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  1. /*  linux/include/linux/clocksource.h
  2.  *
  3.  *  This file contains the structure definitions for clocksources.
  4.  *
  5.  *  If you are not a clocksource, or timekeeping code, you should
  6.  *  not be including this file!
  7.  */
  8. #ifndef _LINUX_CLOCKSOURCE_H
  9. #define _LINUX_CLOCKSOURCE_H
  10.  
  11. #include <linux/types.h>
  12. #include <linux/timex.h>
  13. #include <linux/time.h>
  14. #include <linux/list.h>
  15. #include <linux/cache.h>
  16. #include <linux/timer.h>
  17. #include <linux/init.h>
  18. #include <asm/div64.h>
  19. #include <asm/io.h>
  20.  
  21. struct clocksource;
  22. struct module;
  23.  
  24. #ifdef CONFIG_ARCH_CLOCKSOURCE_DATA
  25. #include <asm/clocksource.h>
  26. #endif
  27.  
  28. /**
  29.  * struct clocksource - hardware abstraction for a free running counter
  30.  *      Provides mostly state-free accessors to the underlying hardware.
  31.  *      This is the structure used for system time.
  32.  *
  33.  * @name:               ptr to clocksource name
  34.  * @list:               list head for registration
  35.  * @rating:             rating value for selection (higher is better)
  36.  *                      To avoid rating inflation the following
  37.  *                      list should give you a guide as to how
  38.  *                      to assign your clocksource a rating
  39.  *                      1-99: Unfit for real use
  40.  *                              Only available for bootup and testing purposes.
  41.  *                      100-199: Base level usability.
  42.  *                              Functional for real use, but not desired.
  43.  *                      200-299: Good.
  44.  *                              A correct and usable clocksource.
  45.  *                      300-399: Desired.
  46.  *                              A reasonably fast and accurate clocksource.
  47.  *                      400-499: Perfect
  48.  *                              The ideal clocksource. A must-use where
  49.  *                              available.
  50.  * @read:               returns a cycle value, passes clocksource as argument
  51.  * @enable:             optional function to enable the clocksource
  52.  * @disable:            optional function to disable the clocksource
  53.  * @mask:               bitmask for two's complement
  54.  *                      subtraction of non 64 bit counters
  55.  * @mult:               cycle to nanosecond multiplier
  56.  * @shift:              cycle to nanosecond divisor (power of two)
  57.  * @max_idle_ns:        max idle time permitted by the clocksource (nsecs)
  58.  * @maxadj:             maximum adjustment value to mult (~11%)
  59.  * @max_cycles:         maximum safe cycle value which won't overflow on multiplication
  60.  * @flags:              flags describing special properties
  61.  * @archdata:           arch-specific data
  62.  * @suspend:            suspend function for the clocksource, if necessary
  63.  * @resume:             resume function for the clocksource, if necessary
  64.  * @owner:              module reference, must be set by clocksource in modules
  65.  *
  66.  * Note: This struct is not used in hotpathes of the timekeeping code
  67.  * because the timekeeper caches the hot path fields in its own data
  68.  * structure, so no line cache alignment is required,
  69.  *
  70.  * The pointer to the clocksource itself is handed to the read
  71.  * callback. If you need extra information there you can wrap struct
  72.  * clocksource into your own struct. Depending on the amount of
  73.  * information you need you should consider to cache line align that
  74.  * structure.
  75.  */
  76. struct clocksource {
  77.         cycle_t (*read)(struct clocksource *cs);
  78.         cycle_t mask;
  79.         u32 mult;
  80.         u32 shift;
  81.         u64 max_idle_ns;
  82.         u32 maxadj;
  83. #ifdef CONFIG_ARCH_CLOCKSOURCE_DATA
  84.         struct arch_clocksource_data archdata;
  85. #endif
  86.         u64 max_cycles;
  87.         const char *name;
  88.         struct list_head list;
  89.         int rating;
  90.         int (*enable)(struct clocksource *cs);
  91.         void (*disable)(struct clocksource *cs);
  92.         unsigned long flags;
  93.         void (*suspend)(struct clocksource *cs);
  94.         void (*resume)(struct clocksource *cs);
  95.  
