| #ifndef _LINUX_JIFFIES_H |
| #define _LINUX_JIFFIES_H |
| |
| #include <linux/calc64.h> |
| #include <linux/kernel.h> |
| #include <linux/types.h> |
| #include <linux/time.h> |
| #include <linux/timex.h> |
| #include <asm/param.h> /* for HZ */ |
| |
| /* |
| * The following defines establish the engineering parameters of the PLL |
| * model. The HZ variable establishes the timer interrupt frequency, 100 Hz |
| * for the SunOS kernel, 256 Hz for the Ultrix kernel and 1024 Hz for the |
| * OSF/1 kernel. The SHIFT_HZ define expresses the same value as the |
| * nearest power of two in order to avoid hardware multiply operations. |
| */ |
| #if HZ >= 12 && HZ < 24 |
| # define SHIFT_HZ 4 |
| #elif HZ >= 24 && HZ < 48 |
| # define SHIFT_HZ 5 |
| #elif HZ >= 48 && HZ < 96 |
| # define SHIFT_HZ 6 |
| #elif HZ >= 96 && HZ < 192 |
| # define SHIFT_HZ 7 |
| #elif HZ >= 192 && HZ < 384 |
| # define SHIFT_HZ 8 |
| #elif HZ >= 384 && HZ < 768 |
| # define SHIFT_HZ 9 |
| #elif HZ >= 768 && HZ < 1536 |
| # define SHIFT_HZ 10 |
| #else |
| # error You lose. |
| #endif |
| |
| /* LATCH is used in the interval timer and ftape setup. */ |
| #define LATCH ((CLOCK_TICK_RATE + HZ/2) / HZ) /* For divider */ |
| |
| /* Suppose we want to devide two numbers NOM and DEN: NOM/DEN, the we can |
| * improve accuracy by shifting LSH bits, hence calculating: |
| * (NOM << LSH) / DEN |
| * This however means trouble for large NOM, because (NOM << LSH) may no |
| * longer fit in 32 bits. The following way of calculating this gives us |
| * some slack, under the following conditions: |
| * - (NOM / DEN) fits in (32 - LSH) bits. |
| * - (NOM % DEN) fits in (32 - LSH) bits. |
| */ |
| #define SH_DIV(NOM,DEN,LSH) ( (((NOM) / (DEN)) << (LSH)) \ |
| + ((((NOM) % (DEN)) << (LSH)) + (DEN) / 2) / (DEN)) |
| |
| /* HZ is the requested value. ACTHZ is actual HZ ("<< 8" is for accuracy) */ |
| #define ACTHZ (SH_DIV (CLOCK_TICK_RATE, LATCH, 8)) |
| |
| /* TICK_NSEC is the time between ticks in nsec assuming real ACTHZ */ |
| #define TICK_NSEC (SH_DIV (1000000UL * 1000, ACTHZ, 8)) |
| |
| /* TICK_USEC is the time between ticks in usec assuming fake USER_HZ */ |
| #define TICK_USEC ((1000000UL + USER_HZ/2) / USER_HZ) |
| |
| /* TICK_USEC_TO_NSEC is the time between ticks in nsec assuming real ACTHZ and */ |
| /* a value TUSEC for TICK_USEC (can be set bij adjtimex) */ |
| #define TICK_USEC_TO_NSEC(TUSEC) (SH_DIV (TUSEC * USER_HZ * 1000, ACTHZ, 8)) |
| |
| /* some arch's have a small-data section that can be accessed register-relative |
| * but that can only take up to, say, 4-byte variables. jiffies being part of |
| * an 8-byte variable may not be correctly accessed unless we force the issue |
| */ |
| #define __jiffy_data __attribute__((section(".data"))) |
| |
| /* |
| * The 64-bit value is not atomic - you MUST NOT read it |
| * without sampling the sequence number in xtime_lock. |
| * get_jiffies_64() will do this for you as appropriate. |
| */ |
| extern u64 __jiffy_data jiffies_64; |
| extern unsigned long volatile __jiffy_data jiffies; |
| |
| #if (BITS_PER_LONG < 64) |
| u64 get_jiffies_64(void); |
| #else |
| static inline u64 get_jiffies_64(void) |
| { |
| return (u64)jiffies; |
| } |
| #endif |
| |
| /* |
| * These inlines deal with timer wrapping correctly. You are |
| * strongly encouraged to use them |
| * 1. Because people otherwise forget |
| * 2. Because if the timer wrap changes in future you won't have to |
| * alter your driver code. |
| * |
| * time_after(a,b) returns true if the time a is after time b. |
| * |
| * Do this with "<0" and ">=0" to only test the sign of the result. A |
| * good compiler would generate better code (and a really good compiler |
| * wouldn't care). Gcc is currently neither. |
| */ |
| #define time_after(a,b) \ |
| (typecheck(unsigned long, a) && \ |
