include/linux/clocksource.h

   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 static inline u32 clocksource_freq2mult(u32 freq, u32 shift_constant, u64 from)
 122 {
 123         /*  freq = cyc/from
 124          *  mult/2^shift  = ns/cyc
 125          *  mult = ns/cyc * 2^shift
 126          *  mult = from/freq * 2^shift
 127          *  mult = from * 2^shift / freq
 128          *  mult = (from<<shift) / freq
 129          */
 130         u64 tmp = ((u64)from) << shift_constant;
 131
 132         tmp += freq/2; /* round for do_div */
 133         do_div(tmp, freq);
 134
 135         return (u32)tmp;
 136 }
 137
 138 /**
 139  * clocksource_khz2mult - calculates mult from khz and shift
 140  * @khz:                Clocksource frequency in KHz
 141  * @shift_constant:     Clocksource shift factor
 142  *
 143  * Helper functions that converts a khz counter frequency to a timsource
 144  * multiplier, given the clocksource shift value
 145  */
 146 static inline u32 clocksource_khz2mult(u32 khz, u32 shift_constant)
 147 {
 148         return clocksource_freq2mult(khz, shift_constant, NSEC_PER_MSEC);
 149 }
 150
 151 /**
 152  * clocksource_hz2mult - calculates mult from hz and shift
 153  * @hz:                 Clocksource frequency in Hz
 154  * @shift_constant:     Clocksource shift factor
 155  *
 156  * Helper functions that converts a hz counter
 157  * frequency to a timsource multiplier, given the
 158  * clocksource shift value
 159  */
 160 static inline u32 clocksource_hz2mult(u32 hz, u32 shift_constant)
 161 {
 162         return clocksource_freq2mult(hz, shift_constant, NSEC_PER_SEC);
 163 }
 164
 165 /**
 166  * clocksource_cyc2ns - converts clocksource cycles to nanoseconds
 167  * @cycles:     cycles
 168  * @mult:       cycle to nanosecond multiplier
 169  * @shift:      cycle to nanosecond divisor (power of two)
 170  *
 171  * Converts cycles to nanoseconds, using the given mult and shift.
 172  *
 173  * XXX - This could use some mult_lxl_ll() asm optimization
 174  */
 175 static inline s64 clocksource_cyc2ns(cycle_t cycles, u32 mult, u32 shift)
 176 {
 177         return ((u64) cycles * mult) >> shift;
 178 }
 179
 180
 181 extern int clocksource_unregister(struct clocksource*);
 182 extern void clocksource_touch_watchdog(void);
 183 extern void clocksource_change_rating(struct clocksource *cs, int rating);
 184 extern void clocksource_suspend(void);
 185 extern void clocksource_resume(void);
 186 extern struct clocksource * __init clocksource_default_clock(void);
 187 extern void clocksource_mark_unstable(struct clocksource *cs);
 188
 189 extern u64
 190 clocks_calc_max_nsecs(u32 mult, u32 shift, u32 maxadj, u64 mask, u64 *max_cycles);
 191 extern void
 192 clocks_calc_mult_shift(u32 *mult, u32 *shift, u32 from, u32 to, u32 minsec);
 193
 194 /*
 195  * Don't call __clocksource_register_scale directly, use
 196  * clocksource_register_hz/khz
 197  */
 198 extern int
 199 __clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq);
 200 extern void
 201 __clocksource_update_freq_scale(struct clocksource *cs, u32 scale, u32 freq);
 202
 203 /*
 204  * Don't call this unless you are a default clocksource
 205  * (AKA: jiffies) and absolutely have to.
 206  */
 207 static inline int __clocksource_register(struct clocksource *cs)
 208 {
 209         return __clocksource_register_scale(cs, 1, 0);
 210 }
 211
 212 static inline int clocksource_register_hz(struct clocksource *cs, u32 hz)
 213 {
 214         return __clocksource_register_scale(cs, 1, hz);
 215 }
 216
 217 static inline int clocksource_register_khz(struct clocksource *cs, u32 khz)
 218 {
 219         return __clocksource_register_scale(cs, 1000, khz);
 220 }
 221
 222 static inline void __clocksource_update_freq_hz(struct clocksource *cs, u32 hz)
 223 {
 224         __clocksource_update_freq_scale(cs, 1, hz);
 225 }
 226
 227 static inline void __clocksource_update_freq_khz(struct clocksource *cs, u32 khz)
 228 {
 229         __clocksource_update_freq_scale(cs, 1000, khz);
 230 }
 231
 232
 233 extern int timekeeping_notify(struct clocksource *clock);
 234
 235 extern cycle_t clocksource_mmio_readl_up(struct clocksource *);
 236 extern cycle_t clocksource_mmio_readl_down(struct clocksource *);
 237 extern cycle_t clocksource_mmio_readw_up(struct clocksource *);
 238 extern cycle_t clocksource_mmio_readw_down(struct clocksource *);
 239
 240 extern int clocksource_mmio_init(void __iomem *, const char *,
 241         unsigned long, int, unsigned, cycle_t (*)(struct clocksource *));
 242
 243 extern int clocksource_i8253_init(void);
 244
 245 #define CLOCKSOURCE_OF_DECLARE(name, compat, fn) \
 246         OF_DECLARE_1(clksrc, name, compat, fn)
 247
 248 #ifdef CONFIG_CLKSRC_PROBE
 249 extern void clocksource_probe(void);
 250 #else
 251 static inline void clocksource_probe(void) {}
 252 #endif
 253
 254 #define CLOCKSOURCE_ACPI_DECLARE(name, table_id, fn)            \
 255         ACPI_DECLARE_PROBE_ENTRY(clksrc, name, table_id, 0, NULL, 0, fn)
 256
 257 #endif /* _LINUX_CLOCKSOURCE_H */