian Sun
 *      Shifted LATCH define to allow access to alpha machines.
 *
 * 26 Sep 94	David L. Mills
 *	Added defines for hybrid phase/frequency-lock loop.
 *
 * 19 Mar 94	David L. Mills
 *	Moved defines from kernel routines to header file and added new
 *	defines for PPS phase-lock loop.
 *
 * 20 Feb 94	David L. Mills
 *	Revised status codes and structures for external clock and PPS
 *	signal discipline.
 *
 * 28 Nov 93	David L. Mills
 *	Adjusted parameters to improve stability and increase poll
 *	interval.
 *
 * 17 Sep 93    David L. Mills
 *      Created file $NTP/include/sys/timex.h
 * 07 Oct 93    Torsten Duwe
 *      Derived linux/timex.h
 * 1995-08-13    Torsten Duwe
 *      kernel PLL updated to 1994-12-13 specs (rfc-1589)
 * 1997-08-30    Ulrich Windl
 *      Added new constant NTP_PHASE_LIMIT
 * 2004-08-12    Christoph Lameter
 *      Reworked time interpolation logic
 */
#ifndef _LINUX_TIMEX_H
#define _LINUX_TIMEX_H

#include <linux/compiler.h>
#include <linux/time.h>

#include <asm/param.h>

/*
 * SHIFT_KG and SHIFT_KF establish the damping of the PLL and are chosen
 * for a slightly underdamped convergence characteristic. SHIFT_KH
 * establishes the damping of the FLL and is chosen by wisdom and black
 * art.
 *
 * MAXTC establishes the maximum time constant of the PLL. With the
 * SHIFT_KG and SHIFT_KF values given and a time constant range from
 * zero to MAXTC, the PLL will converge in 15 minutes to 16 hours,
 * respectively.
 */
#define SHIFT_KG 6		/* phase factor (shift) */
#define SHIFT_KF 16		/* PLL frequency factor (shift) */
#define SHIFT_KH 2		/* FLL frequency factor (shift) */
#define MAXTC 6			/* maximum time constant (shift) */

/*
 * The SHIFT_SCALE define establishes the decimal point of the time_phase
 * variable which serves as an extension to the low-order bits of the
 * system clock variable. The SHIFT_UPDATE define establishes the decimal
 * point of the time_offset variable which represents the current offset
 * with respect to standard time. The FINENSEC define represents 1 nsec in
 * scaled units.
 *
 * SHIFT_USEC defines the scaling (shift) of the time_freq and
 * time_tolerance variables, which represent the current frequency
 * offset and maximum frequency tolerance.
 *
 * FINENSEC is 1 ns in SHIFT_UPDATE units of the time_phase variable.
 */
#define SHIFT_SCALE 22		/* phase scale (shift) */
#define SHIFT_UPDATE (SHIFT_HZ + 1) /* time offset scale (shift) */
#define SHIFT_USEC 16		/* frequency offset scale (shift) */
#define SHIFT_NSEC 12		/* kernel frequency offset scale */
#define FINENSEC (1L << (SHIFT_SCALE - 10)) /* ~1 ns in phase units */

#define MAXPHASE 512000L        /* max phase error (us) */
#define MAXFREQ (512L << SHIFT_USEC)  /* max frequency error (ppm) */
#define MAXFREQ_NSEC (512000L << SHIFT_NSEC) /* max frequency error (ppb) */
#define MINSEC 16L              /* min interval between updates (s) */
#define MAXSEC 1200L            /* max interval between updates (s) */
#define	NTP_PHASE_LIMIT	(MAXPHASE << 5)	/* beyond max. dispersion */

