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linux-next/include/linux/timex.h
john stultz 1bb34a4127 [PATCH] NTP shift_right cleanup 
Create a macro shift_right() that avoids the numerous ugly conditionals in the
NTP code that look like:

        if(a < 0)
                b = -(-a >> shift);
        else
                b = a >> shift;

Replacing it with:

        b = shift_right(a, shift);

This should have zero effect on the logic, however it should probably have
a bit of testing just to be sure.

Also replace open-coded min/max with the macros.

Signed-off-by : John Stultz <johnstul@us.ibm.com>

Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-10-30 17:37:18 -08:00

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/*****************************************************************************
* *
* 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/config.h>
#include <linux/compiler.h>
#include <linux/time.h>
#include <asm/param.h>
#include <asm/timex.h>
/*
* SHIFT_KG and SHIFT_KF establish the damping of the PLL and are chosen
* for a slightly underdamped convergence characteristic. SHIFT_KH
* establishes the damping of the FLL and is chosen by wisdom and black
* art.
*
* MAXTC establishes the maximum time constant of the PLL. With the
* SHIFT_KG and SHIFT_KF values given and a time constant range from
* zero to MAXTC, the PLL will converge in 15 minutes to 16 hours,
* respectively.
*/
#define SHIFT_KG 6 /* phase factor (shift) */
#define SHIFT_KF 16 /* PLL frequency factor (shift) */
#define SHIFT_KH 2 /* FLL frequency factor (shift) */
#define MAXTC 6 /* maximum time constant (shift) */
/*
* The SHIFT_SCALE define establishes the decimal point of the time_phase
* variable which serves as an extension to the low-order bits of the
* system clock variable. The SHIFT_UPDATE define establishes the decimal
* point of the time_offset variable which represents the current offset
* with respect to standard time. The FINENSEC define represents 1 nsec in
* scaled units.
*
* SHIFT_USEC defines the scaling (shift) of the time_freq and
* time_tolerance variables, which represent the current frequency
* offset and maximum frequency tolerance.
*
* FINENSEC is 1 ns in SHIFT_UPDATE units of the time_phase variable.
*/
#define SHIFT_SCALE 22 /* phase scale (shift) */
#define SHIFT_UPDATE (SHIFT_KG + MAXTC) /* time offset scale (shift) */
#define SHIFT_USEC 16 /* frequency offset scale (shift) */
#define FINENSEC (1L << (SHIFT_SCALE - 10)) /* ~1 ns in phase units */
#define MAXPHASE 512000L /* max phase error (us) */
#define MAXFREQ (512L << SHIFT_USEC) /* max frequency error (ppm) */
#define MAXTIME (200L << PPS_AVG) /* max PPS error (jitter) (200 us) */
#define MINSEC 16L /* min interval between updates (s) */
#define MAXSEC 1200L /* max interval between updates (s) */
#define NTP_PHASE_LIMIT (MAXPHASE << 5) /* beyond max. dispersion */
/*
* The following defines are used only if a pulse-per-second (PPS)
* signal is available and connected via a modem control lead, such as
* produced by the optional ppsclock feature incorporated in the Sun
* asynch driver. They establish the design parameters of the frequency-
* lock loop used to discipline the CPU clock oscillator to the PPS
* signal.
*
* PPS_AVG is the averaging factor for the frequency loop, as well as
* the time and frequency dispersion.
*
* PPS_SHIFT and PPS_SHIFTMAX specify the minimum and maximum
* calibration intervals, respectively, in seconds as a power of two.
*
* PPS_VALID is the maximum interval before the PPS signal is considered
* invalid and protocol updates used directly instead.
*
* MAXGLITCH is the maximum interval before a time offset of more than
* MAXTIME is believed.
*/
#define PPS_AVG 2 /* pps averaging constant (shift) */
#define PPS_SHIFT 2 /* min interval duration (s) (shift) */
#define PPS_SHIFTMAX 8 /* max interval duration (s) (shift) */
#define PPS_VALID 120 /* pps signal watchdog max (s) */
#define MAXGLITCH 30 /* pps signal glitch max (s) */
/*
* 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 :32; 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_TICK 0x4000 /* tick value */
#define ADJ_OFFSET_SINGLESHOT 0x8001 /* old-fashioned adjtime */
/* xntp 3.4 compatibility names */
#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_CLKB ADJ_TICK
#define MOD_CLKA ADJ_OFFSET_SINGLESHOT /* 0x8000 in original */
