/* linux/include/linux/clocksource.h
*
* This file contains the structure definitions for clocksources.
*
* If you are not a clocksource, or timekeeping code, you should
* not be including this file!
*/
#ifndef _LINUX_CLOCKSOURCE_H
#define _LINUX_CLOCKSOURCE_H
#include <linux/types.h>
#include <linux/timex.h>
#include <linux/time.h>
#include <linux/list.h>
#include <linux/cache.h>
#include <linux/timer.h>
#include <linux/init.h>
#include <asm/div64.h>
#include <asm/io.h>
/* clocksource cycle base type */
typedef u64 cycle_t;
struct clocksource;
/**
* struct cyclecounter - hardware abstraction for a free running counter
* Provides completely state-free accessors to the underlying hardware.
* Depending on which hardware it reads, the cycle counter may wrap
* around quickly. Locking rules (if necessary) have to be defined
* by the implementor and user of specific instances of this API.
*
* @read: returns the current cycle value
* @mask: bitmask for two's complement
* subtraction of non 64 bit counters,
* see CLOCKSOURCE_MASK() helper macro
* @mult: cycle to nanosecond multiplier
* @shift: cycle to nanosecond divisor (power of two)
*/
struct cyclecounter {
cycle_t (*read)(const struct cyclecounter *cc);
cycle_t mask;
u32 mult;
u32 shift;
};
/**
* struct timecounter - layer above a %struct cyclecounter which counts nanoseconds
* Contains the state needed by timecounter_read() to detect
* cycle counter wrap around. Initialize with
* timecounter_init(). Also used to convert cycle counts into the
* corresponding nanosecond counts with timecounter_cyc2time(). Users
* of this code are responsible for initializing the underlying
* cycle counter hardware, locking issues and reading the time
* more often than the cycle counter wraps around. The nanosecond
* counter will only wrap around after ~585 years.
*
* @cc: the cycle counter used by this instance
* @cycle_last: most recent cycle counter value seen by
* timecounter_read()
* @nsec: continuously increasing count
*/
struct timecounter {
const struct cyclecounter *cc;
cycle_t cycle_last;
u64 nsec;
};
/**
* cyclecounter_cyc2ns - converts cycle counter cycles to nanoseconds
* @tc: Pointer to cycle counter.
* @cycles: Cycles
*
* XXX - This could use some mult_lxl_ll() asm optimization. Same code
* as in cyc2ns, but with unsigned result.
*/
static inline u64 cyclecounter_cyc2ns(const struct cyclecounter *cc,
cycle_t cycles)
{
u64 ret = (u64)cycles;
ret = (ret * cc->mult) >> cc->shift;
return ret;
}
/**
* timecounter_init - initialize a time counter
* @tc: Pointer to time counter which is to be initialized/reset
* @cc: A cycle counter, ready to be used.
* @start_tstamp: Arbitrary initial time stamp.
*
* After this call the current cycle register (roughly) corresponds to
* the initial time stamp. Every call to timecounter_read() increments
* the time stamp counter by the number of elapsed nanoseconds.
*/
extern void timecounter_init(struct timecounter *tc,
const struct cyclecounter *cc,
u64 start_tstamp);
/**
* timecounter_read - return nanoseconds elapsed since timecounter_init()
* plus the initial time stamp
* @tc: Pointer to time counter.
*
* In other words, keeps track of time since the same epoch as
* the function which generated the initial time stamp.
*/
extern u64 timecounter_read(struct timecounter *tc);
/**
* timecounter_cyc2time - convert a cycle counter to same
* time base as values returned by
* timecounter_read()
* @tc: Pointer to time counter.
* @cycle: a value returned by tc->cc->read()
*
* Cycle counts that are converted correctly as long as they
* fall into the interval [-1/2 max cycle count, +1/2 max cycle count],
* with "max cycle count" == cs->mask+1.
*
* This allows conversion of cycle counter values which were generated
* in the past.
*/
extern u64 timecounter_cyc2time(struct timecounter *tc,
cycle_t cycle_tstamp);
/**
* struct clocksource - hardware abstraction for a free running counter
* Provides mostly state-free accessors to the underlying hardware.
* This is the structure used for system time.
*
* @name: ptr to clocksource name
* @list: list head for registration
* @rating: rating value for selection (higher is better)
* To avoid rating inflation the following
* list should give you a guide as to how
* to assign your clocksource a rating
* 1-99: Unfit for real use
* Only available for bootup and testing purposes.
* 100-199: Base level usability.
* Functional for real use, but not desired.
* 200-299: Good.
* A correct and usable clocksource.
* 300-399: Desired.
* A reasonably fast and accurate clocksource.
* 400-499: Perfect
* The ideal clocksource. A must-use where
* available.
