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10a398d04c
The first version of the ntp_interval/tick_length inconsistent usage patch was recently merged asbbe4d18ac2http://git.kernel.org/gitweb.cgi?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=bbe4d18ac2e058c56adb0cd71f49d9ed3216a405 While the fix did greatly improve the situation, it was correctly pointed out by Roman that it does have a small bug: If the users change clocksources after the system has been running and NTP has made corrections, the correctoins made against the old clocksource will be applied against the new clocksource, causing error. The second attempt, which corrects the issue in the NTP_INTERVAL_LENGTH definition has also made it up-stream as commite13a2e61ddhttp://git.kernel.org/gitweb.cgi?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=e13a2e61dd5152f5499d2003470acf9c838eab84 Roman has correctly pointed out that CLOCK_TICK_ADJUST is calculated based on the PIT's frequency, and isn't really relevant to non-PIT driven clocksources (that is, clocksources other then jiffies and pit). This patch reverts both of those changes, and simply removes CLOCK_TICK_ADJUST. This does remove the granularity error correction for users of PIT and Jiffies clocksource users, but the granularity error but for the majority of users, it should be within the 500ppm range NTP can accommodate for. For systems that have granularity errors greater then 500ppm, the "ntp_tick_adj=" boot option can be used to compensate. [johnstul@us.ibm.com: provided changelog] [mattilinnanvuori@yahoo.com: maek ntp_tick_adj static] Signed-off-by: Roman Zippel <zippel@linux-m68k.org> Acked-by: john stultz <johnstul@us.ibm.com> Signed-off-by: Matti Linnanvuori <mattilinnanvuori@yahoo.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Cc: mingo@elte.hu Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
252 lines
8.8 KiB
C
252 lines
8.8 KiB
C
/*****************************************************************************
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* *
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* Copyright (c) David L. Mills 1993 *
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* *
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* Permission to use, copy, modify, and distribute this software and its *
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* documentation for any purpose and without fee is hereby granted, provided *
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* that the above copyright notice appears in all copies and that both the *
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* copyright notice and this permission notice appear in supporting *
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* documentation, and that the name University of Delaware not be used in *
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* advertising or publicity pertaining to distribution of the software *
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* without specific, written prior permission. The University of Delaware *
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* makes no representations about the suitability this software for any *
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* purpose. It is provided "as is" without express or implied warranty. *
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* *
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*****************************************************************************/
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/*
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* Modification history timex.h
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*
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* 29 Dec 97 Russell King
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* Moved CLOCK_TICK_RATE, CLOCK_TICK_FACTOR and FINETUNE to asm/timex.h
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* for ARM machines
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*
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* 9 Jan 97 Adrian Sun
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* Shifted LATCH define to allow access to alpha machines.
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*
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* 26 Sep 94 David L. Mills
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* Added defines for hybrid phase/frequency-lock loop.
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*
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* 19 Mar 94 David L. Mills
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* Moved defines from kernel routines to header file and added new
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* defines for PPS phase-lock loop.
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*
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* 20 Feb 94 David L. Mills
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* Revised status codes and structures for external clock and PPS
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* signal discipline.
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*
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* 28 Nov 93 David L. Mills
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* Adjusted parameters to improve stability and increase poll
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* interval.
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*
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* 17 Sep 93 David L. Mills
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* Created file $NTP/include/sys/timex.h
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* 07 Oct 93 Torsten Duwe
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* Derived linux/timex.h
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* 1995-08-13 Torsten Duwe
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* kernel PLL updated to 1994-12-13 specs (rfc-1589)
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* 1997-08-30 Ulrich Windl
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* Added new constant NTP_PHASE_LIMIT
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* 2004-08-12 Christoph Lameter
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* Reworked time interpolation logic
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*/
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#ifndef _LINUX_TIMEX_H
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#define _LINUX_TIMEX_H
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#include <linux/compiler.h>
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#include <linux/time.h>
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#include <asm/param.h>
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/*
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* SHIFT_KG and SHIFT_KF establish the damping of the PLL and are chosen
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* for a slightly underdamped convergence characteristic. SHIFT_KH
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* establishes the damping of the FLL and is chosen by wisdom and black
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* art.
