1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef _LINUX_JIFFIES_H
3#define _LINUX_JIFFIES_H
4
5#include <linux/cache.h>
6#include <linux/limits.h>
7#include <linux/math64.h>
8#include <linux/minmax.h>
9#include <linux/types.h>
10#include <linux/time.h>
11#include <linux/timex.h>
12#include <vdso/jiffies.h>
13#include <asm/param.h> /* for HZ */
14#include <generated/timeconst.h>
15
16/*
17 * The following defines establish the engineering parameters of the PLL
18 * model. The HZ variable establishes the timer interrupt frequency, 100 Hz
19 * for the SunOS kernel, 256 Hz for the Ultrix kernel and 1024 Hz for the
20 * OSF/1 kernel. The SHIFT_HZ define expresses the same value as the
21 * nearest power of two in order to avoid hardware multiply operations.
22 */
23#if HZ >= 12 && HZ < 24
24# define SHIFT_HZ 4
25#elif HZ >= 24 && HZ < 48
26# define SHIFT_HZ 5
27#elif HZ >= 48 && HZ < 96
28# define SHIFT_HZ 6
29#elif HZ >= 96 && HZ < 192
30# define SHIFT_HZ 7
31#elif HZ >= 192 && HZ < 384
32# define SHIFT_HZ 8
33#elif HZ >= 384 && HZ < 768
34# define SHIFT_HZ 9
35#elif HZ >= 768 && HZ < 1536
36# define SHIFT_HZ 10
37#elif HZ >= 1536 && HZ < 3072
38# define SHIFT_HZ 11
39#elif HZ >= 3072 && HZ < 6144
40# define SHIFT_HZ 12
41#elif HZ >= 6144 && HZ < 12288
42# define SHIFT_HZ 13
43#else
44# error Invalid value of HZ.
45#endif
46
47/* Suppose we want to divide two numbers NOM and DEN: NOM/DEN, then we can
48 * improve accuracy by shifting LSH bits, hence calculating:
49 * (NOM << LSH) / DEN
50 * This however means trouble for large NOM, because (NOM << LSH) may no
51 * longer fit in 32 bits. The following way of calculating this gives us
52 * some slack, under the following conditions:
53 * - (NOM / DEN) fits in (32 - LSH) bits.
54 * - (NOM % DEN) fits in (32 - LSH) bits.
55 */
56#define SH_DIV(NOM,DEN,LSH) ( (((NOM) / (DEN)) << (LSH)) \
57 + ((((NOM) % (DEN)) << (LSH)) + (DEN) / 2) / (DEN))
58
59/* LATCH is used in the interval timer and ftape setup. */
60#define LATCH ((CLOCK_TICK_RATE + HZ/2) / HZ) /* For divider */
61
62extern int register_refined_jiffies(long clock_tick_rate);
63
64/* TICK_USEC is the time between ticks in usec assuming SHIFTED_HZ */
65#define TICK_USEC ((USEC_PER_SEC + HZ/2) / HZ)
66
67/* USER_TICK_USEC is the time between ticks in usec assuming fake USER_HZ */
68#define USER_TICK_USEC ((1000000UL + USER_HZ/2) / USER_HZ)
69
70#ifndef __jiffy_arch_data
71#define __jiffy_arch_data
72#endif
73
74/*
75 * The 64-bit value is not atomic on 32-bit systems - you MUST NOT read it
76 * without sampling the sequence number in jiffies_lock.
77 * get_jiffies_64() will do this for you as appropriate.
78 *
79 * jiffies and jiffies_64 are at the same address for little-endian systems
80 * and for 64-bit big-endian systems.
81 * On 32-bit big-endian systems, jiffies is the lower 32 bits of jiffies_64
82 * (i.e., at address @jiffies_64 + 4).
83 * See arch/ARCH/kernel/vmlinux.lds.S
84 */
85extern u64 __cacheline_aligned_in_smp jiffies_64;
86extern unsigned long volatile __cacheline_aligned_in_smp __jiffy_arch_data jiffies;
87
88#if (BITS_PER_LONG < 64)
89u64 get_jiffies_64(void);
90#else
91/**
92 * get_jiffies_64 - read the 64-bit non-atomic jiffies_64 value
93 *
94 * When BITS_PER_LONG < 64, this uses sequence number sampling using
95 * jiffies_lock to protect the 64-bit read.
