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1 | #ifndef _LINUX_JIFFIES_H |
2 | #define _LINUX_JIFFIES_H | |
3 | ||
5cca7619 | 4 | #include <linux/calc64.h> |
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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 */ | |
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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 | #else | |
33 | # error You lose. | |
34 | #endif | |
35 | ||
36 | /* LATCH is used in the interval timer and ftape setup. */ | |
37 | #define LATCH ((CLOCK_TICK_RATE + HZ/2) / HZ) /* For divider */ | |
38 | ||
39 | /* Suppose we want to devide two numbers NOM and DEN: NOM/DEN, the we can | |
40 | * improve accuracy by shifting LSH bits, hence calculating: | |
41 | * (NOM << LSH) / DEN | |
42 | * This however means trouble for large NOM, because (NOM << LSH) may no | |
43 | * longer fit in 32 bits. The following way of calculating this gives us | |
44 | * some slack, under the following conditions: | |
45 | * - (NOM / DEN) fits in (32 - LSH) bits. | |
46 | * - (NOM % DEN) fits in (32 - LSH) bits. | |
47 | */ | |
0d94df56 UZ |
48 | #define SH_DIV(NOM,DEN,LSH) ( (((NOM) / (DEN)) << (LSH)) \ |
49 | + ((((NOM) % (DEN)) << (LSH)) + (DEN) / 2) / (DEN)) | |
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50 | |
51 | /* HZ is the requested value. ACTHZ is actual HZ ("<< 8" is for accuracy) */ | |
52 | #define ACTHZ (SH_DIV (CLOCK_TICK_RATE, LATCH, 8)) | |
53 | ||
54 | /* TICK_NSEC is the time between ticks in nsec assuming real ACTHZ */ | |
55 | #define TICK_NSEC (SH_DIV (1000000UL * 1000, ACTHZ, 8)) | |
56 | ||
57 | /* TICK_USEC is the time between ticks in usec assuming fake USER_HZ */ | |
58 | #define TICK_USEC ((1000000UL + USER_HZ/2) / USER_HZ) | |
59 | ||
60 | /* TICK_USEC_TO_NSEC is the time between ticks in nsec assuming real ACTHZ and */ | |
61 | /* a value TUSEC for TICK_USEC (can be set bij adjtimex) */ | |
62 | #define TICK_USEC_TO_NSEC(TUSEC) (SH_DIV (TUSEC * USER_HZ * 1000, ACTHZ, 8)) | |
63 | ||
64 | /* some arch's have a small-data section that can be accessed register-relative | |
65 | * but that can only take up to, say, 4-byte variables. jiffies being part of | |
66 | * an 8-byte variable may not be correctly accessed unless we force the issue | |
67 | */ | |
68 | #define __jiffy_data __attribute__((section(".data"))) | |
69 | ||
70 | /* | |
98c4f0c3 | 71 | * The 64-bit value is not atomic - you MUST NOT read it |
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72 | * without sampling the sequence number in xtime_lock. |
73 | * get_jiffies_64() will do this for you as appropriate. | |
74 | */ | |
75 | extern u64 __jiffy_data jiffies_64; | |
76 | extern unsigned long volatile __jiffy_data jiffies; | |
77 | ||
78 | #if (BITS_PER_LONG < 64) | |
79 | u64 get_jiffies_64(void); | |
80 | #else | |
81 | static inline u64 get_jiffies_64(void) | |
82 | { | |
83 | return (u64)jiffies; | |
84 | } | |
85 | #endif | |
86 | ||
87 | /* | |
88 | * These inlines deal with timer wrapping correctly. You are | |
89 | * strongly encouraged to use them | |
90 | * 1. Because people otherwise forget | |
91 | * 2. Because if the timer wrap changes in future you won't have to | |
92 | * alter your driver code. | |
93 | * | |
94 | * time_after(a,b) returns true if the time a is after time b. | |
95 | * | |
96 | * Do this with "<0" and ">=0" to only test the sign of the result. A | |
97 | * good compiler would generate better code (and a really good compiler | |
98 | * wouldn't care). Gcc is currently neither. | |
99 | */ | |
100 | #define time_after(a,b) \ | |
101 | (typecheck(unsigned long, a) && \ | |
102 | typecheck(unsigned long, b) && \ | |
103 | ((long)(b) - (long)(a) < 0)) | |
104 | #define time_before(a,b) time_after(b,a) | |
105 | ||
106 | #define time_after_eq(a,b) \ | |
107 | (typecheck(unsigned long, a) && \ | |
108 | typecheck(unsigned long, b) && \ | |
109 | ((long)(a) - (long)(b) >= 0)) | |
110 | #define time_before_eq(a,b) time_after_eq(b,a) | |
111 | ||
3b171672 DZ |
112 | /* Same as above, but does so with platform independent 64bit types. |
113 | * These must be used when utilizing jiffies_64 (i.e. return value of | |
