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| 6588 | serge | 1 | /***************************************************************************** |
| 2 | * * |
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| 3 | * Copyright (c) David L. Mills 1993 * |
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| 4 | * * |
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| 5 | * Permission to use, copy, modify, and distribute this software and its * |
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| 6 | * documentation for any purpose and without fee is hereby granted, provided * |
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| 7 | * that the above copyright notice appears in all copies and that both the * |
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| 8 | * copyright notice and this permission notice appear in supporting * |
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| 9 | * documentation, and that the name University of Delaware not be used in * |
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| 10 | * advertising or publicity pertaining to distribution of the software * |
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| 11 | * without specific, written prior permission. The University of Delaware * |
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| 12 | * makes no representations about the suitability this software for any * |
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| 13 | * purpose. It is provided "as is" without express or implied warranty. * |
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| 14 | * * |
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| 15 | *****************************************************************************/ |
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| 16 | |||
| 17 | /* |
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| 18 | * Modification history timex.h |
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| 19 | * |
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| 20 | * 29 Dec 97 Russell King |
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| 21 | * Moved CLOCK_TICK_RATE, CLOCK_TICK_FACTOR and FINETUNE to asm/timex.h |
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| 22 | * for ARM machines |
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| 23 | * |
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| 24 | * 9 Jan 97 Adrian Sun |
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| 25 | * Shifted LATCH define to allow access to alpha machines. |
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| 26 | * |
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| 27 | * 26 Sep 94 David L. Mills |
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| 28 | * Added defines for hybrid phase/frequency-lock loop. |
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| 29 | * |
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| 30 | * 19 Mar 94 David L. Mills |
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| 31 | * Moved defines from kernel routines to header file and added new |
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| 32 | * defines for PPS phase-lock loop. |
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| 33 | * |
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| 34 | * 20 Feb 94 David L. Mills |
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| 35 | * Revised status codes and structures for external clock and PPS |
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| 36 | * signal discipline. |
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| 37 | * |
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| 38 | * 28 Nov 93 David L. Mills |
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| 39 | * Adjusted parameters to improve stability and increase poll |
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| 40 | * interval. |
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| 41 | * |
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| 42 | * 17 Sep 93 David L. Mills |
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| 43 | * Created file $NTP/include/sys/timex.h |
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| 44 | * 07 Oct 93 Torsten Duwe |
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| 45 | * Derived linux/timex.h |
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| 46 | * 1995-08-13 Torsten Duwe |
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| 47 | * kernel PLL updated to 1994-12-13 specs (rfc-1589) |
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| 48 | * 1997-08-30 Ulrich Windl |
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| 49 | * Added new constant NTP_PHASE_LIMIT |
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| 50 | * 2004-08-12 Christoph Lameter |
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| 51 | * Reworked time interpolation logic |
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| 52 | */ |
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| 53 | #ifndef _LINUX_TIMEX_H |
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| 54 | #define _LINUX_TIMEX_H |
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| 55 | |||
| 6934 | serge | 56 | #include |
| 57 | |||
| 6588 | serge | 58 | #define ADJ_ADJTIME 0x8000 /* switch between adjtime/adjtimex modes */ |
| 59 | #define ADJ_OFFSET_SINGLESHOT 0x0001 /* old-fashioned adjtime */ |
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| 60 | #define ADJ_OFFSET_READONLY 0x2000 /* read-only adjtime */ |
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| 61 | #include |
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| 62 | #include |
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| 63 | |||
| 6934 | serge | 64 | #include |
| 6588 | serge | 65 | |
| 66 | #ifndef random_get_entropy |
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| 67 | /* |
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| 68 | * The random_get_entropy() function is used by the /dev/random driver |
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| 69 | * in order to extract entropy via the relative unpredictability of |
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| 70 | * when an interrupt takes places versus a high speed, fine-grained |
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| 71 | * timing source or cycle counter. Since it will be occurred on every |
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| 72 | * single interrupt, it must have a very low cost/overhead. |
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| 73 | * |
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| 74 | * By default we use get_cycles() for this purpose, but individual |
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| 75 | * architectures may override this in their asm/timex.h header file. |
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| 76 | */ |
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| 77 | #define random_get_entropy() get_cycles() |
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| 78 | #endif |
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| 79 | |||
| 80 | /* |
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| 81 | * SHIFT_PLL is used as a dampening factor to define how much we |
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| 82 | * adjust the frequency correction for a given offset in PLL mode. |
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| 83 | * It also used in dampening the offset correction, to define how |
