include/linux/timex.h

   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
  56 #include <linux/time.h>
  57
  58 #define NTP_API         4       /* NTP API version */
  59
  60 /*
  61  * syscall interface - used (mainly by NTP daemon)
  62  * to discipline kernel clock oscillator
  63  */
  64 struct timex {
  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)
  74                                  * (read only)
  75                                  */
  76         struct timeval time;    /* (read only) */
  77         long tick;              /* (modified) usecs between clock ticks */
  78
  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) */
  87
  88         int tai;                /* TAI offset (ro) */
  89
  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;
  93 };
  94
  95 /*
  96  * Mode codes (timex.mode)
  97  */
  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_MICRO               0x1000  /* select microsecond resolution */
 106 #define ADJ_NANO                0x2000  /* select nanosecond resolution */
 107 #define ADJ_TICK                0x4000  /* tick value */
 108
 109 #ifdef __KERNEL__
 110 #define ADJ_ADJTIME             0x8000  /* switch between adjtime/adjtimex modes */
 111 #define ADJ_OFFSET_SINGLESHOT   0x0001  /* old-fashioned adjtime */
 112 #define ADJ_OFFSET_READONLY     0x2000  /* read-only adjtime */
 113 #else
 114 #define ADJ_OFFSET_SINGLESHOT   0x8001  /* old-fashioned adjtime */
 115 #define ADJ_OFFSET_SS_READ      0xa001  /* read-only adjtime */
 116 #endif
 117
 118 /* NTP userland likes the MOD_ prefix better */
 119 #define MOD_OFFSET      ADJ_OFFSET
 120 #define MOD_FREQUENCY   ADJ_FREQUENCY
 121 #define MOD_MAXERROR    ADJ_MAXERROR
 122 #define MOD_ESTERROR    ADJ_ESTERROR
 123 #define MOD_STATUS      ADJ_STATUS
 124 #define MOD_TIMECONST   ADJ_TIMECONST
 125 #define MOD_TAI ADJ_TAI
 126 #define MOD_MICRO       ADJ_MICRO
 127 #define MOD_NANO        ADJ_NANO
 128
 129
 130 /*
 131  * Status codes (timex.status)
 132  */
 133 #define STA_PLL         0x0001  /* enable PLL updates (rw) */
 134 #define STA_PPSFREQ     0x0002  /* enable PPS freq discipline (rw) */
 135 #define STA_PPSTIME     0x0004  /* enable PPS time discipline (rw) */
 136 #define STA_FLL         0x0008  /* select frequency-lock mode (rw) */
 137
 138 #define STA_INS         0x0010  /* insert leap (rw) */
 139 #define STA_DEL         0x0020  /* delete leap (rw) */
 140 #define STA_UNSYNC      0x0040  /* clock unsynchronized (rw) */
 141 #define STA_FREQHOLD    0x0080  /* hold frequency (rw) */
 142
 143 #define STA_PPSSIGNAL   0x0100  /* PPS signal present (ro) */
 144 #define STA_PPSJITTER   0x0200  /* PPS signal jitter exceeded (ro) */
 145 #define STA_PPSWANDER   0x0400  /* PPS signal wander exceeded (ro) */
 146 #define STA_PPSERROR    0x0800  /* PPS signal calibration error (ro) */
 147
 148 #define STA_CLOCKERR    0x1000  /* clock hardware fault (ro) */
 149 #define STA_NANO        0x2000  /* resolution (0 = us, 1 = ns) (ro) */
 150 #define STA_MODE        0x4000  /* mode (0 = PLL, 1 = FLL) (ro) */
 151 #define STA_CLK         0x8000  /* clock source (0 = A, 1 = B) (ro) */
 152
 153 /* read-only bits */
 154 #define STA_RONLY (STA_PPSSIGNAL | STA_PPSJITTER | STA_PPSWANDER | \
 155         STA_PPSERROR | STA_CLOCKERR | STA_NANO | STA_MODE | STA_CLK)
 156
 157 /*
 158  * Clock states (time_state)
 159  */
 160 #define TIME_OK         0       /* clock synchronized, no leap second */
 161 #define TIME_INS        1       /* insert leap second */
 162 #define TIME_DEL        2       /* delete leap second */
 163 #define TIME_OOP        3       /* leap second in progress */
 164 #define TIME_WAIT       4       /* leap second has occurred */
 165 #define TIME_ERROR      5       /* clock not synchronized */
 166 #define TIME_BAD        TIME_ERROR /* bw compat */
 167
 168 #ifdef __KERNEL__
 169 #include <linux/compiler.h>
 170 #include <linux/types.h>
 171 #include <linux/param.h>
 172
 173 #include <asm/timex.h>
 174
 175 /*
 176  * SHIFT_PLL is used as a dampening factor to define how much we
 177  * adjust the frequency correction for a given offset in PLL mode.
