[deliverable/linux.git] / include / linux / jiffies.h

#ifndef _LINUX_JIFFIES_H
#define _LINUX_JIFFIES_H

#include <linux/calc64.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
#else
# error You lose.
#endif

/* LATCH is used in the interval timer and ftape setup. */
#define LATCH  ((CLOCK_TICK_RATE + HZ/2) / HZ)	/* For divider */

/* Suppose we want to devide two numbers NOM and DEN: NOM/DEN, the 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))

/* HZ is the requested value. ACTHZ is actual HZ ("<< 8" is for accuracy) */
#define ACTHZ (SH_DIV (CLOCK_TICK_RATE, LATCH, 8))

/* TICK_NSEC is the time between ticks in nsec assuming real ACTHZ */
#define TICK_NSEC (SH_DIV (1000000UL * 1000, ACTHZ, 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 real ACTHZ and	*/
/* a value TUSEC for TICK_USEC (can be set bij adjtimex)		*/
#define TICK_USEC_TO_NSEC(TUSEC) (SH_DIV (TUSEC * USER_HZ * 1000, ACTHZ, 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)

#define time_in_range(a,b,c) \
	(time_after_eq(a,b) && \
	 time_before_eq(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)

/*
 * 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)

/*
 * 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 used 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 take 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(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);

