kernel / pub / scm / linux / kernel / git / mraynal / linux / refs/tags/v3.16-rc4 / . / include / linux / jiffies.h

#ifndef _LINUX_JIFFIES_H | |

#define _LINUX_JIFFIES_H | |

#include <linux/math64.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 | |

#elif HZ >= 1536 && HZ < 3072 | |

# define SHIFT_HZ 11 | |

#elif HZ >= 3072 && HZ < 6144 | |

# define SHIFT_HZ 12 | |

#elif HZ >= 6144 && HZ < 12288 | |

# define SHIFT_HZ 13 | |

#else | |

# error Invalid value of HZ. | |

#endif | |

/* Suppose we want to divide two numbers NOM and DEN: NOM/DEN, then 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)) | |

/* LATCH is used in the interval timer and ftape setup. */ | |

#define LATCH ((CLOCK_TICK_RATE + HZ/2) / HZ) /* For divider */ | |

extern int register_refined_jiffies(long clock_tick_rate); | |

/* TICK_NSEC is the time between ticks in nsec assuming SHIFTED_HZ */ | |

#define TICK_NSEC ((NSEC_PER_SEC+HZ/2)/HZ) | |

/* TICK_USEC is the time between ticks in usec assuming fake USER_HZ */ | |

#define TICK_USEC ((1000000UL + USER_HZ/2) / USER_HZ) | |

/* 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 jiffies_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) - (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) - (b)) >= 0)) | |

#define time_before_eq(a,b) time_after_eq(b,a) | |

/* | |

* Calculate whether a is in the range of [b, c]. | |

*/ | |

#define time_in_range(a,b,c) \ | |

(time_after_eq(a,b) && \ | |

time_before_eq(a,c)) | |

/* | |

* Calculate whether a is in the range of [b, c). | |

*/ | |

#define time_in_range_open(a,b,c) \ | |

(time_after_eq(a,b) && \ | |

time_before(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) - (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) - (b)) >= 0)) | |

#define time_before_eq64(a,b) time_after_eq64(b,a) | |

#define time_in_range64(a, b, c) \ | |

(time_after_eq64(a, b) && \ | |

time_before_eq64(a, c)) | |

/* | |

* These four macros compare jiffies and 'a' for convenience. | |

*/ | |

/* time_is_before_jiffies(a) return true if a is before jiffies */ | |

#define time_is_before_jiffies(a) time_after(jiffies, a) | |

/* time_is_after_jiffies(a) return true if a is after jiffies */ | |

#define time_is_after_jiffies(a) time_before(jiffies, a) | |

/* time_is_before_eq_jiffies(a) return true if a is before or equal to jiffies*/ | |

#define time_is_before_eq_jiffies(a) time_after_eq(jiffies, a) | |

/* time_is_after_eq_jiffies(a) return true if a is after or equal to jiffies*/ | |

#define time_is_after_eq_jiffies(a) time_before_eq(jiffies, 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) | |

extern unsigned long preset_lpj; | |

/* | |

* 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 use 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 takes 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); | |

static inline u64 jiffies_to_nsecs(const unsigned long j) | |

{ | |

return (u64)jiffies_to_usecs(j) * NSEC_PER_USEC; | |

} | |

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(unsigned long x); | |

static inline clock_t jiffies_delta_to_clock_t(long delta) | |

{ | |

return jiffies_to_clock_t(max(0L, delta)); | |

} | |

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); | |

extern u64 nsecs_to_jiffies64(u64 n); | |

extern unsigned long nsecs_to_jiffies(u64 n); | |

#define TIMESTAMP_SIZE 30 | |

#endif |