325 lines
12 KiB
C
325 lines
12 KiB
C
#ifndef _LINUX_JIFFIES_H
|
|
#define _LINUX_JIFFIES_H
|
|
|
|
#include <linux/math64.h>
|
|
#include <linux/kernel.h>
|
|
#include <linux/types.h>
|
|
#include <linux/time.h>
|
|
#include <linux/timex.h>
|
|
#include <asm/param.h> /* for HZ */
|
|
|
|
/*
|
|
* The following defines establish the engineering parameters of the PLL
|
|
* model. The HZ variable establishes the timer interrupt frequency, 100 Hz
|
|
* for the SunOS kernel, 256 Hz for the Ultrix kernel and 1024 Hz for the
|
|
* OSF/1 kernel. The SHIFT_HZ define expresses the same value as the
|
|
* nearest power of two in order to avoid hardware multiply operations.
|
|
*/
|
|
#if HZ >= 12 && HZ < 24
|
|
# define SHIFT_HZ 4
|
|
#elif HZ >= 24 && HZ < 48
|
|
# define SHIFT_HZ 5
|
|
#elif HZ >= 48 && HZ < 96
|
|
# define SHIFT_HZ 6
|
|
#elif HZ >= 96 && HZ < 192
|
|
# define SHIFT_HZ 7
|
|
#elif HZ >= 192 && HZ < 384
|
|
# define SHIFT_HZ 8
|
|
#elif HZ >= 384 && HZ < 768
|
|
# define SHIFT_HZ 9
|
|
#elif HZ >= 768 && HZ < 1536
|
|
# define SHIFT_HZ 10
|
|
#elif HZ >= 1536 && HZ < 3072
|
|
# define SHIFT_HZ 11
|
|
#elif HZ >= 3072 && HZ < 6144
|
|
# define SHIFT_HZ 12
|
|
#elif HZ >= 6144 && HZ < 12288
|
|
# define SHIFT_HZ 13
|
|
#else
|
|
# error Invalid value of HZ.
|
|
#endif
|
|
|
|
/* Suppose we want to divide two numbers NOM and DEN: NOM/DEN, then we can
|
|
* improve accuracy by shifting LSH bits, hence calculating:
|
|
* (NOM << LSH) / DEN
|
|
* This however means trouble for large NOM, because (NOM << LSH) may no
|
|
* longer fit in 32 bits. The following way of calculating this gives us
|
|
* some slack, under the following conditions:
|
|
* - (NOM / DEN) fits in (32 - LSH) bits.
|
|
* - (NOM % DEN) fits in (32 - LSH) bits.
|
|
*/
|
|
#define SH_DIV(NOM,DEN,LSH) ( (((NOM) / (DEN)) << (LSH)) \
|
|
+ ((((NOM) % (DEN)) << (LSH)) + (DEN) / 2) / (DEN))
|
|
|
|
#ifdef CLOCK_TICK_RATE
|
|
/* LATCH is used in the interval timer and ftape setup. */
|
|
# define LATCH ((CLOCK_TICK_RATE + HZ/2) / HZ) /* For divider */
|
|
|
|
/*
|
|
* HZ is the requested value. However the CLOCK_TICK_RATE may not allow
|
|
* for exactly HZ. So SHIFTED_HZ is high res HZ ("<< 8" is for accuracy)
|
|
*/
|
|
# define SHIFTED_HZ (SH_DIV(CLOCK_TICK_RATE, LATCH, 8))
|
|
#else
|
|
# define SHIFTED_HZ (HZ << 8)
|
|
#endif
|
|
|
|
/* TICK_NSEC is the time between ticks in nsec assuming SHIFTED_HZ */
|
|
#define TICK_NSEC (SH_DIV(1000000UL * 1000, SHIFTED_HZ, 8))
|
|
|
|
/* TICK_USEC is the time between ticks in usec assuming fake USER_HZ */
|
|
#define TICK_USEC ((1000000UL + USER_HZ/2) / USER_HZ)
|
|
|
|
/*
|
|
* TICK_USEC_TO_NSEC is the time between ticks in nsec assuming SHIFTED_HZ and
|
|
* a value TUSEC for TICK_USEC (can be set bij adjtimex)
|
|
*/
|
|
#define TICK_USEC_TO_NSEC(TUSEC) (SH_DIV(TUSEC * USER_HZ * 1000, SHIFTED_HZ, 8))
|
|
|
|
/* some arch's have a small-data section that can be accessed register-relative
|
|
* but that can only take up to, say, 4-byte variables. jiffies being part of
|
|
* an 8-byte variable may not be correctly accessed unless we force the issue
|
|
*/
|
|
#define __jiffy_data __attribute__((section(".data")))
|
|
|
|
/*
|
|
* The 64-bit value is not atomic - you MUST NOT read it
|
|
* without sampling the sequence number in xtime_lock.