#define TIMESTAMP_SIZE	30

#endif
Commit	Line	Data
1da177e4 LT	1	#ifndef _LINUX_JIFFIES_H
	2	#define _LINUX_JIFFIES_H
	3
5cca7619	4	#include <linux/calc64.h>
1da177e4 LT	5	#include <linux/kernel.h>
	6	#include <linux/types.h>
	7	#include <linux/time.h>
	8	#include <linux/timex.h>
	9	#include <asm/param.h> /* for HZ */
1da177e4 LT	10
	11	/*
	12	* The following defines establish the engineering parameters of the PLL
	13	* model. The HZ variable establishes the timer interrupt frequency, 100 Hz
	14	* for the SunOS kernel, 256 Hz for the Ultrix kernel and 1024 Hz for the
	15	* OSF/1 kernel. The SHIFT_HZ define expresses the same value as the
	16	* nearest power of two in order to avoid hardware multiply operations.
	17	*/
	18	#if HZ >= 12 && HZ < 24
	19	# define SHIFT_HZ 4
	20	#elif HZ >= 24 && HZ < 48
	21	# define SHIFT_HZ 5
	22	#elif HZ >= 48 && HZ < 96
	23	# define SHIFT_HZ 6
	24	#elif HZ >= 96 && HZ < 192
	25	# define SHIFT_HZ 7
	26	#elif HZ >= 192 && HZ < 384
	27	# define SHIFT_HZ 8
	28	#elif HZ >= 384 && HZ < 768
	29	# define SHIFT_HZ 9
	30	#elif HZ >= 768 && HZ < 1536
	31	# define SHIFT_HZ 10
	32	#else
	33	# error You lose.
	34	#endif
	35
	36	/* LATCH is used in the interval timer and ftape setup. */
	37	#define LATCH ((CLOCK_TICK_RATE + HZ/2) / HZ) /* For divider */
	38
	39	/* Suppose we want to devide two numbers NOM and DEN: NOM/DEN, the we can
	40	* improve accuracy by shifting LSH bits, hence calculating:
	41	* (NOM << LSH) / DEN
	42	* This however means trouble for large NOM, because (NOM << LSH) may no
	43	* longer fit in 32 bits. The following way of calculating this gives us
	44	* some slack, under the following conditions:
	45	* - (NOM / DEN) fits in (32 - LSH) bits.
	46	* - (NOM % DEN) fits in (32 - LSH) bits.
	47	*/
0d94df56 UZ	48	#define SH_DIV(NOM,DEN,LSH) ( (((NOM) / (DEN)) << (LSH)) \
0d94df56 UZ	49	+ ((((NOM) % (DEN)) << (LSH)) + (DEN) / 2) / (DEN))
1da177e4 LT	50
	51	/* HZ is the requested value. ACTHZ is actual HZ ("<< 8" is for accuracy) */
	52	#define ACTHZ (SH_DIV (CLOCK_TICK_RATE, LATCH, 8))
	53
	54	/* TICK_NSEC is the time between ticks in nsec assuming real ACTHZ */
	55	#define TICK_NSEC (SH_DIV (1000000UL * 1000, ACTHZ, 8))
	56
	57	/* TICK_USEC is the time between ticks in usec assuming fake USER_HZ */
	58	#define TICK_USEC ((1000000UL + USER_HZ/2) / USER_HZ)
	59
	60	/* TICK_USEC_TO_NSEC is the time between ticks in nsec assuming real ACTHZ and */
	61	/* a value TUSEC for TICK_USEC (can be set bij adjtimex) */
	62	#define TICK_USEC_TO_NSEC(TUSEC) (SH_DIV (TUSEC * USER_HZ * 1000, ACTHZ, 8))
	63
	64	/* some arch's have a small-data section that can be accessed register-relative
	65	* but that can only take up to, say, 4-byte variables. jiffies being part of
	66	* an 8-byte variable may not be correctly accessed unless we force the issue
	67	*/
	68	#define __jiffy_data __attribute__((section(".data")))
	69
	70	/*
98c4f0c3	71	* The 64-bit value is not atomic - you MUST NOT read it
1da177e4 LT	72	* without sampling the sequence number in xtime_lock.
	73	* get_jiffies_64() will do this for you as appropriate.
	74	*/
	75	extern u64 __jiffy_data jiffies_64;
	76	extern unsigned long volatile __jiffy_data jiffies;
	77
	78	#if (BITS_PER_LONG < 64)
	79	u64 get_jiffies_64(void);
	80	#else
	81	static inline u64 get_jiffies_64(void)
	82	{
	83	return (u64)jiffies;
	84	}
	85	#endif
	86
	87	/*
	88	* These inlines deal with timer wrapping correctly. You are
	89	* strongly encouraged to use them
	90	* 1. Because people otherwise forget
	91	* 2. Because if the timer wrap changes in future you won't have to
	92	* alter your driver code.
	93	*
	94	* time_after(a,b) returns true if the time a is after time b.
	95	*
	96	* Do this with "<0" and ">=0" to only test the sign of the result. A
	97	* good compiler would generate better code (and a really good compiler
	98	* wouldn't care). Gcc is currently neither.
	99	*/
	100	#define time_after(a,b) \
	101	(typecheck(unsigned long, a) && \
