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/math64.h>
7 #include <linux/kernel.h>
8 #include <linux/types.h>
9 #include <linux/time.h>
10 #include <linux/timex.h>
11 #include <asm/param.h> /* for HZ */
12 #include <generated/timeconst.h>
13
14 /*
15 * The following defines establish the engineering parameters of the PLL
16 * model. The HZ variable establishes the timer interrupt frequency, 100 Hz
17 * for the SunOS kernel, 256 Hz for the Ultrix kernel and 1024 Hz for the
18 * OSF/1 kernel. The SHIFT_HZ define expresses the same value as the
19 * nearest power of two in order to avoid hardware multiply operations.
20 */
21 #if HZ >= 12 && HZ < 24
22 # define SHIFT_HZ 4
23 #elif HZ >= 24 && HZ < 48
24 # define SHIFT_HZ 5
25 #elif HZ >= 48 && HZ < 96
26 # define SHIFT_HZ 6
27 #elif HZ >= 96 && HZ < 192
28 # define SHIFT_HZ 7
29 #elif HZ >= 192 && HZ < 384
30 # define SHIFT_HZ 8
31 #elif HZ >= 384 && HZ < 768
32 # define SHIFT_HZ 9
33 #elif HZ >= 768 && HZ < 1536
34 # define SHIFT_HZ 10
35 #elif HZ >= 1536 && HZ < 3072
36 # define SHIFT_HZ 11
37 #elif HZ >= 3072 && HZ < 6144
38 # define SHIFT_HZ 12
39 #elif HZ >= 6144 && HZ < 12288
40 # define SHIFT_HZ 13
41 #else
42 # error Invalid value of HZ.
43 #endif
44
45 /* Suppose we want to divide two numbers NOM and DEN: NOM/DEN, then we can
46 * improve accuracy by shifting LSH bits, hence calculating:
47 * (NOM << LSH) / DEN
48 * This however means trouble for large NOM, because (NOM << LSH) may no
49 * longer fit in 32 bits. The following way of calculating this gives us
50 * some slack, under the following conditions:
51 * - (NOM / DEN) fits in (32 - LSH) bits.
52 * - (NOM % DEN) fits in (32 - LSH) bits.
53 */
54 #define SH_DIV(NOM,DEN,LSH) ( (((NOM) / (DEN)) << (LSH)) \
55 + ((((NOM) % (DEN)) << (LSH)) + (DEN) / 2) / (DEN))
56
57 /* LATCH is used in the interval timer and ftape setup. */
58 #define LATCH ((CLOCK_TICK_RATE + HZ/2) / HZ) /* For divider */
59
60 extern int register_refined_jiffies(long clock_tick_rate);
61
62 /* TICK_NSEC is the time between ticks in nsec assuming SHIFTED_HZ */
63 #define TICK_NSEC ((NSEC_PER_SEC+HZ/2)/HZ)
64
65 /* TICK_USEC is the time between ticks in usec assuming SHIFTED_HZ */
66 #define TICK_USEC ((USEC_PER_SEC + HZ/2) / HZ)
67
68 /* USER_TICK_USEC is the time between ticks in usec assuming fake USER_HZ */
69 #define USER_TICK_USEC ((1000000UL + USER_HZ/2) / USER_HZ)
70
71 #ifndef __jiffy_arch_data
72 #define __jiffy_arch_data
73 #endif
74
75 /*
76 * The 64-bit value is not atomic - you MUST NOT read it
77 * without sampling the sequence number in jiffies_lock.
78 * get_jiffies_64() will do this for you as appropriate.
79 */
80 extern u64 __cacheline_aligned_in_smp jiffies_64;
81 extern unsigned long volatile __cacheline_aligned_in_smp __jiffy_arch_data jiffies;
82
83 #if (BITS_PER_LONG < 64)
84 u64 get_jiffies_64(void);
85 #else
86 static inline u64 get_jiffies_64(void)
87 {
88 return (u64)jiffies;
89 }
90 #endif
91
92 /*
93 * These inlines deal with timer wrapping correctly. You are
94 * strongly encouraged to use them
95 * 1. Because people otherwise forget
96 * 2. Because if the timer wrap changes in future you won't have to
97 * alter your driver code.