96 *
97 * Return: current 64-bit jiffies value
98 */
99static inline u64 get_jiffies_64(void)
100{
101 return (u64)jiffies;
102}
103#endif
104
105/*
106 * These inlines deal with timer wrapping correctly. You are
107 * strongly encouraged to use them:
108 * 1. Because people otherwise forget
109 * 2. Because if the timer wrap changes in future you won't have to
110 * alter your driver code.
111 */
112
113/**
114 * time_after - returns true if the time a is after time b.
115 * @a: first comparable as unsigned long
116 * @b: second comparable as unsigned long
117 *
118 * Do this with "<0" and ">=0" to only test the sign of the result. A
119 * good compiler would generate better code (and a really good compiler
120 * wouldn't care). Gcc is currently neither.
121 *
122 * Return: %true is time a is after time b, otherwise %false.
123 */
124#define time_after(a,b) \
125 (typecheck(unsigned long, a) && \
126 typecheck(unsigned long, b) && \
127 ((long)((b) - (a)) < 0))
128/**
129 * time_before - returns true if the time a is before time b.
130 * @a: first comparable as unsigned long
131 * @b: second comparable as unsigned long
132 *
133 * Return: %true is time a is before time b, otherwise %false.
134 */
135#define time_before(a,b) time_after(b,a)
136
137/**
138 * time_after_eq - returns true if the time a is after or the same as time b.
139 * @a: first comparable as unsigned long
140 * @b: second comparable as unsigned long
141 *
142 * Return: %true is time a is after or the same as time b, otherwise %false.
143 */
144#define time_after_eq(a,b) \
145 (typecheck(unsigned long, a) && \
146 typecheck(unsigned long, b) && \
147 ((long)((a) - (b)) >= 0))
148/**
149 * time_before_eq - returns true if the time a is before or the same as time b.
150 * @a: first comparable as unsigned long
151 * @b: second comparable as unsigned long
152 *
153 * Return: %true is time a is before or the same as time b, otherwise %false.
154 */
155#define time_before_eq(a,b) time_after_eq(b,a)
156
157/**
158 * time_in_range - Calculate whether a is in the range of [b, c].
159 * @a: time to test
160 * @b: beginning of the range
161 * @c: end of the range
162 *
163 * Return: %true is time a is in the range [b, c], otherwise %false.
164 */
165#define time_in_range(a,b,c) \
166 (time_after_eq(a,b) && \
167 time_before_eq(a,c))
168
169/**
170 * time_in_range_open - Calculate whether a is in the range of [b, c).
171 * @a: time to test
172 * @b: beginning of the range
173 * @c: end of the range
174 *
175 * Return: %true is time a is in the range [b, c), otherwise %false.
176 */
177#define time_in_range_open(a,b,c) \
178 (time_after_eq(a,b) && \
179 time_before(a,c))
180
181/* Same as above, but does so with platform independent 64bit types.
182 * These must be used when utilizing jiffies_64 (i.e. return value of
183 * get_jiffies_64()). */
184
185/**
186 * time_after64 - returns true if the time a is after time b.
187 * @a: first comparable as __u64
188 * @b: second comparable as __u64
189 *
190 * This must be used when utilizing jiffies_64 (i.e. return value of
191 * get_jiffies_64()).
192 *
193 * Return: %true is time a is after time b, otherwise %false.
194 */
195#define time_after64(a,b) \
196 (typecheck(__u64, a) && \
197 typecheck(__u64, b) && \
198 ((__s64)((b) - (a)) < 0))
199/**
200 * time_before64 - returns true if the time a is before time b.
201 * @a: first comparable as __u64
202 * @b: second comparable as __u64
203 *
204 * This must be used when utilizing jiffies_64 (i.e. return value of
205 * get_jiffies_64()).
206 *
207 * Return: %true is time a is before time b, otherwise %false.
208 */
209#define time_before64(a,b) time_after64(b,a)
210
211/**
212 * time_after_eq64 - returns true if the time a is after or the same as time b.
213 * @a: first comparable as __u64
214 * @b: second comparable as __u64
215 *
216 * This must be used when utilizing jiffies_64 (i.e. return value of
217 * get_jiffies_64()).
