1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef _LINUX_JIFFIES_H
3 #define _LINUX_JIFFIES_H
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 <vdso/jiffies.h>
12 #include <asm/param.h> /* for HZ */
13 #include <generated/timeconst.h>
16 * The following defines establish the engineering parameters of the PLL
17 * model. The HZ variable establishes the timer interrupt frequency, 100 Hz
18 * for the SunOS kernel, 256 Hz for the Ultrix kernel and 1024 Hz for the
19 * OSF/1 kernel. The SHIFT_HZ define expresses the same value as the
20 * nearest power of two in order to avoid hardware multiply operations.
22 #if HZ >= 12 && HZ < 24
24 #elif HZ >= 24 && HZ < 48
26 #elif HZ >= 48 && HZ < 96
28 #elif HZ >= 96 && HZ < 192
30 #elif HZ >= 192 && HZ < 384
32 #elif HZ >= 384 && HZ < 768
34 #elif HZ >= 768 && HZ < 1536
36 #elif HZ >= 1536 && HZ < 3072
38 #elif HZ >= 3072 && HZ < 6144
40 #elif HZ >= 6144 && HZ < 12288
43 # error Invalid value of HZ.
46 /* Suppose we want to divide two numbers NOM and DEN: NOM/DEN, then we can
47 * improve accuracy by shifting LSH bits, hence calculating:
49 * This however means trouble for large NOM, because (NOM << LSH) may no
50 * longer fit in 32 bits. The following way of calculating this gives us
51 * some slack, under the following conditions:
52 * - (NOM / DEN) fits in (32 - LSH) bits.
53 * - (NOM % DEN) fits in (32 - LSH) bits.
55 #define SH_DIV(NOM,DEN,LSH) ( (((NOM) / (DEN)) << (LSH)) \
56 + ((((NOM) % (DEN)) << (LSH)) + (DEN) / 2) / (DEN))
58 /* LATCH is used in the interval timer and ftape setup. */
59 #define LATCH ((CLOCK_TICK_RATE + HZ/2) / HZ) /* For divider */
61 extern int register_refined_jiffies(long clock_tick_rate
);
63 /* TICK_USEC is the time between ticks in usec assuming SHIFTED_HZ */
64 #define TICK_USEC ((USEC_PER_SEC + HZ/2) / HZ)
66 /* USER_TICK_USEC is the time between ticks in usec assuming fake USER_HZ */
67 #define USER_TICK_USEC ((1000000UL + USER_HZ/2) / USER_HZ)
69 #ifndef __jiffy_arch_data
70 #define __jiffy_arch_data
74 * The 64-bit value is not atomic - you MUST NOT read it
75 * without sampling the sequence number in jiffies_lock.
76 * get_jiffies_64() will do this for you as appropriate.
78 extern u64 __cacheline_aligned_in_smp jiffies_64
;
79 extern unsigned long volatile __cacheline_aligned_in_smp __jiffy_arch_data jiffies
;
81 #if (BITS_PER_LONG < 64)
82 u64
get_jiffies_64(void);
84 static inline u64
get_jiffies_64(void)
91 * These inlines deal with timer wrapping correctly. You are
92 * strongly encouraged to use them
93 * 1. Because people otherwise forget
94 * 2. Because if the timer wrap changes in future you won't have to
95 * alter your driver code.
97 * time_after(a,b) returns true if the time a is after time b.
99 * Do this with "<0" and ">=0" to only test the sign of the result. A
100 * good compiler would generate better code (and a really good compiler
101 * wouldn't care). Gcc is currently neither.
103 #define time_after(a,b) \
104 (typecheck(unsigned long, a) && \
105 typecheck(unsigned long, b) && \
106 ((long)((b) - (a)) < 0))
107 #define time_before(a,b) time_after(b,a)
109 #define time_after_eq(a,b) \
110 (typecheck(unsigned long, a) && \
111 typecheck(unsigned long, b) && \
112 ((long)((a) - (b)) >= 0))
113 #define time_before_eq(a,b) time_after_eq(b,a)
116 * Calculate whether a is in the range of [b, c].
118 #define time_in_range(a,b,c) \
119 (time_after_eq(a,b) && \
123 * Calculate whether a is in the range of [b, c).
125 #define time_in_range_open(a,b,c) \
126 (time_after_eq(a,b) && \
129 /* Same as above, but does so with platform independent 64bit types.
