Branch data Line data Source code
1 : : #ifndef _LINUX_JIFFIES_H
2 : : #define _LINUX_JIFFIES_H
3 : :
4 : : #include <linux/math64.h>
5 : : #include <linux/kernel.h>
6 : : #include <linux/types.h>
7 : : #include <linux/time.h>
8 : : #include <linux/timex.h>
9 : : #include <asm/param.h> /* for HZ */
10 : :
11 : : /*
12 : : * The following defines establish the engineering parameters of the PLL
13 : : * model. The HZ variable establishes the timer interrupt frequency, 100 Hz
14 : : * for the SunOS kernel, 256 Hz for the Ultrix kernel and 1024 Hz for the
15 : : * OSF/1 kernel. The SHIFT_HZ define expresses the same value as the
16 : : * nearest power of two in order to avoid hardware multiply operations.
17 : : */
18 : : #if HZ >= 12 && HZ < 24
19 : : # define SHIFT_HZ 4
20 : : #elif HZ >= 24 && HZ < 48
21 : : # define SHIFT_HZ 5
22 : : #elif HZ >= 48 && HZ < 96
23 : : # define SHIFT_HZ 6
24 : : #elif HZ >= 96 && HZ < 192
25 : : # define SHIFT_HZ 7
26 : : #elif HZ >= 192 && HZ < 384
27 : : # define SHIFT_HZ 8
28 : : #elif HZ >= 384 && HZ < 768
29 : : # define SHIFT_HZ 9
30 : : #elif HZ >= 768 && HZ < 1536
31 : : # define SHIFT_HZ 10
32 : : #elif HZ >= 1536 && HZ < 3072
33 : : # define SHIFT_HZ 11
34 : : #elif HZ >= 3072 && HZ < 6144
35 : : # define SHIFT_HZ 12
36 : : #elif HZ >= 6144 && HZ < 12288
37 : : # define SHIFT_HZ 13
38 : : #else
39 : : # error Invalid value of HZ.
40 : : #endif
41 : :
42 : : /* Suppose we want to divide two numbers NOM and DEN: NOM/DEN, then we can
43 : : * improve accuracy by shifting LSH bits, hence calculating:
44 : : * (NOM << LSH) / DEN
45 : : * This however means trouble for large NOM, because (NOM << LSH) may no
46 : : * longer fit in 32 bits. The following way of calculating this gives us
47 : : * some slack, under the following conditions:
48 : : * - (NOM / DEN) fits in (32 - LSH) bits.
49 : : * - (NOM % DEN) fits in (32 - LSH) bits.
50 : : */
51 : : #define SH_DIV(NOM,DEN,LSH) ( (((NOM) / (DEN)) << (LSH)) \
52 : : + ((((NOM) % (DEN)) << (LSH)) + (DEN) / 2) / (DEN))
53 : :
54 : : /* LATCH is used in the interval timer and ftape setup. */
55 : : #define LATCH ((CLOCK_TICK_RATE + HZ/2) / HZ) /* For divider */
56 : :
57 : : extern int register_refined_jiffies(long clock_tick_rate);
58 : :
59 : : /* TICK_NSEC is the time between ticks in nsec assuming SHIFTED_HZ */
60 : : #define TICK_NSEC ((NSEC_PER_SEC+HZ/2)/HZ)
61 : :
62 : : /* TICK_USEC is the time between ticks in usec assuming fake USER_HZ */
63 : : #define TICK_USEC ((1000000UL + USER_HZ/2) / USER_HZ)
64 : :
65 : : /* some arch's have a small-data section that can be accessed register-relative
66 : : * but that can only take up to, say, 4-byte variables. jiffies being part of
67 : : * an 8-byte variable may not be correctly accessed unless we force the issue
68 : : */
69 : : #define __jiffy_data __attribute__((section(".data")))
70 : :
71 : : /*
72 : : * The 64-bit value is not atomic - you MUST NOT read it
73 : : * without sampling the sequence number in jiffies_lock.
74 : : * get_jiffies_64() will do this for you as appropriate.
