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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> |
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 | * |
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) |
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); |
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 */ |