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163 lines
6.3 KiB
163 lines
6.3 KiB
/***************************************************************************** |
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* * |
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* Copyright (c) David L. Mills 1993 * |
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* * |
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* Permission to use, copy, modify, and distribute this software and its * |
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* documentation for any purpose and without fee is hereby granted, provided * |
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* that the above copyright notice appears in all copies and that both the * |
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* copyright notice and this permission notice appear in supporting * |
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* documentation, and that the name University of Delaware not be used in * |
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* advertising or publicity pertaining to distribution of the software * |
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* without specific, written prior permission. The University of Delaware * |
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* makes no representations about the suitability this software for any * |
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* purpose. It is provided "as is" without express or implied warranty. * |
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* * |
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*****************************************************************************/ |
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/* |
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* Modification history timex.h |
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* |
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* 29 Dec 97 Russell King |
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* Moved CLOCK_TICK_RATE, CLOCK_TICK_FACTOR and FINETUNE to asm/timex.h |
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* for ARM machines |
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* |
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* 9 Jan 97 Adrian Sun |
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* Shifted LATCH define to allow access to alpha machines. |
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* |
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* 26 Sep 94 David L. Mills |
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* Added defines for hybrid phase/frequency-lock loop. |
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* |
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* 19 Mar 94 David L. Mills |
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* Moved defines from kernel routines to header file and added new |
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* defines for PPS phase-lock loop. |
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* |
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* 20 Feb 94 David L. Mills |
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* Revised status codes and structures for external clock and PPS |
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* signal discipline. |
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* |
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* 28 Nov 93 David L. Mills |
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* Adjusted parameters to improve stability and increase poll |
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* interval. |
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* |
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* 17 Sep 93 David L. Mills |
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* Created file $NTP/include/sys/timex.h |
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* 07 Oct 93 Torsten Duwe |
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* Derived linux/timex.h |
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* 1995-08-13 Torsten Duwe |
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* kernel PLL updated to 1994-12-13 specs (rfc-1589) |
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* 1997-08-30 Ulrich Windl |
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* Added new constant NTP_PHASE_LIMIT |
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* 2004-08-12 Christoph Lameter |
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* Reworked time interpolation logic |
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*/ |
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#ifndef _LINUX_TIMEX_H |
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#define _LINUX_TIMEX_H |
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#include <uapi/linux/timex.h> |
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#define ADJ_ADJTIME 0x8000 /* switch between adjtime/adjtimex modes */ |
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#define ADJ_OFFSET_SINGLESHOT 0x0001 /* old-fashioned adjtime */ |
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#define ADJ_OFFSET_READONLY 0x2000 /* read-only adjtime */ |
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#include <linux/compiler.h> |
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#include <linux/types.h> |
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#include <linux/param.h> |
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#include <asm/timex.h> |
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#ifndef random_get_entropy |
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/* |
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* The random_get_entropy() function is used by the /dev/random driver |
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* in order to extract entropy via the relative unpredictability of |
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* when an interrupt takes places versus a high speed, fine-grained |
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* timing source or cycle counter. Since it will be occurred on every |
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* single interrupt, it must have a very low cost/overhead. |
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* |
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* By default we use get_cycles() for this purpose, but individual |
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* architectures may override this in their asm/timex.h header file. |
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*/ |
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#define random_get_entropy() get_cycles() |
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#endif |
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/* |
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* SHIFT_PLL is used as a dampening factor to define how much we |
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* adjust the frequency correction for a given offset in PLL mode. |
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* It also used in dampening the offset correction, to define how |
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* much of the current value in time_offset we correct for each |
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* second. Changing this value changes the stiffness of the ntp |
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* adjustment code. A lower value makes it more flexible, reducing |
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* NTP convergence time. A higher value makes it stiffer, increasing |
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* convergence time, but making the clock more stable. |
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* |
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* In David Mills' nanokernel reference implementation SHIFT_PLL is 4. |
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* However this seems to increase convergence time much too long. |
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* |
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* https://lists.ntp.org/pipermail/hackers/2008-January/003487.html |
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* |
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* In the above mailing list discussion, it seems the value of 4 |
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* was appropriate for other Unix systems with HZ=100, and that |
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* SHIFT_PLL should be decreased as HZ increases. However, Linux's |
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* clock steering implementation is HZ independent. |
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* |
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* Through experimentation, a SHIFT_PLL value of 2 was found to allow |
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* for fast convergence (very similar to the NTPv3 code used prior to |
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* v2.6.19), with good clock stability. |
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* |
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* |
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* SHIFT_FLL is used as a dampening factor to define how much we |
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* adjust the frequency correction for a given offset in FLL mode. |
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* In David Mills' nanokernel reference implementation SHIFT_FLL is 2. |
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* |
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* MAXTC establishes the maximum time constant of the PLL. |
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*/ |
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#define SHIFT_PLL 2 /* PLL frequency factor (shift) */ |
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#define SHIFT_FLL 2 /* FLL frequency factor (shift) */ |
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#define MAXTC 10 /* maximum time constant (shift) */ |
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/* |
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* SHIFT_USEC defines the scaling (shift) of the time_freq and |
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* time_tolerance variables, which represent the current frequency |
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* offset and maximum frequency tolerance. |
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*/ |
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#define SHIFT_USEC 16 /* frequency offset scale (shift) */ |
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#define PPM_SCALE ((s64)NSEC_PER_USEC << (NTP_SCALE_SHIFT - SHIFT_USEC)) |
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#define PPM_SCALE_INV_SHIFT 19 |
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#define PPM_SCALE_INV ((1LL << (PPM_SCALE_INV_SHIFT + NTP_SCALE_SHIFT)) / \ |
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PPM_SCALE + 1) |
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#define MAXPHASE 500000000L /* max phase error (ns) */ |
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#define MAXFREQ 500000 /* max frequency error (ns/s) */ |
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#define MAXFREQ_SCALED ((s64)MAXFREQ << NTP_SCALE_SHIFT) |
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#define MINSEC 256 /* min interval between updates (s) */ |
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#define MAXSEC 2048 /* max interval between updates (s) */ |
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#define NTP_PHASE_LIMIT ((MAXPHASE / NSEC_PER_USEC) << 5) /* beyond max. dispersion */ |
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/* |
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* kernel variables |
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* Note: maximum error = NTP synch distance = dispersion + delay / 2; |
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* estimated error = NTP dispersion. |
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*/ |
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extern unsigned long tick_usec; /* USER_HZ period (usec) */ |
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extern unsigned long tick_nsec; /* SHIFTED_HZ period (nsec) */ |
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/* Required to safely shift negative values */ |
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#define shift_right(x, s) ({ \ |
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__typeof__(x) __x = (x); \ |
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__typeof__(s) __s = (s); \ |
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__x < 0 ? -(-__x >> __s) : __x >> __s; \ |
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}) |
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#define NTP_SCALE_SHIFT 32 |
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#define NTP_INTERVAL_FREQ (HZ) |
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#define NTP_INTERVAL_LENGTH (NSEC_PER_SEC/NTP_INTERVAL_FREQ) |
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extern int do_adjtimex(struct timex *); |
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extern void hardpps(const struct timespec64 *, const struct timespec64 *); |
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int read_current_timer(unsigned long *timer_val); |
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void ntp_notify_cmos_timer(void); |
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/* The clock frequency of the i8253/i8254 PIT */ |
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#define PIT_TICK_RATE 1193182ul |
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#endif /* LINUX_TIMEX_H */
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