  96.         /* private: */
  97. #ifdef CONFIG_CLOCKSOURCE_WATCHDOG
  98.         /* Watchdog related data, used by the framework */
  99.         struct list_head wd_list;
  100.         cycle_t cs_last;
  101.         cycle_t wd_last;
  102. #endif
  103.         struct module *owner;
  104. };
  105.  
  106. /*
  107.  * Clock source flags bits::
  108.  */
  109. #define CLOCK_SOURCE_IS_CONTINUOUS              0x01
  110. #define CLOCK_SOURCE_MUST_VERIFY                0x02
  111.  
  112. #define CLOCK_SOURCE_WATCHDOG                   0x10
  113. #define CLOCK_SOURCE_VALID_FOR_HRES             0x20
  114. #define CLOCK_SOURCE_UNSTABLE                   0x40
  115. #define CLOCK_SOURCE_SUSPEND_NONSTOP            0x80
  116. #define CLOCK_SOURCE_RESELECT                   0x100
  117.  
  118. /* simplify initialization of mask field */
  119. #define CLOCKSOURCE_MASK(bits) (cycle_t)((bits) < 64 ? ((1ULL<<(bits))-1) : -1)
  120.  
  121. /**
  122.  * clocksource_khz2mult - calculates mult from khz and shift
  123.  * @khz:                Clocksource frequency in KHz
  124.  * @shift_constant:     Clocksource shift factor
  125.  *
  126.  * Helper functions that converts a khz counter frequency to a timsource
  127.  * multiplier, given the clocksource shift value
  128.  */
  129. static inline u32 clocksource_khz2mult(u32 khz, u32 shift_constant)
  130. {
  131.         /*  khz = cyc/(Million ns)
  132.          *  mult/2^shift  = ns/cyc
  133.          *  mult = ns/cyc * 2^shift
  134.          *  mult = 1Million/khz * 2^shift
  135.          *  mult = 1000000 * 2^shift / khz
  136.          *  mult = (1000000<<shift) / khz
  137.          */
  138.         u64 tmp = ((u64)1000000) << shift_constant;
  139.  
  140.         tmp += khz/2; /* round for do_div */
  141.         do_div(tmp, khz);
  142.  
  143.         return (u32)tmp;
  144. }
  145.  
  146. /**
  147.  * clocksource_hz2mult - calculates mult from hz and shift
  148.  * @hz:                 Clocksource frequency in Hz
  149.  * @shift_constant:     Clocksource shift factor
  150.  *
  151.  * Helper functions that converts a hz counter
  152.  * frequency to a timsource multiplier, given the
  153.  * clocksource shift value
  154.  */
  155. static inline u32 clocksource_hz2mult(u32 hz, u32 shift_constant)
  156. {
  157.         /*  hz = cyc/(Billion ns)
  158.          *  mult/2^shift  = ns/cyc
  159.          *  mult = ns/cyc * 2^shift
  160.          *  mult = 1Billion/hz * 2^shift
  161.          *  mult = 1000000000 * 2^shift / hz
  162.          *  mult = (1000000000<<shift) / hz
  163.          */
  164.         u64 tmp = ((u64)1000000000) << shift_constant;
  165.  
  166.         tmp += hz/2; /* round for do_div */
  167.         do_div(tmp, hz);
  168.  
  169.         return (u32)tmp;
  170. }
  171.  
  172. /**
  173.  * clocksource_cyc2ns - converts clocksource cycles to nanoseconds
  174.  * @cycles:     cycles
  175.  * @mult:       cycle to nanosecond multiplier
  176.  * @shift:      cycle to nanosecond divisor (power of two)
  177.  *
  178.  * Converts cycles to nanoseconds, using the given mult and shift.