218 *
219 * Return: %true is time a is after or the same as time b, otherwise %false.
220 */
221#define time_after_eq64(a,b) \
222 (typecheck(__u64, a) && \
223 typecheck(__u64, b) && \
224 ((__s64)((a) - (b)) >= 0))
225/**
226 * time_before_eq64 - returns true if the time a is before or the same as time b.
227 * @a: first comparable as __u64
228 * @b: second comparable as __u64
229 *
230 * This must be used when utilizing jiffies_64 (i.e. return value of
231 * get_jiffies_64()).
232 *
233 * Return: %true is time a is before or the same as time b, otherwise %false.
234 */
235#define time_before_eq64(a,b) time_after_eq64(b,a)
236
237/**
238 * time_in_range64 - Calculate whether a is in the range of [b, c].
239 * @a: time to test
240 * @b: beginning of the range
241 * @c: end of the range
242 *
243 * Return: %true is time a is in the range [b, c], otherwise %false.
244 */
245#define time_in_range64(a, b, c) \
246 (time_after_eq64(a, b) && \
247 time_before_eq64(a, c))
248
249/*
250 * These eight macros compare jiffies[_64] and 'a' for convenience.
251 */
252
253/**
254 * time_is_before_jiffies - return true if a is before jiffies
255 * @a: time (unsigned long) to compare to jiffies
256 *
257 * Return: %true is time a is before jiffies, otherwise %false.
258 */
259#define time_is_before_jiffies(a) time_after(jiffies, a)
260/**
261 * time_is_before_jiffies64 - return true if a is before jiffies_64
262 * @a: time (__u64) to compare to jiffies_64
263 *
264 * Return: %true is time a is before jiffies_64, otherwise %false.
265 */
266#define time_is_before_jiffies64(a) time_after64(get_jiffies_64(), a)
267
268/**
269 * time_is_after_jiffies - return true if a is after jiffies
270 * @a: time (unsigned long) to compare to jiffies
271 *
272 * Return: %true is time a is after jiffies, otherwise %false.
273 */
274#define time_is_after_jiffies(a) time_before(jiffies, a)
275/**
276 * time_is_after_jiffies64 - return true if a is after jiffies_64
277 * @a: time (__u64) to compare to jiffies_64
278 *
279 * Return: %true is time a is after jiffies_64, otherwise %false.
280 */
281#define time_is_after_jiffies64(a) time_before64(get_jiffies_64(), a)
282
283/**
284 * time_is_before_eq_jiffies - return true if a is before or equal to jiffies
285 * @a: time (unsigned long) to compare to jiffies
286 *
287 * Return: %true is time a is before or the same as jiffies, otherwise %false.
288 */
289#define time_is_before_eq_jiffies(a) time_after_eq(jiffies, a)
290/**
291 * time_is_before_eq_jiffies64 - return true if a is before or equal to jiffies_64
292 * @a: time (__u64) to compare to jiffies_64
293 *
294 * Return: %true is time a is before or the same jiffies_64, otherwise %false.
295 */
296#define time_is_before_eq_jiffies64(a) time_after_eq64(get_jiffies_64(), a)
297
298/**
299 * time_is_after_eq_jiffies - return true if a is after or equal to jiffies
300 * @a: time (unsigned long) to compare to jiffies
301 *
302 * Return: %true is time a is after or the same as jiffies, otherwise %false.
303 */
304#define time_is_after_eq_jiffies(a) time_before_eq(jiffies, a)
305/**
306 * time_is_after_eq_jiffies64 - return true if a is after or equal to jiffies_64
307 * @a: time (__u64) to compare to jiffies_64
308 *
309 * Return: %true is time a is after or the same as jiffies_64, otherwise %false.
310 */
311#define time_is_after_eq_jiffies64(a) time_before_eq64(get_jiffies_64(), a)
312
313/*
314 * Have the 32-bit jiffies value wrap 5 minutes after boot
315 * so jiffies wrap bugs show up earlier.
316 */
317#define INITIAL_JIFFIES ((unsigned long)(unsigned int) (-300*HZ))
318
319/*
320 * Change timeval to jiffies, trying to avoid the
321 * most obvious overflows..
