1 /*****************************************************************************
3 * Copyright (c) David L. Mills 1993 *
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. *
15 *****************************************************************************/
18 * Modification history timex.h
20 * 29 Dec 97 Russell King
21 * Moved CLOCK_TICK_RATE, CLOCK_TICK_FACTOR and FINETUNE to asm/timex.h
25 * Shifted LATCH define to allow access to alpha machines.
27 * 26 Sep 94 David L. Mills
28 * Added defines for hybrid phase/frequency-lock loop.
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.
34 * 20 Feb 94 David L. Mills
35 * Revised status codes and structures for external clock and PPS
38 * 28 Nov 93 David L. Mills
39 * Adjusted parameters to improve stability and increase poll
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
53 #ifndef _LINUX_TIMEX_H
54 #define _LINUX_TIMEX_H
56 #include <linux/time.h>
58 #define NTP_API 4 /* NTP API version */
61 * syscall interface - used (mainly by NTP daemon)
62 * to discipline kernel clock oscillator
65 unsigned int modes
; /* mode selector */
66 long offset
; /* time offset (usec) */
67 long freq
; /* frequency offset (scaled ppm) */
68 long maxerror
; /* maximum error (usec) */
69 long esterror
; /* estimated error (usec) */
70 int status
; /* clock command/status */
71 long constant
; /* pll time constant */
72 long precision
; /* clock precision (usec) (read only) */
73 long tolerance
; /* clock frequency tolerance (ppm)
76 struct timeval time
; /* (read only, except for ADJ_SETOFFSET) */
77 long tick
; /* (modified) usecs between clock ticks */
79 long ppsfreq
; /* pps frequency (scaled ppm) (ro) */
80 long jitter
; /* pps jitter (us) (ro) */
81 int shift
; /* interval duration (s) (shift) (ro) */
82 long stabil
; /* pps stability (scaled ppm) (ro) */
83 long jitcnt
; /* jitter limit exceeded (ro) */
84 long calcnt
; /* calibration intervals (ro) */
85 long errcnt
; /* calibration errors (ro) */
86 long stbcnt
; /* stability limit exceeded (ro) */
88 int tai
; /* TAI offset (ro) */
90 int :32; int :32; int :32; int :32;
91 int :32; int :32; int :32; int :32;
92 int :32; int :32; int :32;
96 * Mode codes (timex.mode)
98 #define ADJ_OFFSET 0x0001 /* time offset */
99 #define ADJ_FREQUENCY 0x0002 /* frequency offset */
100 #define ADJ_MAXERROR 0x0004 /* maximum time error */
101 #define ADJ_ESTERROR 0x0008 /* estimated time error */
102 #define ADJ_STATUS 0x0010 /* clock status */
103 #define ADJ_TIMECONST 0x0020 /* pll time constant */
104 #define ADJ_TAI 0x0080 /* set TAI offset */
105 #define ADJ_SETOFFSET 0x0100 /* add 'time' to current time */
106 #define ADJ_MICRO 0x1000 /* select microsecond resolution */
107 #define ADJ_NANO 0x2000 /* select nanosecond resolution */
108 #define ADJ_TICK 0x4000 /* tick value */
111 #define ADJ_ADJTIME 0x8000 /* switch between adjtime/adjtimex modes */
112 #define ADJ_OFFSET_SINGLESHOT 0x0001 /* old-fashioned adjtime */
113 #define ADJ_OFFSET_READONLY 0x2000 /* read-only adjtime */
115 #define ADJ_OFFSET_SINGLESHOT 0x8001 /* old-fashioned adjtime */
116 #define ADJ_OFFSET_SS_READ 0xa001 /* read-only adjtime */
119 /* NTP userland likes the MOD_ prefix better */
120 #define MOD_OFFSET ADJ_OFFSET
121 #define MOD_FREQUENCY ADJ_FREQUENCY
122 #define MOD_MAXERROR ADJ_MAXERROR
123 #define MOD_ESTERROR ADJ_ESTERROR
124 #define MOD_STATUS ADJ_STATUS
125 #define MOD_TIMECONST ADJ_TIMECONST
126 #define MOD_TAI ADJ_TAI
127 #define MOD_MICRO ADJ_MICRO
128 #define MOD_NANO ADJ_NANO
132 * Status codes (timex.status)
134 #define STA_PLL 0x0001 /* enable PLL updates (rw) */
135 #define STA_PPSFREQ 0x0002 /* enable PPS freq discipline (rw) */
136 #define STA_PPSTIME 0x0004 /* enable PPS time discipline (rw) */
137 #define STA_FLL 0x0008 /* select frequency-lock mode (rw) */
139 #define STA_INS 0x0010 /* insert leap (rw) */
140 #define STA_DEL 0x0020 /* delete leap (rw) */
141 #define STA_UNSYNC 0x0040 /* clock unsynchronized (rw) */
142 #define STA_FREQHOLD 0x0080 /* hold frequency (rw) */
144 #define STA_PPSSIGNAL 0x0100 /* PPS signal present (ro) */
145 #define STA_PPSJITTER 0x0200 /* PPS signal jitter exceeded (ro) */
146 #define STA_PPSWANDER 0x0400 /* PPS signal wander exceeded (ro) */
147 #define STA_PPSERROR 0x0800 /* PPS signal calibration error (ro) */
149 #define STA_CLOCKERR 0x1000 /* clock hardware fault (ro) */
150 #define STA_NANO 0x2000 /* resolution (0 = us, 1 = ns) (ro) */
151 #define STA_MODE 0x4000 /* mode (0 = PLL, 1 = FLL) (ro) */
152 #define STA_CLK 0x8000 /* clock source (0 = A, 1 = B) (ro) */
155 #define STA_RONLY (STA_PPSSIGNAL | STA_PPSJITTER | STA_PPSWANDER | \
156 STA_PPSERROR | STA_CLOCKERR | STA_NANO | STA_MODE | STA_CLK)
159 * Clock states (time_state)
161 #define TIME_OK 0 /* clock synchronized, no leap second */
162 #define TIME_INS 1 /* insert leap second */
163 #define TIME_DEL 2 /* delete leap second */
164 #define TIME_OOP 3 /* leap second in progress */
165 #define TIME_WAIT 4 /* leap second has occurred */
166 #define TIME_ERROR 5 /* clock not synchronized */
167 #define TIME_BAD TIME_ERROR /* bw compat */
170 #include <linux/compiler.h>
171 #include <linux/types.h>
172 #include <linux/param.h>
174 #include <asm/timex.h>
177 * SHIFT_PLL is used as a dampening factor to define how much we
178 * adjust the frequency correction for a given offset in PLL mode.
