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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 extern seqlock_t jiffies_lock;
79
80 #if (BITS_PER_LONG < 64)
81 u64 get_jiffies_64(void);
82 #else
83 static inline u64 get_jiffies_64(void)
84 {
85 return (u64)jiffies;
86 }
87 #endif
88
89 /*
90 * These inlines deal with timer wrapping correctly. You are
91 * strongly encouraged to use them
92 * 1. Because people otherwise forget
93 * 2. Because if the timer wrap changes in future you won't have to
94 * alter your driver code.
95 *
96 * time_after(a,b) returns true if the time a is after time b.
97 *
98 * Do this with "<0" and ">=0" to only test the sign of the result. A
99 * good compiler would generate better code (and a really good compiler
100 * wouldn't care). Gcc is currently neither.
101 */
102 #define time_after(a,b) \
103 (typecheck(unsigned long, a) && \
104 typecheck(unsigned long, b) && \
105 ((long)(b) - (long)(a) < 0))
106 #define time_before(a,b) time_after(b,a)
107
108 #define time_after_eq(a,b) \
109 (typecheck(unsigned long, a) && \
110 typecheck(unsigned long, b) && \
111 ((long)(a) - (long)(b) >= 0))
112 #define time_before_eq(a,b) time_after_eq(b,a)
113
114 /*
115 * Calculate whether a is in the range of [b, c].
116 */
117 #define time_in_range(a,b,c) \
118 (time_after_eq(a,b) && \
119 time_before_eq(a,c))
120
121 /*
122 * Calculate whether a is in the range of [b, c).
123 */
124 #define time_in_range_open(a,b,c) \
125 (time_after_eq(a,b) && \
126 time_before(a,c))
127
128 /* Same as above, but does so with platform independent 64bit types.
129 * These must be used when utilizing jiffies_64 (i.e. return value of
130 * get_jiffies_64() */
131 #define time_after64(a,b) \
132 (typecheck(__u64, a) && \
133 typecheck(__u64, b) && \
134 ((__s64)(b) - (__s64)(a) < 0))
135 #define time_before64(a,b) time_after64(b,a)
136
137 #define time_after_eq64(a,b) \
138 (typecheck(__u64, a) && \
139 typecheck(__u64, b) && \
140 ((__s64)(a) - (__s64)(b) >= 0))
141 #define time_before_eq64(a,b) time_after_eq64(b,a)
142
143 /*
144 * These four macros compare jiffies and 'a' for convenience.
145 */
146
147 /* time_is_before_jiffies(a) return true if a is before jiffies */
148 #define time_is_before_jiffies(a) time_after(jiffies, a)
149
150 /* time_is_after_jiffies(a) return true if a is after jiffies */
151 #define time_is_after_jiffies(a) time_before(jiffies, a)
152
153 /* time_is_before_eq_jiffies(a) return true if a is before or equal to jiffies*/
154 #define time_is_before_eq_jiffies(a) time_after_eq(jiffies, a)
155
156 /* time_is_after_eq_jiffies(a) return true if a is after or equal to jiffies*/
157 #define time_is_after_eq_jiffies(a) time_before_eq(jiffies, a)
158
159 /*
160 * Have the 32 bit jiffies value wrap 5 minutes after boot
161 * so jiffies wrap bugs show up earlier.
162 */
163 #define INITIAL_JIFFIES ((unsigned long)(unsigned int) (-300*HZ))
164
165 /*
166 * Change timeval to jiffies, trying to avoid the
167 * most obvious overflows..
168 *
169 * And some not so obvious.
170 *
171 * Note that we don't want to return LONG_MAX, because
172 * for various timeout reasons we often end up having
173 * to wait "jiffies+1" in order to guarantee that we wait
174 * at _least_ "jiffies" - so "jiffies+1" had better still
175 * be positive.
176 */
177 #define MAX_JIFFY_OFFSET ((LONG_MAX >> 1)-1)
178
179 extern unsigned long preset_lpj;
180
181 /*
182 * We want to do realistic conversions of time so we need to use the same
183 * values the update wall clock code uses as the jiffies size. This value
184 * is: TICK_NSEC (which is defined in timex.h). This
185 * is a constant and is in nanoseconds. We will use scaled math
186 * with a set of scales defined here as SEC_JIFFIE_SC, USEC_JIFFIE_SC and
187 * NSEC_JIFFIE_SC. Note that these defines contain nothing but
188 * constants and so are computed at compile time. SHIFT_HZ (computed in
189 * timex.h) adjusts the scaling for different HZ values.
190
191 * Scaled math??? What is that?
192 *
193 * Scaled math is a way to do integer math on values that would,
194 * otherwise, either overflow, underflow, or cause undesired div
195 * instructions to appear in the execution path. In short, we "scale"
196 * up the operands so they take more bits (more precision, less
197 * underflow), do the desired operation and then "scale" the result back
198 * by the same amount. If we do the scaling by shifting we avoid the
199 * costly mpy and the dastardly div instructions.
200
201 * Suppose, for example, we want to convert from seconds to jiffies
202 * where jiffies is defined in nanoseconds as NSEC_PER_JIFFIE. The
203 * simple math is: jiff = (sec * NSEC_PER_SEC) / NSEC_PER_JIFFIE; We
204 * observe that (NSEC_PER_SEC / NSEC_PER_JIFFIE) is a constant which we
205 * might calculate at compile time, however, the result will only have
206 * about 3-4 bits of precision (less for smaller values of HZ).
