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 - 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 */
79extern u64 __cacheline_aligned_in_smp jiffies_64;
80extern unsigned long volatile __cacheline_aligned_in_smp __jiffy_arch_data jiffies;
81
82#if (BITS_PER_LONG < 64)
83u64 get_jiffies_64(void);
84#else
85static inline u64 get_jiffies_64(void)
86{
87 return (u64)jiffies;
88}
89#endif
90
91/*
92 * These inlines deal with timer wrapping correctly. You are
93 * strongly encouraged to use them
94 * 1. Because people otherwise forget
95 * 2. Because if the timer wrap changes in future you won't have to
96 * alter your driver code.
97 *
98 * time_after(a,b) returns true if the time a is after time b.
99 *
100 * Do this with "<0" and ">=0" to only test the sign of the result. A
101 * good compiler would generate better code (and a really good compiler
102 * wouldn't care). Gcc is currently neither.
103 */
104#define time_after(a,b) \
105 (typecheck(unsigned long, a) && \
106 typecheck(unsigned long, b) && \
107 ((long)((b) - (a)) < 0))
108#define time_before(a,b) time_after(b,a)
109
110#define time_after_eq(a,b) \
111 (typecheck(unsigned long, a) && \
112 typecheck(unsigned long, b) && \
113 ((long)((a) - (b)) >= 0))
114#define time_before_eq(a,b) time_after_eq(b,a)
115
116/*
117 * Calculate whether a is in the range of [b, c].
118 */
119#define time_in_range(a,b,c) \
120 (time_after_eq(a,b) && \
121 time_before_eq(a,c))
122
123/*
124 * Calculate whether a is in the range of [b, c).
125 */
126#define time_in_range_open(a,b,c) \
127 (time_after_eq(a,b) && \
128 time_before(a,c))
129
130/* Same as above, but does so with platform independent 64bit types.
131 * These must be used when utilizing jiffies_64 (i.e. return value of
132 * get_jiffies_64() */
133#define time_after64(a,b) \
134 (typecheck(__u64, a) && \
135 typecheck(__u64, b) && \
136 ((__s64)((b) - (a)) < 0))
137#define time_before64(a,b) time_after64(b,a)
138
139#define time_after_eq64(a,b) \
140 (typecheck(__u64, a) && \
141 typecheck(__u64, b) && \
142 ((__s64)((a) - (b)) >= 0))
143#define time_before_eq64(a,b) time_after_eq64(b,a)
144
145#define time_in_range64(a, b, c) \
146 (time_after_eq64(a, b) && \
147 time_before_eq64(a, c))
148
149/*
150 * These four macros compare jiffies and 'a' for convenience.
151 */
152
153/* time_is_before_jiffies(a) return true if a is before jiffies */
154#define time_is_before_jiffies(a) time_after(jiffies, a)
155#define time_is_before_jiffies64(a) time_after64(get_jiffies_64(), a)
156
157/* time_is_after_jiffies(a) return true if a is after jiffies */
158#define time_is_after_jiffies(a) time_before(jiffies, a)
159#define time_is_after_jiffies64(a) time_before64(get_jiffies_64(), a)
160
161/* time_is_before_eq_jiffies(a) return true if a is before or equal to jiffies*/
162#define time_is_before_eq_jiffies(a) time_after_eq(jiffies, a)
163#define time_is_before_eq_jiffies64(a) time_after_eq64(get_jiffies_64(), a)
164
165/* time_is_after_eq_jiffies(a) return true if a is after or equal to jiffies*/
166#define time_is_after_eq_jiffies(a) time_before_eq(jiffies, a)
167#define time_is_after_eq_jiffies64(a) time_before_eq64(get_jiffies_64(), a)
168
169/*
170 * Have the 32 bit jiffies value wrap 5 minutes after boot
171 * so jiffies wrap bugs show up earlier.
172 */
173#define INITIAL_JIFFIES ((unsigned long)(unsigned int) (-300*HZ))
174
175/*
176 * Change timeval to jiffies, trying to avoid the
177 * most obvious overflows..
178 *
179 * And some not so obvious.