 178  * It also used in dampening the offset correction, to define how
 179  * much of the current value in time_offset we correct for each
 180  * second. Changing this value changes the stiffness of the ntp
 181  * adjustment code. A lower value makes it more flexible, reducing
 182  * NTP convergence time. A higher value makes it stiffer, increasing
 183  * convergence time, but making the clock more stable.
 184  *
 185  * In David Mills' nanokernel reference implementation SHIFT_PLL is 4.
 186  * However this seems to increase convergence time much too long.
 187  *
 188  * https://lists.ntp.org/pipermail/hackers/2008-January/003487.html
 189  *
 190  * In the above mailing list discussion, it seems the value of 4
 191  * was appropriate for other Unix systems with HZ=100, and that
 192  * SHIFT_PLL should be decreased as HZ increases. However, Linux's
 193  * clock steering implementation is HZ independent.
 194  *
 195  * Through experimentation, a SHIFT_PLL value of 2 was found to allow
 196  * for fast convergence (very similar to the NTPv3 code used prior to
 197  * v2.6.19), with good clock stability.
 198  *
 199  *
 200  * SHIFT_FLL is used as a dampening factor to define how much we
 201  * adjust the frequency correction for a given offset in FLL mode.
 202  * In David Mills' nanokernel reference implementation SHIFT_FLL is 2.
 203  *
 204  * MAXTC establishes the maximum time constant of the PLL.
 205  */
 206 #define SHIFT_PLL       2       /* PLL frequency factor (shift) */
 207 #define SHIFT_FLL       2       /* FLL frequency factor (shift) */
 208 #define MAXTC           10      /* maximum time constant (shift) */
 209
 210 /*
 211  * SHIFT_USEC defines the scaling (shift) of the time_freq and
 212  * time_tolerance variables, which represent the current frequency
 213  * offset and maximum frequency tolerance.
 214  */
 215 #define SHIFT_USEC 16           /* frequency offset scale (shift) */
 216 #define PPM_SCALE ((s64)NSEC_PER_USEC << (NTP_SCALE_SHIFT - SHIFT_USEC))
 217 #define PPM_SCALE_INV_SHIFT 19
 218 #define PPM_SCALE_INV ((1LL << (PPM_SCALE_INV_SHIFT + NTP_SCALE_SHIFT)) / \
 219                        PPM_SCALE + 1)
 220
 221 #define MAXPHASE 500000000L     /* max phase error (ns) */
 222 #define MAXFREQ 500000          /* max frequency error (ns/s) */
 223 #define MAXFREQ_SCALED ((s64)MAXFREQ << NTP_SCALE_SHIFT)
 224 #define MINSEC 256              /* min interval between updates (s) */
 225 #define MAXSEC 2048             /* max interval between updates (s) */
 226 #define NTP_PHASE_LIMIT ((MAXPHASE / NSEC_PER_USEC) << 5) /* beyond max. dispersion */
 227
 228 /*
 229  * kernel variables
 230  * Note: maximum error = NTP synch distance = dispersion + delay / 2;
 231  * estimated error = NTP dispersion.
 232  */
 233 extern unsigned long tick_usec;         /* USER_HZ period (usec) */
 234 extern unsigned long tick_nsec;         /* ACTHZ          period (nsec) */
 235
 236 /*
 237  * phase-lock loop variables
 238  */
 239 extern int time_status;         /* clock synchronization status bits */
 240
 241 extern void ntp_init(void);
 242 extern void ntp_clear(void);
 243
 244 /**
 245  * ntp_synced - Returns 1 if the NTP status is not UNSYNC
 246  *
 247  */
 248 static inline int ntp_synced(void)
 249 {
 250         return !(time_status & STA_UNSYNC);
 251 }
 252
 253 /* Required to safely shift negative values */
 254 #define shift_right(x, s) ({    \
 255         __typeof__(x) __x = (x);        \
 256         __typeof__(s) __s = (s);        \
 257         __x < 0 ? -(-__x >> __s) : __x >> __s;  \
 258 })
 259
 260 #define NTP_SCALE_SHIFT         32
 261
 262 #define NTP_INTERVAL_FREQ  (HZ)
 263 #define NTP_INTERVAL_LENGTH (NSEC_PER_SEC/NTP_INTERVAL_FREQ)
 264
 265 /* Returns how long ticks are at present, in ns / 2^NTP_SCALE_SHIFT. */
 266 extern u64 tick_length;
 267
 268 extern void second_overflow(void);
 269 extern void update_ntp_one_tick(void);
 270 extern int do_adjtimex(struct timex *);
 271
 272 int read_current_timer(unsigned long *timer_val);
 273
 274 /* The clock frequency of the i8253/i8254 PIT */
 275 #define PIT_TICK_RATE 1193182ul
 276
 277 #endif /* KERNEL */
 278
 279 #endif /* LINUX_TIMEX_H */