322 *
323 * And some not so obvious.
324 *
325 * Note that we don't want to return LONG_MAX, because
326 * for various timeout reasons we often end up having
327 * to wait "jiffies+1" in order to guarantee that we wait
328 * at _least_ "jiffies" - so "jiffies+1" had better still
329 * be positive.
330 */
331#define MAX_JIFFY_OFFSET ((LONG_MAX >> 1)-1)
332
333extern unsigned long preset_lpj;
334
335/*
336 * We want to do realistic conversions of time so we need to use the same
337 * values the update wall clock code uses as the jiffies size. This value
338 * is: TICK_NSEC (which is defined in timex.h). This
339 * is a constant and is in nanoseconds. We will use scaled math
340 * with a set of scales defined here as SEC_JIFFIE_SC, USEC_JIFFIE_SC and
341 * NSEC_JIFFIE_SC. Note that these defines contain nothing but
342 * constants and so are computed at compile time. SHIFT_HZ (computed in
343 * timex.h) adjusts the scaling for different HZ values.
344
345 * Scaled math??? What is that?
346 *
347 * Scaled math is a way to do integer math on values that would,
348 * otherwise, either overflow, underflow, or cause undesired div
349 * instructions to appear in the execution path. In short, we "scale"
350 * up the operands so they take more bits (more precision, less
351 * underflow), do the desired operation and then "scale" the result back
352 * by the same amount. If we do the scaling by shifting we avoid the
353 * costly mpy and the dastardly div instructions.
354
355 * Suppose, for example, we want to convert from seconds to jiffies
356 * where jiffies is defined in nanoseconds as NSEC_PER_JIFFIE. The
357 * simple math is: jiff = (sec * NSEC_PER_SEC) / NSEC_PER_JIFFIE; We
358 * observe that (NSEC_PER_SEC / NSEC_PER_JIFFIE) is a constant which we
359 * might calculate at compile time, however, the result will only have
360 * about 3-4 bits of precision (less for smaller values of HZ).
361 *
362 * So, we scale as follows:
363 * jiff = (sec) * (NSEC_PER_SEC / NSEC_PER_JIFFIE);
364 * jiff = ((sec) * ((NSEC_PER_SEC * SCALE)/ NSEC_PER_JIFFIE)) / SCALE;
365 * Then we make SCALE a power of two so:
366 * jiff = ((sec) * ((NSEC_PER_SEC << SCALE)/ NSEC_PER_JIFFIE)) >> SCALE;
367 * Now we define:
368 * #define SEC_CONV = ((NSEC_PER_SEC << SCALE)/ NSEC_PER_JIFFIE))
369 * jiff = (sec * SEC_CONV) >> SCALE;
370 *
371 * Often the math we use will expand beyond 32-bits so we tell C how to
372 * do this and pass the 64-bit result of the mpy through the ">> SCALE"
373 * which should take the result back to 32-bits. We want this expansion
374 * to capture as much precision as possible. At the same time we don't
375 * want to overflow so we pick the SCALE to avoid this. In this file,
376 * that means using a different scale for each range of HZ values (as
377 * defined in timex.h).
378 *
379 * For those who want to know, gcc will give a 64-bit result from a "*"
380 * operator if the result is a long long AND at least one of the
381 * operands is cast to long long (usually just prior to the "*" so as
382 * not to confuse it into thinking it really has a 64-bit operand,
383 * which, buy the way, it can do, but it takes more code and at least 2
384 * mpys).
385
386 * We also need to be aware that one second in nanoseconds is only a
387 * couple of bits away from overflowing a 32-bit word, so we MUST use
388 * 64-bits to get the full range time in nanoseconds.
389
390 */
391
392/*
393 * Here are the scales we will use. One for seconds, nanoseconds and
394 * microseconds.
395 *
396 * Within the limits of cpp we do a rough cut at the SEC_JIFFIE_SC and
397 * check if the sign bit is set. If not, we bump the shift count by 1.
398 * (Gets an extra bit of precision where we can use it.)
399 * We know it is set for HZ = 1024 and HZ = 100 not for 1000.
400 * Haven't tested others.
401
402 * Limits of cpp (for #if expressions) only long (no long long), but
403 * then we only need the most signicant bit.