180 *
181 * Note that we don't want to return LONG_MAX, because
182 * for various timeout reasons we often end up having
183 * to wait "jiffies+1" in order to guarantee that we wait
184 * at _least_ "jiffies" - so "jiffies+1" had better still
185 * be positive.
186 */
187#define MAX_JIFFY_OFFSET ((LONG_MAX >> 1)-1)
188
189extern unsigned long preset_lpj;
190
191/*
192 * We want to do realistic conversions of time so we need to use the same
193 * values the update wall clock code uses as the jiffies size. This value
194 * is: TICK_NSEC (which is defined in timex.h). This
195 * is a constant and is in nanoseconds. We will use scaled math
196 * with a set of scales defined here as SEC_JIFFIE_SC, USEC_JIFFIE_SC and
197 * NSEC_JIFFIE_SC. Note that these defines contain nothing but
198 * constants and so are computed at compile time. SHIFT_HZ (computed in
199 * timex.h) adjusts the scaling for different HZ values.
200
201 * Scaled math??? What is that?
202 *
203 * Scaled math is a way to do integer math on values that would,
204 * otherwise, either overflow, underflow, or cause undesired div
205 * instructions to appear in the execution path. In short, we "scale"
206 * up the operands so they take more bits (more precision, less
207 * underflow), do the desired operation and then "scale" the result back
208 * by the same amount. If we do the scaling by shifting we avoid the
209 * costly mpy and the dastardly div instructions.
210
211 * Suppose, for example, we want to convert from seconds to jiffies
212 * where jiffies is defined in nanoseconds as NSEC_PER_JIFFIE. The
213 * simple math is: jiff = (sec * NSEC_PER_SEC) / NSEC_PER_JIFFIE; We
214 * observe that (NSEC_PER_SEC / NSEC_PER_JIFFIE) is a constant which we
215 * might calculate at compile time, however, the result will only have
216 * about 3-4 bits of precision (less for smaller values of HZ).
217 *
218 * So, we scale as follows:
219 * jiff = (sec) * (NSEC_PER_SEC / NSEC_PER_JIFFIE);
220 * jiff = ((sec) * ((NSEC_PER_SEC * SCALE)/ NSEC_PER_JIFFIE)) / SCALE;
221 * Then we make SCALE a power of two so:
222 * jiff = ((sec) * ((NSEC_PER_SEC << SCALE)/ NSEC_PER_JIFFIE)) >> SCALE;
223 * Now we define:
224 * #define SEC_CONV = ((NSEC_PER_SEC << SCALE)/ NSEC_PER_JIFFIE))
225 * jiff = (sec * SEC_CONV) >> SCALE;
226 *
227 * Often the math we use will expand beyond 32-bits so we tell C how to
228 * do this and pass the 64-bit result of the mpy through the ">> SCALE"
229 * which should take the result back to 32-bits. We want this expansion
230 * to capture as much precision as possible. At the same time we don't
231 * want to overflow so we pick the SCALE to avoid this. In this file,
232 * that means using a different scale for each range of HZ values (as
233 * defined in timex.h).
234 *
235 * For those who want to know, gcc will give a 64-bit result from a "*"
236 * operator if the result is a long long AND at least one of the
237 * operands is cast to long long (usually just prior to the "*" so as
238 * not to confuse it into thinking it really has a 64-bit operand,
239 * which, buy the way, it can do, but it takes more code and at least 2
240 * mpys).
241
242 * We also need to be aware that one second in nanoseconds is only a
243 * couple of bits away from overflowing a 32-bit word, so we MUST use
244 * 64-bits to get the full range time in nanoseconds.
245
246 */
247
248/*
249 * Here are the scales we will use. One for seconds, nanoseconds and
250 * microseconds.
251 *
252 * Within the limits of cpp we do a rough cut at the SEC_JIFFIE_SC and
253 * check if the sign bit is set. If not, we bump the shift count by 1.
254 * (Gets an extra bit of precision where we can use it.)
255 * We know it is set for HZ = 1024 and HZ = 100 not for 1000.
256 * Haven't tested others.
