include/linux/jiffies.h - kernel/msm-4.9 - Gitiles

 #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);
 static inline clock_t jiffies_delta_to_clock_t(long delta)
 {
 	return jiffies_to_clock_t(max(0L, delta));
 }

 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
	#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);
	static inline clock_t jiffies_delta_to_clock_t(long delta)
	{
	return jiffies_to_clock_t(max(0L, delta));
	}

	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