* @read: returns a cycle value, passes clocksource as argument
* @enable: optional function to enable the clocksource
* @disable: optional function to disable the clocksource
* @mask: bitmask for two's complement
* subtraction of non 64 bit counters
* @mult: cycle to nanosecond multiplier
* @shift: cycle to nanosecond divisor (power of two)
* @flags: flags describing special properties
* @vread: vsyscall based read
* @resume: resume function for the clocksource, if necessary
*/
struct clocksource {
/*
* First part of structure is read mostly
*/
char *name;
struct list_head list;
int rating;
cycle_t (*read)(struct clocksource *cs);
int (*enable)(struct clocksource *cs);
void (*disable)(struct clocksource *cs);
cycle_t mask;
u32 mult;
u32 shift;
unsigned long flags;
cycle_t (*vread)(void);
void (*resume)(void);
#ifdef CONFIG_IA64
void *fsys_mmio; /* used by fsyscall asm code */
#define CLKSRC_FSYS_MMIO_SET(mmio, addr) ((mmio) = (addr))
#else
#define CLKSRC_FSYS_MMIO_SET(mmio, addr) do { } while (0)
#endif
/*
* Second part is written at each timer interrupt
* Keep it in a different cache line to dirty no
* more than one cache line.
*/
cycle_t cycle_last ____cacheline_aligned_in_smp;
#ifdef CONFIG_CLOCKSOURCE_WATCHDOG
/* Watchdog related data, used by the framework */
struct list_head wd_list;
cycle_t wd_last;
#endif
};
/*
* Clock source flags bits::
*/
#define CLOCK_SOURCE_IS_CONTINUOUS 0x01
#define CLOCK_SOURCE_MUST_VERIFY 0x02
#define CLOCK_SOURCE_WATCHDOG 0x10
#define CLOCK_SOURCE_VALID_FOR_HRES 0x20
#define CLOCK_SOURCE_UNSTABLE 0x40
/* simplify initialization of mask field */
#define CLOCKSOURCE_MASK(bits) (cycle_t)((bits) < 64 ? ((1ULL<<(bits))-1) : -1)
/**
* clocksource_khz2mult - calculates mult from khz and shift
* @khz: Clocksource frequency in KHz
* @shift_constant: Clocksource shift factor
*
* Helper functions that converts a khz counter frequency to a timsource
* multiplier, given the clocksource shift value
*/
static inline u32 clocksource_khz2mult(u32 khz, u32 shift_constant)
{
/* khz = cyc/(Million ns)
* mult/2^shift = ns/cyc
* mult = ns/cyc * 2^shift
* mult = 1Million/khz * 2^shift
* mult = 1000000 * 2^shift / khz
* mult = (1000000<<shift) / khz
*/
u64 tmp = ((u64)1000000) << shift_constant;
tmp += khz/2; /* round for do_div */
do_div(tmp, khz);
return (u32)tmp;
}
/**
* clocksource_hz2mult - calculates mult from hz and shift
* @hz: Clocksource frequency in Hz
* @shift_constant: Clocksource shift factor
*
* Helper functions that converts a hz counter
* frequency to a timsource multiplier, given the
* clocksource shift value
*/
static inline u32 clocksource_hz2mult(u32 hz, u32 shift_constant)
{
/* hz = cyc/(Billion ns)
* mult/2^shift = ns/cyc
* mult = ns/cyc * 2^shift
* mult = 1Billion/hz * 2^shift
* mult = 1000000000 * 2^shift / hz
* mult = (1000000000<<shift) / hz
*/
u64 tmp = ((u64)1000000000) << shift_constant;
tmp += hz/2; /* round for do_div */
do_div(tmp, hz);
return (u32)tmp;
}
/**
* clocksource_cyc2ns - converts clocksource cycles to nanoseconds
*
* Converts cycles to nanoseconds, using the given mult and shift.
*
* XXX - This could use some mult_lxl_ll() asm optimization
*/
static inline s64 clocksource_cyc2ns(cycle_t cycles, u32 mult, u32 shift)
{
return ((u64) cycles * mult) >> shift;
}
/* used to install a new clocksource */
extern int clocksource_register(struct clocksource*);
extern void clocksource_unregister(struct clocksource*);
extern void clocksource_touch_watchdog(void);
extern struct clocksource* clocksource_get_next(void);
extern void clocksource_change_rating(struct clocksource *cs, int rating);
extern void clocksource_resume(void);
extern struct clocksource * __init __weak clocksource_default_clock(void);
extern void clocksource_mark_unstable(struct clocksource *cs);
extern void
clocks_calc_mult_shift(u32 *mult, u32 *shift, u32 from, u32 to, u32 minsec);
static inline void
clocksource_calc_mult_shift(struct clocksource *cs, u32 freq, u32 minsec)
{
return clocks_calc_mult_shift(&cs->mult, &cs->shift, freq,
NSEC_PER_SEC, minsec);
}
#ifdef CONFIG_GENERIC_TIME_VSYSCALL
extern void update_vsyscall(struct timespec *ts, struct clocksource *c);
extern void update_vsyscall_tz(void);
#else
static inline void update_vsyscall(struct timespec *ts, struct clocksource *c)
{
}
static inline void update_vsyscall_tz(void)
{
}
#endif
extern void timekeeping_notify(struct clocksource *clock);
#endif /* _LINUX_CLOCKSOURCE_H */