257
258 * Limits of cpp (for #if expressions) only long (no long long), but
259 * then we only need the most signicant bit.
260 */
261
262#define SEC_JIFFIE_SC (31 - SHIFT_HZ)
263#if !((((NSEC_PER_SEC << 2) / TICK_NSEC) << (SEC_JIFFIE_SC - 2)) & 0x80000000)
264#undef SEC_JIFFIE_SC
265#define SEC_JIFFIE_SC (32 - SHIFT_HZ)
266#endif
267#define NSEC_JIFFIE_SC (SEC_JIFFIE_SC + 29)
268#define SEC_CONVERSION ((unsigned long)((((u64)NSEC_PER_SEC << SEC_JIFFIE_SC) +\
269 TICK_NSEC -1) / (u64)TICK_NSEC))
270
271#define NSEC_CONVERSION ((unsigned long)((((u64)1 << NSEC_JIFFIE_SC) +\
272 TICK_NSEC -1) / (u64)TICK_NSEC))
273/*
274 * The maximum jiffie value is (MAX_INT >> 1). Here we translate that
275 * into seconds. The 64-bit case will overflow if we are not careful,
276 * so use the messy SH_DIV macro to do it. Still all constants.
277 */
278#if BITS_PER_LONG < 64
279# define MAX_SEC_IN_JIFFIES \
280 (long)((u64)((u64)MAX_JIFFY_OFFSET * TICK_NSEC) / NSEC_PER_SEC)
281#else /* take care of overflow on 64 bits machines */
282# define MAX_SEC_IN_JIFFIES \
283 (SH_DIV((MAX_JIFFY_OFFSET >> SEC_JIFFIE_SC) * TICK_NSEC, NSEC_PER_SEC, 1) - 1)
284
285#endif
286
287/*
288 * Convert various time units to each other:
289 */
290extern unsigned int jiffies_to_msecs(const unsigned long j);
291extern unsigned int jiffies_to_usecs(const unsigned long j);
292
293static inline u64 jiffies_to_nsecs(const unsigned long j)
294{
295 return (u64)jiffies_to_usecs(j) * NSEC_PER_USEC;
296}
297
298extern u64 jiffies64_to_nsecs(u64 j);
299extern u64 jiffies64_to_msecs(u64 j);
300
301extern unsigned long __msecs_to_jiffies(const unsigned int m);
302#if HZ <= MSEC_PER_SEC && !(MSEC_PER_SEC % HZ)
303/*
304 * HZ is equal to or smaller than 1000, and 1000 is a nice round
305 * multiple of HZ, divide with the factor between them, but round
306 * upwards:
307 */
308static inline unsigned long _msecs_to_jiffies(const unsigned int m)
309{
310 return (m + (MSEC_PER_SEC / HZ) - 1) / (MSEC_PER_SEC / HZ);
311}
312#elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC)
313/*
314 * HZ is larger than 1000, and HZ is a nice round multiple of 1000 -
315 * simply multiply with the factor between them.
316 *
317 * But first make sure the multiplication result cannot overflow:
318 */
319static inline unsigned long _msecs_to_jiffies(const unsigned int m)
320{
321 if (m > jiffies_to_msecs(MAX_JIFFY_OFFSET))
322 return MAX_JIFFY_OFFSET;
323 return m * (HZ / MSEC_PER_SEC);
324}
325#else
326/*
327 * Generic case - multiply, round and divide. But first check that if
328 * we are doing a net multiplication, that we wouldn't overflow:
329 */
330static inline unsigned long _msecs_to_jiffies(const unsigned int m)
331{
332 if (HZ > MSEC_PER_SEC && m > jiffies_to_msecs(MAX_JIFFY_OFFSET))
333 return MAX_JIFFY_OFFSET;
334
335 return (MSEC_TO_HZ_MUL32 * m + MSEC_TO_HZ_ADJ32) >> MSEC_TO_HZ_SHR32;
336}
337#endif
338/**
339 * msecs_to_jiffies: - convert milliseconds to jiffies
340 * @m: time in milliseconds
341 *
342 * conversion is done as follows:
343 *
344 * - negative values mean 'infinite timeout' (MAX_JIFFY_OFFSET)
345 *
346 * - 'too large' values [that would result in larger than
347 * MAX_JIFFY_OFFSET values] mean 'infinite timeout' too.
