[mirror_ubuntu-jammy-kernel.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

/* CONFIG_64BIT_TIME enables new 64 bit time_t syscalls in the compat path
 * and 32-bit emulation.
 */
#ifndef CONFIG_64BIT_TIME
#define __kernel_timex timex
#endif

#include <uapi/linux/timex.h>

#define ADJ_ADJTIME		0x8000	/* switch between adjtime/adjtimex modes */
#define ADJ_OFFSET_SINGLESHOT	0x0001	/* old-fashioned adjtime */
#define ADJ_OFFSET_READONLY	0x2000	/* read-only adjtime */
#include <linux/compiler.h>
#include <linux/types.h>
#include <linux/param.h>

#include <asm/timex.h>

#ifndef random_get_entropy
/*
 * The random_get_entropy() function is used by the /dev/random driver
 * in order to extract entropy via the relative unpredictability of
 * when an interrupt takes places versus a high speed, fine-grained
 * timing source or cycle counter.  Since it will be occurred on every
 * single interrupt, it must have a very low cost/overhead.
 *
 * By default we use get_cycles() for this purpose, but individual
 * architectures may override this in their asm/timex.h header file.
 */
#define random_get_entropy()	get_cycles()
#endif

/*
 * SHIFT_PLL is used as a dampening factor to define how much we
 * adjust the frequency correction for a given offset in PLL mode.
 * It also used in dampening the offset correction, to define how
 * much of the current value in time_offset we correct for each
 * second. Changing this value changes the stiffness of the ntp
 * adjustment code. A lower value makes it more flexible, reducing
 * NTP convergence time. A higher value makes it stiffer, increasing
 * convergence time, but making the clock more stable.
 *
 * In David Mills' nanokernel reference implementation SHIFT_PLL is 4.
 * However this seems to increase convergence time much too long.
 *
 * https://lists.ntp.org/pipermail/hackers/2008-January/003487.html
 *
 * In the above mailing list discussion, it seems the value of 4
 * was appropriate for other Unix systems with HZ=100, and that
 * SHIFT_PLL should be decreased as HZ increases. However, Linux's
 * clock steering implementation is HZ independent.
 *
 * Through experimentation, a SHIFT_PLL value of 2 was found to allow
 * for fast convergence (very similar to the NTPv3 code used prior to
 * v2.6.19), with good clock stability.
 *
 *
 * SHIFT_FLL is used as a dampening factor to define how much we
 * adjust the frequency correction for a given offset in FLL mode.
 * In David Mills' nanokernel reference implementation SHIFT_FLL is 2.
 *
 * MAXTC establishes the maximum time constant of the PLL.
 */
#define SHIFT_PLL	2	/* PLL frequency factor (shift) */
#define SHIFT_FLL	2	/* FLL frequency factor (shift) */
#define MAXTC		10	/* maximum time constant (shift) */

/*
 * SHIFT_USEC defines the scaling (shift) of the time_freq and
 * time_tolerance variables, which represent the current frequency
 * offset and maximum frequency tolerance.
 */
#define SHIFT_USEC 16		/* frequency offset scale (shift) */
#define PPM_SCALE ((s64)NSEC_PER_USEC << (NTP_SCALE_SHIFT - SHIFT_USEC))
#define PPM_SCALE_INV_SHIFT 19
#define PPM_SCALE_INV ((1LL << (PPM_SCALE_INV_SHIFT + NTP_SCALE_SHIFT)) / \
		       PPM_SCALE + 1)

#define MAXPHASE 500000000L	/* max phase error (ns) */
#define MAXFREQ 500000		/* max frequency error (ns/s) */
#define MAXFREQ_SCALED ((s64)MAXFREQ << NTP_SCALE_SHIFT)
#define MINSEC 256		/* min interval between updates (s) */
#define MAXSEC 2048		/* max interval between updates (s) */
#define NTP_PHASE_LIMIT ((MAXPHASE / NSEC_PER_USEC) << 5) /* beyond max. dispersion */

/*
 * 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;		/* SHIFTED_HZ period (nsec) */

/* 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;	\
})

#define NTP_SCALE_SHIFT		32

#define NTP_INTERVAL_FREQ  (HZ)
#define NTP_INTERVAL_LENGTH (NSEC_PER_SEC/NTP_INTERVAL_FREQ)

extern int do_adjtimex(struct timex *);
extern int do_clock_adjtime(const clockid_t which_clock, struct timex * ktx);

extern void hardpps(const struct timespec64 *, const struct timespec64 *);

int read_current_timer(unsigned long *timer_val);
void ntp_notify_cmos_timer(void);