98 *
99 * time_after(a,b) returns true if the time a is after time b.
100 *
101 * Do this with "<0" and ">=0" to only test the sign of the result. A
102 * good compiler would generate better code (and a really good compiler
103 * wouldn't care). Gcc is currently neither.
104 */
105 #define time_after(a,b) \
106 (typecheck(unsigned long, a) && \
107 typecheck(unsigned long, b) && \
108 ((long)((b) - (a)) < 0))
109 #define time_before(a,b) time_after(b,a)
110
111 #define time_after_eq(a,b) \
112 (typecheck(unsigned long, a) && \
113 typecheck(unsigned long, b) && \
114 ((long)((a) - (b)) >= 0))
115 #define time_before_eq(a,b) time_after_eq(b,a)
116
117 /*
118 * Calculate whether a is in the range of [b, c].
119 */
120 #define time_in_range(a,b,c) \
121 (time_after_eq(a,b) && \
122 time_before_eq(a,c))
123
124 /*
125 * Calculate whether a is in the range of [b, c).
126 */
127 #define time_in_range_open(a,b,c) \
128 (time_after_eq(a,b) && \
129 time_before(a,c))
130
131 /* Same as above, but does so with platform independent 64bit types.
132 * These must be used when utilizing jiffies_64 (i.e. return value of
133 * get_jiffies_64() */
134 #define time_after64(a,b) \
135 (typecheck(__u64, a) && \
136 typecheck(__u64, b) && \
137 ((__s64)((b) - (a)) < 0))
138 #define time_before64(a,b) time_after64(b,a)
139
140 #define time_after_eq64(a,b) \
141 (typecheck(__u64, a) && \
142 typecheck(__u64, b) && \
143 ((__s64)((a) - (b)) >= 0))
144 #define time_before_eq64(a,b) time_after_eq64(b,a)
145
146 #define time_in_range64(a, b, c) \
147 (time_after_eq64(a, b) && \
148 time_before_eq64(a, c))
149
150 /*
151 * These four macros compare jiffies and 'a' for convenience.
152 */
153
154 /* time_is_before_jiffies(a) return true if a is before jiffies */
155 #define time_is_before_jiffies(a) time_after(jiffies, a)
156 #define time_is_before_jiffies64(a) time_after64(get_jiffies_64(), a)
157
158 /* time_is_after_jiffies(a) return true if a is after jiffies */
159 #define time_is_after_jiffies(a) time_before(jiffies, a)
160 #define time_is_after_jiffies64(a) time_before64(get_jiffies_64(), a)
161
162 /* time_is_before_eq_jiffies(a) return true if a is before or equal to jiffies*/
163 #define time_is_before_eq_jiffies(a) time_after_eq(jiffies, a)
164 #define time_is_before_eq_jiffies64(a) time_after_eq64(get_jiffies_64(), a)
165
166 /* time_is_after_eq_jiffies(a) return true if a is after or equal to jiffies*/
167 #define time_is_after_eq_jiffies(a) time_before_eq(jiffies, a)
168 #define time_is_after_eq_jiffies64(a) time_before_eq64(get_jiffies_64(), a)
169
170 /*
171 * Have the 32 bit jiffies value wrap 5 minutes after boot
172 * so jiffies wrap bugs show up earlier.
173 */
174 #define INITIAL_JIFFIES ((unsigned long)(unsigned int) (-300*HZ))
175
176 /*
177 * Change timeval to jiffies, trying to avoid the
178 * most obvious overflows..
179 *
180 * And some not so obvious.
181 *
182 * Note that we don't want to return LONG_MAX, because
183 * for various timeout reasons we often end up having
184 * to wait "jiffies+1" in order to guarantee that we wait
185 * at _least_ "jiffies" - so "jiffies+1" had better still
186 * be positive.
187 */
188 #define MAX_JIFFY_OFFSET ((LONG_MAX >> 1)-1)
189
190 extern unsigned long preset_lpj;
191
192 /*
193 * We want to do realistic conversions of time so we need to use the same
194 * values the update wall clock code uses as the jiffies size. This value
195 * is: TICK_NSEC (which is defined in timex.h). This
196 * is a constant and is in nanoseconds. We will use scaled math
197 * with a set of scales defined here as SEC_JIFFIE_SC, USEC_JIFFIE_SC and
198 * NSEC_JIFFIE_SC. Note that these defines contain nothing but
199 * constants and so are computed at compile time. SHIFT_HZ (computed in
200 * timex.h) adjusts the scaling for different HZ values.