114 | * get_jiffies_64() */ | |
115 | #define time_after64(a,b) \ | |
116 | (typecheck(__u64, a) && \ | |
117 | typecheck(__u64, b) && \ | |
118 | ((__s64)(b) - (__s64)(a) < 0)) | |
119 | #define time_before64(a,b) time_after64(b,a) | |
120 | ||
121 | #define time_after_eq64(a,b) \ | |
122 | (typecheck(__u64, a) && \ | |
123 | typecheck(__u64, b) && \ | |
124 | ((__s64)(a) - (__s64)(b) >= 0)) | |
125 | #define time_before_eq64(a,b) time_after_eq64(b,a) | |
126 | ||
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127 | /* |
128 | * Have the 32 bit jiffies value wrap 5 minutes after boot | |
129 | * so jiffies wrap bugs show up earlier. | |
130 | */ | |
131 | #define INITIAL_JIFFIES ((unsigned long)(unsigned int) (-300*HZ)) | |
132 | ||
133 | /* | |
134 | * Change timeval to jiffies, trying to avoid the | |
135 | * most obvious overflows.. | |
136 | * | |
137 | * And some not so obvious. | |
138 | * | |
9f907c01 | 139 | * Note that we don't want to return LONG_MAX, because |
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140 | * for various timeout reasons we often end up having |
141 | * to wait "jiffies+1" in order to guarantee that we wait | |
142 | * at _least_ "jiffies" - so "jiffies+1" had better still | |
143 | * be positive. | |
144 | */ | |
9f907c01 | 145 | #define MAX_JIFFY_OFFSET ((LONG_MAX >> 1)-1) |
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146 | |
147 | /* | |
148 | * We want to do realistic conversions of time so we need to use the same | |
149 | * values the update wall clock code uses as the jiffies size. This value | |
150 | * is: TICK_NSEC (which is defined in timex.h). This | |
151 | * is a constant and is in nanoseconds. We will used scaled math | |
152 | * with a set of scales defined here as SEC_JIFFIE_SC, USEC_JIFFIE_SC and | |
153 | * NSEC_JIFFIE_SC. Note that these defines contain nothing but | |
154 | * constants and so are computed at compile time. SHIFT_HZ (computed in | |
155 | * timex.h) adjusts the scaling for different HZ values. | |
156 | ||
157 | * Scaled math??? What is that? | |
158 | * | |
159 | * Scaled math is a way to do integer math on values that would, | |
160 | * otherwise, either overflow, underflow, or cause undesired div | |
161 | * instructions to appear in the execution path. In short, we "scale" | |
162 | * up the operands so they take more bits (more precision, less | |
163 | * underflow), do the desired operation and then "scale" the result back | |
164 | * by the same amount. If we do the scaling by shifting we avoid the | |
165 | * costly mpy and the dastardly div instructions. | |
166 | ||
167 | * Suppose, for example, we want to convert from seconds to jiffies | |
168 | * where jiffies is defined in nanoseconds as NSEC_PER_JIFFIE. The | |
169 | * simple math is: jiff = (sec * NSEC_PER_SEC) / NSEC_PER_JIFFIE; We | |
170 | * observe that (NSEC_PER_SEC / NSEC_PER_JIFFIE) is a constant which we | |
171 | * might calculate at compile time, however, the result will only have | |
172 | * about 3-4 bits of precision (less for smaller values of HZ). | |
173 | * | |
174 | * So, we scale as follows: | |
175 | * jiff = (sec) * (NSEC_PER_SEC / NSEC_PER_JIFFIE); | |
176 | * jiff = ((sec) * ((NSEC_PER_SEC * SCALE)/ NSEC_PER_JIFFIE)) / SCALE; | |
177 | * Then we make SCALE a power of two so: | |
178 | * jiff = ((sec) * ((NSEC_PER_SEC << SCALE)/ NSEC_PER_JIFFIE)) >> SCALE; | |
179 | * Now we define: | |
180 | * #define SEC_CONV = ((NSEC_PER_SEC << SCALE)/ NSEC_PER_JIFFIE)) | |
181 | * jiff = (sec * SEC_CONV) >> SCALE; | |
182 | * | |
183 | * Often the math we use will expand beyond 32-bits so we tell C how to | |
184 | * do this and pass the 64-bit result of the mpy through the ">> SCALE" | |
185 | * which should take the result back to 32-bits. We want this expansion | |
186 | * to capture as much precision as possible. At the same time we don't | |
187 | * want to overflow so we pick the SCALE to avoid this. In this file, | |
188 | * that means using a different scale for each range of HZ values (as | |
189 | * defined in timex.h). | |
190 | * | |
191 | * For those who want to know, gcc will give a 64-bit result from a "*" | |