/*
 * syscall interface - used (mainly by NTP daemon)
 * to discipline kernel clock oscillator
 */
struct timex {
	unsigned int modes;	/* mode selector */
	long offset;		/* time offset (usec) */
	long freq;		/* frequency offset (scaled ppm) */
	long maxerror;		/* maximum error (usec) */
	long esterror;		/* estimated error (usec) */
	int status;		/* clock command/status */
	long constant;		/* pll time constant */
	long precision;		/* clock precision (usec) (read only) */
	long tolerance;		/* clock frequency tolerance (ppm)
				 * (read only)
				 */
	struct timeval time;	/* (read only) */
	long tick;		/* (modified) usecs between clock ticks */

	long ppsfreq;           /* pps frequency (scaled ppm) (ro) */
	long jitter;            /* pps jitter (us) (ro) */
	int shift;              /* interval duration (s) (shift) (ro) */
	long stabil;            /* pps stability (scaled ppm) (ro) */
	long jitcnt;            /* jitter limit exceeded (ro) */
	long calcnt;            /* calibration intervals (ro) */
	long errcnt;            /* calibration errors (ro) */
	long stbcnt;            /* stability limit exceeded (ro) */

	int  :32; int  :32; int  :32; int  :32;
	int  :32; int  :32; int  :32; int  :32;
	int  :32; int  :32; int  :32; int  :32;
};

/*
 * Mode codes (timex.mode)
 */
#define ADJ_OFFSET		0x0001	/* time offset */
#define ADJ_FREQUENCY		0x0002	/* frequency offset */
#define ADJ_MAXERROR		0x0004	/* maximum time error */
#define ADJ_ESTERROR		0x0008	/* estimated time error */
#define ADJ_STATUS		0x0010	/* clock status */
#define ADJ_TIMECONST		0x0020	/* pll time constant */
#define ADJ_TICK		0x4000	/* tick value */
#define ADJ_OFFSET_SINGLESHOT	0x8001	/* old-fashioned adjtime */

/* xntp 3.4 compatibility names */
#define MOD_OFFSET	ADJ_OFFSET
#define MOD_FREQUENCY	ADJ_FREQUENCY
#define MOD_MAXERROR	ADJ_MAXERROR
#define MOD_ESTERROR	ADJ_ESTERROR
#define MOD_STATUS	ADJ_STATUS
#define MOD_TIMECONST	ADJ_TIMECONST
#define MOD_CLKB	ADJ_TICK
#define MOD_CLKA	ADJ_OFFSET_SINGLESHOT /* 0x8000 in original */


/*
 * Status codes (timex.status)
 */
#define STA_PLL		0x0001	/* enable PLL updates (rw) */
#define STA_PPSFREQ	0x0002	/* enable PPS freq discipline (rw) */
#define STA_PPSTIME	0x0004	/* enable PPS time discipline (rw) */
#define STA_FLL		0x0008	/* select frequency-lock mode (rw) */

#define STA_INS		0x0010	/* insert leap (rw) */
#define STA_DEL		0x0020	/* delete leap (rw) */
#define STA_UNSYNC	0x0040	/* clock unsynchronized (rw) */
#define STA_FREQHOLD	0x0080	/* hold frequency (rw) */

#define STA_PPSSIGNAL	0x0100	/* PPS signal present (ro) */
#define STA_PPSJITTER	0x0200	/* PPS signal jitter exceeded (ro) */
#define STA_PPSWANDER	0x0400	/* PPS signal wander exceeded (ro) */
#define STA_PPSERROR	0x0800	/* PPS signal calibration error (ro) */

#define STA_CLOCKERR	0x1000	/* clock hardware fault (ro) */

#define STA_RONLY (STA_PPSSIGNAL | STA_PPSJITTER | STA_PPSWANDER | \
    STA_PPSERROR | STA_CLOCKERR) /* read-only bits */

/*
 * Clock states (time_state)
 */
#define TIME_OK		0	/* clock synchronized, no leap second */
#define TIME_INS	1	/* insert leap second */
#define TIME_DEL	2	/* delete leap second */
#define TIME_OOP	3	/* leap second in progress */
#define TIME_WAIT	4	/* leap second has occurred */
#define TIME_ERROR	5	/* clock not synchronized */
#define TIME_BAD	TIME_ERROR /* bw compat */

