/*  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 module;
  
  #ifdef CONFIG_ARCH_CLOCKSOURCE_DATA
  #include <asm/clocksource.h>
  #endif
  
  /**
   * 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
   * @cc:		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_tstamp:	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)
   * @max_idle_ns:	max idle time permitted by the clocksource (nsecs)
   * @maxadj:		maximum adjustment value to mult (~11%)
   * @flags:		flags describing special properties
   * @archdata:		arch-specific data
   * @suspend:		suspend function for the clocksource, if necessary
   * @resume:		resume function for the clocksource, if necessary
   * @cycle_last:		most recent cycle counter value seen by ::read()
   * @owner:		module reference, must be set by clocksource in modules
   */
  struct clocksource {
  	/*
  	 * Hotpath data, fits in a single cache line when the
  	 * clocksource itself is cacheline aligned.
  	 */
  	cycle_t (*read)(struct clocksource *cs);
  	cycle_t cycle_last;
  	cycle_t mask;
  	u32 mult;
  	u32 shift;
  	u64 max_idle_ns;
  	u32 maxadj;
  #ifdef CONFIG_ARCH_CLOCKSOURCE_DATA
  	struct arch_clocksource_data archdata;
  #endif
  
  	const char *name;
  	struct list_head list;
  	int rating;
  	int (*enable)(struct clocksource *cs);
  	void (*disable)(struct clocksource *cs);
  	unsigned long flags;
  	void (*suspend)(struct clocksource *cs);
  	void (*resume)(struct clocksource *cs);
  
  	/* private: */
  #ifdef CONFIG_CLOCKSOURCE_WATCHDOG
  	/* Watchdog related data, used by the framework */
  	struct list_head wd_list;
  	cycle_t cs_last;
  	cycle_t wd_last;
  #endif
  	struct module *owner;
  } ____cacheline_aligned;
  
  /*
   * 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
  #define CLOCK_SOURCE_SUSPEND_NONSTOP		0x80
  #define CLOCK_SOURCE_RESELECT			0x100
  
  /* 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
   * @cycles:	cycles
   * @mult:	cycle to nanosecond multiplier
   * @shift:	cycle to nanosecond divisor (power of two)
   *
   * 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;
  }
  
  
  extern int clocksource_register(struct clocksource*);
  extern int 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_suspend(void);
  extern void clocksource_resume(void);
  extern struct clocksource * __init clocksource_default_clock(void);
  extern void clocksource_mark_unstable(struct clocksource *cs);
  
  extern u64
  clocks_calc_max_nsecs(u32 mult, u32 shift, u32 maxadj, u64 mask);
  extern void
  clocks_calc_mult_shift(u32 *mult, u32 *shift, u32 from, u32 to, u32 minsec);
  
  /*
   * Don't call __clocksource_register_scale directly, use
   * clocksource_register_hz/khz
   */
  extern int
  __clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq);
  extern void
  __clocksource_updatefreq_scale(struct clocksource *cs, u32 scale, u32 freq);
  
  static inline int clocksource_register_hz(struct clocksource *cs, u32 hz)
  {
  	return __clocksource_register_scale(cs, 1, hz);
  }
  
  static inline int clocksource_register_khz(struct clocksource *cs, u32 khz)
  {
  	return __clocksource_register_scale(cs, 1000, khz);
  }
  
  static inline void __clocksource_updatefreq_hz(struct clocksource *cs, u32 hz)
  {
  	__clocksource_updatefreq_scale(cs, 1, hz);
  }
  
  static inline void __clocksource_updatefreq_khz(struct clocksource *cs, u32 khz)
  {
  	__clocksource_updatefreq_scale(cs, 1000, khz);
  }
  
  
  extern int timekeeping_notify(struct clocksource *clock);
  
  extern cycle_t clocksource_mmio_readl_up(struct clocksource *);
  extern cycle_t clocksource_mmio_readl_down(struct clocksource *);
  extern cycle_t clocksource_mmio_readw_up(struct clocksource *);
  extern cycle_t clocksource_mmio_readw_down(struct clocksource *);
  
  extern int clocksource_mmio_init(void __iomem *, const char *,
  	unsigned long, int, unsigned, cycle_t (*)(struct clocksource *));
  
  extern int clocksource_i8253_init(void);
  
  struct device_node;
  typedef void(*clocksource_of_init_fn)(struct device_node *);
  #ifdef CONFIG_CLKSRC_OF
  extern void clocksource_of_init(void);
  
  #define CLOCKSOURCE_OF_DECLARE(name, compat, fn)			\
  	static const struct of_device_id __clksrc_of_table_##name	\
  		__used __section(__clksrc_of_table)			\
  		 = { .compatible = compat,				\
  		     .data = (fn == (clocksource_of_init_fn)NULL) ? fn : fn }
  #else
  static inline void clocksource_of_init(void) {}
  #define CLOCKSOURCE_OF_DECLARE(name, compat, fn)			\
  	static const struct of_device_id __clksrc_of_table_##name	\
  		__attribute__((unused))					\
  		 = { .compatible = compat,				\
  		     .data = (fn == (clocksource_of_init_fn)NULL) ? fn : fn }
  #endif
  
  #endif /* _LINUX_CLOCKSOURCE_H */