201
202 * Scaled math??? What is that?
203 *
204 * Scaled math is a way to do integer math on values that would,
205 * otherwise, either overflow, underflow, or cause undesired div
206 * instructions to appear in the execution path. In short, we "scale"
207 * up the operands so they take more bits (more precision, less
208 * underflow), do the desired operation and then "scale" the result back
209 * by the same amount. If we do the scaling by shifting we avoid the
210 * costly mpy and the dastardly div instructions.
211
212 * Suppose, for example, we want to convert from seconds to jiffies
213 * where jiffies is defined in nanoseconds as NSEC_PER_JIFFIE. The
214 * simple math is: jiff = (sec * NSEC_PER_SEC) / NSEC_PER_JIFFIE; We
215 * observe that (NSEC_PER_SEC / NSEC_PER_JIFFIE) is a constant which we
216 * might calculate at compile time, however, the result will only have
217 * about 3-4 bits of precision (less for smaller values of HZ).
218 *
219 * So, we scale as follows:
220 * jiff = (sec) * (NSEC_PER_SEC / NSEC_PER_JIFFIE);
221 * jiff = ((sec) * ((NSEC_PER_SEC * SCALE)/ NSEC_PER_JIFFIE)) / SCALE;
222 * Then we make SCALE a power of two so:
223 * jiff = ((sec) * ((NSEC_PER_SEC << SCALE)/ NSEC_PER_JIFFIE)) >> SCALE;
224 * Now we define:
225 * #define SEC_CONV = ((NSEC_PER_SEC << SCALE)/ NSEC_PER_JIFFIE))
226 * jiff = (sec * SEC_CONV) >> SCALE;
227 *
228 * Often the math we use will expand beyond 32-bits so we tell C how to
229 * do this and pass the 64-bit result of the mpy through the ">> SCALE"
230 * which should take the result back to 32-bits. We want this expansion
231 * to capture as much precision as possible. At the same time we don't
232 * want to overflow so we pick the SCALE to avoid this. In this file,
233 * that means using a different scale for each range of HZ values (as
234 * defined in timex.h).
235 *
236 * For those who want to know, gcc will give a 64-bit result from a "*"
237 * operator if the result is a long long AND at least one of the
238 * operands is cast to long long (usually just prior to the "*" so as
239 * not to confuse it into thinking it really has a 64-bit operand,
240 * which, buy the way, it can do, but it takes more code and at least 2
241 * mpys).
242
243 * We also need to be aware that one second in nanoseconds is only a
244 * couple of bits away from overflowing a 32-bit word, so we MUST use
245 * 64-bits to get the full range time in nanoseconds.
246
247 */
248
249 /*
250 * Here are the scales we will use. One for seconds, nanoseconds and
251 * microseconds.
252 *
253 * Within the limits of cpp we do a rough cut at the SEC_JIFFIE_SC and
254 * check if the sign bit is set. If not, we bump the shift count by 1.
255 * (Gets an extra bit of precision where we can use it.)
256 * We know it is set for HZ = 1024 and HZ = 100 not for 1000.
257 * Haven't tested others.
258
259 * Limits of cpp (for #if expressions) only long (no long long), but
260 * then we only need the most signicant bit.
261 */
262
263 #define SEC_JIFFIE_SC (31 - SHIFT_HZ)
264 #if !((((NSEC_PER_SEC << 2) / TICK_NSEC) << (SEC_JIFFIE_SC - 2)) & 0x80000000)
265 #undef SEC_JIFFIE_SC
266 #define SEC_JIFFIE_SC (32 - SHIFT_HZ)
267 #endif
268 #define NSEC_JIFFIE_SC (SEC_JIFFIE_SC + 29)
269 #define SEC_CONVERSION ((unsigned long)((((u64)NSEC_PER_SEC << SEC_JIFFIE_SC) +\
270 TICK_NSEC -1) / (u64)TICK_NSEC))
271
272 #define NSEC_CONVERSION ((unsigned long)((((u64)1 << NSEC_JIFFIE_SC) +\
273 TICK_NSEC -1) / (u64)TICK_NSEC))
274 /*
275 * The maximum jiffie value is (MAX_INT >> 1). Here we translate that
276 * into seconds. The 64-bit case will overflow if we are not careful,
277 * so use the messy SH_DIV macro to do it. Still all constants.