#ifdef __KERNEL__
#include <asm/timex.h>

/*
 * kernel variables
 * Note: maximum error = NTP synch distance = dispersion + delay / 2;
 * estimated error = NTP dispersion.
 */
extern unsigned long tick_usec;		/* USER_HZ period (usec) */
extern unsigned long tick_nsec;		/* ACTHZ          period (nsec) */
extern int tickadj;			/* amount of adjustment per tick */

/*
 * phase-lock loop variables
 */
extern int time_state;		/* clock status */
extern int time_status;		/* clock synchronization status bits */
extern long time_offset;	/* time adjustment (us) */
extern long time_constant;	/* pll time constant */
extern long time_precision;	/* clock precision (us) */
extern long time_maxerror;	/* maximum error */
extern long time_esterror;	/* estimated error */

extern long time_freq;		/* frequency offset (scaled ppm) */
extern long time_reftime;	/* time at last adjustment (s) */

extern long time_adjust;	/* The amount of adjtime left */

extern void ntp_clear(void);
extern void ntp_update_frequency(void);

/**
 * ntp_synced - Returns 1 if the NTP status is not UNSYNC
 *
 */
static inline int ntp_synced(void)
{
	return !(time_status & STA_UNSYNC);
}

/* Required to safely shift negative values */
#define shift_right(x, s) ({	\
	__typeof__(x) __x = (x);	\
	__typeof__(s) __s = (s);	\
	__x < 0 ? -(-__x >> __s) : __x >> __s;	\
})


#ifdef CONFIG_TIME_INTERPOLATION

#define TIME_SOURCE_CPU 0
#define TIME_SOURCE_MMIO64 1
#define TIME_SOURCE_MMIO32 2
#define TIME_SOURCE_FUNCTION 3

/* For proper operations time_interpolator clocks must run slightly slower
 * than the standard clock since the interpolator may only correct by having
 * time jump forward during a tick. A slower clock is usually a side effect
 * of the integer divide of the nanoseconds in a second by the frequency.
 * The accuracy of the division can be increased by specifying a shift.
 * However, this may cause the clock not to be slow enough.
 * The interpolator will self-tune the clock by slowing down if no
 * resets occur or speeding up if the time jumps per analysis cycle
 * become too high.
 *
 * Setting jitter compensates for a fluctuating timesource by comparing
 * to the last value read from the timesource to insure that an earlier value
 * is not returned by a later call. The price to pay
 * for the compensation is that the timer routines are not as scalable anymore.
 */

struct time_interpolator {
	u16 source;			/* time source flags */
	u8 shift;			/* increases accuracy of multiply by shifting. */
				/* Note that bits may be lost if shift is set too high */
	u8 jitter;			/* if set compensate for fluctuations */
	u32 nsec_per_cyc;		/* set by register_time_interpolator() */
	void *addr;			/* address of counter or function */
	u64 mask;			/* mask the valid bits of the counter */
	unsigned long offset;		/* nsec offset at last update of interpolator */
	u64 last_counter;		/* counter value in units of the counter at last update */
	u64 last_cycle;			/* Last timer value if TIME_SOURCE_JITTER is set */
	u64 frequency;			/* frequency in counts/second */
	long drift;			/* drift in parts-per-million (or -1) */
	unsigned long skips;		/* skips forward */
	unsigned long ns_skipped;	/* nanoseconds skipped */
	struct time_interpolator *next;
};

extern void register_time_interpolator(struct time_interpolator *);
extern void unregister_time_interpolator(struct time_interpolator *);
extern void time_interpolator_reset(void);
extern unsigned long time_interpolator_get_offset(void);
extern void time_interpolator_update(long delta_nsec);

#else /* !CONFIG_TIME_INTERPOLATION */

static inline void time_interpolator_reset(void)
{
}

static inline void time_interpolator_update(long delta_nsec)
{
}

#endif /* !CONFIG_TIME_INTERPOLATION */

#define TICK_LENGTH_SHIFT	32

/* Returns how long ticks are at present, in ns / 2^(SHIFT_SCALE-10). */
extern u64 current_tick_length(void);

extern void second_overflow(void);
extern void update_ntp_one_tick(void);
extern int do_adjtimex(struct timex *);