/*
* 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_RONLY (STA_PPSSIGNAL | STA_PPSJITTER | STA_PPSWANDER | \
STA_PPSERROR | STA_CLOCKERR) /* read-only bits */
/*
* 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__
/*
* 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) */
extern int tickadj; /* amount of adjustment per tick */
/*
* phase-lock loop variables
*/
extern int time_state; /* clock status */
extern int time_status; /* clock synchronization status bits */
extern long time_offset; /* time adjustment (us) */
extern long time_constant; /* pll time constant */
extern long time_tolerance; /* frequency tolerance (ppm) */
extern long time_precision; /* clock precision (us) */
extern long time_maxerror; /* maximum error */
extern long time_esterror; /* estimated error */
extern long time_freq; /* frequency offset (scaled ppm) */
extern long time_reftime; /* time at last adjustment (s) */
extern long time_adjust; /* The amount of adjtime left */
extern long time_next_adjust; /* Value for time_adjust at next tick */
/* interface variables pps->timer interrupt */
extern long pps_offset; /* pps time offset (us) */
extern long pps_jitter; /* time dispersion (jitter) (us) */
extern long pps_freq; /* frequency offset (scaled ppm) */
extern long pps_stabil; /* frequency dispersion (scaled ppm) */
extern long pps_valid; /* pps signal watchdog counter */
/* interface variables pps->adjtimex */
extern int pps_shift; /* interval duration (s) (shift) */
extern long pps_jitcnt; /* jitter limit exceeded */
extern long pps_calcnt; /* calibration intervals */
extern long pps_errcnt; /* calibration errors */
extern long pps_stbcnt; /* stability limit exceeded */
/**
* ntp_clear - Clears the NTP state variables
*
* Must be called while holding a write on the xtime_lock
*/
static inline void ntp_clear(void)
{
time_adjust = 0; /* stop active adjtime() */
time_status |= STA_UNSYNC;
time_maxerror = NTP_PHASE_LIMIT;
time_esterror = NTP_PHASE_LIMIT;
}
/**
* 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; \
})
#ifdef CONFIG_TIME_INTERPOLATION
#define TIME_SOURCE_CPU 0
#define TIME_SOURCE_MMIO64 1
#define TIME_SOURCE_MMIO32 2
#define TIME_SOURCE_FUNCTION 3
/* For proper operations time_interpolator clocks must run slightly slower
* than the standard clock since the interpolator may only correct by having
* time jump forward during a tick. A slower clock is usually a side effect
* of the integer divide of the nanoseconds in a second by the frequency.
* The accuracy of the division can be increased by specifying a shift.
* However, this may cause the clock not to be slow enough.
* The interpolator will self-tune the clock by slowing down if no
* resets occur or speeding up if the time jumps per analysis cycle
* become too high.
*
* Setting jitter compensates for a fluctuating timesource by comparing
* to the last value read from the timesource to insure that an earlier value
* is not returned by a later call. The price to pay
* for the compensation is that the timer routines are not as scalable anymore.
*/
struct time_interpolator {
u16 source; /* time source flags */
u8 shift; /* increases accuracy of multiply by shifting. */
/* Note that bits may be lost if shift is set too high */
u8 jitter; /* if set compensate for fluctuations */
u32 nsec_per_cyc; /* set by register_time_interpolator() */
void *addr; /* address of counter or function */
u64 mask; /* mask the valid bits of the counter */
unsigned long offset; /* nsec offset at last update of interpolator */
u64 last_counter; /* counter value in units of the counter at last update */
u64 last_cycle; /* Last timer value if TIME_SOURCE_JITTER is set */
u64 frequency; /* frequency in counts/second */
long drift; /* drift in parts-per-million (or -1) */
unsigned long skips; /* skips forward */
unsigned long ns_skipped; /* nanoseconds skipped */
struct time_interpolator *next;
};
extern void register_time_interpolator(struct time_interpolator *);
extern void unregister_time_interpolator(struct time_interpolator *);
extern void time_interpolator_reset(void);
extern unsigned long time_interpolator_get_offset(void);
#else /* !CONFIG_TIME_INTERPOLATION */
static inline void
time_interpolator_reset(void)
{
}
#endif /* !CONFIG_TIME_INTERPOLATION */
#endif /* KERNEL */
#endif /* LINUX_TIMEX_H */
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