207 *
208 * So, we scale as follows:
209 * jiff = (sec) * (NSEC_PER_SEC / NSEC_PER_JIFFIE);
210 * jiff = ((sec) * ((NSEC_PER_SEC * SCALE)/ NSEC_PER_JIFFIE)) / SCALE;
211 * Then we make SCALE a power of two so:
212 * jiff = ((sec) * ((NSEC_PER_SEC << SCALE)/ NSEC_PER_JIFFIE)) >> SCALE;
213 * Now we define:
214 * #define SEC_CONV = ((NSEC_PER_SEC << SCALE)/ NSEC_PER_JIFFIE))
215 * jiff = (sec * SEC_CONV) >> SCALE;
216 *
217 * Often the math we use will expand beyond 32-bits so we tell C how to
218 * do this and pass the 64-bit result of the mpy through the ">> SCALE"
219 * which should take the result back to 32-bits. We want this expansion
220 * to capture as much precision as possible. At the same time we don't
221 * want to overflow so we pick the SCALE to avoid this. In this file,
222 * that means using a different scale for each range of HZ values (as
223 * defined in timex.h).
224 *
225 * For those who want to know, gcc will give a 64-bit result from a "*"
226 * operator if the result is a long long AND at least one of the
227 * operands is cast to long long (usually just prior to the "*" so as
228 * not to confuse it into thinking it really has a 64-bit operand,
229 * which, buy the way, it can do, but it takes more code and at least 2
230 * mpys).
231
232 * We also need to be aware that one second in nanoseconds is only a
233 * couple of bits away from overflowing a 32-bit word, so we MUST use
234 * 64-bits to get the full range time in nanoseconds.
235
236 */
237
238 /*
239 * Here are the scales we will use. One for seconds, nanoseconds and
240 * microseconds.
241 *
242 * Within the limits of cpp we do a rough cut at the SEC_JIFFIE_SC and
243 * check if the sign bit is set. If not, we bump the shift count by 1.
244 * (Gets an extra bit of precision where we can use it.)
245 * We know it is set for HZ = 1024 and HZ = 100 not for 1000.
246 * Haven't tested others.
247
248 * Limits of cpp (for #if expressions) only long (no long long), but
249 * then we only need the most signicant bit.
250 */
251
252 #define SEC_JIFFIE_SC (31 - SHIFT_HZ)
253 #if !((((NSEC_PER_SEC << 2) / TICK_NSEC) << (SEC_JIFFIE_SC - 2)) & 0x80000000)
254 #undef SEC_JIFFIE_SC
255 #define SEC_JIFFIE_SC (32 - SHIFT_HZ)
256 #endif
257 #define NSEC_JIFFIE_SC (SEC_JIFFIE_SC + 29)
258 #define USEC_JIFFIE_SC (SEC_JIFFIE_SC + 19)
259 #define SEC_CONVERSION ((unsigned long)((((u64)NSEC_PER_SEC << SEC_JIFFIE_SC) +\
260 TICK_NSEC -1) / (u64)TICK_NSEC))
261
262 #define NSEC_CONVERSION ((unsigned long)((((u64)1 << NSEC_JIFFIE_SC) +\
263 TICK_NSEC -1) / (u64)TICK_NSEC))
264 #define USEC_CONVERSION \
265 ((unsigned long)((((u64)NSEC_PER_USEC << USEC_JIFFIE_SC) +\
266 TICK_NSEC -1) / (u64)TICK_NSEC))
267 /*
268 * USEC_ROUND is used in the timeval to jiffie conversion. See there
269 * for more details. It is the scaled resolution rounding value. Note
270 * that it is a 64-bit value. Since, when it is applied, we are already
271 * in jiffies (albit scaled), it is nothing but the bits we will shift
272 * off.
273 */
274 #define USEC_ROUND (u64)(((u64)1 << USEC_JIFFIE_SC) - 1)
275 /*
276 * The maximum jiffie value is (MAX_INT >> 1). Here we translate that
277 * into seconds. The 64-bit case will overflow if we are not careful,
278 * so use the messy SH_DIV macro to do it. Still all constants.
279 */
280 #if BITS_PER_LONG < 64
281 # define MAX_SEC_IN_JIFFIES \
282 (long)((u64)((u64)MAX_JIFFY_OFFSET * TICK_NSEC) / NSEC_PER_SEC)
283 #else /* take care of overflow on 64 bits machines */
284 # define MAX_SEC_IN_JIFFIES \
285 (SH_DIV((MAX_JIFFY_OFFSET >> SEC_JIFFIE_SC) * TICK_NSEC, NSEC_PER_SEC, 1) - 1)
286
287 #endif
288
289 /*
290 * Convert various time units to each other:
291 */
292 extern unsigned int jiffies_to_msecs(const unsigned long j);
293 extern unsigned int jiffies_to_usecs(const unsigned long j);
294 extern unsigned long msecs_to_jiffies(const unsigned int m);
295 extern unsigned long usecs_to_jiffies(const unsigned int u);
296 extern unsigned long timespec_to_jiffies(const struct timespec *value);
297 extern void jiffies_to_timespec(const unsigned long jiffies,
298 struct timespec *value);
299 extern unsigned long timeval_to_jiffies(const struct timeval *value);
300 extern void jiffies_to_timeval(const unsigned long jiffies,
301 struct timeval *value);
302
303 extern clock_t jiffies_to_clock_t(unsigned long x);
304 static inline clock_t jiffies_delta_to_clock_t(long delta)
305 {
306 return jiffies_to_clock_t(max(0L, delta));
307 }
308
309 extern unsigned long clock_t_to_jiffies(unsigned long x);
310 extern u64 jiffies_64_to_clock_t(u64 x);
311 extern u64 nsec_to_clock_t(u64 x);
312 extern u64 nsecs_to_jiffies64(u64 n);
313 extern unsigned long nsecs_to_jiffies(u64 n);
314
315 #define TIMESTAMP_SIZE 30
316
317 #endif