/*****************************************************************************
   *                                                                           *
   * Copyright (c) David L. Mills 1993                                         *
   *                                                                           *
   * Permission to use, copy, modify, and distribute this software and its     *
   * documentation for any purpose and without fee is hereby granted, provided *
   * that the above copyright notice appears in all copies and that both the   *
   * copyright notice and this permission notice appear in supporting          *
   * documentation, and that the name University of Delaware not be used in    *
   * advertising or publicity pertaining to distribution of the software       *
   * without specific, written prior permission.  The University of Delaware   *
   * makes no representations about the suitability this software for any      *
   * purpose.  It is provided "as is" without express or implied warranty.     *
   *                                                                           *
   *****************************************************************************/
  
  /*
   * Modification history timex.h
   *
   * 29 Dec 97	Russell King
   *	Moved CLOCK_TICK_RATE, CLOCK_TICK_FACTOR and FINETUNE to asm/timex.h
   *	for ARM machines
   *
   *  9 Jan 97    Adrian Sun
   *      Shifted LATCH define to allow access to alpha machines.
   *
   * 26 Sep 94	David L. Mills
   *	Added defines for hybrid phase/frequency-lock loop.
   *
   * 19 Mar 94	David L. Mills
   *	Moved defines from kernel routines to header file and added new
   *	defines for PPS phase-lock loop.
   *
   * 20 Feb 94	David L. Mills
   *	Revised status codes and structures for external clock and PPS
   *	signal discipline.
   *
   * 28 Nov 93	David L. Mills
   *	Adjusted parameters to improve stability and increase poll
   *	interval.
   *
   * 17 Sep 93    David L. Mills
   *      Created file $NTP/include/sys/timex.h
   * 07 Oct 93    Torsten Duwe
   *      Derived linux/timex.h
   * 1995-08-13    Torsten Duwe
   *      kernel PLL updated to 1994-12-13 specs (rfc-1589)
   * 1997-08-30    Ulrich Windl
   *      Added new constant NTP_PHASE_LIMIT
   * 2004-08-12    Christoph Lameter
   *      Reworked time interpolation logic
   */
  #ifndef _LINUX_TIMEX_H
  #define _LINUX_TIMEX_H

  #include <linux/time.h>

  #define NTP_API		4	/* NTP API version */

  /*

   * syscall interface - used (mainly by NTP daemon)
   * to discipline kernel clock oscillator
   */
  struct timex {
  	unsigned int modes;	/* mode selector */
  	long offset;		/* time offset (usec) */
  	long freq;		/* frequency offset (scaled ppm) */
  	long maxerror;		/* maximum error (usec) */
  	long esterror;		/* estimated error (usec) */
  	int status;		/* clock command/status */
  	long constant;		/* pll time constant */
  	long precision;		/* clock precision (usec) (read only) */
  	long tolerance;		/* clock frequency tolerance (ppm)
  				 * (read only)
  				 */
  	struct timeval time;	/* (read only) */
  	long tick;		/* (modified) usecs between clock ticks */
  
  	long ppsfreq;           /* pps frequency (scaled ppm) (ro) */
  	long jitter;            /* pps jitter (us) (ro) */
  	int shift;              /* interval duration (s) (shift) (ro) */
  	long stabil;            /* pps stability (scaled ppm) (ro) */
  	long jitcnt;            /* jitter limit exceeded (ro) */
  	long calcnt;            /* calibration intervals (ro) */
  	long errcnt;            /* calibration errors (ro) */
  	long stbcnt;            /* stability limit exceeded (ro) */

  	int tai;		/* TAI offset (ro) */

  	int  :32; int  :32; int  :32; int  :32;
  	int  :32; int  :32; int  :32; int  :32;

  	int  :32; int  :32; int  :32;

  };
  
  /*
   * Mode codes (timex.mode)
   */
  #define ADJ_OFFSET		0x0001	/* time offset */
  #define ADJ_FREQUENCY		0x0002	/* frequency offset */
  #define ADJ_MAXERROR		0x0004	/* maximum time error */
  #define ADJ_ESTERROR		0x0008	/* estimated time error */
  #define ADJ_STATUS		0x0010	/* clock status */
  #define ADJ_TIMECONST		0x0020	/* pll time constant */