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*
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* MAXTC establishes the maximum time constant of the PLL. With the
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* SHIFT_KG and SHIFT_KF values given and a time constant range from
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* zero to MAXTC, the PLL will converge in 15 minutes to 16 hours,
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* respectively.
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*/
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#define SHIFT_PLL 4 /* PLL frequency factor (shift) */
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#define SHIFT_FLL 2 /* FLL frequency factor (shift) */
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#define MAXTC 10 /* maximum time constant (shift) */
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/*
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* The SHIFT_UPDATE define establishes the decimal point of the
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* time_offset variable which represents the current offset with
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* respect to standard time.
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*
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* SHIFT_USEC defines the scaling (shift) of the time_freq and
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* time_tolerance variables, which represent the current frequency
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* offset and maximum frequency tolerance.
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*/
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#define SHIFT_UPDATE (SHIFT_HZ + 1) /* time offset scale (shift) */
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#define SHIFT_USEC 16 /* frequency offset scale (shift) */
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#define SHIFT_NSEC 12 /* kernel frequency offset scale */
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#define MAXPHASE 512000L /* max phase error (us) */
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#define MAXFREQ (512L << SHIFT_USEC) /* max frequency error (ppm) */
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#define MAXFREQ_NSEC (512000L << SHIFT_NSEC) /* max frequency error (ppb) */
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#define MINSEC 256 /* min interval between updates (s) */
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#define MAXSEC 2048 /* max interval between updates (s) */
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#define NTP_PHASE_LIMIT (MAXPHASE << 5) /* beyond max. dispersion */
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/*
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* syscall interface - used (mainly by NTP daemon)
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* to discipline kernel clock oscillator
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*/
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struct timex {
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unsigned int modes; /* mode selector */
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long offset; /* time offset (usec) */
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long freq; /* frequency offset (scaled ppm) */
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long maxerror; /* maximum error (usec) */
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long esterror; /* estimated error (usec) */
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int status; /* clock command/status */
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long constant; /* pll time constant */
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long precision; /* clock precision (usec) (read only) */
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long tolerance; /* clock frequency tolerance (ppm)
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* (read only)
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*/
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struct timeval time; /* (read only) */
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long tick; /* (modified) usecs between clock ticks */
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long ppsfreq; /* pps frequency (scaled ppm) (ro) */
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long jitter; /* pps jitter (us) (ro) */
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int shift; /* interval duration (s) (shift) (ro) */
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long stabil; /* pps stability (scaled ppm) (ro) */
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long jitcnt; /* jitter limit exceeded (ro) */
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long calcnt; /* calibration intervals (ro) */
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long errcnt; /* calibration errors (ro) */
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long stbcnt; /* stability limit exceeded (ro) */
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int :32; int :32; int :32; int :32;
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int :32; int :32; int :32; int :32;
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int :32; int :32; int :32; int :32;
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};
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/*
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* Mode codes (timex.mode)
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*/
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#define ADJ_OFFSET 0x0001 /* time offset */
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#define ADJ_FREQUENCY 0x0002 /* frequency offset */
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#define ADJ_MAXERROR 0x0004 /* maximum time error */
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#define ADJ_ESTERROR 0x0008 /* estimated time error */
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#define ADJ_STATUS 0x0010 /* clock status */
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#define ADJ_TIMECONST 0x0020 /* pll time constant */
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#define ADJ_TICK 0x4000 /* tick value */
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#define ADJ_OFFSET_SINGLESHOT 0x8001 /* old-fashioned adjtime */
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#define ADJ_OFFSET_SS_READ 0xa001 /* read-only adjtime */
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/* xntp 3.4 compatibility names */
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#define MOD_OFFSET ADJ_OFFSET
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#define MOD_FREQUENCY ADJ_FREQUENCY
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#define MOD_MAXERROR ADJ_MAXERROR
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#define MOD_ESTERROR ADJ_ESTERROR
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#define MOD_STATUS ADJ_STATUS
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#define MOD_TIMECONST ADJ_TIMECONST
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#define MOD_CLKB ADJ_TICK
