Line data Source code
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 :
62 : extern 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 : */
79 : extern u64 __cacheline_aligned_in_smp jiffies_64;
80 : extern unsigned long volatile __cacheline_aligned_in_smp __jiffy_arch_data jiffies;
81 :
82 : #if (BITS_PER_LONG < 64)
83 : u64 get_jiffies_64(void);
84 : #else
85 : static 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 :
189 : extern 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 : */
290 : extern unsigned int jiffies_to_msecs(const unsigned long j);
291 : extern unsigned int jiffies_to_usecs(const unsigned long j);
292 :
293 : static inline u64 jiffies_to_nsecs(const unsigned long j)
294 : {
295 : return (u64)jiffies_to_usecs(j) * NSEC_PER_USEC;
296 : }
297 :
298 : extern u64 jiffies64_to_nsecs(u64 j);
299 : extern u64 jiffies64_to_msecs(u64 j);
300 :
301 : extern 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 : */
308 : static inline unsigned long _msecs_to_jiffies(const unsigned int m)
309 : {
310 0 : 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 : */
319 : static 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 : */
330 : static 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 : */
363 : static __always_inline unsigned long msecs_to_jiffies(const unsigned int m)
364 : {
365 63207880 : if (__builtin_constant_p(m)) {
366 0 : if ((int)m < 0)
367 : return MAX_JIFFY_OFFSET;
368 0 : return _msecs_to_jiffies(m);
369 : } else {
370 63207880 : return __msecs_to_jiffies(m);
371 : }
372 : }
373 :
374 : extern unsigned long __usecs_to_jiffies(const unsigned int u);
375 : #if !(USEC_PER_SEC % HZ)
376 : static 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
381 : static 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 : */
410 : static __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 :
421 : extern unsigned long timespec64_to_jiffies(const struct timespec64 *value);
422 : extern void jiffies_to_timespec64(const unsigned long jiffies,
423 : struct timespec64 *value);
424 : extern clock_t jiffies_to_clock_t(unsigned long x);
425 : static inline clock_t jiffies_delta_to_clock_t(long delta)
426 : {
427 : return jiffies_to_clock_t(max(0L, delta));
428 : }
429 :
430 : static inline unsigned int jiffies_delta_to_msecs(long delta)
431 : {
432 : return jiffies_to_msecs(max(0L, delta));
433 : }
434 :
435 : extern unsigned long clock_t_to_jiffies(unsigned long x);
436 : extern u64 jiffies_64_to_clock_t(u64 x);
437 : extern u64 nsec_to_clock_t(u64 x);
438 : extern u64 nsecs_to_jiffies64(u64 n);
439 : extern unsigned long nsecs_to_jiffies(u64 n);
440 :
441 : #define TIMESTAMP_SIZE 30
442 :
443 : #endif
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