	102	typecheck(unsigned long, b) && \
	103	((long)(b) - (long)(a) < 0))
	104	#define time_before(a,b) time_after(b,a)
	105
	106	#define time_after_eq(a,b) \
	107	(typecheck(unsigned long, a) && \
	108	typecheck(unsigned long, b) && \
	109	((long)(a) - (long)(b) >= 0))
	110	#define time_before_eq(a,b) time_after_eq(b,a)
	111
c7e15961 FOL	112	#define time_in_range(a,b,c) \
	113	(time_after_eq(a,b) && \
	114	time_before_eq(a,c))
	115
3b171672 DZ	116	/* Same as above, but does so with platform independent 64bit types.
	117	* These must be used when utilizing jiffies_64 (i.e. return value of
	118	* get_jiffies_64() */
	119	#define time_after64(a,b) \
	120	(typecheck(__u64, a) && \
	121	typecheck(__u64, b) && \
	122	((__s64)(b) - (__s64)(a) < 0))
	123	#define time_before64(a,b) time_after64(b,a)
	124
	125	#define time_after_eq64(a,b) \
	126	(typecheck(__u64, a) && \
	127	typecheck(__u64, b) && \
	128	((__s64)(a) - (__s64)(b) >= 0))
	129	#define time_before_eq64(a,b) time_after_eq64(b,a)
	130
1da177e4 LT	131	/*
	132	* Have the 32 bit jiffies value wrap 5 minutes after boot
	133	* so jiffies wrap bugs show up earlier.
	134	*/
	135	#define INITIAL_JIFFIES ((unsigned long)(unsigned int) (-300*HZ))
	136
	137	/*
	138	* Change timeval to jiffies, trying to avoid the
	139	* most obvious overflows..
	140	*
	141	* And some not so obvious.
	142	*
9f907c01	143	* Note that we don't want to return LONG_MAX, because
1da177e4 LT	144	* for various timeout reasons we often end up having
	145	* to wait "jiffies+1" in order to guarantee that we wait
	146	* at _least_ "jiffies" - so "jiffies+1" had better still
	147	* be positive.
	148	*/
9f907c01	149	#define MAX_JIFFY_OFFSET ((LONG_MAX >> 1)-1)
1da177e4 LT	150
	151	/*
	152	* We want to do realistic conversions of time so we need to use the same
	153	* values the update wall clock code uses as the jiffies size. This value
	154	* is: TICK_NSEC (which is defined in timex.h). This
	155	* is a constant and is in nanoseconds. We will used scaled math
	156	* with a set of scales defined here as SEC_JIFFIE_SC, USEC_JIFFIE_SC and
	157	* NSEC_JIFFIE_SC. Note that these defines contain nothing but
	158	* constants and so are computed at compile time. SHIFT_HZ (computed in
	159	* timex.h) adjusts the scaling for different HZ values.
	160
	161	* Scaled math??? What is that?
	162	*
	163	* Scaled math is a way to do integer math on values that would,
	164	* otherwise, either overflow, underflow, or cause undesired div
	165	* instructions to appear in the execution path. In short, we "scale"
	166	* up the operands so they take more bits (more precision, less
	167	* underflow), do the desired operation and then "scale" the result back
	168	* by the same amount. If we do the scaling by shifting we avoid the
	169	* costly mpy and the dastardly div instructions.
	170
	171	* Suppose, for example, we want to convert from seconds to jiffies
	172	* where jiffies is defined in nanoseconds as NSEC_PER_JIFFIE. The
	173	* simple math is: jiff = (sec * NSEC_PER_SEC) / NSEC_PER_JIFFIE; We
	174	* observe that (NSEC_PER_SEC / NSEC_PER_JIFFIE) is a constant which we
	175	* might calculate at compile time, however, the result will only have
	176	* about 3-4 bits of precision (less for smaller values of HZ).
	177	*
	178	* So, we scale as follows:
	179	* jiff = (sec) * (NSEC_PER_SEC / NSEC_PER_JIFFIE);
	180	* jiff = ((sec) * ((NSEC_PER_SEC * SCALE)/ NSEC_PER_JIFFIE)) / SCALE;
	181	* Then we make SCALE a power of two so:
	182	* jiff = ((sec) * ((NSEC_PER_SEC << SCALE)/ NSEC_PER_JIFFIE)) >> SCALE;
	183	* Now we define:
	184	* #define SEC_CONV = ((NSEC_PER_SEC << SCALE)/ NSEC_PER_JIFFIE))
	185	* jiff = (sec * SEC_CONV) >> SCALE;
	186	*
	187	* Often the math we use will expand beyond 32-bits so we tell C how to
	188	* do this and pass the 64-bit result of the mpy through the ">> SCALE"
	189	* which should take the result back to 32-bits. We want this expansion
