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