75 : : */
76 : : extern u64 __jiffy_data jiffies_64;
77 : : extern unsigned long volatile __jiffy_data jiffies;
78 : :
79 : : #if (BITS_PER_LONG < 64)
80 : : u64 get_jiffies_64(void);
81 : : #else
82 : : static inline u64 get_jiffies_64(void)
83 : : {
84 : : return (u64)jiffies;
85 : : }
86 : : #endif
87 : :
88 : : /*
89 : : * These inlines deal with timer wrapping correctly. You are
90 : : * strongly encouraged to use them
91 : : * 1. Because people otherwise forget
92 : : * 2. Because if the timer wrap changes in future you won't have to
93 : : * alter your driver code.
94 : : *
95 : : * time_after(a,b) returns true if the time a is after time b.
96 : : *
97 : : * Do this with "<0" and ">=0" to only test the sign of the result. A
98 : : * good compiler would generate better code (and a really good compiler
99 : : * wouldn't care). Gcc is currently neither.
100 : : */
101 : : #define time_after(a,b) \
102 : : (typecheck(unsigned long, a) && \
103 : : typecheck(unsigned long, b) && \
104 : : ((long)((b) - (a)) < 0))
105 : : #define time_before(a,b) time_after(b,a)
106 : :
107 : : #define time_after_eq(a,b) \
108 : : (typecheck(unsigned long, a) && \
109 : : typecheck(unsigned long, b) && \
110 : : ((long)((a) - (b)) >= 0))
111 : : #define time_before_eq(a,b) time_after_eq(b,a)
112 : :
113 : : /*
114 : : * Calculate whether a is in the range of [b, c].
115 : : */
116 : : #define time_in_range(a,b,c) \
117 : : (time_after_eq(a,b) && \
118 : : time_before_eq(a,c))
119 : :
120 : : /*
121 : : * Calculate whether a is in the range of [b, c).
122 : : */
123 : : #define time_in_range_open(a,b,c) \
124 : : (time_after_eq(a,b) && \
125 : : time_before(a,c))
126 : :
127 : : /* Same as above, but does so with platform independent 64bit types.
128 : : * These must be used when utilizing jiffies_64 (i.e. return value of
129 : : * get_jiffies_64() */
130 : : #define time_after64(a,b) \
131 : : (typecheck(__u64, a) && \
132 : : typecheck(__u64, b) && \
133 : : ((__s64)((b) - (a)) < 0))
134 : : #define time_before64(a,b) time_after64(b,a)
135 : :
136 : : #define time_after_eq64(a,b) \
137 : : (typecheck(__u64, a) && \
138 : : typecheck(__u64, b) && \
139 : : ((__s64)((a) - (b)) >= 0))
140 : : #define time_before_eq64(a,b) time_after_eq64(b,a)
141 : :
142 : : #define time_in_range64(a, b, c) \
143 : : (time_after_eq64(a, b) && \
144 : : time_before_eq64(a, c))
145 : :
146 : : /*
147 : : * These four macros compare jiffies and 'a' for convenience.
148 : : */
149 : :
150 : : /* time_is_before_jiffies(a) return true if a is before jiffies */
151 : : #define time_is_before_jiffies(a) time_after(jiffies, a)
152 : :
153 : : /* time_is_after_jiffies(a) return true if a is after jiffies */
154 : : #define time_is_after_jiffies(a) time_before(jiffies, a)
155 : :
156 : : /* time_is_before_eq_jiffies(a) return true if a is before or equal to jiffies*/
157 : : #define time_is_before_eq_jiffies(a) time_after_eq(jiffies, a)
158 : :
159 : : /* time_is_after_eq_jiffies(a) return true if a is after or equal to jiffies*/
160 : : #define time_is_after_eq_jiffies(a) time_before_eq(jiffies, a)
161 : :
162 : : /*
163 : : * Have the 32 bit jiffies value wrap 5 minutes after boot
164 : : * so jiffies wrap bugs show up earlier.
165 : : */
166 : : #define INITIAL_JIFFIES ((unsigned long)(unsigned int) (-300*HZ))
167 : :
168 : : /*
169 : : * Change timeval to jiffies, trying to avoid the
170 : : * most obvious overflows..
171 : : *
172 : : * And some not so obvious.
173 : : *
174 : : * Note that we don't want to return LONG_MAX, because
175 : : * for various timeout reasons we often end up having
176 : : * to wait "jiffies+1" in order to guarantee that we wait
177 : : * at _least_ "jiffies" - so "jiffies+1" had better still
178 : : * be positive.