| typecheck(unsigned long, b) && \ |
| ((long)(b) - (long)(a) < 0)) |
| #define time_before(a,b) time_after(b,a) |
| |
| #define time_after_eq(a,b) \ |
| (typecheck(unsigned long, a) && \ |
| typecheck(unsigned long, b) && \ |
| ((long)(a) - (long)(b) >= 0)) |
| #define time_before_eq(a,b) time_after_eq(b,a) |
| |
| #define time_in_range(a,b,c) \ |
| (time_after_eq(a,b) && \ |
| time_before_eq(a,c)) |
| |
| /* Same as above, but does so with platform independent 64bit types. |
| * These must be used when utilizing jiffies_64 (i.e. return value of |
| * get_jiffies_64() */ |
| #define time_after64(a,b) \ |
| (typecheck(__u64, a) && \ |
| typecheck(__u64, b) && \ |
| ((__s64)(b) - (__s64)(a) < 0)) |
| #define time_before64(a,b) time_after64(b,a) |
| |
| #define time_after_eq64(a,b) \ |
| (typecheck(__u64, a) && \ |
| typecheck(__u64, b) && \ |
| ((__s64)(a) - (__s64)(b) >= 0)) |
| #define time_before_eq64(a,b) time_after_eq64(b,a) |
| |
| /* |
| * Have the 32 bit jiffies value wrap 5 minutes after boot |
| * so jiffies wrap bugs show up earlier. |
| */ |
| #define INITIAL_JIFFIES ((unsigned long)(unsigned int) (-300*HZ)) |
| |
| /* |
| * Change timeval to jiffies, trying to avoid the |
| * most obvious overflows.. |
| * |
| * And some not so obvious. |
| * |
| * Note that we don't want to return LONG_MAX, because |
| * for various timeout reasons we often end up having |
| * to wait "jiffies+1" in order to guarantee that we wait |
| * at _least_ "jiffies" - so "jiffies+1" had better still |
| * be positive. |
| */ |
| #define MAX_JIFFY_OFFSET ((LONG_MAX >> 1)-1) |
| |
| /* |
| * We want to do realistic conversions of time so we need to use the same |
| * values the update wall clock code uses as the jiffies size. This value |
| * is: TICK_NSEC (which is defined in timex.h). This |
| * is a constant and is in nanoseconds. We will used scaled math |
| * with a set of scales defined here as SEC_JIFFIE_SC, USEC_JIFFIE_SC and |
| * NSEC_JIFFIE_SC. Note that these defines contain nothing but |
| * constants and so are computed at compile time. SHIFT_HZ (computed in |
| * timex.h) adjusts the scaling for different HZ values. |
| |
| * Scaled math??? What is that? |
| * |
| * Scaled math is a way to do integer math on values that would, |
| * otherwise, either overflow, underflow, or cause undesired div |
| * instructions to appear in the execution path. In short, we "scale" |
| * up the operands so they take more bits (more precision, less |
| * underflow), do the desired operation and then "scale" the result back |
| * by the same amount. If we do the scaling by shifting we avoid the |
| * costly mpy and the dastardly div instructions. |
| |
| * Suppose, for example, we want to convert from seconds to jiffies |
| * where jiffies is defined in nanoseconds as NSEC_PER_JIFFIE. The |
| * simple math is: jiff = (sec * NSEC_PER_SEC) / NSEC_PER_JIFFIE; We |
| * observe that (NSEC_PER_SEC / NSEC_PER_JIFFIE) is a constant which we |
| * might calculate at compile time, however, the result will only have |
| * about 3-4 bits of precision (less for smaller values of HZ). |
| * |
| * So, we scale as follows: |
| * jiff = (sec) * (NSEC_PER_SEC / NSEC_PER_JIFFIE); |
| * jiff = ((sec) * ((NSEC_PER_SEC * SCALE)/ NSEC_PER_JIFFIE)) / SCALE; |
| * Then we make SCALE a power of two so: |
| * jiff = ((sec) * ((NSEC_PER_SEC << SCALE)/ NSEC_PER_JIFFIE)) >> SCALE; |
| * Now we define: |
| * #define SEC_CONV = ((NSEC_PER_SEC << SCALE)/ NSEC_PER_JIFFIE)) |
| * jiff = (sec * SEC_CONV) >> SCALE; |
| * |
| * Often the math we use will expand beyond 32-bits so we tell C how to |
| * do this and pass the 64-bit result of the mpy through the ">> SCALE" |
| * which should take the result back to 32-bits. We want this expansion |
| * to capture as much precision as possible. At the same time we don't |