404 */
405
406#define SEC_JIFFIE_SC (31 - SHIFT_HZ)
407#if !((((NSEC_PER_SEC << 2) / TICK_NSEC) << (SEC_JIFFIE_SC - 2)) & 0x80000000)
408#undef SEC_JIFFIE_SC
409#define SEC_JIFFIE_SC (32 - SHIFT_HZ)
410#endif
411#define NSEC_JIFFIE_SC (SEC_JIFFIE_SC + 29)
412#define SEC_CONVERSION ((unsigned long)((((u64)NSEC_PER_SEC << SEC_JIFFIE_SC) +\
413 TICK_NSEC -1) / (u64)TICK_NSEC))
414
415#define NSEC_CONVERSION ((unsigned long)((((u64)1 << NSEC_JIFFIE_SC) +\
416 TICK_NSEC -1) / (u64)TICK_NSEC))
417/*
418 * The maximum jiffie value is (MAX_INT >> 1). Here we translate that
419 * into seconds. The 64-bit case will overflow if we are not careful,
420 * so use the messy SH_DIV macro to do it. Still all constants.
421 */
422#if BITS_PER_LONG < 64
423# define MAX_SEC_IN_JIFFIES \
424 (long)((u64)((u64)MAX_JIFFY_OFFSET * TICK_NSEC) / NSEC_PER_SEC)
425#else /* take care of overflow on 64-bit machines */
426# define MAX_SEC_IN_JIFFIES \
427 (SH_DIV((MAX_JIFFY_OFFSET >> SEC_JIFFIE_SC) * TICK_NSEC, NSEC_PER_SEC, 1) - 1)
428
429#endif
430
431/*
432 * Convert various time units to each other:
433 */
434extern unsigned int jiffies_to_msecs(const unsigned long j);
435extern unsigned int jiffies_to_usecs(const unsigned long j);
436
437/**
438 * jiffies_to_nsecs - Convert jiffies to nanoseconds
439 * @j: jiffies value
440 *
441 * Return: nanoseconds value
442 */
443static inline u64 jiffies_to_nsecs(const unsigned long j)
444{
445 return (u64)jiffies_to_usecs(j) * NSEC_PER_USEC;
446}
447
448extern u64 jiffies64_to_nsecs(u64 j);
449extern u64 jiffies64_to_msecs(u64 j);
450
451extern unsigned long __msecs_to_jiffies(const unsigned int m);
452#if HZ <= MSEC_PER_SEC && !(MSEC_PER_SEC % HZ)
453/*
454 * HZ is equal to or smaller than 1000, and 1000 is a nice round
455 * multiple of HZ, divide with the factor between them, but round
456 * upwards:
457 */
458static inline unsigned long _msecs_to_jiffies(const unsigned int m)
459{
460 return (m + (MSEC_PER_SEC / HZ) - 1) / (MSEC_PER_SEC / HZ);
461}
462#elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC)
463/*
464 * HZ is larger than 1000, and HZ is a nice round multiple of 1000 -
465 * simply multiply with the factor between them.
466 *
467 * But first make sure the multiplication result cannot overflow:
468 */
469static inline unsigned long _msecs_to_jiffies(const unsigned int m)
470{
471 if (m > jiffies_to_msecs(MAX_JIFFY_OFFSET))
472 return MAX_JIFFY_OFFSET;
473 return m * (HZ / MSEC_PER_SEC);
474}
475#else
476/*
477 * Generic case - multiply, round and divide. But first check that if
478 * we are doing a net multiplication, that we wouldn't overflow:
479 */
480static inline unsigned long _msecs_to_jiffies(const unsigned int m)
481{
482 if (HZ > MSEC_PER_SEC && m > jiffies_to_msecs(MAX_JIFFY_OFFSET))
483 return MAX_JIFFY_OFFSET;
484
485 return (MSEC_TO_HZ_MUL32 * m + MSEC_TO_HZ_ADJ32) >> MSEC_TO_HZ_SHR32;
486}
487#endif
488/**
489 * msecs_to_jiffies: - convert milliseconds to jiffies
490 * @m: time in milliseconds
491 *
492 * conversion is done as follows:
493 *
494 * - negative values mean 'infinite timeout' (MAX_JIFFY_OFFSET)
495 *
496 * - 'too large' values [that would result in larger than
497 * MAX_JIFFY_OFFSET values] mean 'infinite timeout' too.