#endif /* KERNEL */

#endif /* LINUX_TIMEX_H */
Commit	Line	Data
1da177e4 LT	1	/*****************************************************************************
	2	* *
	3	* Copyright (c) David L. Mills 1993 *
	4	* *
	5	* Permission to use, copy, modify, and distribute this software and its *
	6	* documentation for any purpose and without fee is hereby granted, provided *
	7	* that the above copyright notice appears in all copies and that both the *
	8	* copyright notice and this permission notice appear in supporting *
	9	* documentation, and that the name University of Delaware not be used in *
	10	* advertising or publicity pertaining to distribution of the software *
	11	* without specific, written prior permission. The University of Delaware *
	12	* makes no representations about the suitability this software for any *
	13	* purpose. It is provided "as is" without express or implied warranty. *
	14	* *
	15	*****************************************************************************/
	16
	17	/*
	18	* Modification history timex.h
	19	*
	20	* 29 Dec 97 Russell King
	21	* Moved CLOCK_TICK_RATE, CLOCK_TICK_FACTOR and FINETUNE to asm/timex.h
	22	* for ARM machines
	23	*
	24	* 9 Jan 97 Adrian Sun
	25	* Shifted LATCH define to allow access to alpha machines.
	26	*
	27	* 26 Sep 94 David L. Mills
	28	* Added defines for hybrid phase/frequency-lock loop.
	29	*
	30	* 19 Mar 94 David L. Mills
	31	* Moved defines from kernel routines to header file and added new
	32	* defines for PPS phase-lock loop.
	33	*
	34	* 20 Feb 94 David L. Mills
	35	* Revised status codes and structures for external clock and PPS
	36	* signal discipline.
	37	*
	38	* 28 Nov 93 David L. Mills
	39	* Adjusted parameters to improve stability and increase poll
	40	* interval.
	41	*
	42	* 17 Sep 93 David L. Mills
	43	* Created file $NTP/include/sys/timex.h
	44	* 07 Oct 93 Torsten Duwe
	45	* Derived linux/timex.h
	46	* 1995-08-13 Torsten Duwe
	47	* kernel PLL updated to 1994-12-13 specs (rfc-1589)
	48	* 1997-08-30 Ulrich Windl
	49	* Added new constant NTP_PHASE_LIMIT
	50	* 2004-08-12 Christoph Lameter
	51	* Reworked time interpolation logic
	52	*/
	53	#ifndef _LINUX_TIMEX_H
	54	#define _LINUX_TIMEX_H
	55
1da177e4 LT	56	#include <linux/compiler.h>
	57	#include <linux/time.h>
	58
	59	#include <asm/param.h>
1da177e4 LT	60
	61	/*
	62	* SHIFT_KG and SHIFT_KF establish the damping of the PLL and are chosen
	63	* for a slightly underdamped convergence characteristic. SHIFT_KH
	64	* establishes the damping of the FLL and is chosen by wisdom and black
	65	* art.
	66	*
	67	* MAXTC establishes the maximum time constant of the PLL. With the
	68	* SHIFT_KG and SHIFT_KF values given and a time constant range from
	69	* zero to MAXTC, the PLL will converge in 15 minutes to 16 hours,
	70	* respectively.
	71	*/
	72	#define SHIFT_KG 6 /* phase factor (shift) */
	73	#define SHIFT_KF 16 /* PLL frequency factor (shift) */
	74	#define SHIFT_KH 2 /* FLL frequency factor (shift) */
	75	#define MAXTC 6 /* maximum time constant (shift) */
	76
	77	/*
	78	* The SHIFT_SCALE define establishes the decimal point of the time_phase
	79	* variable which serves as an extension to the low-order bits of the
	80	* system clock variable. The SHIFT_UPDATE define establishes the decimal
