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/compiler.h>
  57 #include <linux/time.h>
  58
  59 #include <asm/param.h>
  60 #include <asm/timex.h>
  61
  62 /*
  63  * SHIFT_KG and SHIFT_KF establish the damping of the PLL and are chosen
  64  * for a slightly underdamped convergence characteristic. SHIFT_KH
  65  * establishes the damping of the FLL and is chosen by wisdom and black
  66  * art.
  67  *
  68  * MAXTC establishes the maximum time constant of the PLL. With the
  69  * SHIFT_KG and SHIFT_KF values given and a time constant range from
  70  * zero to MAXTC, the PLL will converge in 15 minutes to 16 hours,
  71  * respectively.
  72  */
  73 #define SHIFT_KG 6              /* phase factor (shift) */
  74 #define SHIFT_KF 16             /* PLL frequency factor (shift) */
  75 #define SHIFT_KH 2              /* FLL frequency factor (shift) */
  76 #define MAXTC 6                 /* maximum time constant (shift) */
  77
  78 /*
  79  * The SHIFT_SCALE define establishes the decimal point of the time_phase
  80  * variable which serves as an extension to the low-order bits of the
  81  * system clock variable. The SHIFT_UPDATE define establishes the decimal
  82  * point of the time_offset variable which represents the current offset
  83  * with respect to standard time. The FINENSEC define represents 1 nsec in
  84  * scaled units.
  85  *
  86  * SHIFT_USEC defines the scaling (shift) of the time_freq and
  87  * time_tolerance variables, which represent the current frequency
  88  * offset and maximum frequency tolerance.
  89  *
  90  * FINENSEC is 1 ns in SHIFT_UPDATE units of the time_phase variable.
  91  */
  92 #define SHIFT_SCALE 22          /* phase scale (shift) */
  93 #define SHIFT_UPDATE (SHIFT_KG + MAXTC) /* time offset scale (shift) */
  94 #define SHIFT_USEC 16           /* frequency offset scale (shift) */
  95 #define FINENSEC (1L << (SHIFT_SCALE - 10)) /* ~1 ns in phase units */
  96
  97 #define MAXPHASE 512000L        /* max phase error (us) */
  98 #define MAXFREQ (512L << SHIFT_USEC)  /* max frequency error (ppm) */
  99 #define MINSEC 16L              /* min interval between updates (s) */
 100 #define MAXSEC 1200L            /* max interval between updates (s) */
 101 #define NTP_PHASE_LIMIT (MAXPHASE << 5) /* beyond max. dispersion */
 102
 103 /*
 104  * syscall interface - used (mainly by NTP daemon)
 105  * to discipline kernel clock oscillator
 106  */
 107 struct timex {
 108         unsigned int modes;     /* mode selector */
 109         long offset;            /* time offset (usec) */
 110         long freq;              /* frequency offset (scaled ppm) */
 111         long maxerror;          /* maximum error (usec) */
 112         long esterror;          /* estimated error (usec) */
 113         int status;             /* clock command/status */
 114         long constant;          /* pll time constant */
 115         long precision;         /* clock precision (usec) (read only) */
 116         long tolerance;         /* clock frequency tolerance (ppm)
 117                                  * (read only)
 118                                  */
 119         struct timeval time;    /* (read only) */
 120         long tick;              /* (modified) usecs between clock ticks */
 121
 122         long ppsfreq;           /* pps frequency (scaled ppm) (ro) */
 123         long jitter;            /* pps jitter (us) (ro) */