192 | * operator if the result is a long long AND at least one of the | |
193 | * operands is cast to long long (usually just prior to the "*" so as | |
194 | * not to confuse it into thinking it really has a 64-bit operand, | |
195 | * which, buy the way, it can do, but it take more code and at least 2 | |
196 | * mpys). | |
197 | ||
198 | * We also need to be aware that one second in nanoseconds is only a | |
199 | * couple of bits away from overflowing a 32-bit word, so we MUST use | |
200 | * 64-bits to get the full range time in nanoseconds. | |
201 | ||
202 | */ | |
203 | ||
204 | /* | |
205 | * Here are the scales we will use. One for seconds, nanoseconds and | |
206 | * microseconds. | |
207 | * | |
208 | * Within the limits of cpp we do a rough cut at the SEC_JIFFIE_SC and | |
209 | * check if the sign bit is set. If not, we bump the shift count by 1. | |
210 | * (Gets an extra bit of precision where we can use it.) | |
211 | * We know it is set for HZ = 1024 and HZ = 100 not for 1000. | |
212 | * Haven't tested others. | |
213 | ||
214 | * Limits of cpp (for #if expressions) only long (no long long), but | |
215 | * then we only need the most signicant bit. | |
216 | */ | |
217 | ||
218 | #define SEC_JIFFIE_SC (31 - SHIFT_HZ) | |
219 | #if !((((NSEC_PER_SEC << 2) / TICK_NSEC) << (SEC_JIFFIE_SC - 2)) & 0x80000000) | |
220 | #undef SEC_JIFFIE_SC | |
221 | #define SEC_JIFFIE_SC (32 - SHIFT_HZ) | |
222 | #endif | |
223 | #define NSEC_JIFFIE_SC (SEC_JIFFIE_SC + 29) | |
224 | #define USEC_JIFFIE_SC (SEC_JIFFIE_SC + 19) | |
225 | #define SEC_CONVERSION ((unsigned long)((((u64)NSEC_PER_SEC << SEC_JIFFIE_SC) +\ | |
226 | TICK_NSEC -1) / (u64)TICK_NSEC)) | |
227 | ||
228 | #define NSEC_CONVERSION ((unsigned long)((((u64)1 << NSEC_JIFFIE_SC) +\ | |
229 | TICK_NSEC -1) / (u64)TICK_NSEC)) | |
230 | #define USEC_CONVERSION \ | |
231 | ((unsigned long)((((u64)NSEC_PER_USEC << USEC_JIFFIE_SC) +\ | |
232 | TICK_NSEC -1) / (u64)TICK_NSEC)) | |
233 | /* | |
234 | * USEC_ROUND is used in the timeval to jiffie conversion. See there | |
235 | * for more details. It is the scaled resolution rounding value. Note | |
236 | * that it is a 64-bit value. Since, when it is applied, we are already | |
237 | * in jiffies (albit scaled), it is nothing but the bits we will shift | |
238 | * off. | |
239 | */ | |
240 | #define USEC_ROUND (u64)(((u64)1 << USEC_JIFFIE_SC) - 1) | |
241 | /* | |
242 | * The maximum jiffie value is (MAX_INT >> 1). Here we translate that | |
243 | * into seconds. The 64-bit case will overflow if we are not careful, | |
244 | * so use the messy SH_DIV macro to do it. Still all constants. | |
245 | */ | |
246 | #if BITS_PER_LONG < 64 | |
247 | # define MAX_SEC_IN_JIFFIES \ | |
248 | (long)((u64)((u64)MAX_JIFFY_OFFSET * TICK_NSEC) / NSEC_PER_SEC) | |
249 | #else /* take care of overflow on 64 bits machines */ | |
250 | # define MAX_SEC_IN_JIFFIES \ | |
251 | (SH_DIV((MAX_JIFFY_OFFSET >> SEC_JIFFIE_SC) * TICK_NSEC, NSEC_PER_SEC, 1) - 1) | |
252 | ||
253 | #endif | |
254 | ||
255 | /* | |
8b9365d7 | 256 | * Convert various time units to each other: |
1da177e4 | 257 | */ |
8b9365d7 IM |
258 | extern unsigned int jiffies_to_msecs(const unsigned long j); |
259 | extern unsigned int jiffies_to_usecs(const unsigned long j); | |
260 | extern unsigned long msecs_to_jiffies(const unsigned int m); | |
261 | extern unsigned long usecs_to_jiffies(const unsigned int u); | |
262 | extern unsigned long timespec_to_jiffies(const struct timespec *value); | |
263 | extern void jiffies_to_timespec(const unsigned long jiffies, | |
264 | struct timespec *value); | |
265 | extern unsigned long timeval_to_jiffies(const struct timeval *value); | |
266 | extern void jiffies_to_timeval(const unsigned long jiffies, | |
267 | struct timeval *value); | |
268 | extern clock_t jiffies_to_clock_t(long x); | |
269 | extern unsigned long clock_t_to_jiffies(unsigned long x); | |
270 | extern u64 jiffies_64_to_clock_t(u64 x); | |
271 | extern u64 nsec_to_clock_t(u64 x); | |
272 | ||
273 | #define TIMESTAMP_SIZE 30 | |
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274 | |
275 | #endif |