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Linus Torvalds1da177e2005-04-16 15:20:36 -07001#ifndef _LINUX_JIFFIES_H
2#define _LINUX_JIFFIES_H
3
Roman Zippelf8bd2252008-05-01 04:34:31 -07004#include <linux/math64.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -07005#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 */
Linus Torvalds1da177e2005-04-16 15:20:36 -070010
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
Pavel Macheke118ade2008-01-25 21:08:34 +010032#elif HZ >= 1536 && HZ < 3072
33# define SHIFT_HZ 11
34#elif HZ >= 3072 && HZ < 6144
35# define SHIFT_HZ 12
36#elif HZ >= 6144 && HZ < 12288
37# define SHIFT_HZ 13
Linus Torvalds1da177e2005-04-16 15:20:36 -070038#else
Robert P. J. Day37679012008-04-21 22:56:14 +000039# error Invalid value of HZ.
Linus Torvalds1da177e2005-04-16 15:20:36 -070040#endif
41
Lucas De Marchi25985ed2011-03-30 22:57:33 -030042/* Suppose we want to divide two numbers NOM and DEN: NOM/DEN, then we can
Linus Torvalds1da177e2005-04-16 15:20:36 -070043 * improve accuracy by shifting LSH bits, hence calculating:
44 * (NOM << LSH) / DEN
45 * This however means trouble for large NOM, because (NOM << LSH) may no
46 * longer fit in 32 bits. The following way of calculating this gives us
47 * some slack, under the following conditions:
48 * - (NOM / DEN) fits in (32 - LSH) bits.
49 * - (NOM % DEN) fits in (32 - LSH) bits.
50 */
Uwe Zeisberger0d94df52006-07-30 03:04:02 -070051#define SH_DIV(NOM,DEN,LSH) ( (((NOM) / (DEN)) << (LSH)) \
52 + ((((NOM) % (DEN)) << (LSH)) + (DEN) / 2) / (DEN))
Linus Torvalds1da177e2005-04-16 15:20:36 -070053
Catalin Marinasa7ea3bb2012-07-27 14:48:09 -040054/* LATCH is used in the interval timer and ftape setup. */
Arnd Bergmann015a8302012-09-28 23:36:17 +020055#define LATCH ((CLOCK_TICK_RATE + HZ/2) / HZ) /* For divider */
Linus Torvalds1da177e2005-04-16 15:20:36 -070056
John Stultzb3c869d2012-09-04 12:42:27 -040057extern int register_refined_jiffies(long clock_tick_rate);
Linus Torvalds1da177e2005-04-16 15:20:36 -070058
John Stultz02ab20a2012-07-27 14:48:10 -040059/* TICK_NSEC is the time between ticks in nsec assuming SHIFTED_HZ */
John Stultzb3c869d2012-09-04 12:42:27 -040060#define TICK_NSEC ((NSEC_PER_SEC+HZ/2)/HZ)
Linus Torvalds1da177e2005-04-16 15:20:36 -070061
62/* TICK_USEC is the time between ticks in usec assuming fake USER_HZ */
63#define TICK_USEC ((1000000UL + USER_HZ/2) / USER_HZ)
64
Linus Torvalds1da177e2005-04-16 15:20:36 -070065/* some arch's have a small-data section that can be accessed register-relative
66 * but that can only take up to, say, 4-byte variables. jiffies being part of
67 * an 8-byte variable may not be correctly accessed unless we force the issue
68 */
69#define __jiffy_data __attribute__((section(".data")))
70
71/*
Chase Venters98c4f0c2006-11-30 04:53:49 +010072 * The 64-bit value is not atomic - you MUST NOT read it
John Stultzd6ad4182012-02-28 16:50:11 -080073 * without sampling the sequence number in jiffies_lock.
Linus Torvalds1da177e2005-04-16 15:20:36 -070074 * get_jiffies_64() will do this for you as appropriate.
75 */
76extern u64 __jiffy_data jiffies_64;
77extern unsigned long volatile __jiffy_data jiffies;
John Stultzd6ad4182012-02-28 16:50:11 -080078extern seqlock_t jiffies_lock;
Linus Torvalds1da177e2005-04-16 15:20:36 -070079
80#if (BITS_PER_LONG < 64)
81u64 get_jiffies_64(void);
82#else
83static inline u64 get_jiffies_64(void)
84{
85 return (u64)jiffies;
86}
87#endif
88
89/*
90 * These inlines deal with timer wrapping correctly. You are
91 * strongly encouraged to use them
92 * 1. Because people otherwise forget
93 * 2. Because if the timer wrap changes in future you won't have to
94 * alter your driver code.