  #define ADJ_TAI			0x0080	/* set TAI offset */

  #define ADJ_MICRO		0x1000	/* select microsecond resolution */
  #define ADJ_NANO		0x2000	/* select nanosecond resolution */

  #define ADJ_TICK		0x4000	/* tick value */

  
  #ifdef __KERNEL__
  #define ADJ_ADJTIME		0x8000	/* switch between adjtime/adjtimex modes */
  #define ADJ_OFFSET_SINGLESHOT	0x0001	/* old-fashioned adjtime */
  #define ADJ_OFFSET_READONLY	0x2000	/* read-only adjtime */
  #else

  #define ADJ_OFFSET_SINGLESHOT	0x8001	/* old-fashioned adjtime */

  #define ADJ_OFFSET_SS_READ	0xa001	/* read-only adjtime */
  #endif

  /* NTP userland likes the MOD_ prefix better */

  #define MOD_OFFSET	ADJ_OFFSET
  #define MOD_FREQUENCY	ADJ_FREQUENCY
  #define MOD_MAXERROR	ADJ_MAXERROR
  #define MOD_ESTERROR	ADJ_ESTERROR
  #define MOD_STATUS	ADJ_STATUS
  #define MOD_TIMECONST	ADJ_TIMECONST

  #define MOD_TAI	ADJ_TAI
  #define MOD_MICRO	ADJ_MICRO
  #define MOD_NANO	ADJ_NANO

  
  
  /*
   * Status codes (timex.status)
   */
  #define STA_PLL		0x0001	/* enable PLL updates (rw) */
  #define STA_PPSFREQ	0x0002	/* enable PPS freq discipline (rw) */
  #define STA_PPSTIME	0x0004	/* enable PPS time discipline (rw) */
  #define STA_FLL		0x0008	/* select frequency-lock mode (rw) */
  
  #define STA_INS		0x0010	/* insert leap (rw) */
  #define STA_DEL		0x0020	/* delete leap (rw) */
  #define STA_UNSYNC	0x0040	/* clock unsynchronized (rw) */
  #define STA_FREQHOLD	0x0080	/* hold frequency (rw) */
  
  #define STA_PPSSIGNAL	0x0100	/* PPS signal present (ro) */
  #define STA_PPSJITTER	0x0200	/* PPS signal jitter exceeded (ro) */
  #define STA_PPSWANDER	0x0400	/* PPS signal wander exceeded (ro) */
  #define STA_PPSERROR	0x0800	/* PPS signal calibration error (ro) */
  
  #define STA_CLOCKERR	0x1000	/* clock hardware fault (ro) */

  #define STA_NANO	0x2000	/* resolution (0 = us, 1 = ns) (ro) */
  #define STA_MODE	0x4000	/* mode (0 = PLL, 1 = FLL) (ro) */
  #define STA_CLK		0x8000	/* clock source (0 = A, 1 = B) (ro) */

  /* read-only bits */

  #define STA_RONLY (STA_PPSSIGNAL | STA_PPSJITTER | STA_PPSWANDER | \

  	STA_PPSERROR | STA_CLOCKERR | STA_NANO | STA_MODE | STA_CLK)

  
  /*
   * Clock states (time_state)
   */
  #define TIME_OK		0	/* clock synchronized, no leap second */
  #define TIME_INS	1	/* insert leap second */
  #define TIME_DEL	2	/* delete leap second */
  #define TIME_OOP	3	/* leap second in progress */
  #define TIME_WAIT	4	/* leap second has occurred */
  #define TIME_ERROR	5	/* clock not synchronized */
  #define TIME_BAD	TIME_ERROR /* bw compat */
  
  #ifdef __KERNEL__

  #include <linux/compiler.h>
  #include <linux/types.h>
  #include <linux/param.h>

  #include <asm/timex.h>

  /*

   * SHIFT_PLL is used as a dampening factor to define how much we
   * adjust the frequency correction for a given offset in PLL mode.
   * It also used in dampening the offset correction, to define how
   * much of the current value in time_offset we correct for each
   * second. Changing this value changes the stiffness of the ntp
   * adjustment code. A lower value makes it more flexible, reducing
   * NTP convergence time. A higher value makes it stiffer, increasing
   * convergence time, but making the clock more stable.