179 * It also used in dampening the offset correction, to define how
180 * much of the current value in time_offset we correct for each
181 * second. Changing this value changes the stiffness of the ntp
182 * adjustment code. A lower value makes it more flexible, reducing
183 * NTP convergence time. A higher value makes it stiffer, increasing
184 * convergence time, but making the clock more stable.
186 * In David Mills' nanokernel reference implementation SHIFT_PLL is 4.
187 * However this seems to increase convergence time much too long.
189 * https://lists.ntp.org/pipermail/hackers/2008-January/003487.html
191 * In the above mailing list discussion, it seems the value of 4
192 * was appropriate for other Unix systems with HZ=100, and that
193 * SHIFT_PLL should be decreased as HZ increases. However, Linux's
194 * clock steering implementation is HZ independent.
196 * Through experimentation, a SHIFT_PLL value of 2 was found to allow
197 * for fast convergence (very similar to the NTPv3 code used prior to
198 * v2.6.19), with good clock stability.
201 * SHIFT_FLL is used as a dampening factor to define how much we
202 * adjust the frequency correction for a given offset in FLL mode.
203 * In David Mills' nanokernel reference implementation SHIFT_FLL is 2.
205 * MAXTC establishes the maximum time constant of the PLL.
207 #define SHIFT_PLL 2 /* PLL frequency factor (shift) */
208 #define SHIFT_FLL 2 /* FLL frequency factor (shift) */
209 #define MAXTC 10 /* maximum time constant (shift) */
212 * SHIFT_USEC defines the scaling (shift) of the time_freq and
213 * time_tolerance variables, which represent the current frequency
214 * offset and maximum frequency tolerance.
216 #define SHIFT_USEC 16 /* frequency offset scale (shift) */
217 #define PPM_SCALE ((s64)NSEC_PER_USEC << (NTP_SCALE_SHIFT - SHIFT_USEC))
218 #define PPM_SCALE_INV_SHIFT 19
219 #define PPM_SCALE_INV ((1LL << (PPM_SCALE_INV_SHIFT + NTP_SCALE_SHIFT)) / \
222 #define MAXPHASE 500000000L /* max phase error (ns) */
223 #define MAXFREQ 500000 /* max frequency error (ns/s) */
224 #define MAXFREQ_SCALED ((s64)MAXFREQ << NTP_SCALE_SHIFT)
225 #define MINSEC 256 /* min interval between updates (s) */
226 #define MAXSEC 2048 /* max interval between updates (s) */
227 #define NTP_PHASE_LIMIT ((MAXPHASE / NSEC_PER_USEC) << 5) /* beyond max. dispersion */
231 * Note: maximum error = NTP synch distance = dispersion + delay / 2;
232 * estimated error = NTP dispersion.
234 extern unsigned long tick_usec
; /* USER_HZ period (usec) */
235 extern unsigned long tick_nsec
; /* SHIFTED_HZ period (nsec) */
237 extern void ntp_init(void);
238 extern void ntp_clear(void);
240 /* Required to safely shift negative values */
241 #define shift_right(x, s) ({ \
242 __typeof__(x) __x = (x); \
243 __typeof__(s) __s = (s); \
244 __x < 0 ? -(-__x >> __s) : __x >> __s; \
247 #define NTP_SCALE_SHIFT 32
249 #define NTP_INTERVAL_FREQ (HZ)
250 #define NTP_INTERVAL_LENGTH (NSEC_PER_SEC/NTP_INTERVAL_FREQ)
252 /* Returns how long ticks are at present, in ns / 2^NTP_SCALE_SHIFT. */
253 extern u64
ntp_tick_length(void);
255 extern int second_overflow(unsigned long secs
);
256 extern int do_adjtimex(struct timex
*);
257 extern void hardpps(const struct timespec
*, const struct timespec
*);
259 int read_current_timer(unsigned long *timer_val
);
261 /* The clock frequency of the i8253/i8254 PIT */
262 #define PIT_TICK_RATE 1193182ul
266 #endif /* LINUX_TIMEX_H */
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