| * want to overflow so we pick the SCALE to avoid this. In this file, |
| * that means using a different scale for each range of HZ values (as |
| * defined in timex.h). |
| * |
| * For those who want to know, gcc will give a 64-bit result from a "*" |
| * operator if the result is a long long AND at least one of the |
| * operands is cast to long long (usually just prior to the "*" so as |
| * not to confuse it into thinking it really has a 64-bit operand, |
| * which, buy the way, it can do, but it take more code and at least 2 |
| * mpys). |
| |
| * We also need to be aware that one second in nanoseconds is only a |
| * couple of bits away from overflowing a 32-bit word, so we MUST use |
| * 64-bits to get the full range time in nanoseconds. |
| |
| */ |
| |
| /* |
| * Here are the scales we will use. One for seconds, nanoseconds and |
| * microseconds. |
| * |
| * Within the limits of cpp we do a rough cut at the SEC_JIFFIE_SC and |
| * check if the sign bit is set. If not, we bump the shift count by 1. |
| * (Gets an extra bit of precision where we can use it.) |
| * We know it is set for HZ = 1024 and HZ = 100 not for 1000. |
| * Haven't tested others. |
| |
| * Limits of cpp (for #if expressions) only long (no long long), but |
| * then we only need the most signicant bit. |
| */ |
| |
| #define SEC_JIFFIE_SC (31 - SHIFT_HZ) |
| #if !((((NSEC_PER_SEC << 2) / TICK_NSEC) << (SEC_JIFFIE_SC - 2)) & 0x80000000) |
| #undef SEC_JIFFIE_SC |
| #define SEC_JIFFIE_SC (32 - SHIFT_HZ) |
| #endif |
| #define NSEC_JIFFIE_SC (SEC_JIFFIE_SC + 29) |
| #define USEC_JIFFIE_SC (SEC_JIFFIE_SC + 19) |
| #define SEC_CONVERSION ((unsigned long)((((u64)NSEC_PER_SEC << SEC_JIFFIE_SC) +\ |
| TICK_NSEC -1) / (u64)TICK_NSEC)) |
| |
| #define NSEC_CONVERSION ((unsigned long)((((u64)1 << NSEC_JIFFIE_SC) +\ |
| TICK_NSEC -1) / (u64)TICK_NSEC)) |
| #define USEC_CONVERSION \ |
| ((unsigned long)((((u64)NSEC_PER_USEC << USEC_JIFFIE_SC) +\ |
| TICK_NSEC -1) / (u64)TICK_NSEC)) |
| /* |
| * USEC_ROUND is used in the timeval to jiffie conversion. See there |
| * for more details. It is the scaled resolution rounding value. Note |
| * that it is a 64-bit value. Since, when it is applied, we are already |
| * in jiffies (albit scaled), it is nothing but the bits we will shift |
| * off. |
| */ |
| #define USEC_ROUND (u64)(((u64)1 << USEC_JIFFIE_SC) - 1) |
| /* |
| * The maximum jiffie value is (MAX_INT >> 1). Here we translate that |
| * into seconds. The 64-bit case will overflow if we are not careful, |
| * so use the messy SH_DIV macro to do it. Still all constants. |
| */ |
| #if BITS_PER_LONG < 64 |
| # define MAX_SEC_IN_JIFFIES \ |
| (long)((u64)((u64)MAX_JIFFY_OFFSET * TICK_NSEC) / NSEC_PER_SEC) |
| #else /* take care of overflow on 64 bits machines */ |
| # define MAX_SEC_IN_JIFFIES \ |
| (SH_DIV((MAX_JIFFY_OFFSET >> SEC_JIFFIE_SC) * TICK_NSEC, NSEC_PER_SEC, 1) - 1) |
| |
| #endif |
| |
| /* |
| * Convert various time units to each other: |
| */ |
| extern unsigned int jiffies_to_msecs(const unsigned long j); |
| extern unsigned int jiffies_to_usecs(const unsigned long j); |
| extern unsigned long msecs_to_jiffies(const unsigned int m); |
| extern unsigned long usecs_to_jiffies(const unsigned int u); |
| extern unsigned long timespec_to_jiffies(const struct timespec *value); |
| extern void jiffies_to_timespec(const unsigned long jiffies, |
| struct timespec *value); |
| extern unsigned long timeval_to_jiffies(const struct timeval *value); |
| extern void jiffies_to_timeval(const unsigned long jiffies, |
| struct timeval *value); |
| extern clock_t jiffies_to_clock_t(long x); |
| extern unsigned long clock_t_to_jiffies(unsigned long x); |
| extern u64 jiffies_64_to_clock_t(u64 x); |
| extern u64 nsec_to_clock_t(u64 x); |
| |
| #define TIMESTAMP_SIZE 30 |
| |
| #endif |