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/*  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 <asm/div64.h>

#include <asm/io.h>

/* clocksource cycle base type */

typedef u64 cycle_t;

struct clocksource;

/**

 * struct clocksource - hardware abstraction for a free running counter

 *      Provides mostly state-free accessors to the underlying hardware.

 *

 * @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

 * @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

 * @cycle_interval:     Used internally by timekeeping core, please ignore.

 * @xtime_interval:     Used internally by timekeeping core, please ignore.

 */

struct clocksource {

        /*

         * First part of structure is read mostly

         */

        char *name;

        struct list_head list;

        int rating;

        cycle_t (*read)(void);

        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

        /* timekeeping specific data, ignore */

        cycle_t cycle_interval;

        u64     xtime_interval;

        /*

         * 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;

        u64 xtime_nsec;

        s64 error;

#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

/* 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_read: - Access the clocksource's current cycle value

 * @cs:         pointer to clocksource being read

 *

 * Uses the clocksource to return the current cycle_t value

 */

static inline cycle_t clocksource_read(struct clocksource *cs)

{

        return cs->read();

}

/**

 * cyc2ns - converts clocksource cycles to nanoseconds

 * @cs:         Pointer to clocksource

 * @cycles:     Cycles

 *

 * Uses the clocksource and ntp ajdustment to convert cycle_ts to nanoseconds.

 *

 * XXX - This could use some mult_lxl_ll() asm optimization

 */

static inline s64 cyc2ns(struct clocksource *cs, cycle_t cycles)

{

        u64 ret = (u64)cycles;

        ret = (ret * cs->mult) >> cs->shift;

        return ret;

}

/**

 * clocksource_calculate_interval - Calculates a clocksource interval struct

 *

 * @c:          Pointer to clocksource.

 * @length_nsec: Desired interval length in nanoseconds.

 *

 * Calculates a fixed cycle/nsec interval for a given clocksource/adjustment

 * pair and interval request.

 *

 * Unless you're the timekeeping code, you should not be using this!

 */

static inline void clocksource_calculate_interval(struct clocksource *c,

                                                  unsigned long length_nsec)

{

        u64 tmp;

        /* XXX - All of this could use a whole lot of optimization */

        tmp = length_nsec;

        tmp <<= c->shift;

        tmp += c->mult/2;

        do_div(tmp, c->mult);

        c->cycle_interval = (cycle_t)tmp;

        if (c->cycle_interval == 0)

                c->cycle_interval = 1;

        c->xtime_interval = (u64)c->cycle_interval * c->mult;

}

/* used to install a new clocksource */

extern int clocksource_register(struct clocksource*);

extern struct clocksource* clocksource_get_next(void);

extern void clocksource_change_rating(struct clocksource *cs, int rating);

extern void clocksource_resume(void);

#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

#endif /* _LINUX_CLOCKSOURCE_H */