95 *
96 * time_after(a,b) returns true if the time a is after time b.
97 *
98 * Do this with "<0" and ">=0" to only test the sign of the result. A
99 * good compiler would generate better code (and a really good compiler
100 * wouldn't care). Gcc is currently neither.
101 */
102#define time_after(a,b) \
103 (typecheck(unsigned long, a) && \
104 typecheck(unsigned long, b) && \
105 ((long)(b) - (long)(a) < 0))
106#define time_before(a,b) time_after(b,a)
107
108#define time_after_eq(a,b) \
109 (typecheck(unsigned long, a) && \
110 typecheck(unsigned long, b) && \
111 ((long)(a) - (long)(b) >= 0))
112#define time_before_eq(a,b) time_after_eq(b,a)
113
Peter Staubach64672d52008-12-23 15:21:56 -0500114/*
115 * Calculate whether a is in the range of [b, c].
116 */
Fabio Olive Leitec7e15962007-07-26 22:59:00 -0300117#define time_in_range(a,b,c) \
118 (time_after_eq(a,b) && \
119 time_before_eq(a,c))
120
Peter Staubach64672d52008-12-23 15:21:56 -0500121/*
122 * Calculate whether a is in the range of [b, c).
123 */
124#define time_in_range_open(a,b,c) \
125 (time_after_eq(a,b) && \
126 time_before(a,c))
127
Dmitriy Zavin3b171672006-09-26 10:52:42 +0200128/* Same as above, but does so with platform independent 64bit types.
129 * These must be used when utilizing jiffies_64 (i.e. return value of
130 * get_jiffies_64() */
131#define time_after64(a,b) \
132 (typecheck(__u64, a) && \
133 typecheck(__u64, b) && \
134 ((__s64)(b) - (__s64)(a) < 0))
135#define time_before64(a,b) time_after64(b,a)
136
137#define time_after_eq64(a,b) \
138 (typecheck(__u64, a) && \
139 typecheck(__u64, b) && \
140 ((__s64)(a) - (__s64)(b) >= 0))
141#define time_before_eq64(a,b) time_after_eq64(b,a)
142
Linus Torvalds1da177e2005-04-16 15:20:36 -0700143/*
Dave Young3f34d022008-04-18 13:38:57 -0700144 * These four macros compare jiffies and 'a' for convenience.
145 */
146
147/* time_is_before_jiffies(a) return true if a is before jiffies */
148#define time_is_before_jiffies(a) time_after(jiffies, a)
149
150/* time_is_after_jiffies(a) return true if a is after jiffies */
151#define time_is_after_jiffies(a) time_before(jiffies, a)
152
153/* time_is_before_eq_jiffies(a) return true if a is before or equal to jiffies*/
154#define time_is_before_eq_jiffies(a) time_after_eq(jiffies, a)
155
156/* time_is_after_eq_jiffies(a) return true if a is after or equal to jiffies*/
157#define time_is_after_eq_jiffies(a) time_before_eq(jiffies, a)
158
159/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700160 * Have the 32 bit jiffies value wrap 5 minutes after boot
161 * so jiffies wrap bugs show up earlier.
162 */
163#define INITIAL_JIFFIES ((unsigned long)(unsigned int) (-300*HZ))
164
165/*
166 * Change timeval to jiffies, trying to avoid the
167 * most obvious overflows..
168 *
169 * And some not so obvious.
170 *
Ingo Molnar9f907c02007-02-16 01:27:29 -0800171 * Note that we don't want to return LONG_MAX, because
Linus Torvalds1da177e2005-04-16 15:20:36 -0700172 * for various timeout reasons we often end up having
173 * to wait "jiffies+1" in order to guarantee that we wait
174 * at _least_ "jiffies" - so "jiffies+1" had better still
175 * be positive.