130 * These must be used when utilizing jiffies_64 (i.e. return value of
131 * get_jiffies_64() */
132 #define time_after64(a,b) \
133 (typecheck(__u64, a) && \
134 typecheck(__u64, b) && \
135 ((__s64)((b) - (a)) < 0))
136 #define time_before64(a,b) time_after64(b,a)
138 #define time_after_eq64(a,b) \
139 (typecheck(__u64, a) && \
140 typecheck(__u64, b) && \
141 ((__s64)((a) - (b)) >= 0))
142 #define time_before_eq64(a,b) time_after_eq64(b,a)
144 #define time_in_range64(a, b, c) \
145 (time_after_eq64(a, b) && \
146 time_before_eq64(a, c))
149 * These four macros compare jiffies and 'a' for convenience.
152 /* time_is_before_jiffies(a) return true if a is before jiffies */
153 #define time_is_before_jiffies(a) time_after(jiffies, a)
154 #define time_is_before_jiffies64(a) time_after64(get_jiffies_64(), a)
156 /* time_is_after_jiffies(a) return true if a is after jiffies */
157 #define time_is_after_jiffies(a) time_before(jiffies, a)
158 #define time_is_after_jiffies64(a) time_before64(get_jiffies_64(), a)
160 /* time_is_before_eq_jiffies(a) return true if a is before or equal to jiffies*/
161 #define time_is_before_eq_jiffies(a) time_after_eq(jiffies, a)
162 #define time_is_before_eq_jiffies64(a) time_after_eq64(get_jiffies_64(), a)
164 /* time_is_after_eq_jiffies(a) return true if a is after or equal to jiffies*/
165 #define time_is_after_eq_jiffies(a) time_before_eq(jiffies, a)
166 #define time_is_after_eq_jiffies64(a) time_before_eq64(get_jiffies_64(), a)
169 * Have the 32 bit jiffies value wrap 5 minutes after boot
170 * so jiffies wrap bugs show up earlier.
172 #define INITIAL_JIFFIES ((unsigned long)(unsigned int) (-300*HZ))
175 * Change timeval to jiffies, trying to avoid the
176 * most obvious overflows..
178 * And some not so obvious.
180 * Note that we don't want to return LONG_MAX, because
181 * for various timeout reasons we often end up having
182 * to wait "jiffies+1" in order to guarantee that we wait
183 * at _least_ "jiffies" - so "jiffies+1" had better still
186 #define MAX_JIFFY_OFFSET ((LONG_MAX >> 1)-1)
188 extern unsigned long preset_lpj
;
191 * We want to do realistic conversions of time so we need to use the same
192 * values the update wall clock code uses as the jiffies size. This value
193 * is: TICK_NSEC (which is defined in timex.h). This
194 * is a constant and is in nanoseconds. We will use scaled math
195 * with a set of scales defined here as SEC_JIFFIE_SC, USEC_JIFFIE_SC and
196 * NSEC_JIFFIE_SC. Note that these defines contain nothing but
197 * constants and so are computed at compile time. SHIFT_HZ (computed in
198 * timex.h) adjusts the scaling for different HZ values.
200 * Scaled math??? What is that?
202 * Scaled math is a way to do integer math on values that would,
203 * otherwise, either overflow, underflow, or cause undesired div
204 * instructions to appear in the execution path. In short, we "scale"
205 * up the operands so they take more bits (more precision, less
206 * underflow), do the desired operation and then "scale" the result back
207 * by the same amount. If we do the scaling by shifting we avoid the
208 * costly mpy and the dastardly div instructions.
210 * Suppose, for example, we want to convert from seconds to jiffies
211 * where jiffies is defined in nanoseconds as NSEC_PER_JIFFIE. The
212 * simple math is: jiff = (sec * NSEC_PER_SEC) / NSEC_PER_JIFFIE; We
213 * observe that (NSEC_PER_SEC / NSEC_PER_JIFFIE) is a constant which we
214 * might calculate at compile time, however, the result will only have
215 * about 3-4 bits of precision (less for smaller values of HZ).
217 * So, we scale as follows:
218 * jiff = (sec) * (NSEC_PER_SEC / NSEC_PER_JIFFIE);
219 * jiff = ((sec) * ((NSEC_PER_SEC * SCALE)/ NSEC_PER_JIFFIE)) / SCALE;
220 * Then we make SCALE a power of two so:
221 * jiff = ((sec) * ((NSEC_PER_SEC << SCALE)/ NSEC_PER_JIFFIE)) >> SCALE;
223 * #define SEC_CONV = ((NSEC_PER_SEC << SCALE)/ NSEC_PER_JIFFIE))
224 * jiff = (sec * SEC_CONV) >> SCALE;
226 * Often the math we use will expand beyond 32-bits so we tell C how to
227 * do this and pass the 64-bit result of the mpy through the ">> SCALE"
228 * which should take the result back to 32-bits. We want this expansion
229 * to capture as much precision as possible. At the same time we don't
230 * want to overflow so we pick the SCALE to avoid this. In this file,
231 * that means using a different scale for each range of HZ values (as
232 * defined in timex.h).
