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