 124         int shift;              /* interval duration (s) (shift) (ro) */
 125         long stabil;            /* pps stability (scaled ppm) (ro) */
 126         long jitcnt;            /* jitter limit exceeded (ro) */
 127         long calcnt;            /* calibration intervals (ro) */
 128         long errcnt;            /* calibration errors (ro) */
 129         long stbcnt;            /* stability limit exceeded (ro) */
 130
 131         int  :32; int  :32; int  :32; int  :32;
 132         int  :32; int  :32; int  :32; int  :32;
 133         int  :32; int  :32; int  :32; int  :32;
 134 };
 135
 136 /*
 137  * Mode codes (timex.mode)
 138  */
 139 #define ADJ_OFFSET              0x0001  /* time offset */
 140 #define ADJ_FREQUENCY           0x0002  /* frequency offset */
 141 #define ADJ_MAXERROR            0x0004  /* maximum time error */
 142 #define ADJ_ESTERROR            0x0008  /* estimated time error */
 143 #define ADJ_STATUS              0x0010  /* clock status */
 144 #define ADJ_TIMECONST           0x0020  /* pll time constant */
 145 #define ADJ_TICK                0x4000  /* tick value */
 146 #define ADJ_OFFSET_SINGLESHOT   0x8001  /* old-fashioned adjtime */
 147
 148 /* xntp 3.4 compatibility names */
 149 #define MOD_OFFSET      ADJ_OFFSET
 150 #define MOD_FREQUENCY   ADJ_FREQUENCY
 151 #define MOD_MAXERROR    ADJ_MAXERROR
 152 #define MOD_ESTERROR    ADJ_ESTERROR
 153 #define MOD_STATUS      ADJ_STATUS
 154 #define MOD_TIMECONST   ADJ_TIMECONST
 155 #define MOD_CLKB        ADJ_TICK
 156 #define MOD_CLKA        ADJ_OFFSET_SINGLESHOT /* 0x8000 in original */
 157
 158
 159 /*
 160  * Status codes (timex.status)
 161  */
 162 #define STA_PLL         0x0001  /* enable PLL updates (rw) */
 163 #define STA_PPSFREQ     0x0002  /* enable PPS freq discipline (rw) */
 164 #define STA_PPSTIME     0x0004  /* enable PPS time discipline (rw) */
 165 #define STA_FLL         0x0008  /* select frequency-lock mode (rw) */
 166
 167 #define STA_INS         0x0010  /* insert leap (rw) */
 168 #define STA_DEL         0x0020  /* delete leap (rw) */
 169 #define STA_UNSYNC      0x0040  /* clock unsynchronized (rw) */
 170 #define STA_FREQHOLD    0x0080  /* hold frequency (rw) */
 171
 172 #define STA_PPSSIGNAL   0x0100  /* PPS signal present (ro) */
 173 #define STA_PPSJITTER   0x0200  /* PPS signal jitter exceeded (ro) */
 174 #define STA_PPSWANDER   0x0400  /* PPS signal wander exceeded (ro) */
 175 #define STA_PPSERROR    0x0800  /* PPS signal calibration error (ro) */
 176
 177 #define STA_CLOCKERR    0x1000  /* clock hardware fault (ro) */
 178
 179 #define STA_RONLY (STA_PPSSIGNAL | STA_PPSJITTER | STA_PPSWANDER | \
 180     STA_PPSERROR | STA_CLOCKERR) /* read-only bits */
 181
 182 /*
 183  * Clock states (time_state)
 184  */
 185 #define TIME_OK         0       /* clock synchronized, no leap second */
 186 #define TIME_INS        1       /* insert leap second */
 187 #define TIME_DEL        2       /* delete leap second */
 188 #define TIME_OOP        3       /* leap second in progress */
 189 #define TIME_WAIT       4       /* leap second has occurred */
 190 #define TIME_ERROR      5       /* clock not synchronized */
 191 #define TIME_BAD        TIME_ERROR /* bw compat */
 192
 193 #ifdef __KERNEL__
 194 /*
 195  * kernel variables
 196  * Note: maximum error = NTP synch distance = dispersion + delay / 2;
 197  * estimated error = NTP dispersion.