278 */
279 #if BITS_PER_LONG < 64
280 # define MAX_SEC_IN_JIFFIES \
281 (long)((u64)((u64)MAX_JIFFY_OFFSET * TICK_NSEC) / NSEC_PER_SEC)
282 #else /* take care of overflow on 64 bits machines */
283 # define MAX_SEC_IN_JIFFIES \
284 (SH_DIV((MAX_JIFFY_OFFSET >> SEC_JIFFIE_SC) * TICK_NSEC, NSEC_PER_SEC, 1) - 1)
285
286 #endif
287
288 /*
289 * Convert various time units to each other:
290 */
291 extern unsigned int jiffies_to_msecs(const unsigned long j);
292 extern unsigned int jiffies_to_usecs(const unsigned long j);
293
294 static inline u64 jiffies_to_nsecs(const unsigned long j)
295 {
296 return (u64)jiffies_to_usecs(j) * NSEC_PER_USEC;
297 }
298
299 extern u64 jiffies64_to_nsecs(u64 j);
300 extern u64 jiffies64_to_msecs(u64 j);
301
302 extern unsigned long __msecs_to_jiffies(const unsigned int m);
303 #if HZ <= MSEC_PER_SEC && !(MSEC_PER_SEC % HZ)
304 /*
305 * HZ is equal to or smaller than 1000, and 1000 is a nice round
306 * multiple of HZ, divide with the factor between them, but round
307 * upwards:
308 */
309 static inline unsigned long _msecs_to_jiffies(const unsigned int m)
310 {
311 return (m + (MSEC_PER_SEC / HZ) - 1) / (MSEC_PER_SEC / HZ);
312 }
313 #elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC)
314 /*
315 * HZ is larger than 1000, and HZ is a nice round multiple of 1000 -
316 * simply multiply with the factor between them.
317 *
318 * But first make sure the multiplication result cannot overflow:
319 */
320 static inline unsigned long _msecs_to_jiffies(const unsigned int m)
321 {
322 if (m > jiffies_to_msecs(MAX_JIFFY_OFFSET))
323 return MAX_JIFFY_OFFSET;
324 return m * (HZ / MSEC_PER_SEC);
325 }
326 #else
327 /*
328 * Generic case - multiply, round and divide. But first check that if
329 * we are doing a net multiplication, that we wouldn't overflow:
330 */
331 static inline unsigned long _msecs_to_jiffies(const unsigned int m)
332 {
333 if (HZ > MSEC_PER_SEC && m > jiffies_to_msecs(MAX_JIFFY_OFFSET))
334 return MAX_JIFFY_OFFSET;
335
336 return (MSEC_TO_HZ_MUL32 * m + MSEC_TO_HZ_ADJ32) >> MSEC_TO_HZ_SHR32;
337 }
338 #endif
339 /**
340 * msecs_to_jiffies: - convert milliseconds to jiffies
341 * @m: time in milliseconds
342 *
343 * conversion is done as follows:
344 *
345 * - negative values mean 'infinite timeout' (MAX_JIFFY_OFFSET)
346 *
347 * - 'too large' values [that would result in larger than
348 * MAX_JIFFY_OFFSET values] mean 'infinite timeout' too.
349 *
350 * - all other values are converted to jiffies by either multiplying
351 * the input value by a factor or dividing it with a factor and
352 * handling any 32-bit overflows.
353 * for the details see __msecs_to_jiffies()
354 *
355 * msecs_to_jiffies() checks for the passed in value being a constant
356 * via __builtin_constant_p() allowing gcc to eliminate most of the
357 * code, __msecs_to_jiffies() is called if the value passed does not
358 * allow constant folding and the actual conversion must be done at
359 * runtime.