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#define MOD_CLKA ADJ_OFFSET_SINGLESHOT /* 0x8000 in original */
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/*
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* Status codes (timex.status)
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*/
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#define STA_PLL 0x0001 /* enable PLL updates (rw) */
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#define STA_PPSFREQ 0x0002 /* enable PPS freq discipline (rw) */
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#define STA_PPSTIME 0x0004 /* enable PPS time discipline (rw) */
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#define STA_FLL 0x0008 /* select frequency-lock mode (rw) */
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#define STA_INS 0x0010 /* insert leap (rw) */
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#define STA_DEL 0x0020 /* delete leap (rw) */
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#define STA_UNSYNC 0x0040 /* clock unsynchronized (rw) */
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#define STA_FREQHOLD 0x0080 /* hold frequency (rw) */
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#define STA_PPSSIGNAL 0x0100 /* PPS signal present (ro) */
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#define STA_PPSJITTER 0x0200 /* PPS signal jitter exceeded (ro) */
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#define STA_PPSWANDER 0x0400 /* PPS signal wander exceeded (ro) */
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#define STA_PPSERROR 0x0800 /* PPS signal calibration error (ro) */
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#define STA_CLOCKERR 0x1000 /* clock hardware fault (ro) */
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#define STA_RONLY (STA_PPSSIGNAL | STA_PPSJITTER | STA_PPSWANDER | \
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STA_PPSERROR | STA_CLOCKERR) /* read-only bits */
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/*
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* Clock states (time_state)
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*/
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#define TIME_OK 0 /* clock synchronized, no leap second */
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#define TIME_INS 1 /* insert leap second */
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#define TIME_DEL 2 /* delete leap second */
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#define TIME_OOP 3 /* leap second in progress */
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#define TIME_WAIT 4 /* leap second has occurred */
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#define TIME_ERROR 5 /* clock not synchronized */
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#define TIME_BAD TIME_ERROR /* bw compat */
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#ifdef __KERNEL__
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#include <asm/timex.h>
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/*
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* kernel variables
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* Note: maximum error = NTP synch distance = dispersion + delay / 2;
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* estimated error = NTP dispersion.
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*/
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extern unsigned long tick_usec; /* USER_HZ period (usec) */
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extern unsigned long tick_nsec; /* ACTHZ period (nsec) */
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extern int tickadj; /* amount of adjustment per tick */
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/*
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* phase-lock loop variables
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*/
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extern int time_status; /* clock synchronization status bits */
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extern long time_maxerror; /* maximum error */
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extern long time_esterror; /* estimated error */
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extern long time_freq; /* frequency offset (scaled ppm) */
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extern long time_adjust; /* The amount of adjtime left */
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extern void ntp_clear(void);
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/**
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* ntp_synced - Returns 1 if the NTP status is not UNSYNC
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*
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*/
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static inline int ntp_synced(void)
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{
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return !(time_status & STA_UNSYNC);
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}
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/* Required to safely shift negative values */
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#define shift_right(x, s) ({ \
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__typeof__(x) __x = (x); \
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__typeof__(s) __s = (s); \
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__x < 0 ? -(-__x >> __s) : __x >> __s; \
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})
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#define TICK_LENGTH_SHIFT 32
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#ifdef CONFIG_NO_HZ
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#define NTP_INTERVAL_FREQ (2)
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#else
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#define NTP_INTERVAL_FREQ (HZ)
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#endif
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#define NTP_INTERVAL_LENGTH (NSEC_PER_SEC/NTP_INTERVAL_FREQ)
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/* Returns how long ticks are at present, in ns / 2^(SHIFT_SCALE-10). */
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extern u64 current_tick_length(void);
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extern void second_overflow(void);
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extern void update_ntp_one_tick(void);
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extern int do_adjtimex(struct timex *);
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/* Don't use! Compatibility define for existing users. */
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#define tickadj (500/HZ ? : 1)
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int read_current_timer(unsigned long *timer_val);
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#endif /* KERNEL */
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#endif /* LINUX_TIMEX_H */
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