2005-04-17 06:20:36 +08:00
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/*****************************************************************************
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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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2012-10-13 17:46:48 +08:00
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#include <uapi/linux/timex.h>
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2005-04-17 06:20:36 +08:00
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2008-08-21 07:46:08 +08:00
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#define ADJ_ADJTIME 0x8000 /* switch between adjtime/adjtimex modes */
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#define ADJ_OFFSET_SINGLESHOT 0x0001 /* old-fashioned adjtime */
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#define ADJ_OFFSET_READONLY 0x2000 /* read-only adjtime */
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2008-12-02 06:18:11 +08:00
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#include <linux/compiler.h>
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#include <linux/types.h>
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#include <linux/param.h>
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timekeeping: Add raw clock fallback for random_get_entropy()
The addition of random_get_entropy_fallback() provides access to
whichever time source has the highest frequency, which is useful for
gathering entropy on platforms without available cycle counters. It's
not necessarily as good as being able to quickly access a cycle counter
that the CPU has, but it's still something, even when it falls back to
being jiffies-based.
In the event that a given arch does not define get_cycles(), falling
back to the get_cycles() default implementation that returns 0 is really
not the best we can do. Instead, at least calling
random_get_entropy_fallback() would be preferable, because that always
needs to return _something_, even falling back to jiffies eventually.
It's not as though random_get_entropy_fallback() is super high precision
or guaranteed to be entropic, but basically anything that's not zero all
the time is better than returning zero all the time.
Finally, since random_get_entropy_fallback() is used during extremely
early boot when randomizing freelists in mm_init(), it can be called
before timekeeping has been initialized. In that case there really is
nothing we can do; jiffies hasn't even started ticking yet. So just give
up and return 0.
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Theodore Ts'o <tytso@mit.edu>
2022-04-10 22:49:50 +08:00
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unsigned long random_get_entropy_fallback(void);
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2006-09-13 11:36:03 +08:00
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#include <asm/timex.h>
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2013-09-22 01:58:22 +08:00
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#ifndef random_get_entropy
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/*
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* The random_get_entropy() function is used by the /dev/random driver
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* in order to extract entropy via the relative unpredictability of
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* when an interrupt takes places versus a high speed, fine-grained
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* timing source or cycle counter. Since it will be occurred on every
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* single interrupt, it must have a very low cost/overhead.
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*
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* By default we use get_cycles() for this purpose, but individual
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* architectures may override this in their asm/timex.h header file.
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timekeeping: Add raw clock fallback for random_get_entropy()
The addition of random_get_entropy_fallback() provides access to
whichever time source has the highest frequency, which is useful for
gathering entropy on platforms without available cycle counters. It's
not necessarily as good as being able to quickly access a cycle counter
that the CPU has, but it's still something, even when it falls back to
being jiffies-based.
In the event that a given arch does not define get_cycles(), falling
back to the get_cycles() default implementation that returns 0 is really
not the best we can do. Instead, at least calling
random_get_entropy_fallback() would be preferable, because that always
needs to return _something_, even falling back to jiffies eventually.
It's not as though random_get_entropy_fallback() is super high precision
or guaranteed to be entropic, but basically anything that's not zero all
the time is better than returning zero all the time.
Finally, since random_get_entropy_fallback() is used during extremely
early boot when randomizing freelists in mm_init(), it can be called
before timekeeping has been initialized. In that case there really is
nothing we can do; jiffies hasn't even started ticking yet. So just give
up and return 0.
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Theodore Ts'o <tytso@mit.edu>
2022-04-10 22:49:50 +08:00
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* If a given arch does not have get_cycles(), then we fallback to
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* using random_get_entropy_fallback().
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2013-09-22 01:58:22 +08:00
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*/
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timekeeping: Add raw clock fallback for random_get_entropy()
The addition of random_get_entropy_fallback() provides access to
whichever time source has the highest frequency, which is useful for
gathering entropy on platforms without available cycle counters. It's
not necessarily as good as being able to quickly access a cycle counter
that the CPU has, but it's still something, even when it falls back to
being jiffies-based.
In the event that a given arch does not define get_cycles(), falling
back to the get_cycles() default implementation that returns 0 is really
not the best we can do. Instead, at least calling
random_get_entropy_fallback() would be preferable, because that always
needs to return _something_, even falling back to jiffies eventually.
It's not as though random_get_entropy_fallback() is super high precision
or guaranteed to be entropic, but basically anything that's not zero all
the time is better than returning zero all the time.
Finally, since random_get_entropy_fallback() is used during extremely
early boot when randomizing freelists in mm_init(), it can be called
before timekeeping has been initialized. In that case there really is
nothing we can do; jiffies hasn't even started ticking yet. So just give
up and return 0.
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Theodore Ts'o <tytso@mit.edu>
2022-04-10 22:49:50 +08:00
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#ifdef get_cycles
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2022-04-09 00:14:57 +08:00
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#define random_get_entropy() ((unsigned long)get_cycles())
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timekeeping: Add raw clock fallback for random_get_entropy()
The addition of random_get_entropy_fallback() provides access to
whichever time source has the highest frequency, which is useful for
gathering entropy on platforms without available cycle counters. It's
not necessarily as good as being able to quickly access a cycle counter
that the CPU has, but it's still something, even when it falls back to
being jiffies-based.
In the event that a given arch does not define get_cycles(), falling
back to the get_cycles() default implementation that returns 0 is really
not the best we can do. Instead, at least calling
random_get_entropy_fallback() would be preferable, because that always
needs to return _something_, even falling back to jiffies eventually.
It's not as though random_get_entropy_fallback() is super high precision
or guaranteed to be entropic, but basically anything that's not zero all
the time is better than returning zero all the time.