|
|
* get_jiffies_64() will do this for you as appropriate.
|
|
*/
|
|
extern u64 __jiffy_data jiffies_64;
|
|
extern unsigned long volatile __jiffy_data jiffies;
|
|
|
|
#if (BITS_PER_LONG < 64)
|
|
u64 get_jiffies_64(void);
|
|
#else
|
|
static inline u64 get_jiffies_64(void)
|
|
{
|
|
return (u64)jiffies;
|
|
}
|
|
#endif
|
|
|
|
/*
|
|
* These inlines deal with timer wrapping correctly. You are
|
|
* strongly encouraged to use them
|
|
* 1. Because people otherwise forget
|
|
* 2. Because if the timer wrap changes in future you won't have to
|
|
* alter your driver code.
|
|
*
|
|
* time_after(a,b) returns true if the time a is after time b.
|
|
*
|
|
* Do this with "<0" and ">=0" to only test the sign of the result. A
|
|
* good compiler would generate better code (and a really good compiler
|
|
* wouldn't care). Gcc is currently neither.
|
|
*/
|
|
#define time_after(a,b) \
|
|
(typecheck(unsigned long, a) && \
|
|
typecheck(unsigned long, b) && \
|
|
((long)(b) - (long)(a) < 0))
|
|
#define time_before(a,b) time_after(b,a)
|
|
|
|
#define time_after_eq(a,b) \
|
|
(typecheck(unsigned long, a) && \
|
|
typecheck(unsigned long, b) && \
|
|
((long)(a) - (long)(b) >= 0))
|
|
#define time_before_eq(a,b) time_after_eq(b,a)
|
|
|
|
/*
|
|
* Calculate whether a is in the range of [b, c].
|
|
*/
|
|
#define time_in_range(a,b,c) \
|
|
(time_after_eq(a,b) && \
|
|
time_before_eq(a,c))
|
|
|
|
/*
|
|
* Calculate whether a is in the range of [b, c).
|
|
*/
|
|
#define time_in_range_open(a,b,c) \
|
|
(time_after_eq(a,b) && \
|
|
time_before(a,c))
|
|
|
|
/* Same as above, but does so with platform independent 64bit types.
|
|
* These must be used when utilizing jiffies_64 (i.e. return value of
|
|
* get_jiffies_64() */
|
|
#define time_after64(a,b) \
|
|
(typecheck(__u64, a) && \
|
|
typecheck(__u64, b) && \
|
|
((__s64)(b) - (__s64)(a) < 0))
|
|
#define time_before64(a,b) time_after64(b,a)
|
|
|
|
#define time_after_eq64(a,b) \
|
|
(typecheck(__u64, a) && \
|
|
typecheck(__u64, b) && \
|
|
((__s64)(a) - (__s64)(b) >= 0))
|
|
#define time_before_eq64(a,b) time_after_eq64(b,a)
|
|
|
|
/*
|
|
* These four macros compare jiffies and 'a' for convenience.
|
|
*/
|
|
|
|
/* time_is_before_jiffies(a) return true if a is before jiffies */
|
|
#define time_is_before_jiffies(a) time_after(jiffies, a)
|
|
|
|
/* time_is_after_jiffies(a) return true if a is after jiffies */
|
|
#define time_is_after_jiffies(a) time_before(jiffies, a)
|
|
|
|
/* time_is_before_eq_jiffies(a) return true if a is before or equal to jiffies*/
|
|
#define time_is_before_eq_jiffies(a) time_after_eq(jiffies, a)
|
|
|
|
/* time_is_after_eq_jiffies(a) return true if a is after or equal to jiffies*/
|
|
#define time_is_after_eq_jiffies(a) time_before_eq(jiffies, a)
|
|
|
|
/*
|
|
* Have the 32 bit jiffies value wrap 5 minutes after boot
|
|
* so jiffies wrap bugs show up earlier.