498 *
499 * - all other values are converted to jiffies by either multiplying
500 * the input value by a factor or dividing it with a factor and
501 * handling any 32-bit overflows.
502 * for the details see __msecs_to_jiffies()
503 *
504 * msecs_to_jiffies() checks for the passed in value being a constant
505 * via __builtin_constant_p() allowing gcc to eliminate most of the
506 * code. __msecs_to_jiffies() is called if the value passed does not
507 * allow constant folding and the actual conversion must be done at
508 * runtime.
509 * The HZ range specific helpers _msecs_to_jiffies() are called both
510 * directly here and from __msecs_to_jiffies() in the case where
511 * constant folding is not possible.
512 *
513 * Return: jiffies value
514 */
515static __always_inline unsigned long msecs_to_jiffies(const unsigned int m)
516{
517 if (__builtin_constant_p(m)) {
518 if ((int)m < 0)
519 return MAX_JIFFY_OFFSET;
520 return _msecs_to_jiffies(m);
521 } else {
522 return __msecs_to_jiffies(m);
523 }
524}
525
526extern unsigned long __usecs_to_jiffies(const unsigned int u);
527#if !(USEC_PER_SEC % HZ)
528static inline unsigned long _usecs_to_jiffies(const unsigned int u)
529{
530 return (u + (USEC_PER_SEC / HZ) - 1) / (USEC_PER_SEC / HZ);
531}
532#else
533static inline unsigned long _usecs_to_jiffies(const unsigned int u)
534{
535 return (USEC_TO_HZ_MUL32 * u + USEC_TO_HZ_ADJ32)
536 >> USEC_TO_HZ_SHR32;
537}
538#endif
539
540/**
541 * usecs_to_jiffies: - convert microseconds to jiffies
542 * @u: time in microseconds
543 *
544 * conversion is done as follows:
545 *
546 * - 'too large' values [that would result in larger than
547 * MAX_JIFFY_OFFSET values] mean 'infinite timeout' too.
548 *
549 * - all other values are converted to jiffies by either multiplying
550 * the input value by a factor or dividing it with a factor and
551 * handling any 32-bit overflows as for msecs_to_jiffies.
552 *
553 * usecs_to_jiffies() checks for the passed in value being a constant
554 * via __builtin_constant_p() allowing gcc to eliminate most of the
555 * code. __usecs_to_jiffies() is called if the value passed does not
556 * allow constant folding and the actual conversion must be done at
557 * runtime.
558 * The HZ range specific helpers _usecs_to_jiffies() are called both
559 * directly here and from __msecs_to_jiffies() in the case where
560 * constant folding is not possible.
561 *
562 * Return: jiffies value
563 */
564static __always_inline unsigned long usecs_to_jiffies(const unsigned int u)
565{
566 if (__builtin_constant_p(u)) {
567 if (u > jiffies_to_usecs(MAX_JIFFY_OFFSET))
568 return MAX_JIFFY_OFFSET;
569 return _usecs_to_jiffies(u);
570 } else {
571 return __usecs_to_jiffies(u);
572 }
573}
574
575extern unsigned long timespec64_to_jiffies(const struct timespec64 *value);
576extern void jiffies_to_timespec64(const unsigned long jiffies,
577 struct timespec64 *value);
578extern clock_t jiffies_to_clock_t(unsigned long x);
579
580static inline clock_t jiffies_delta_to_clock_t(long delta)
581{
582 return jiffies_to_clock_t(max(0L, delta));
583}
584
585static inline unsigned int jiffies_delta_to_msecs(long delta)
586{
587 return jiffies_to_msecs(max(0L, delta));
588}
589
590extern unsigned long clock_t_to_jiffies(unsigned long x);
591extern u64 jiffies_64_to_clock_t(u64 x);
592extern u64 nsec_to_clock_t(u64 x);
593extern u64 nsecs_to_jiffies64(u64 n);
594extern unsigned long nsecs_to_jiffies(u64 n);
595
596#define TIMESTAMP_SIZE 30
597
598#endif
599

source code of linux/include/linux/jiffies.h