Finally, since random_get_entropy_fallback() is used during extremely
early boot when randomizing freelists in mm_init(), it can be called
before timekeeping has been initialized. In that case there really is
nothing we can do; jiffies hasn't even started ticking yet. So just give
up and return 0.
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Theodore Ts'o <tytso@mit.edu>
2022-04-10 22:49:50 +08:00
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#else
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#define random_get_entropy() random_get_entropy_fallback()
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#endif
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2013-09-22 01:58:22 +08:00
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#endif
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2008-12-02 06:18:11 +08:00
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/*
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2009-05-06 17:43:57 +08:00
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* SHIFT_PLL is used as a dampening factor to define how much we
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* adjust the frequency correction for a given offset in PLL mode.
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* It also used in dampening the offset correction, to define how
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* much of the current value in time_offset we correct for each
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* second. Changing this value changes the stiffness of the ntp
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* adjustment code. A lower value makes it more flexible, reducing
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* NTP convergence time. A higher value makes it stiffer, increasing
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* convergence time, but making the clock more stable.
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2008-12-02 06:18:11 +08:00
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*
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2009-05-12 09:13:13 +08:00
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* In David Mills' nanokernel reference implementation SHIFT_PLL is 4.
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2009-05-06 17:43:57 +08:00
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* However this seems to increase convergence time much too long.
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*
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* https://lists.ntp.org/pipermail/hackers/2008-January/003487.html
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*
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* In the above mailing list discussion, it seems the value of 4
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* was appropriate for other Unix systems with HZ=100, and that
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* SHIFT_PLL should be decreased as HZ increases. However, Linux's
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* clock steering implementation is HZ independent.
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*
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* Through experimentation, a SHIFT_PLL value of 2 was found to allow
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* for fast convergence (very similar to the NTPv3 code used prior to
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* v2.6.19), with good clock stability.
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*
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*
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* SHIFT_FLL is used as a dampening factor to define how much we
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* adjust the frequency correction for a given offset in FLL mode.
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2009-05-12 09:13:13 +08:00
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* In David Mills' nanokernel reference implementation SHIFT_FLL is 2.
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2009-05-06 17:43:57 +08:00
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*
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* MAXTC establishes the maximum time constant of the PLL.
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2008-12-02 06:18:11 +08:00
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*/
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2009-05-06 17:43:57 +08:00
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#define SHIFT_PLL 2 /* PLL frequency factor (shift) */
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2008-12-02 06:18:11 +08:00
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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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* 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_USEC 16 /* frequency offset scale (shift) */
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2009-02-22 22:48:43 +08:00
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#define PPM_SCALE ((s64)NSEC_PER_USEC << (NTP_SCALE_SHIFT - SHIFT_USEC))
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2008-12-02 06:18:11 +08:00
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#define PPM_SCALE_INV_SHIFT 19
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2009-05-06 17:43:57 +08:00
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#define PPM_SCALE_INV ((1LL << (PPM_SCALE_INV_SHIFT + NTP_SCALE_SHIFT)) / \
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2008-12-02 06:18:11 +08:00
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PPM_SCALE + 1)
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2009-05-06 17:43:57 +08:00
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#define MAXPHASE 500000000L /* max phase error (ns) */
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2008-12-02 06:18:11 +08:00
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#define MAXFREQ 500000 /* max frequency error (ns/s) */
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#define MAXFREQ_SCALED ((s64)MAXFREQ << NTP_SCALE_SHIFT)
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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 / NSEC_PER_USEC) << 5) /* beyond max. dispersion */
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2005-04-17 06:20:36 +08:00
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/*
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* kernel variables
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2021-03-23 05:39:03 +08:00
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* Note: maximum error = NTP sync distance = dispersion + delay / 2;
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2005-04-17 06:20:36 +08:00
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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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2012-07-28 02:48:10 +08:00
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extern unsigned long tick_nsec; /* SHIFTED_HZ period (nsec) */
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2005-04-17 06:20:36 +08:00
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2005-10-31 07:01:42 +08:00
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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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2008-05-01 19:34:38 +08:00
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#define NTP_SCALE_SHIFT 32
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2006-06-26 15:25:18 +08:00
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2007-02-16 17:27:26 +08:00
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#define NTP_INTERVAL_FREQ (HZ)
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time: remove obsolete CLOCK_TICK_ADJUST
The first version of the ntp_interval/tick_length inconsistent usage patch was
recently merged as bbe4d18ac2e058c56adb0cd71f49d9ed3216a405
http://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 commit
e13a2e61dd5152f5499d2003470acf9c838eab84
http://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>
2008-03-05 07:14:26 +08:00
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#define NTP_INTERVAL_LENGTH (NSEC_PER_SEC/NTP_INTERVAL_FREQ)
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2007-02-16 17:27:26 +08:00
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2018-07-03 13:44:21 +08:00
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extern int do_adjtimex(struct __kernel_timex *);
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extern int do_clock_adjtime(const clockid_t which_clock, struct __kernel_timex * ktx);
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2019-01-04 04:12:39 +08:00
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2015-09-29 04:21:28 +08:00
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extern void hardpps(const struct timespec64 *, const struct timespec64 *);
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2006-03-26 17:37:29 +08:00
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2008-02-06 17:36:42 +08:00
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int read_current_timer(unsigned long *timer_val);
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2009-06-17 06:31:12 +08:00
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/* The clock frequency of the i8253/i8254 PIT */
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#define PIT_TICK_RATE 1193182ul
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2005-04-17 06:20:36 +08:00
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#endif /* LINUX_TIMEX_H */
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