179 : : */
180 : : #define MAX_JIFFY_OFFSET ((LONG_MAX >> 1)-1)
181 : :
182 : : extern unsigned long preset_lpj;
183 : :
184 : : /*
185 : : * We want to do realistic conversions of time so we need to use the same
186 : : * values the update wall clock code uses as the jiffies size. This value
187 : : * is: TICK_NSEC (which is defined in timex.h). This
188 : : * is a constant and is in nanoseconds. We will use scaled math
189 : : * with a set of scales defined here as SEC_JIFFIE_SC, USEC_JIFFIE_SC and
190 : : * NSEC_JIFFIE_SC. Note that these defines contain nothing but
191 : : * constants and so are computed at compile time. SHIFT_HZ (computed in
192 : : * timex.h) adjusts the scaling for different HZ values.
193 : :
194 : : * Scaled math??? What is that?
195 : : *
196 : : * Scaled math is a way to do integer math on values that would,
197 : : * otherwise, either overflow, underflow, or cause undesired div
198 : : * instructions to appear in the execution path. In short, we "scale"
199 : : * up the operands so they take more bits (more precision, less
200 : : * underflow), do the desired operation and then "scale" the result back
201 : : * by the same amount. If we do the scaling by shifting we avoid the
202 : : * costly mpy and the dastardly div instructions.
203 : :
204 : : * Suppose, for example, we want to convert from seconds to jiffies
205 : : * where jiffies is defined in nanoseconds as NSEC_PER_JIFFIE. The
206 : : * simple math is: jiff = (sec * NSEC_PER_SEC) / NSEC_PER_JIFFIE; We
207 : : * observe that (NSEC_PER_SEC / NSEC_PER_JIFFIE) is a constant which we
208 : : * might calculate at compile time, however, the result will only have
209 : : * about 3-4 bits of precision (less for smaller values of HZ).
210 : : *
211 : : * So, we scale as follows:
212 : : * jiff = (sec) * (NSEC_PER_SEC / NSEC_PER_JIFFIE);
213 : : * jiff = ((sec) * ((NSEC_PER_SEC * SCALE)/ NSEC_PER_JIFFIE)) / SCALE;
214 : : * Then we make SCALE a power of two so:
215 : : * jiff = ((sec) * ((NSEC_PER_SEC << SCALE)/ NSEC_PER_JIFFIE)) >> SCALE;
216 : : * Now we define:
217 : : * #define SEC_CONV = ((NSEC_PER_SEC << SCALE)/ NSEC_PER_JIFFIE))
218 : : * jiff = (sec * SEC_CONV) >> SCALE;
219 : : *
220 : : * Often the math we use will expand beyond 32-bits so we tell C how to
221 : : * do this and pass the 64-bit result of the mpy through the ">> SCALE"
222 : : * which should take the result back to 32-bits. We want this expansion
223 : : * to capture as much precision as possible. At the same time we don't
224 : : * want to overflow so we pick the SCALE to avoid this. In this file,
225 : : * that means using a different scale for each range of HZ values (as
226 : : * defined in timex.h).
227 : : *
228 : : * For those who want to know, gcc will give a 64-bit result from a "*"
229 : : * operator if the result is a long long AND at least one of the
230 : : * operands is cast to long long (usually just prior to the "*" so as
231 : : * not to confuse it into thinking it really has a 64-bit operand,
232 : : * which, buy the way, it can do, but it takes more code and at least 2
233 : : * mpys).
234 : :
235 : : * We also need to be aware that one second in nanoseconds is only a
236 : : * couple of bits away from overflowing a 32-bit word, so we MUST use
237 : : * 64-bits to get the full range time in nanoseconds.
238 : :
239 : : */
240 : :
241 : : /*
242 : : * Here are the scales we will use. One for seconds, nanoseconds and
243 : : * microseconds.
244 : : *
245 : : * Within the limits of cpp we do a rough cut at the SEC_JIFFIE_SC and
246 : : * check if the sign bit is set. If not, we bump the shift count by 1.
247 : : * (Gets an extra bit of precision where we can use it.)
248 : : * We know it is set for HZ = 1024 and HZ = 100 not for 1000.
249 : : * Haven't tested others.