	81	* point of the time_offset variable which represents the current offset
	82	* with respect to standard time. The FINENSEC define represents 1 nsec in
	83	* scaled units.
	84	*
	85	* SHIFT_USEC defines the scaling (shift) of the time_freq and
	86	* time_tolerance variables, which represent the current frequency
	87	* offset and maximum frequency tolerance.
	88	*
	89	* FINENSEC is 1 ns in SHIFT_UPDATE units of the time_phase variable.
	90	*/
	91	#define SHIFT_SCALE 22 /* phase scale (shift) */
3d3675cc	92	#define SHIFT_UPDATE (SHIFT_HZ + 1) /* time offset scale (shift) */
1da177e4	93	#define SHIFT_USEC 16 /* frequency offset scale (shift) */
04b617e7	94	#define SHIFT_NSEC 12 /* kernel frequency offset scale */
1da177e4 LT	95	#define FINENSEC (1L << (SHIFT_SCALE - 10)) /* ~1 ns in phase units */
	96
	97	#define MAXPHASE 512000L /* max phase error (us) */
	98	#define MAXFREQ (512L << SHIFT_USEC) /* max frequency error (ppm) */
04b617e7	99	#define MAXFREQ_NSEC (512000L << SHIFT_NSEC) /* max frequency error (ppb) */
1da177e4 LT	100	#define MINSEC 16L /* min interval between updates (s) */
	101	#define MAXSEC 1200L /* max interval between updates (s) */
	102	#define NTP_PHASE_LIMIT (MAXPHASE << 5) /* beyond max. dispersion */
	103
1da177e4 LT	104	/*
	105	* syscall interface - used (mainly by NTP daemon)
	106	* to discipline kernel clock oscillator
	107	*/
	108	struct timex {
	109	unsigned int modes; /* mode selector */
	110	long offset; /* time offset (usec) */
	111	long freq; /* frequency offset (scaled ppm) */
	112	long maxerror; /* maximum error (usec) */
	113	long esterror; /* estimated error (usec) */
	114	int status; /* clock command/status */
	115	long constant; /* pll time constant */
	116	long precision; /* clock precision (usec) (read only) */
	117	long tolerance; /* clock frequency tolerance (ppm)
	118	* (read only)
	119	*/
	120	struct timeval time; /* (read only) */
	121	long tick; /* (modified) usecs between clock ticks */
	122
	123	long ppsfreq; /* pps frequency (scaled ppm) (ro) */
	124	long jitter; /* pps jitter (us) (ro) */
	125	int shift; /* interval duration (s) (shift) (ro) */
	126	long stabil; /* pps stability (scaled ppm) (ro) */
	127	long jitcnt; /* jitter limit exceeded (ro) */
	128	long calcnt; /* calibration intervals (ro) */
	129	long errcnt; /* calibration errors (ro) */
	130	long stbcnt; /* stability limit exceeded (ro) */
	131
	132	int :32; int :32; int :32; int :32;
	133	int :32; int :32; int :32; int :32;
	134	int :32; int :32; int :32; int :32;
	135	};
	136
	137	/*
	138	* Mode codes (timex.mode)
	139	*/
	140	#define ADJ_OFFSET 0x0001 /* time offset */
	141	#define ADJ_FREQUENCY 0x0002 /* frequency offset */
	142	#define ADJ_MAXERROR 0x0004 /* maximum time error */
	143	#define ADJ_ESTERROR 0x0008 /* estimated time error */
	144	#define ADJ_STATUS 0x0010 /* clock status */
	145	#define ADJ_TIMECONST 0x0020 /* pll time constant */
	146	#define ADJ_TICK 0x4000 /* tick value */
	147	#define ADJ_OFFSET_SINGLESHOT 0x8001 /* old-fashioned adjtime */
	148
	149	/* xntp 3.4 compatibility names */
	150	#define MOD_OFFSET ADJ_OFFSET
	151	#define MOD_FREQUENCY ADJ_FREQUENCY
	152	#define MOD_MAXERROR ADJ_MAXERROR