|
|
*/
|
|
#define INITIAL_JIFFIES ((unsigned long)(unsigned int) (-300*HZ))
|
|
|
|
/*
|
|
* Change timeval to jiffies, trying to avoid the
|
|
* most obvious overflows..
|
|
*
|
|
* And some not so obvious.
|
|
*
|
|
* Note that we don't want to return LONG_MAX, because
|
|
* for various timeout reasons we often end up having
|
|
* to wait "jiffies+1" in order to guarantee that we wait
|
|
* at _least_ "jiffies" - so "jiffies+1" had better still
|
|
* be positive.
|
|
*/
|
|
#define MAX_JIFFY_OFFSET ((LONG_MAX >> 1)-1)
|
|
|
|
extern unsigned long preset_lpj;
|
|
|
|
/*
|
|
* We want to do realistic conversions of time so we need to use the same
|
|
* values the update wall clock code uses as the jiffies size. This value
|
|
* is: TICK_NSEC (which is defined in timex.h). This
|
|
* is a constant and is in nanoseconds. We will use scaled math
|
|
* with a set of scales defined here as SEC_JIFFIE_SC, USEC_JIFFIE_SC and
|
|
* NSEC_JIFFIE_SC. Note that these defines contain nothing but
|
|
* constants and so are computed at compile time. SHIFT_HZ (computed in
|
|
* timex.h) adjusts the scaling for different HZ values.
|
|
|
|
* Scaled math??? What is that?
|
|
*
|
|
* Scaled math is a way to do integer math on values that would,
|
|
* otherwise, either overflow, underflow, or cause undesired div
|
|
* instructions to appear in the execution path. In short, we "scale"
|
|
* up the operands so they take more bits (more precision, less
|
|
* underflow), do the desired operation and then "scale" the result back
|
|
* by the same amount. If we do the scaling by shifting we avoid the
|
|
* costly mpy and the dastardly div instructions.
|
|
|
|
* Suppose, for example, we want to convert from seconds to jiffies
|
|
* where jiffies is defined in nanoseconds as NSEC_PER_JIFFIE. The
|
|
* simple math is: jiff = (sec * NSEC_PER_SEC) / NSEC_PER_JIFFIE; We
|
|
* observe that (NSEC_PER_SEC / NSEC_PER_JIFFIE) is a constant which we
|
|
* might calculate at compile time, however, the result will only have
|
|
* about 3-4 bits of precision (less for smaller values of HZ).
|
|
*
|
|
* So, we scale as follows:
|
|
* jiff = (sec) * (NSEC_PER_SEC / NSEC_PER_JIFFIE);
|
|
* jiff = ((sec) * ((NSEC_PER_SEC * SCALE)/ NSEC_PER_JIFFIE)) / SCALE;
|
|
* Then we make SCALE a power of two so:
|
|
* jiff = ((sec) * ((NSEC_PER_SEC << SCALE)/ NSEC_PER_JIFFIE)) >> SCALE;
|
|
* Now we define:
|
|
* #define SEC_CONV = ((NSEC_PER_SEC << SCALE)/ NSEC_PER_JIFFIE))
|
|
* jiff = (sec * SEC_CONV) >> SCALE;
|
|
*
|
|
* Often the math we use will expand beyond 32-bits so we tell C how to
|
|
* do this and pass the 64-bit result of the mpy through the ">> SCALE"
|
|
* which should take the result back to 32-bits. We want this expansion
|
|
* to capture as much precision as possible. At the same time we don't
|
|
* want to overflow so we pick the SCALE to avoid this. In this file,
|
|
* that means using a different scale for each range of HZ values (as
|
|
* defined in timex.h).
|
|
*
|
|
* For those who want to know, gcc will give a 64-bit result from a "*"
|
|
* operator if the result is a long long AND at least one of the
|
|
* operands is cast to long long (usually just prior to the "*" so as
|
|
* not to confuse it into thinking it really has a 64-bit operand,
|
|
* which, buy the way, it can do, but it takes more code and at least 2
|
|
* mpys).
|
|
|
|
* We also need to be aware that one second in nanoseconds is only a
|
|
* couple of bits away from overflowing a 32-bit word, so we MUST use
|
|
* 64-bits to get the full range time in nanoseconds.
|
|
|
|
*/
|
|
|
|
/*
|
|
* Here are the scales we will use. One for seconds, nanoseconds and
|
|
* microseconds.