   *

   * In David Mills' nanokernel reference implementation SHIFT_PLL is 4.

   * However this seems to increase convergence time much too long.
   *
   * https://lists.ntp.org/pipermail/hackers/2008-January/003487.html
   *
   * In the above mailing list discussion, it seems the value of 4
   * was appropriate for other Unix systems with HZ=100, and that
   * SHIFT_PLL should be decreased as HZ increases. However, Linux's
   * clock steering implementation is HZ independent.
   *
   * Through experimentation, a SHIFT_PLL value of 2 was found to allow
   * for fast convergence (very similar to the NTPv3 code used prior to
   * v2.6.19), with good clock stability.
   *
   *
   * SHIFT_FLL is used as a dampening factor to define how much we
   * adjust the frequency correction for a given offset in FLL mode.

   * In David Mills' nanokernel reference implementation SHIFT_FLL is 2.

   *
   * MAXTC establishes the maximum time constant of the PLL.

   */

  #define SHIFT_PLL	2	/* PLL frequency factor (shift) */

  #define SHIFT_FLL	2	/* FLL frequency factor (shift) */
  #define MAXTC		10	/* maximum time constant (shift) */
  
  /*
   * SHIFT_USEC defines the scaling (shift) of the time_freq and
   * time_tolerance variables, which represent the current frequency
   * offset and maximum frequency tolerance.
   */
  #define SHIFT_USEC 16		/* frequency offset scale (shift) */

  #define PPM_SCALE ((s64)NSEC_PER_USEC << (NTP_SCALE_SHIFT - SHIFT_USEC))

  #define PPM_SCALE_INV_SHIFT 19

  #define PPM_SCALE_INV ((1LL << (PPM_SCALE_INV_SHIFT + NTP_SCALE_SHIFT)) / \

  		       PPM_SCALE + 1)

  #define MAXPHASE 500000000L	/* max phase error (ns) */

  #define MAXFREQ 500000		/* max frequency error (ns/s) */
  #define MAXFREQ_SCALED ((s64)MAXFREQ << NTP_SCALE_SHIFT)
  #define MINSEC 256		/* min interval between updates (s) */
  #define MAXSEC 2048		/* max interval between updates (s) */
  #define NTP_PHASE_LIMIT ((MAXPHASE / NSEC_PER_USEC) << 5) /* beyond max. dispersion */
  
  /*

   * kernel variables
   * Note: maximum error = NTP synch distance = dispersion + delay / 2;
   * estimated error = NTP dispersion.
   */
  extern unsigned long tick_usec;		/* USER_HZ period (usec) */
  extern unsigned long tick_nsec;		/* ACTHZ          period (nsec) */

  
  /*
   * phase-lock loop variables
   */

  extern int time_status;		/* clock synchronization status bits */

  extern void ntp_init(void);

  extern void ntp_clear(void);

  
  /**
   * ntp_synced - Returns 1 if the NTP status is not UNSYNC
   *
   */
  static inline int ntp_synced(void)
  {
  	return !(time_status & STA_UNSYNC);
  }

  /* Required to safely shift negative values */
  #define shift_right(x, s) ({	\
  	__typeof__(x) __x = (x);	\
  	__typeof__(s) __s = (s);	\
  	__x < 0 ? -(-__x >> __s) : __x >> __s;	\
  })

  #define NTP_SCALE_SHIFT		32

  #define NTP_INTERVAL_FREQ  (HZ)

  #define NTP_INTERVAL_LENGTH (NSEC_PER_SEC/NTP_INTERVAL_FREQ)

  /* Returns how long ticks are at present, in ns / 2^NTP_SCALE_SHIFT. */
  extern u64 tick_length;

  extern void second_overflow(void);
  extern void update_ntp_one_tick(void);

  extern int do_adjtimex(struct timex *);

  extern void hardpps(const struct timespec *, const struct timespec *);

  int read_current_timer(unsigned long *timer_val);

  /* The clock frequency of the i8253/i8254 PIT */
  #define PIT_TICK_RATE 1193182ul

  #endif /* KERNEL */
  
  #endif /* LINUX_TIMEX_H */