	153	#define MOD_ESTERROR ADJ_ESTERROR
	154	#define MOD_STATUS ADJ_STATUS
	155	#define MOD_TIMECONST ADJ_TIMECONST
	156	#define MOD_CLKB ADJ_TICK
	157	#define MOD_CLKA ADJ_OFFSET_SINGLESHOT /* 0x8000 in original */
	158
	159
	160	/*
	161	* Status codes (timex.status)
	162	*/
	163	#define STA_PLL 0x0001 /* enable PLL updates (rw) */
	164	#define STA_PPSFREQ 0x0002 /* enable PPS freq discipline (rw) */
	165	#define STA_PPSTIME 0x0004 /* enable PPS time discipline (rw) */
	166	#define STA_FLL 0x0008 /* select frequency-lock mode (rw) */
	167
168	#define STA_INS 0x0010 /* insert leap (rw) */
169	#define STA_DEL 0x0020 /* delete leap (rw) */
170	#define STA_UNSYNC 0x0040 /* clock unsynchronized (rw) */
171	#define STA_FREQHOLD 0x0080 /* hold frequency (rw) */
172
173	#define STA_PPSSIGNAL 0x0100 /* PPS signal present (ro) */
174	#define STA_PPSJITTER 0x0200 /* PPS signal jitter exceeded (ro) */
175	#define STA_PPSWANDER 0x0400 /* PPS signal wander exceeded (ro) */
176	#define STA_PPSERROR 0x0800 /* PPS signal calibration error (ro) */
177
178	#define STA_CLOCKERR 0x1000 /* clock hardware fault (ro) */
179
180	#define STA_RONLY (STA_PPSSIGNAL \| STA_PPSJITTER \| STA_PPSWANDER \| \
181	STA_PPSERROR \| STA_CLOCKERR) /* read-only bits */
182
183	/*
184	* Clock states (time_state)
185	*/
186	#define TIME_OK 0 /* clock synchronized, no leap second */
187	#define TIME_INS 1 /* insert leap second */
188	#define TIME_DEL 2 /* delete leap second */
189	#define TIME_OOP 3 /* leap second in progress */
190	#define TIME_WAIT 4 /* leap second has occurred */
191	#define TIME_ERROR 5 /* clock not synchronized */
192	#define TIME_BAD TIME_ERROR /* bw compat */
193
194	#ifdef __KERNEL__
ee6baf88 DW	195	#include <asm/timex.h>
ee6baf88 DW	196
1da177e4 LT	197	/*
	198	* kernel variables
	199	* Note: maximum error = NTP synch distance = dispersion + delay / 2;
	200	* estimated error = NTP dispersion.
	201	*/
	202	extern unsigned long tick_usec; /* USER_HZ period (usec) */
	203	extern unsigned long tick_nsec; /* ACTHZ period (nsec) */
	204	extern int tickadj; /* amount of adjustment per tick */
	205
	206	/*
	207	* phase-lock loop variables
	208	*/
	209	extern int time_state; /* clock status */
	210	extern int time_status; /* clock synchronization status bits */
	211	extern long time_offset; /* time adjustment (us) */
	212	extern long time_constant; /* pll time constant */
1da177e4 LT	213	extern long time_precision; /* clock precision (us) */
	214	extern long time_maxerror; /* maximum error */
	215	extern long time_esterror; /* estimated error */
	216
	217	extern long time_freq; /* frequency offset (scaled ppm) */
	218	extern long time_reftime; /* time at last adjustment (s) */
	219
	220	extern long time_adjust; /* The amount of adjtime left */
1da177e4	221
b0ee7556 RZ	222	extern void ntp_clear(void);
b0ee7556 RZ	223	extern void ntp_update_frequency(void);
b149ee22	224
	225	/**
	226	* ntp_synced - Returns 1 if the NTP status is not UNSYNC
	227	*
	228	*/
	229	static inline int ntp_synced(void)
	230	{
	231	return !(time_status & STA_UNSYNC);
	232	}
	233
1bb34a41	234	/* Required to safely shift negative values */
	235	#define shift_right(x, s) ({ \
	236	__typeof__(x) __x = (x); \
	237	__typeof__(s) __s = (s); \