/* The clock frequency of the i8253/i8254 PIT */
#define PIT_TICK_RATE 1193182ul

#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
2c620ff9 DD	56	/* CONFIG_64BIT_TIME enables new 64 bit time_t syscalls in the compat path
	57	* and 32-bit emulation.
	58	*/
	59	#ifndef CONFIG_64BIT_TIME
	60	#define __kernel_timex timex
	61	#endif
	62
607ca46e	63	#include <uapi/linux/timex.h>
1da177e4	64
916c7a85 RZ	65	#define ADJ_ADJTIME 0x8000 /* switch between adjtime/adjtimex modes */
	66	#define ADJ_OFFSET_SINGLESHOT 0x0001 /* old-fashioned adjtime */
	67	#define ADJ_OFFSET_READONLY 0x2000 /* read-only adjtime */
c29541b2 MF	68	#include <linux/compiler.h>
	69	#include <linux/types.h>
	70	#include <linux/param.h>
	71
ee6baf88 DW	72	#include <asm/timex.h>
ee6baf88 DW	73
61875f30 TT	74	#ifndef random_get_entropy
	75	/*
	76	* The random_get_entropy() function is used by the /dev/random driver
	77	* in order to extract entropy via the relative unpredictability of
	78	* when an interrupt takes places versus a high speed, fine-grained
	79	* timing source or cycle counter. Since it will be occurred on every
	80	* single interrupt, it must have a very low cost/overhead.
	81	*
	82	* By default we use get_cycles() for this purpose, but individual
	83	* architectures may override this in their asm/timex.h header file.
	84	*/
	85	#define random_get_entropy() get_cycles()
	86	#endif
	87
c29541b2	88	/*
22cfbbfd JS	89	* SHIFT_PLL is used as a dampening factor to define how much we
	90	* adjust the frequency correction for a given offset in PLL mode.
	91	* It also used in dampening the offset correction, to define how
	92	* much of the current value in time_offset we correct for each
	93	* second. Changing this value changes the stiffness of the ntp
	94	* adjustment code. A lower value makes it more flexible, reducing
	95	* NTP convergence time. A higher value makes it stiffer, increasing
	96	* convergence time, but making the clock more stable.
c29541b2	97	*
e13cf6e0	98	* In David Mills' nanokernel reference implementation SHIFT_PLL is 4.
22cfbbfd JS	99	* However this seems to increase convergence time much too long.
	100	*
	101	* https://lists.ntp.org/pipermail/hackers/2008-January/003487.html
	102	*
	103	* In the above mailing list discussion, it seems the value of 4
	104	* was appropriate for other Unix systems with HZ=100, and that
	105	* SHIFT_PLL should be decreased as HZ increases. However, Linux's
	106	* clock steering implementation is HZ independent.
	107	*
	108	* Through experimentation, a SHIFT_PLL value of 2 was found to allow
	109	* for fast convergence (very similar to the NTPv3 code used prior to
	110	* v2.6.19), with good clock stability.
	111	*
	112	*
	113	* SHIFT_FLL is used as a dampening factor to define how much we
	114	* adjust the frequency correction for a given offset in FLL mode.
e13cf6e0	115	* In David Mills' nanokernel reference implementation SHIFT_FLL is 2.
22cfbbfd JS	116	*
22cfbbfd JS	117	* MAXTC establishes the maximum time constant of the PLL.
c29541b2	118	*/
22cfbbfd	119	#define SHIFT_PLL 2 /* PLL frequency factor (shift) */
c29541b2 MF	120	#define SHIFT_FLL 2 /* FLL frequency factor (shift) */
	121	#define MAXTC 10 /* maximum time constant (shift) */
	122
	123	/*
	124	* SHIFT_USEC defines the scaling (shift) of the time_freq and
	125	* time_tolerance variables, which represent the current frequency
	126	* offset and maximum frequency tolerance.
	127	*/
	128	#define SHIFT_USEC 16 /* frequency offset scale (shift) */
2b9d1496	129	#define PPM_SCALE ((s64)NSEC_PER_USEC << (NTP_SCALE_SHIFT - SHIFT_USEC))
c29541b2	130	#define PPM_SCALE_INV_SHIFT 19
22cfbbfd	131	#define PPM_SCALE_INV ((1LL << (PPM_SCALE_INV_SHIFT + NTP_SCALE_SHIFT)) / \
c29541b2 MF	132	PPM_SCALE + 1)
c29541b2 MF	133
22cfbbfd	134	#define MAXPHASE 500000000L /* max phase error (ns) */
c29541b2 MF	135	#define MAXFREQ 500000 /* max frequency error (ns/s) */
	136	#define MAXFREQ_SCALED ((s64)MAXFREQ << NTP_SCALE_SHIFT)
	137	#define MINSEC 256 /* min interval between updates (s) */
	138	#define MAXSEC 2048 /* max interval between updates (s) */
	139	#define NTP_PHASE_LIMIT ((MAXPHASE / NSEC_PER_USEC) << 5) /* beyond max. dispersion */
	140
1da177e4 LT	141	/*
	142	* kernel variables
	143	* Note: maximum error = NTP synch distance = dispersion + delay / 2;
	144	* estimated error = NTP dispersion.
	145	*/
	146	extern unsigned long tick_usec; /* USER_HZ period (usec) */
02ab20ae	147	extern unsigned long tick_nsec; /* SHIFTED_HZ period (nsec) */
1da177e4	148
1bb34a41 JS	149	/* Required to safely shift negative values */
	150	#define shift_right(x, s) ({ \
	151	__typeof__(x) __x = (x); \
	152	__typeof__(s) __s = (s); \
	153	__x < 0 ? -(-__x >> __s) : __x >> __s; \
	154	})
	155
7fc5c784	156	#define NTP_SCALE_SHIFT 32
19923c19	157
f4304ab2	158	#define NTP_INTERVAL_FREQ (HZ)
10a398d0	159	#define NTP_INTERVAL_LENGTH (NSEC_PER_SEC/NTP_INTERVAL_FREQ)
f4304ab2	160
3158e941	161	extern int do_adjtimex(struct timex *);
1a596398 AB	162	extern int do_clock_adjtime(const clockid_t which_clock, struct timex * ktx);
1a596398 AB	163
7ec88e4b	164	extern void hardpps(const struct timespec64 , const struct timespec64 );
3158e941	165
941e492b	166	int read_current_timer(unsigned long *timer_val);
7bd36014	167	void ntp_notify_cmos_timer(void);
941e492b	168
08604bd9 AB	169	/* The clock frequency of the i8253/i8254 PIT */
	170	#define PIT_TICK_RATE 1193182ul
	171
1da177e4	172	#endif /* LINUX_TIMEX_H */