348 *
349 * - all other values are converted to jiffies by either multiplying
350 * the input value by a factor or dividing it with a factor and
351 * handling any 32-bit overflows.
352 * for the details see __msecs_to_jiffies()
353 *
354 * msecs_to_jiffies() checks for the passed in value being a constant
355 * via __builtin_constant_p() allowing gcc to eliminate most of the
356 * code, __msecs_to_jiffies() is called if the value passed does not
357 * allow constant folding and the actual conversion must be done at
358 * runtime.
359 * the HZ range specific helpers _msecs_to_jiffies() are called both
360 * directly here and from __msecs_to_jiffies() in the case where
361 * constant folding is not possible.
362 */
363static __always_inline unsigned long msecs_to_jiffies(const unsigned int m)
364{
365 if (__builtin_constant_p(m)) {
366 if ((int)m < 0)
367 return MAX_JIFFY_OFFSET;
368 return _msecs_to_jiffies(m);
369 } else {
370 return __msecs_to_jiffies(m);
371 }
372}
373
374extern unsigned long __usecs_to_jiffies(const unsigned int u);
375#if !(USEC_PER_SEC % HZ)
376static inline unsigned long _usecs_to_jiffies(const unsigned int u)
377{
378 return (u + (USEC_PER_SEC / HZ) - 1) / (USEC_PER_SEC / HZ);
379}
380#else
381static inline unsigned long _usecs_to_jiffies(const unsigned int u)
382{
383 return (USEC_TO_HZ_MUL32 * u + USEC_TO_HZ_ADJ32)
384 >> USEC_TO_HZ_SHR32;
385}
386#endif
387
388/**
389 * usecs_to_jiffies: - convert microseconds to jiffies
390 * @u: time in microseconds
391 *
392 * conversion is done as follows:
393 *
394 * - 'too large' values [that would result in larger than
395 * MAX_JIFFY_OFFSET values] mean 'infinite timeout' too.
396 *
397 * - all other values are converted to jiffies by either multiplying
398 * the input value by a factor or dividing it with a factor and
399 * handling any 32-bit overflows as for msecs_to_jiffies.
400 *
401 * usecs_to_jiffies() checks for the passed in value being a constant
402 * via __builtin_constant_p() allowing gcc to eliminate most of the
403 * code, __usecs_to_jiffies() is called if the value passed does not
404 * allow constant folding and the actual conversion must be done at
405 * runtime.
406 * the HZ range specific helpers _usecs_to_jiffies() are called both
407 * directly here and from __msecs_to_jiffies() in the case where
408 * constant folding is not possible.
409 */
410static __always_inline unsigned long usecs_to_jiffies(const unsigned int u)
411{
412 if (__builtin_constant_p(u)) {
413 if (u > jiffies_to_usecs(MAX_JIFFY_OFFSET))
414 return MAX_JIFFY_OFFSET;
415 return _usecs_to_jiffies(u);
416 } else {
417 return __usecs_to_jiffies(u);
418 }
419}
420
421extern unsigned long timespec64_to_jiffies(const struct timespec64 *value);
422extern void jiffies_to_timespec64(const unsigned long jiffies,
423 struct timespec64 *value);
424extern clock_t jiffies_to_clock_t(unsigned long x);
425static inline clock_t jiffies_delta_to_clock_t(long delta)
426{
427 return jiffies_to_clock_t(max(0L, delta));
428}
429
430static inline unsigned int jiffies_delta_to_msecs(long delta)
431{
432 return jiffies_to_msecs(max(0L, delta));
433}
434
435extern unsigned long clock_t_to_jiffies(unsigned long x);
436extern u64 jiffies_64_to_clock_t(u64 x);
437extern u64 nsec_to_clock_t(u64 x);
438extern u64 nsecs_to_jiffies64(u64 n);
439extern unsigned long nsecs_to_jiffies(u64 n);
440
441#define TIMESTAMP_SIZE 30
442
443#endif
444

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