173 lines
6.7 KiB
C
173 lines
6.7 KiB
C
/*****************************************************************************
|
|
* *
|
|
* 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 <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>
|
|
|
|
unsigned long random_get_entropy_fallback(void);
|
|
|
|
#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.
|
|
* If a given arch does not have get_cycles(), then we fallback to
|
|
* using random_get_entropy_fallback().
|
|
*/
|
|
#ifdef get_cycles
|
|
#define random_get_entropy() ((unsigned long)get_cycles())
|
|
#else
|
|
#define random_get_entropy() random_get_entropy_fallback()
|
|
#endif
|
|
#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 sync 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 __kernel_timex *);
|
|
extern int do_clock_adjtime(const clockid_t which_clock, struct __kernel_timex * ktx);
|
|
|
|
extern void hardpps(const struct timespec64 *, const struct timespec64 *);
|
|
|
|
int read_current_timer(unsigned long *timer_val);
|
|
|
|
/* The clock frequency of the i8253/i8254 PIT */
|
|
#define PIT_TICK_RATE 1193182ul
|
|
|
|
#endif /* LINUX_TIMEX_H */
|