	190	* to capture as much precision as possible. At the same time we don't
	191	* want to overflow so we pick the SCALE to avoid this. In this file,
	192	* that means using a different scale for each range of HZ values (as
	193	* defined in timex.h).
	194	*
	195	* For those who want to know, gcc will give a 64-bit result from a "*"
	196	* operator if the result is a long long AND at least one of the
	197	* operands is cast to long long (usually just prior to the "*" so as
	198	* not to confuse it into thinking it really has a 64-bit operand,
	199	* which, buy the way, it can do, but it take more code and at least 2
	200	* mpys).
	201
	202	* We also need to be aware that one second in nanoseconds is only a
	203	* couple of bits away from overflowing a 32-bit word, so we MUST use
	204	* 64-bits to get the full range time in nanoseconds.
	205
	206	*/
	207
	208	/*
	209	* Here are the scales we will use. One for seconds, nanoseconds and
	210	* microseconds.
	211	*
	212	* Within the limits of cpp we do a rough cut at the SEC_JIFFIE_SC and
	213	* check if the sign bit is set. If not, we bump the shift count by 1.
214	* (Gets an extra bit of precision where we can use it.)
215	* We know it is set for HZ = 1024 and HZ = 100 not for 1000.
216	* Haven't tested others.
217
218	* Limits of cpp (for #if expressions) only long (no long long), but
219	* then we only need the most signicant bit.
220	*/
221
222	#define SEC_JIFFIE_SC (31 - SHIFT_HZ)
223	#if !((((NSEC_PER_SEC << 2) / TICK_NSEC) << (SEC_JIFFIE_SC - 2)) & 0x80000000)
224	#undef SEC_JIFFIE_SC
225	#define SEC_JIFFIE_SC (32 - SHIFT_HZ)
226	#endif
227	#define NSEC_JIFFIE_SC (SEC_JIFFIE_SC + 29)
228	#define USEC_JIFFIE_SC (SEC_JIFFIE_SC + 19)
229	#define SEC_CONVERSION ((unsigned long)((((u64)NSEC_PER_SEC << SEC_JIFFIE_SC) +\
230	TICK_NSEC -1) / (u64)TICK_NSEC))
231
232	#define NSEC_CONVERSION ((unsigned long)((((u64)1 << NSEC_JIFFIE_SC) +\
233	TICK_NSEC -1) / (u64)TICK_NSEC))
234	#define USEC_CONVERSION \
235	((unsigned long)((((u64)NSEC_PER_USEC << USEC_JIFFIE_SC) +\
236	TICK_NSEC -1) / (u64)TICK_NSEC))
237	/*
238	* USEC_ROUND is used in the timeval to jiffie conversion. See there
239	* for more details. It is the scaled resolution rounding value. Note
240	* that it is a 64-bit value. Since, when it is applied, we are already
241	* in jiffies (albit scaled), it is nothing but the bits we will shift
242	* off.
243	*/
244	#define USEC_ROUND (u64)(((u64)1 << USEC_JIFFIE_SC) - 1)
245	/*
246	* The maximum jiffie value is (MAX_INT >> 1). Here we translate that
247	* into seconds. The 64-bit case will overflow if we are not careful,
248	* so use the messy SH_DIV macro to do it. Still all constants.
249	*/
250	#if BITS_PER_LONG < 64
251	# define MAX_SEC_IN_JIFFIES \
252	(long)((u64)((u64)MAX_JIFFY_OFFSET * TICK_NSEC) / NSEC_PER_SEC)
253	#else /* take care of overflow on 64 bits machines */
254	# define MAX_SEC_IN_JIFFIES \
255	(SH_DIV((MAX_JIFFY_OFFSET >> SEC_JIFFIE_SC) * TICK_NSEC, NSEC_PER_SEC, 1) - 1)
256
257	#endif
258
259	/*
8b9365d7	260	* Convert various time units to each other:
1da177e4	261	*/
8b9365d7 IM	262	extern unsigned int jiffies_to_msecs(const unsigned long j);
	263	extern unsigned int jiffies_to_usecs(const unsigned long j);
	264	extern unsigned long msecs_to_jiffies(const unsigned int m);
	265	extern unsigned long usecs_to_jiffies(const unsigned int u);
	266	extern unsigned long timespec_to_jiffies(const struct timespec *value);
	267	extern void jiffies_to_timespec(const unsigned long jiffies,
	268	struct timespec *value);
	269	extern unsigned long timeval_to_jiffies(const struct timeval *value);
	270	extern void jiffies_to_timeval(const unsigned long jiffies,
	271	struct timeval *value);
	272	extern clock_t jiffies_to_clock_t(long x);
	273	extern unsigned long clock_t_to_jiffies(unsigned long x);
	274	extern u64 jiffies_64_to_clock_t(u64 x);
	275	extern u64 nsec_to_clock_t(u64 x);
	276
	277	#define TIMESTAMP_SIZE 30
1da177e4 LT	278
1da177e4 LT	279	#endif