Root/
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) - (long)(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) - (long)(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) - (__s64)(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) - (__s64)(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 | 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 |
321 |
Branches:
ben-wpan
ben-wpan-stefan
javiroman/ks7010
jz-2.6.34
jz-2.6.34-rc5
jz-2.6.34-rc6
jz-2.6.34-rc7
jz-2.6.35
jz-2.6.36
jz-2.6.37
jz-2.6.38
jz-2.6.39
jz-3.0
jz-3.1
jz-3.11
jz-3.12
jz-3.13
jz-3.15
jz-3.16
jz-3.18-dt
jz-3.2
jz-3.3
jz-3.4
jz-3.5
jz-3.6
jz-3.6-rc2-pwm
jz-3.9
jz-3.9-clk
jz-3.9-rc8
jz47xx
jz47xx-2.6.38
master
Tags:
od-2011-09-04
od-2011-09-18
v2.6.34-rc5
v2.6.34-rc6
v2.6.34-rc7
v3.9