468 lines
16 KiB
C
468 lines
16 KiB
C
/* SPDXLicenseIdentifier: GPL2.0 */


#ifndef _LINUX_JIFFIES_H


#define _LINUX_JIFFIES_H




#include <linux/cache.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 */


#include <generated/timeconst.h>




/*


* 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.


*/


/* CONFIG_MCST: support low HZ values (10) for prototypes */


#if HZ >= 6 && HZ < 12


# define SHIFT_HZ 3


#elif 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 SHIFTED_HZ */


#define TICK_USEC ((USEC_PER_SEC + HZ/2) / HZ)




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


#define USER_TICK_USEC ((1000000UL + USER_HZ/2) / USER_HZ)




#ifndef __jiffy_arch_data


#define __jiffy_arch_data


#endif




/*


* The 64bit 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 __cacheline_aligned_in_smp jiffies_64;


extern unsigned long volatile __cacheline_aligned_in_smp __jiffy_arch_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)


#define time_is_before_jiffies64(a) time_after64(get_jiffies_64(), a)




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


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


#define time_is_after_jiffies64(a) time_before64(get_jiffies_64(), 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)


#define time_is_before_eq_jiffies64(a) time_after_eq64(get_jiffies_64(), 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)


#define time_is_after_eq_jiffies64(a) time_before_eq64(get_jiffies_64(), 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 34 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 32bits so we tell C how to


* do this and pass the 64bit result of the mpy through the ">> SCALE"


* which should take the result back to 32bits. 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 64bit 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 64bit 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 32bit word, so we MUST use


* 64bits 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 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))


/*


* The maximum jiffie value is (MAX_INT >> 1). Here we translate that


* into seconds. The 64bit 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 u64 jiffies64_to_nsecs(u64 j);


extern u64 jiffies64_to_msecs(u64 j);




extern unsigned long __msecs_to_jiffies(const unsigned int m);


#if HZ <= MSEC_PER_SEC && !(MSEC_PER_SEC % HZ)


/*


* HZ is equal to or smaller than 1000, and 1000 is a nice round


* multiple of HZ, divide with the factor between them, but round


* upwards:


*/


static inline unsigned long _msecs_to_jiffies(const unsigned int m)


{


return (m + (MSEC_PER_SEC / HZ)  1) / (MSEC_PER_SEC / HZ);


}


#elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC)


/*


* HZ is larger than 1000, and HZ is a nice round multiple of 1000 


* simply multiply with the factor between them.


*


* But first make sure the multiplication result cannot overflow:


*/


static inline unsigned long _msecs_to_jiffies(const unsigned int m)


{


if (m > jiffies_to_msecs(MAX_JIFFY_OFFSET))


return MAX_JIFFY_OFFSET;


return m * (HZ / MSEC_PER_SEC);


}


#else


/*


* Generic case  multiply, round and divide. But first check that if


* we are doing a net multiplication, that we wouldn't overflow:


*/


static inline unsigned long _msecs_to_jiffies(const unsigned int m)


{


if (HZ > MSEC_PER_SEC && m > jiffies_to_msecs(MAX_JIFFY_OFFSET))


return MAX_JIFFY_OFFSET;




return (MSEC_TO_HZ_MUL32 * m + MSEC_TO_HZ_ADJ32) >> MSEC_TO_HZ_SHR32;


}


#endif


/**


* msecs_to_jiffies:  convert milliseconds to jiffies


* @m: time in milliseconds


*


* conversion is done as follows:


*


*  negative values mean 'infinite timeout' (MAX_JIFFY_OFFSET)


*


*  'too large' values [that would result in larger than


* MAX_JIFFY_OFFSET values] mean 'infinite timeout' too.


*


*  all other values are converted to jiffies by either multiplying


* the input value by a factor or dividing it with a factor and


* handling any 32bit overflows.


* for the details see __msecs_to_jiffies()


*


* msecs_to_jiffies() checks for the passed in value being a constant


* via __builtin_constant_p() allowing gcc to eliminate most of the


* code, __msecs_to_jiffies() is called if the value passed does not


* allow constant folding and the actual conversion must be done at


* runtime.


* the HZ range specific helpers _msecs_to_jiffies() are called both


* directly here and from __msecs_to_jiffies() in the case where


* constant folding is not possible.


*/


static __always_inline unsigned long msecs_to_jiffies(const unsigned int m)


{


if (__builtin_constant_p(m)) {


if ((int)m < 0)


return MAX_JIFFY_OFFSET;


return _msecs_to_jiffies(m);


} else {


return __msecs_to_jiffies(m);


}


}




extern unsigned long __usecs_to_jiffies(const unsigned int u);


#if !(USEC_PER_SEC % HZ)


static inline unsigned long _usecs_to_jiffies(const unsigned int u)


{


return (u + (USEC_PER_SEC / HZ)  1) / (USEC_PER_SEC / HZ);


}


#else


static inline unsigned long _usecs_to_jiffies(const unsigned int u)


{


return (USEC_TO_HZ_MUL32 * u + USEC_TO_HZ_ADJ32)


>> USEC_TO_HZ_SHR32;


}


#endif




/**


* usecs_to_jiffies:  convert microseconds to jiffies


* @u: time in microseconds


*


* conversion is done as follows:


*


*  'too large' values [that would result in larger than


* MAX_JIFFY_OFFSET values] mean 'infinite timeout' too.


*


*  all other values are converted to jiffies by either multiplying


* the input value by a factor or dividing it with a factor and


* handling any 32bit overflows as for msecs_to_jiffies.


*


* usecs_to_jiffies() checks for the passed in value being a constant


* via __builtin_constant_p() allowing gcc to eliminate most of the


* code, __usecs_to_jiffies() is called if the value passed does not


* allow constant folding and the actual conversion must be done at


* runtime.


* the HZ range specific helpers _usecs_to_jiffies() are called both


* directly here and from __msecs_to_jiffies() in the case where


* constant folding is not possible.


*/


static __always_inline unsigned long usecs_to_jiffies(const unsigned int u)


{


if (__builtin_constant_p(u)) {


if (u > jiffies_to_usecs(MAX_JIFFY_OFFSET))


return MAX_JIFFY_OFFSET;


return _usecs_to_jiffies(u);


} else {


return __usecs_to_jiffies(u);


}


}




extern unsigned long timespec64_to_jiffies(const struct timespec64 *value);


extern void jiffies_to_timespec64(const unsigned long jiffies,


struct timespec64 *value);


static inline unsigned long timespec_to_jiffies(const struct timespec *value)


{


struct timespec64 ts = timespec_to_timespec64(*value);




return timespec64_to_jiffies(&ts);


}




static inline void jiffies_to_timespec(const unsigned long jiffies,


struct timespec *value)


{


struct timespec64 ts;




jiffies_to_timespec64(jiffies, &ts);


*value = timespec64_to_timespec(ts);


}




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));


}




static inline unsigned int jiffies_delta_to_msecs(long delta)


{


return jiffies_to_msecs(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