|
|
*
|
|
* Within the limits of cpp we do a rough cut at the SEC_JIFFIE_SC and
|
|
* check if the sign bit is set. If not, we bump the shift count by 1.
|
|
* (Gets an extra bit of precision where we can use it.)
|
|
* We know it is set for HZ = 1024 and HZ = 100 not for 1000.
|
|
* Haven't tested others.
|
|
|
|
* Limits of cpp (for #if expressions) only long (no long long), but
|
|
* then we only need the most signicant bit.
|
|
*/
|
|
|
|
#define SEC_JIFFIE_SC (31 - SHIFT_HZ)
|
|
#if !((((NSEC_PER_SEC << 2) / TICK_NSEC) << (SEC_JIFFIE_SC - 2)) & 0x80000000)
|
|
#undef SEC_JIFFIE_SC
|
|
#define SEC_JIFFIE_SC (32 - SHIFT_HZ)
|
|
#endif
|
|
#define NSEC_JIFFIE_SC (SEC_JIFFIE_SC + 29)
|
|
#define USEC_JIFFIE_SC (SEC_JIFFIE_SC + 19)
|
|
#define SEC_CONVERSION ((unsigned long)((((u64)NSEC_PER_SEC << SEC_JIFFIE_SC) +\
|
|
TICK_NSEC -1) / (u64)TICK_NSEC))
|
|
|
|
#define NSEC_CONVERSION ((unsigned long)((((u64)1 << NSEC_JIFFIE_SC) +\
|
|
TICK_NSEC -1) / (u64)TICK_NSEC))
|
|
#define USEC_CONVERSION \
|
|
((unsigned long)((((u64)NSEC_PER_USEC << USEC_JIFFIE_SC) +\
|
|
TICK_NSEC -1) / (u64)TICK_NSEC))
|
|
/*
|
|
* USEC_ROUND is used in the timeval to jiffie conversion. See there
|
|
* for more details. It is the scaled resolution rounding value. Note
|
|
* that it is a 64-bit value. Since, when it is applied, we are already
|
|
* in jiffies (albit scaled), it is nothing but the bits we will shift
|
|
* off.
|
|
*/
|
|
#define USEC_ROUND (u64)(((u64)1 << USEC_JIFFIE_SC) - 1)
|
|
/*
|
|
* The maximum jiffie value is (MAX_INT >> 1). Here we translate that
|
|
* into seconds. The 64-bit case will overflow if we are not careful,
|
|
* so use the messy SH_DIV macro to do it. Still all constants.
|
|
*/
|
|
#if BITS_PER_LONG < 64
|
|
# define MAX_SEC_IN_JIFFIES \
|
|
(long)((u64)((u64)MAX_JIFFY_OFFSET * TICK_NSEC) / NSEC_PER_SEC)
|
|
#else /* take care of overflow on 64 bits machines */
|
|
# define MAX_SEC_IN_JIFFIES \
|
|
(SH_DIV((MAX_JIFFY_OFFSET >> SEC_JIFFIE_SC) * TICK_NSEC, NSEC_PER_SEC, 1) - 1)
|
|
|
|
#endif
|
|
|
|
/*
|
|
* Convert various time units to each other:
|
|
*/
|
|
extern unsigned int jiffies_to_msecs(const unsigned long j);
|
|
extern unsigned int jiffies_to_usecs(const unsigned long j);
|
|
extern unsigned long msecs_to_jiffies(const unsigned int m);
|
|
extern unsigned long usecs_to_jiffies(const unsigned int u);
|
|
extern unsigned long timespec_to_jiffies(const struct timespec *value);
|
|
extern void jiffies_to_timespec(const unsigned long jiffies,
|
|
struct timespec *value);
|
|
extern unsigned long timeval_to_jiffies(const struct timeval *value);
|
|
extern void jiffies_to_timeval(const unsigned long jiffies,
|
|
struct timeval *value);
|
|
extern clock_t jiffies_to_clock_t(unsigned long x);
|
|
extern unsigned long clock_t_to_jiffies(unsigned long x);
|
|
extern u64 jiffies_64_to_clock_t(u64 x);
|
|
extern u64 nsec_to_clock_t(u64 x);
|
|
extern u64 nsecs_to_jiffies64(u64 n);
|
|
extern unsigned long nsecs_to_jiffies(u64 n);
|
|
|
|
#define TIMESTAMP_SIZE 30
|
|
|
|
#endif
|