176 */
Ingo Molnar9f907c02007-02-16 01:27:29 -0800177#define MAX_JIFFY_OFFSET ((LONG_MAX >> 1)-1)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700178
Randy Dunlapbfe8df32007-10-16 01:23:46 -0700179extern unsigned long preset_lpj;
180
Linus Torvalds1da177e2005-04-16 15:20:36 -0700181/*
182 * We want to do realistic conversions of time so we need to use the same
183 * values the update wall clock code uses as the jiffies size. This value
184 * is: TICK_NSEC (which is defined in timex.h). This
Li Zefan3eb05672008-02-08 04:19:25 -0800185 * is a constant and is in nanoseconds. We will use scaled math
Linus Torvalds1da177e2005-04-16 15:20:36 -0700186 * with a set of scales defined here as SEC_JIFFIE_SC, USEC_JIFFIE_SC and
187 * NSEC_JIFFIE_SC. Note that these defines contain nothing but
188 * constants and so are computed at compile time. SHIFT_HZ (computed in
189 * timex.h) adjusts the scaling for different HZ values.
190
191 * Scaled math??? What is that?
192 *
193 * Scaled math is a way to do integer math on values that would,
194 * otherwise, either overflow, underflow, or cause undesired div
195 * instructions to appear in the execution path. In short, we "scale"
196 * up the operands so they take more bits (more precision, less
197 * underflow), do the desired operation and then "scale" the result back
198 * by the same amount. If we do the scaling by shifting we avoid the
199 * costly mpy and the dastardly div instructions.
200
201 * Suppose, for example, we want to convert from seconds to jiffies
202 * where jiffies is defined in nanoseconds as NSEC_PER_JIFFIE. The
203 * simple math is: jiff = (sec * NSEC_PER_SEC) / NSEC_PER_JIFFIE; We
204 * observe that (NSEC_PER_SEC / NSEC_PER_JIFFIE) is a constant which we
205 * might calculate at compile time, however, the result will only have
206 * about 3-4 bits of precision (less for smaller values of HZ).
207 *
208 * So, we scale as follows:
209 * jiff = (sec) * (NSEC_PER_SEC / NSEC_PER_JIFFIE);
210 * jiff = ((sec) * ((NSEC_PER_SEC * SCALE)/ NSEC_PER_JIFFIE)) / SCALE;
211 * Then we make SCALE a power of two so:
212 * jiff = ((sec) * ((NSEC_PER_SEC << SCALE)/ NSEC_PER_JIFFIE)) >> SCALE;
213 * Now we define:
214 * #define SEC_CONV = ((NSEC_PER_SEC << SCALE)/ NSEC_PER_JIFFIE))
215 * jiff = (sec * SEC_CONV) >> SCALE;
216 *
217 * Often the math we use will expand beyond 32-bits so we tell C how to
218 * do this and pass the 64-bit result of the mpy through the ">> SCALE"
219 * which should take the result back to 32-bits. We want this expansion
220 * to capture as much precision as possible. At the same time we don't
221 * want to overflow so we pick the SCALE to avoid this. In this file,
222 * that means using a different scale for each range of HZ values (as
223 * defined in timex.h).
224 *
225 * For those who want to know, gcc will give a 64-bit result from a "*"
226 * operator if the result is a long long AND at least one of the
227 * operands is cast to long long (usually just prior to the "*" so as
228 * not to confuse it into thinking it really has a 64-bit operand,
Li Zefan3eb05672008-02-08 04:19:25 -0800229 * which, buy the way, it can do, but it takes more code and at least 2
Linus Torvalds1da177e2005-04-16 15:20:36 -0700230 * mpys).
231
232 * We also need to be aware that one second in nanoseconds is only a
233 * couple of bits away from overflowing a 32-bit word, so we MUST use
234 * 64-bits to get the full range time in nanoseconds.
235
236 */
237
238/*
239 * Here are the scales we will use. One for seconds, nanoseconds and
240 * microseconds.
241 *
242 * Within the limits of cpp we do a rough cut at the SEC_JIFFIE_SC and
243 * check if the sign bit is set. If not, we bump the shift count by 1.
244 * (Gets an extra bit of precision where we can use it.)
245 * We know it is set for HZ = 1024 and HZ = 100 not for 1000.
246 * Haven't tested others.
247
248 * Limits of cpp (for #if expressions) only long (no long long), but
249 * then we only need the most signicant bit.