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| 84 | * much of the current value in time_offset we correct for each |
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| 85 | * second. Changing this value changes the stiffness of the ntp |
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| 86 | * adjustment code. A lower value makes it more flexible, reducing |
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| 87 | * NTP convergence time. A higher value makes it stiffer, increasing |
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| 88 | * convergence time, but making the clock more stable. |
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| 89 | * |
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| 90 | * In David Mills' nanokernel reference implementation SHIFT_PLL is 4. |
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| 91 | * However this seems to increase convergence time much too long. |
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| 92 | * |
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| 93 | * https://lists.ntp.org/pipermail/hackers/2008-January/003487.html |
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| 94 | * |
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| 95 | * In the above mailing list discussion, it seems the value of 4 |
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| 96 | * was appropriate for other Unix systems with HZ=100, and that |
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| 97 | * SHIFT_PLL should be decreased as HZ increases. However, Linux's |
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| 98 | * clock steering implementation is HZ independent. |
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| 99 | * |
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| 100 | * Through experimentation, a SHIFT_PLL value of 2 was found to allow |
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| 101 | * for fast convergence (very similar to the NTPv3 code used prior to |
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| 102 | * v2.6.19), with good clock stability. |
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| 103 | * |
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| 104 | * |
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| 105 | * SHIFT_FLL is used as a dampening factor to define how much we |
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| 106 | * adjust the frequency correction for a given offset in FLL mode. |
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| 107 | * In David Mills' nanokernel reference implementation SHIFT_FLL is 2. |
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| 108 | * |
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| 109 | * MAXTC establishes the maximum time constant of the PLL. |
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| 110 | */ |
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| 111 | #define SHIFT_PLL 2 /* PLL frequency factor (shift) */ |
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| 112 | #define SHIFT_FLL 2 /* FLL frequency factor (shift) */ |
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| 113 | #define MAXTC 10 /* maximum time constant (shift) */ |
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| 114 | |||
| 115 | /* |
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| 116 | * SHIFT_USEC defines the scaling (shift) of the time_freq and |
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| 117 | * time_tolerance variables, which represent the current frequency |
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| 118 | * offset and maximum frequency tolerance. |
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| 119 | */ |
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| 120 | #define SHIFT_USEC 16 /* frequency offset scale (shift) */ |
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| 121 | #define PPM_SCALE ((s64)NSEC_PER_USEC << (NTP_SCALE_SHIFT - SHIFT_USEC)) |
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| 122 | #define PPM_SCALE_INV_SHIFT 19 |
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| 123 | #define PPM_SCALE_INV ((1LL << (PPM_SCALE_INV_SHIFT + NTP_SCALE_SHIFT)) / \ |
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| 124 | PPM_SCALE + 1) |
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| 125 | |||
| 126 | #define MAXPHASE 500000000L /* max phase error (ns) */ |
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| 127 | #define MAXFREQ 500000 /* max frequency error (ns/s) */ |
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| 128 | #define MAXFREQ_SCALED ((s64)MAXFREQ << NTP_SCALE_SHIFT) |
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| 129 | #define MINSEC 256 /* min interval between updates (s) */ |
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| 130 | #define MAXSEC 2048 /* max interval between updates (s) */ |
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| 131 | #define NTP_PHASE_LIMIT ((MAXPHASE / NSEC_PER_USEC) << 5) /* beyond max. dispersion */ |
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| 132 | |||
| 133 | /* |
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| 134 | * kernel variables |
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| 135 | * Note: maximum error = NTP synch distance = dispersion + delay / 2; |
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| 136 | * estimated error = NTP dispersion. |
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| 137 | */ |
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| 138 | extern unsigned long tick_usec; /* USER_HZ period (usec) */ |
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| 139 | extern unsigned long tick_nsec; /* SHIFTED_HZ period (nsec) */ |
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| 140 | |||
| 141 | /* Required to safely shift negative values */ |
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| 142 | #define shift_right(x, s) ({ \ |
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| 143 | __typeof__(x) __x = (x); \ |
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| 144 | __typeof__(s) __s = (s); \ |
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| 145 | __x < 0 ? -(-__x >> __s) : __x >> __s; \ |
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| 146 | }) |
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| 147 | |||
| 148 | #define NTP_SCALE_SHIFT 32 |
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| 149 | |||
| 150 | #define NTP_INTERVAL_FREQ (HZ) |
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| 151 | #define NTP_INTERVAL_LENGTH (NSEC_PER_SEC/NTP_INTERVAL_FREQ) |
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| 152 | |||
| 6934 | serge | 153 | extern int do_adjtimex(struct timex *); |
| 154 | extern void hardpps(const struct timespec64 *, const struct timespec64 *); |
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| 6588 | serge | 155 | |
| 156 | int read_current_timer(unsigned long *timer_val); |
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| 157 | void ntp_notify_cmos_timer(void); |
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| 158 | |||
| 159 | /* The clock frequency of the i8253/i8254 PIT */ |
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| 160 | #define PIT_TICK_RATE 1193182ul |
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| 161 | |||
| 162 | #endif /* LINUX_TIMEX_H */ |