  179.  *
  180.  * XXX - This could use some mult_lxl_ll() asm optimization
  181.  */
  182. static inline s64 clocksource_cyc2ns(cycle_t cycles, u32 mult, u32 shift)
  183. {
  184.         return ((u64) cycles * mult) >> shift;
  185. }
  186.  
  187.  
  188. extern int clocksource_unregister(struct clocksource*);
  189. extern void clocksource_touch_watchdog(void);
  190. extern void clocksource_change_rating(struct clocksource *cs, int rating);
  191. extern void clocksource_suspend(void);
  192. extern void clocksource_resume(void);
  193. extern struct clocksource * __init clocksource_default_clock(void);
  194. extern void clocksource_mark_unstable(struct clocksource *cs);
  195.  
  196. extern u64
  197. clocks_calc_max_nsecs(u32 mult, u32 shift, u32 maxadj, u64 mask, u64 *max_cycles);
  198. extern void
  199. clocks_calc_mult_shift(u32 *mult, u32 *shift, u32 from, u32 to, u32 minsec);
  200.  
  201. /*
  202.  * Don't call __clocksource_register_scale directly, use
  203.  * clocksource_register_hz/khz
  204.  */
  205. extern int
  206. __clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq);
  207. extern void
  208. __clocksource_update_freq_scale(struct clocksource *cs, u32 scale, u32 freq);
  209.  
  210. /*
  211.  * Don't call this unless you are a default clocksource
  212.  * (AKA: jiffies) and absolutely have to.
  213.  */
  214. static inline int __clocksource_register(struct clocksource *cs)
  215. {
  216.         return __clocksource_register_scale(cs, 1, 0);
  217. }
  218.  
  219. static inline int clocksource_register_hz(struct clocksource *cs, u32 hz)
  220. {
  221.         return __clocksource_register_scale(cs, 1, hz);
  222. }
  223.  
  224. static inline int clocksource_register_khz(struct clocksource *cs, u32 khz)
  225. {
  226.         return __clocksource_register_scale(cs, 1000, khz);
  227. }
  228.  
  229. static inline void __clocksource_update_freq_hz(struct clocksource *cs, u32 hz)
  230. {
  231.         __clocksource_update_freq_scale(cs, 1, hz);
  232. }
  233.  
  234. static inline void __clocksource_update_freq_khz(struct clocksource *cs, u32 khz)
  235. {
  236.         __clocksource_update_freq_scale(cs, 1000, khz);
  237. }
  238.  
  239.  
  240. extern int timekeeping_notify(struct clocksource *clock);
  241.  
  242. extern cycle_t clocksource_mmio_readl_up(struct clocksource *);
  243. extern cycle_t clocksource_mmio_readl_down(struct clocksource *);
  244. extern cycle_t clocksource_mmio_readw_up(struct clocksource *);
  245. extern cycle_t clocksource_mmio_readw_down(struct clocksource *);
  246.  
  247. extern int clocksource_mmio_init(void __iomem *, const char *,
  248.         unsigned long, int, unsigned, cycle_t (*)(struct clocksource *));
  249.  
  250. extern int clocksource_i8253_init(void);
  251.  
  252. #define CLOCKSOURCE_OF_DECLARE(name, compat, fn) \
  253.         OF_DECLARE_1(clksrc, name, compat, fn)
  254.  
  255. #ifdef CONFIG_CLKSRC_PROBE
  256. extern void clocksource_probe(void);
  257. #else
  258. static inline void clocksource_probe(void) {}
  259. #endif
  260.  
  261. #define CLOCKSOURCE_ACPI_DECLARE(name, table_id, fn)            \
  262.         ACPI_DECLARE_PROBE_ENTRY(clksrc, name, table_id, 0, NULL, 0, fn)
  263.  
  264. #endif /* _LINUX_CLOCKSOURCE_H */
  265.