250 : :
251 : : * Limits of cpp (for #if expressions) only long (no long long), but
252 : : * then we only need the most signicant bit.
253 : : */
254 : :
255 : : #define SEC_JIFFIE_SC (31 - SHIFT_HZ)
256 : : #if !((((NSEC_PER_SEC << 2) / TICK_NSEC) << (SEC_JIFFIE_SC - 2)) & 0x80000000)
257 : : #undef SEC_JIFFIE_SC
258 : : #define SEC_JIFFIE_SC (32 - SHIFT_HZ)
259 : : #endif
260 : : #define NSEC_JIFFIE_SC (SEC_JIFFIE_SC + 29)
261 : : #define USEC_JIFFIE_SC (SEC_JIFFIE_SC + 19)
262 : : #define SEC_CONVERSION ((unsigned long)((((u64)NSEC_PER_SEC << SEC_JIFFIE_SC) +\
263 : : TICK_NSEC -1) / (u64)TICK_NSEC))
264 : :
265 : : #define NSEC_CONVERSION ((unsigned long)((((u64)1 << NSEC_JIFFIE_SC) +\
266 : : TICK_NSEC -1) / (u64)TICK_NSEC))
267 : : #define USEC_CONVERSION \
268 : : ((unsigned long)((((u64)NSEC_PER_USEC << USEC_JIFFIE_SC) +\
269 : : TICK_NSEC -1) / (u64)TICK_NSEC))
270 : : /*
271 : : * USEC_ROUND is used in the timeval to jiffie conversion. See there
272 : : * for more details. It is the scaled resolution rounding value. Note
273 : : * that it is a 64-bit value. Since, when it is applied, we are already
274 : : * in jiffies (albit scaled), it is nothing but the bits we will shift
275 : : * off.
276 : : */
277 : : #define USEC_ROUND (u64)(((u64)1 << USEC_JIFFIE_SC) - 1)
278 : : /*
279 : : * The maximum jiffie value is (MAX_INT >> 1). Here we translate that
280 : : * into seconds. The 64-bit case will overflow if we are not careful,
281 : : * so use the messy SH_DIV macro to do it. Still all constants.
282 : : */
283 : : #if BITS_PER_LONG < 64
284 : : # define MAX_SEC_IN_JIFFIES \
285 : : (long)((u64)((u64)MAX_JIFFY_OFFSET * TICK_NSEC) / NSEC_PER_SEC)
286 : : #else /* take care of overflow on 64 bits machines */
287 : : # define MAX_SEC_IN_JIFFIES \
288 : : (SH_DIV((MAX_JIFFY_OFFSET >> SEC_JIFFIE_SC) * TICK_NSEC, NSEC_PER_SEC, 1) - 1)
289 : :
290 : : #endif
291 : :
292 : : /*
293 : : * Convert various time units to each other:
294 : : */
295 : : extern unsigned int jiffies_to_msecs(const unsigned long j);
296 : : extern unsigned int jiffies_to_usecs(const unsigned long j);
297 : : extern unsigned long msecs_to_jiffies(const unsigned int m);
298 : : extern unsigned long usecs_to_jiffies(const unsigned int u);
299 : : extern unsigned long timespec_to_jiffies(const struct timespec *value);
300 : : extern void jiffies_to_timespec(const unsigned long jiffies,
301 : : struct timespec *value);
302 : : extern unsigned long timeval_to_jiffies(const struct timeval *value);
303 : : extern void jiffies_to_timeval(const unsigned long jiffies,
304 : : struct timeval *value);
305 : :
306 : : extern clock_t jiffies_to_clock_t(unsigned long x);
307 : : static inline clock_t jiffies_delta_to_clock_t(long delta)
308 : : {
309 : 214 : return jiffies_to_clock_t(max(0L, delta));
310 : : }
311 : :
312 : : extern unsigned long clock_t_to_jiffies(unsigned long x);
313 : : extern u64 jiffies_64_to_clock_t(u64 x);
314 : : extern u64 nsec_to_clock_t(u64 x);
315 : : extern u64 nsecs_to_jiffies64(u64 n);
316 : : extern unsigned long nsecs_to_jiffies(u64 n);
317 : :
318 : : #define TIMESTAMP_SIZE 30
319 : :
320 : : #endif
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