	238	__x < 0 ? -(-__x >> __s) : __x >> __s; \
	239	})
	240
b149ee22	241
1da177e4 LT	242	#ifdef CONFIG_TIME_INTERPOLATION
	243
	244	#define TIME_SOURCE_CPU 0
	245	#define TIME_SOURCE_MMIO64 1
	246	#define TIME_SOURCE_MMIO32 2
	247	#define TIME_SOURCE_FUNCTION 3
	248
	249	/* For proper operations time_interpolator clocks must run slightly slower
	250	* than the standard clock since the interpolator may only correct by having
	251	* time jump forward during a tick. A slower clock is usually a side effect
	252	* of the integer divide of the nanoseconds in a second by the frequency.
	253	* The accuracy of the division can be increased by specifying a shift.
	254	* However, this may cause the clock not to be slow enough.
	255	* The interpolator will self-tune the clock by slowing down if no
	256	* resets occur or speeding up if the time jumps per analysis cycle
	257	* become too high.
	258	*
	259	* Setting jitter compensates for a fluctuating timesource by comparing
	260	* to the last value read from the timesource to insure that an earlier value
	261	* is not returned by a later call. The price to pay
	262	* for the compensation is that the timer routines are not as scalable anymore.
	263	*/
	264
	265	struct time_interpolator {
	266	u16 source; /* time source flags */
	267	u8 shift; /* increases accuracy of multiply by shifting. */
	268	/* Note that bits may be lost if shift is set too high */
	269	u8 jitter; /* if set compensate for fluctuations */
	270	u32 nsec_per_cyc; /* set by register_time_interpolator() */
	271	void addr; / address of counter or function */
	272	u64 mask; /* mask the valid bits of the counter */
	273	unsigned long offset; /* nsec offset at last update of interpolator */
	274	u64 last_counter; /* counter value in units of the counter at last update */
	275	u64 last_cycle; /* Last timer value if TIME_SOURCE_JITTER is set */
	276	u64 frequency; /* frequency in counts/second */
	277	long drift; /* drift in parts-per-million (or -1) */
	278	unsigned long skips; /* skips forward */
	279	unsigned long ns_skipped; /* nanoseconds skipped */
	280	struct time_interpolator *next;
	281	};
	282
	283	extern void register_time_interpolator(struct time_interpolator *);
	284	extern void unregister_time_interpolator(struct time_interpolator *);
	285	extern void time_interpolator_reset(void);
	286	extern unsigned long time_interpolator_get_offset(void);
4c7ee8de	287	extern void time_interpolator_update(long delta_nsec);
1da177e4 LT	288
	289	#else /* !CONFIG_TIME_INTERPOLATION */
	290
4c7ee8de	291	static inline void time_interpolator_reset(void)
	292	{
	293	}
	294
	295	static inline void time_interpolator_update(long delta_nsec)
1da177e4 LT	296	{
	297	}
	298
	299	#endif /* !CONFIG_TIME_INTERPOLATION */
	300
19923c19 RZ	301	#define TICK_LENGTH_SHIFT 32
19923c19 RZ	302
726c14bf	303	/* Returns how long ticks are at present, in ns / 2^(SHIFT_SCALE-10). */
19923c19	304	extern u64 current_tick_length(void);
726c14bf	305
4c7ee8de	306	extern void second_overflow(void);
4c7ee8de	307	extern void update_ntp_one_tick(void);
3158e941 SR	308	extern int do_adjtimex(struct timex *);
3158e941 SR	309
1da177e4 LT	310	#endif /* KERNEL */
	311
	312	#endif /* LINUX_TIMEX_H */