| /***************************************************************************** |
| * * |
| * 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 <uapi/linux/timex.h> |
| |
| #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 */ |
| #include <linux/compiler.h> |
| #include <linux/types.h> |
| #include <linux/param.h> |
| |
| #include <asm/timex.h> |
| |
| #ifndef random_get_entropy |
| /* |
| * The random_get_entropy() function is used by the /dev/random driver |
| * in order to extract entropy via the relative unpredictability of |
| * when an interrupt takes places versus a high speed, fine-grained |
| * timing source or cycle counter. Since it will be occurred on every |
| * single interrupt, it must have a very low cost/overhead. |
| * |
| * By default we use get_cycles() for this purpose, but individual |
| * architectures may override this in their asm/timex.h header file. |
| */ |
| #define random_get_entropy() get_cycles() |
| #endif |
| |
| /* |
| * 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; /* SHIFTED_HZ period (nsec) */ |
| |
| /* 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) |
| |
| extern int do_adjtimex(struct __kernel_timex *); |
| extern int do_clock_adjtime(const clockid_t which_clock, struct __kernel_timex * ktx); |
| |
| extern void hardpps(const struct timespec64 *, const struct timespec64 *); |
| |
| int read_current_timer(unsigned long *timer_val); |
| |
| /* The clock frequency of the i8253/i8254 PIT */ |
| #define PIT_TICK_RATE 1193182ul |
| |
| #endif /* LINUX_TIMEX_H */ |