 198  */
 199 extern unsigned long tick_usec;         /* USER_HZ period (usec) */
 200 extern unsigned long tick_nsec;         /* ACTHZ          period (nsec) */
 201 extern int tickadj;                     /* amount of adjustment per tick */
 202
 203 /*
 204  * phase-lock loop variables
 205  */
 206 extern int time_state;          /* clock status */
 207 extern int time_status;         /* clock synchronization status bits */
 208 extern long time_offset;        /* time adjustment (us) */
 209 extern long time_constant;      /* pll time constant */
 210 extern long time_tolerance;     /* frequency tolerance (ppm) */
 211 extern long time_precision;     /* clock precision (us) */
 212 extern long time_maxerror;      /* maximum error */
 213 extern long time_esterror;      /* estimated error */
 214
 215 extern long time_freq;          /* frequency offset (scaled ppm) */
 216 extern long time_reftime;       /* time at last adjustment (s) */
 217
 218 extern long time_adjust;        /* The amount of adjtime left */
 219 extern long time_next_adjust;   /* Value for time_adjust at next tick */
 220
 221 /**
 222  * ntp_clear - Clears the NTP state variables
 223  *
 224  * Must be called while holding a write on the xtime_lock
 225  */
 226 static inline void ntp_clear(void)
 227 {
 228         time_adjust = 0;                /* stop active adjtime() */
 229         time_status |= STA_UNSYNC;
 230         time_maxerror = NTP_PHASE_LIMIT;
 231         time_esterror = NTP_PHASE_LIMIT;
 232 }
 233
 234 /**
 235  * ntp_synced - Returns 1 if the NTP status is not UNSYNC
 236  *
 237  */
 238 static inline int ntp_synced(void)
 239 {
 240         return !(time_status & STA_UNSYNC);
 241 }
 242
 243 /* Required to safely shift negative values */
 244 #define shift_right(x, s) ({    \
 245         __typeof__(x) __x = (x);        \
 246         __typeof__(s) __s = (s);        \
 247         __x < 0 ? -(-__x >> __s) : __x >> __s;  \
 248 })
 249
 250
 251 #ifdef CONFIG_TIME_INTERPOLATION
 252
 253 #define TIME_SOURCE_CPU 0
 254 #define TIME_SOURCE_MMIO64 1
 255 #define TIME_SOURCE_MMIO32 2
 256 #define TIME_SOURCE_FUNCTION 3
 257
 258 /* For proper operations time_interpolator clocks must run slightly slower
 259  * than the standard clock since the interpolator may only correct by having
 260  * time jump forward during a tick. A slower clock is usually a side effect
 261  * of the integer divide of the nanoseconds in a second by the frequency.
 262  * The accuracy of the division can be increased by specifying a shift.
 263  * However, this may cause the clock not to be slow enough.
 264  * The interpolator will self-tune the clock by slowing down if no
 265  * resets occur or speeding up if the time jumps per analysis cycle
 266  * become too high.
 267  *
 268  * Setting jitter compensates for a fluctuating timesource by comparing
 269  * to the last value read from the timesource to insure that an earlier value
 270  * is not returned by a later call. The price to pay
 271  * for the compensation is that the timer routines are not as scalable anymore.
 272  */
 273
 274 struct time_interpolator {
 275         u16 source;                     /* time source flags */
 276         u8 shift;                       /* increases accuracy of multiply by shifting. */
 277                                 /* Note that bits may be lost if shift is set too high */
 278         u8 jitter;                      /* if set compensate for fluctuations */
 279         u32 nsec_per_cyc;               /* set by register_time_interpolator() */
 280         void *addr;                     /* address of counter or function */
 281         u64 mask;                       /* mask the valid bits of the counter */
 282         unsigned long offset;           /* nsec offset at last update of interpolator */
 283         u64 last_counter;               /* counter value in units of the counter at last update */
 284         u64 last_cycle;                 /* Last timer value if TIME_SOURCE_JITTER is set */
 285         u64 frequency;                  /* frequency in counts/second */
 286         long drift;                     /* drift in parts-per-million (or -1) */
 287         unsigned long skips;            /* skips forward */
 288         unsigned long ns_skipped;       /* nanoseconds skipped */
 289         struct time_interpolator *next;
 290 };
 291
 292 extern void register_time_interpolator(struct time_interpolator *);
 293 extern void unregister_time_interpolator(struct time_interpolator *);
 294 extern void time_interpolator_reset(void);
 295 extern unsigned long time_interpolator_get_offset(void);
 296
 297 #else /* !CONFIG_TIME_INTERPOLATION */
 298
 299 static inline void
 300 time_interpolator_reset(void)
 301 {
 302 }
 303
 304 #endif /* !CONFIG_TIME_INTERPOLATION */
 305
 306 /* Returns how long ticks are at present, in ns / 2^(SHIFT_SCALE-10). */
 307 extern u64 current_tick_length(void);
 308
 309 extern int do_adjtimex(struct timex *);
 310
 311 #endif /* KERNEL */
 312
 313 #endif /* LINUX_TIMEX_H */