234 * For those who want to know, gcc will give a 64-bit result from a "*"
235 * operator if the result is a long long AND at least one of the
236 * operands is cast to long long (usually just prior to the "*" so as
237 * not to confuse it into thinking it really has a 64-bit operand,
238 * which, buy the way, it can do, but it takes more code and at least 2
241 * We also need to be aware that one second in nanoseconds is only a
242 * couple of bits away from overflowing a 32-bit word, so we MUST use
243 * 64-bits to get the full range time in nanoseconds.
248 * Here are the scales we will use. One for seconds, nanoseconds and
251 * Within the limits of cpp we do a rough cut at the SEC_JIFFIE_SC and
252 * check if the sign bit is set. If not, we bump the shift count by 1.
253 * (Gets an extra bit of precision where we can use it.)
254 * We know it is set for HZ = 1024 and HZ = 100 not for 1000.
255 * Haven't tested others.
257 * Limits of cpp (for #if expressions) only long (no long long), but
258 * then we only need the most signicant bit.
261 #define SEC_JIFFIE_SC (31 - SHIFT_HZ)
262 #if !((((NSEC_PER_SEC << 2) / TICK_NSEC) << (SEC_JIFFIE_SC - 2)) & 0x80000000)
264 #define SEC_JIFFIE_SC (32 - SHIFT_HZ)
266 #define NSEC_JIFFIE_SC (SEC_JIFFIE_SC + 29)
267 #define SEC_CONVERSION ((unsigned long)((((u64)NSEC_PER_SEC << SEC_JIFFIE_SC) +\
268 TICK_NSEC -1) / (u64)TICK_NSEC))
270 #define NSEC_CONVERSION ((unsigned long)((((u64)1 << NSEC_JIFFIE_SC) +\
271 TICK_NSEC -1) / (u64)TICK_NSEC))
273 * The maximum jiffie value is (MAX_INT >> 1). Here we translate that
274 * into seconds. The 64-bit case will overflow if we are not careful,
275 * so use the messy SH_DIV macro to do it. Still all constants.
277 #if BITS_PER_LONG < 64
278 # define MAX_SEC_IN_JIFFIES \
279 (long)((u64)((u64)MAX_JIFFY_OFFSET * TICK_NSEC) / NSEC_PER_SEC)
280 #else /* take care of overflow on 64 bits machines */
281 # define MAX_SEC_IN_JIFFIES \
282 (SH_DIV((MAX_JIFFY_OFFSET >> SEC_JIFFIE_SC) * TICK_NSEC, NSEC_PER_SEC, 1) - 1)
287 * Convert various time units to each other:
289 extern unsigned int jiffies_to_msecs(const unsigned long j
);
290 extern unsigned int jiffies_to_usecs(const unsigned long j
);
292 static inline u64
jiffies_to_nsecs(const unsigned long j
)
294 return (u64
)jiffies_to_usecs(j
) * NSEC_PER_USEC
;
297 extern u64
jiffies64_to_nsecs(u64 j
);
298 extern u64
jiffies64_to_msecs(u64 j
);
300 extern unsigned long __msecs_to_jiffies(const unsigned int m
);
301 #if HZ <= MSEC_PER_SEC && !(MSEC_PER_SEC % HZ)
303 * HZ is equal to or smaller than 1000, and 1000 is a nice round
304 * multiple of HZ, divide with the factor between them, but round
307 static inline unsigned long _msecs_to_jiffies(const unsigned int m
)
309 return (m
+ (MSEC_PER_SEC
/ HZ
) - 1) / (MSEC_PER_SEC
/ HZ
);
311 #elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC)
313 * HZ is larger than 1000, and HZ is a nice round multiple of 1000 -
314 * simply multiply with the factor between them.
