/*  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);

#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 */