250 */
251
252#define SEC_JIFFIE_SC (31 - SHIFT_HZ)
253#if !((((NSEC_PER_SEC << 2) / TICK_NSEC) << (SEC_JIFFIE_SC - 2)) & 0x80000000)
254#undef SEC_JIFFIE_SC
255#define SEC_JIFFIE_SC (32 - SHIFT_HZ)
256#endif
257#define NSEC_JIFFIE_SC (SEC_JIFFIE_SC + 29)
258#define USEC_JIFFIE_SC (SEC_JIFFIE_SC + 19)
259#define SEC_CONVERSION ((unsigned long)((((u64)NSEC_PER_SEC << SEC_JIFFIE_SC) +\
260 TICK_NSEC -1) / (u64)TICK_NSEC))
261
262#define NSEC_CONVERSION ((unsigned long)((((u64)1 << NSEC_JIFFIE_SC) +\
263 TICK_NSEC -1) / (u64)TICK_NSEC))
264#define USEC_CONVERSION \
265 ((unsigned long)((((u64)NSEC_PER_USEC << USEC_JIFFIE_SC) +\
266 TICK_NSEC -1) / (u64)TICK_NSEC))
267/*
268 * USEC_ROUND is used in the timeval to jiffie conversion. See there
269 * for more details. It is the scaled resolution rounding value. Note
270 * that it is a 64-bit value. Since, when it is applied, we are already
271 * in jiffies (albit scaled), it is nothing but the bits we will shift
272 * off.
273 */
274#define USEC_ROUND (u64)(((u64)1 << USEC_JIFFIE_SC) - 1)
275/*
276 * The maximum jiffie value is (MAX_INT >> 1). Here we translate that
277 * into seconds. The 64-bit case will overflow if we are not careful,
278 * so use the messy SH_DIV macro to do it. Still all constants.
279 */
280#if BITS_PER_LONG < 64
281# define MAX_SEC_IN_JIFFIES \
282 (long)((u64)((u64)MAX_JIFFY_OFFSET * TICK_NSEC) / NSEC_PER_SEC)
283#else /* take care of overflow on 64 bits machines */
284# define MAX_SEC_IN_JIFFIES \
285 (SH_DIV((MAX_JIFFY_OFFSET >> SEC_JIFFIE_SC) * TICK_NSEC, NSEC_PER_SEC, 1) - 1)
286
287#endif
288
289/*
Ingo Molnar8b9365d2007-02-16 01:27:27 -0800290 * Convert various time units to each other:
Linus Torvalds1da177e2005-04-16 15:20:36 -0700291 */
Ingo Molnar8b9365d2007-02-16 01:27:27 -0800292extern unsigned int jiffies_to_msecs(const unsigned long j);
293extern unsigned int jiffies_to_usecs(const unsigned long j);
294extern unsigned long msecs_to_jiffies(const unsigned int m);
295extern unsigned long usecs_to_jiffies(const unsigned int u);
296extern unsigned long timespec_to_jiffies(const struct timespec *value);
297extern void jiffies_to_timespec(const unsigned long jiffies,
298 struct timespec *value);
299extern unsigned long timeval_to_jiffies(const struct timeval *value);
300extern void jiffies_to_timeval(const unsigned long jiffies,
301 struct timeval *value);
Eric Dumazeta399a802012-08-08 21:13:53 +0000302
hankcbbc7192011-09-20 13:53:39 -0700303extern clock_t jiffies_to_clock_t(unsigned long x);
Eric Dumazeta399a802012-08-08 21:13:53 +0000304static inline clock_t jiffies_delta_to_clock_t(long delta)
305{
306 return jiffies_to_clock_t(max(0L, delta));
307}
308
Ingo Molnar8b9365d2007-02-16 01:27:27 -0800309extern unsigned long clock_t_to_jiffies(unsigned long x);
310extern u64 jiffies_64_to_clock_t(u64 x);
311extern u64 nsec_to_clock_t(u64 x);
Venkatesh Pallipadia1dabb62010-12-21 17:09:01 -0800312extern u64 nsecs_to_jiffies64(u64 n);
Hidetoshi Setob7b20df92009-11-26 14:49:27 +0900313extern unsigned long nsecs_to_jiffies(u64 n);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700314
Ingo Molnar8b9365d2007-02-16 01:27:27 -0800315#define TIMESTAMP_SIZE 30
Linus Torvalds1da177e2005-04-16 15:20:36 -0700316
317#endif