316 * But first make sure the multiplication result cannot overflow:
318 static inline unsigned long _msecs_to_jiffies(const unsigned int m
)
320 if (m
> jiffies_to_msecs(MAX_JIFFY_OFFSET
))
321 return MAX_JIFFY_OFFSET
;
322 return m
* (HZ
/ MSEC_PER_SEC
);
326 * Generic case - multiply, round and divide. But first check that if
327 * we are doing a net multiplication, that we wouldn't overflow:
329 static inline unsigned long _msecs_to_jiffies(const unsigned int m
)
331 if (HZ
> MSEC_PER_SEC
&& m
> jiffies_to_msecs(MAX_JIFFY_OFFSET
))
332 return MAX_JIFFY_OFFSET
;
334 return (MSEC_TO_HZ_MUL32
* m
+ MSEC_TO_HZ_ADJ32
) >> MSEC_TO_HZ_SHR32
;
338 * msecs_to_jiffies: - convert milliseconds to jiffies
339 * @m: time in milliseconds
341 * conversion is done as follows:
343 * - negative values mean 'infinite timeout' (MAX_JIFFY_OFFSET)
345 * - 'too large' values [that would result in larger than
346 * MAX_JIFFY_OFFSET values] mean 'infinite timeout' too.
348 * - all other values are converted to jiffies by either multiplying
349 * the input value by a factor or dividing it with a factor and
350 * handling any 32-bit overflows.
351 * for the details see __msecs_to_jiffies()
353 * msecs_to_jiffies() checks for the passed in value being a constant
354 * via __builtin_constant_p() allowing gcc to eliminate most of the
355 * code, __msecs_to_jiffies() is called if the value passed does not
356 * allow constant folding and the actual conversion must be done at
358 * the HZ range specific helpers _msecs_to_jiffies() are called both
359 * directly here and from __msecs_to_jiffies() in the case where
360 * constant folding is not possible.
362 static __always_inline
unsigned long msecs_to_jiffies(const unsigned int m
)
364 if (__builtin_constant_p(m
)) {
366 return MAX_JIFFY_OFFSET
;
367 return _msecs_to_jiffies(m
);
369 return __msecs_to_jiffies(m
);
373 extern unsigned long __usecs_to_jiffies(const unsigned int u
);
374 #if !(USEC_PER_SEC % HZ)
375 static inline unsigned long _usecs_to_jiffies(const unsigned int u
)
377 return (u
+ (USEC_PER_SEC
/ HZ
) - 1) / (USEC_PER_SEC
/ HZ
);
380 static inline unsigned long _usecs_to_jiffies(const unsigned int u
)
382 return (USEC_TO_HZ_MUL32
* u
+ USEC_TO_HZ_ADJ32
)
388 * usecs_to_jiffies: - convert microseconds to jiffies
389 * @u: time in microseconds
391 * conversion is done as follows:
393 * - 'too large' values [that would result in larger than
394 * MAX_JIFFY_OFFSET values] mean 'infinite timeout' too.
396 * - all other values are converted to jiffies by either multiplying
397 * the input value by a factor or dividing it with a factor and
398 * handling any 32-bit overflows as for msecs_to_jiffies.
400 * usecs_to_jiffies() checks for the passed in value being a constant
401 * via __builtin_constant_p() allowing gcc to eliminate most of the
402 * code, __usecs_to_jiffies() is called if the value passed does not
403 * allow constant folding and the actual conversion must be done at
405 * the HZ range specific helpers _usecs_to_jiffies() are called both
406 * directly here and from __msecs_to_jiffies() in the case where
407 * constant folding is not possible.
409 static __always_inline
unsigned long usecs_to_jiffies(const unsigned int u
)
411 if (__builtin_constant_p(u
)) {
412 if (u
> jiffies_to_usecs(MAX_JIFFY_OFFSET
))
413 return MAX_JIFFY_OFFSET
;
414 return _usecs_to_jiffies(u
);
416 return __usecs_to_jiffies(u
);
420 extern unsigned long timespec64_to_jiffies(const struct timespec64
*value
);
421 extern void jiffies_to_timespec64(const unsigned long jiffies
,
422 struct timespec64
*value
);
423 extern clock_t jiffies_to_clock_t(unsigned long x
);
424 static inline clock_t jiffies_delta_to_clock_t(long delta
)
426 return jiffies_to_clock_t(max(0L, delta
));
429 static inline unsigned int jiffies_delta_to_msecs(long delta
)
431 return jiffies_to_msecs(max(0L, delta
));
434 extern unsigned long clock_t_to_jiffies(unsigned long x
);
435 extern u64
jiffies_64_to_clock_t(u64 x
);
436 extern u64
nsec_to_clock_t(u64 x
);
437 extern u64
nsecs_to_jiffies64(u64 n
);
438 extern unsigned long nsecs_to_jiffies(u64 n
);
440 #define TIMESTAMP_SIZE 30