360 * the HZ range specific helpers _msecs_to_jiffies() are called both
361 * directly here and from __msecs_to_jiffies() in the case where
362 * constant folding is not possible.
363 */
364 static __always_inline unsigned long msecs_to_jiffies(const unsigned int m)
365 {
366 if (__builtin_constant_p(m)) {
367 if ((int)m < 0)
368 return MAX_JIFFY_OFFSET;
369 return _msecs_to_jiffies(m);
370 } else {
371 return __msecs_to_jiffies(m);
372 }
373 }
374
375 extern unsigned long __usecs_to_jiffies(const unsigned int u);
376 #if !(USEC_PER_SEC % HZ)
377 static inline unsigned long _usecs_to_jiffies(const unsigned int u)
378 {
379 return (u + (USEC_PER_SEC / HZ) - 1) / (USEC_PER_SEC / HZ);
380 }
381 #else
382 static inline unsigned long _usecs_to_jiffies(const unsigned int u)
383 {
384 return (USEC_TO_HZ_MUL32 * u + USEC_TO_HZ_ADJ32)
385 >> USEC_TO_HZ_SHR32;
386 }
387 #endif
388
389 /**
390 * usecs_to_jiffies: - convert microseconds to jiffies
391 * @u: time in microseconds
392 *
393 * conversion is done as follows:
394 *
395 * - 'too large' values [that would result in larger than
396 * MAX_JIFFY_OFFSET values] mean 'infinite timeout' too.
397 *
398 * - all other values are converted to jiffies by either multiplying
399 * the input value by a factor or dividing it with a factor and
400 * handling any 32-bit overflows as for msecs_to_jiffies.
401 *
402 * usecs_to_jiffies() checks for the passed in value being a constant
403 * via __builtin_constant_p() allowing gcc to eliminate most of the
404 * code, __usecs_to_jiffies() is called if the value passed does not
405 * allow constant folding and the actual conversion must be done at
406 * runtime.
407 * the HZ range specific helpers _usecs_to_jiffies() are called both
408 * directly here and from __msecs_to_jiffies() in the case where
409 * constant folding is not possible.
410 */
411 static __always_inline unsigned long usecs_to_jiffies(const unsigned int u)
412 {
413 if (__builtin_constant_p(u)) {
414 if (u > jiffies_to_usecs(MAX_JIFFY_OFFSET))
415 return MAX_JIFFY_OFFSET;
416 return _usecs_to_jiffies(u);
417 } else {
418 return __usecs_to_jiffies(u);
419 }
420 }
421
422 extern unsigned long timespec64_to_jiffies(const struct timespec64 *value);
423 extern void jiffies_to_timespec64(const unsigned long jiffies,
424 struct timespec64 *value);
425 static inline unsigned long timespec_to_jiffies(const struct timespec *value)
426 {
427 struct timespec64 ts = timespec_to_timespec64(*value);
428
429 return timespec64_to_jiffies(&ts);
430 }
431
432 static inline void jiffies_to_timespec(const unsigned long jiffies,
433 struct timespec *value)
434 {
435 struct timespec64 ts;
436
437 jiffies_to_timespec64(jiffies, &ts);
438 *value = timespec64_to_timespec(ts);
439 }
440
441 extern unsigned long timeval_to_jiffies(const struct timeval *value);
442 extern void jiffies_to_timeval(const unsigned long jiffies,
443 struct timeval *value);
444
445 extern clock_t jiffies_to_clock_t(unsigned long x);
446 static inline clock_t jiffies_delta_to_clock_t(long delta)
447 {
448 return jiffies_to_clock_t(max(0L, delta));
449 }
450
451 static inline unsigned int jiffies_delta_to_msecs(long delta)
452 {
453 return jiffies_to_msecs(max(0L, delta));
454 }
455
456 extern unsigned long clock_t_to_jiffies(unsigned long x);
457 extern u64 jiffies_64_to_clock_t(u64 x);
458 extern u64 nsec_to_clock_t(u64 x);
459 extern u64 nsecs_to_jiffies64(u64 n);
460 extern unsigned long nsecs_to_jiffies(u64 n);
461
462 #define TIMESTAMP_SIZE 30
463
464 #endif