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 /* clocksource cycle base type */
  22 typedef u64 cycle_t;
  23 struct clocksource;
  24 struct module;
  25
  26 #ifdef CONFIG_ARCH_CLOCKSOURCE_DATA
  27 #include <asm/clocksource.h>
  28 #endif
  29
  30 /**
  31  * struct cyclecounter - hardware abstraction for a free running counter
  32  *      Provides completely state-free accessors to the underlying hardware.
  33  *      Depending on which hardware it reads, the cycle counter may wrap
  34  *      around quickly. Locking rules (if necessary) have to be defined
  35  *      by the implementor and user of specific instances of this API.
  36  *
  37  * @read:               returns the current cycle value
  38  * @mask:               bitmask for two's complement
  39  *                      subtraction of non 64 bit counters,
  40  *                      see CLOCKSOURCE_MASK() helper macro
  41  * @mult:               cycle to nanosecond multiplier
  42  * @shift:              cycle to nanosecond divisor (power of two)
  43  */
  44 struct cyclecounter {
  45         cycle_t (*read)(const struct cyclecounter *cc);
  46         cycle_t mask;
  47         u32 mult;
  48         u32 shift;
  49 };
  50
  51 /**
  52  * struct timecounter - layer above a %struct cyclecounter which counts nanoseconds
  53  *      Contains the state needed by timecounter_read() to detect
  54  *      cycle counter wrap around. Initialize with
  55  *      timecounter_init(). Also used to convert cycle counts into the
  56  *      corresponding nanosecond counts with timecounter_cyc2time(). Users
  57  *      of this code are responsible for initializing the underlying
  58  *      cycle counter hardware, locking issues and reading the time
  59  *      more often than the cycle counter wraps around. The nanosecond
  60  *      counter will only wrap around after ~585 years.
  61  *
  62  * @cc:                 the cycle counter used by this instance
  63  * @cycle_last:         most recent cycle counter value seen by
  64  *                      timecounter_read()
  65  * @nsec:               continuously increasing count
  66  */
  67 struct timecounter {
  68         const struct cyclecounter *cc;
  69         cycle_t cycle_last;
  70         u64 nsec;
  71 };
  72
  73 /**
  74  * cyclecounter_cyc2ns - converts cycle counter cycles to nanoseconds
  75  * @cc:         Pointer to cycle counter.
  76  * @cycles:     Cycles
  77  *
  78  * XXX - This could use some mult_lxl_ll() asm optimization. Same code
  79  * as in cyc2ns, but with unsigned result.
  80  */
  81 static inline u64 cyclecounter_cyc2ns(const struct cyclecounter *cc,
  82                                       cycle_t cycles)
  83 {
  84         u64 ret = (u64)cycles;
  85         ret = (ret * cc->mult) >> cc->shift;
  86         return ret;
  87 }
  88
  89 /**
  90  * timecounter_init - initialize a time counter
  91  * @tc:                 Pointer to time counter which is to be initialized/reset
  92  * @cc:                 A cycle counter, ready to be used.
  93  * @start_tstamp:       Arbitrary initial time stamp.
  94  *
  95  * After this call the current cycle register (roughly) corresponds to
  96  * the initial time stamp. Every call to timecounter_read() increments
  97  * the time stamp counter by the number of elapsed nanoseconds.
  98  */
  99 extern void timecounter_init(struct timecounter *tc,
 100                              const struct cyclecounter *cc,
 101                              u64 start_tstamp);
 102
 103 /**
 104  * timecounter_read - return nanoseconds elapsed since timecounter_init()
 105  *                    plus the initial time stamp
 106  * @tc:          Pointer to time counter.
 107  *
 108  * In other words, keeps track of time since the same epoch as
 109  * the function which generated the initial time stamp.
 110  */
 111 extern u64 timecounter_read(struct timecounter *tc);
 112
 113 /**
 114  * timecounter_cyc2time - convert a cycle counter to same
 115  *                        time base as values returned by
 116  *                        timecounter_read()
 117  * @tc:         Pointer to time counter.
 118  * @cycle_tstamp:       a value returned by tc->cc->read()
 119  *
 120  * Cycle counts that are converted correctly as long as they
 121  * fall into the interval [-1/2 max cycle count, +1/2 max cycle count],
 122  * with "max cycle count" == cs->mask+1.
 123  *
 124  * This allows conversion of cycle counter values which were generated
 125  * in the past.
 126  */
 127 extern u64 timecounter_cyc2time(struct timecounter *tc,
 128                                 cycle_t cycle_tstamp);
 129
 130 /**
 131  * struct clocksource - hardware abstraction for a free running counter
 132  *      Provides mostly state-free accessors to the underlying hardware.
 133  *      This is the structure used for system time.
 134  *
 135  * @name:               ptr to clocksource name
 136  * @list:               list head for registration
 137  * @rating:             rating value for selection (higher is better)
 138  *                      To avoid rating inflation the following
 139  *                      list should give you a guide as to how
 140  *                      to assign your clocksource a rating
 141  *                      1-99: Unfit for real use
 142  *                              Only available for bootup and testing purposes.
 143  *                      100-199: Base level usability.
 144  *                              Functional for real use, but not desired.
 145  *                      200-299: Good.
 146  *                              A correct and usable clocksource.
 147  *                      300-399: Desired.
 148  *                              A reasonably fast and accurate clocksource.
 149  *                      400-499: Perfect
 150  *                              The ideal clocksource. A must-use where
 151  *                              available.
 152  * @read:               returns a cycle value, passes clocksource as argument
 153  * @enable:             optional function to enable the clocksource
 154  * @disable:            optional function to disable the clocksource
 155  * @mask:               bitmask for two's complement
 156  *                      subtraction of non 64 bit counters
 157  * @mult:               cycle to nanosecond multiplier
 158  * @shift:              cycle to nanosecond divisor (power of two)
 159  * @max_idle_ns:        max idle time permitted by the clocksource (nsecs)
 160  * @maxadj:             maximum adjustment value to mult (~11%)
 161  * @flags:              flags describing special properties
 162  * @archdata:           arch-specific data
 163  * @suspend:            suspend function for the clocksource, if necessary
 164  * @resume:             resume function for the clocksource, if necessary
 165  * @cycle_last:         most recent cycle counter value seen by ::read()
 166  * @owner:              module reference, must be set by clocksource in modules
 167  */
 168 struct clocksource {
 169         /*
 170          * Hotpath data, fits in a single cache line when the
 171          * clocksource itself is cacheline aligned.
 172          */
 173         cycle_t (*read)(struct clocksource *cs);
 174         cycle_t cycle_last;
 175         cycle_t mask;
 176         u32 mult;
 177         u32 shift;
 178         u64 max_idle_ns;
 179         u32 maxadj;
 180 #ifdef CONFIG_ARCH_CLOCKSOURCE_DATA
 181         struct arch_clocksource_data archdata;
 182 #endif
 183
 184         const char *name;
 185         struct list_head list;
 186         int rating;
 187         int (*enable)(struct clocksource *cs);
 188         void (*disable)(struct clocksource *cs);
 189         unsigned long flags;
 190         void (*suspend)(struct clocksource *cs);
 191         void (*resume)(struct clocksource *cs);
 192
 193         /* private: */
 194 #ifdef CONFIG_CLOCKSOURCE_WATCHDOG
 195         /* Watchdog related data, used by the framework */
 196         struct list_head wd_list;
 197         cycle_t cs_last;
 198         cycle_t wd_last;
 199 #endif
 200         struct module *owner;
 201 } ____cacheline_aligned;
 202
 203 /*
 204  * Clock source flags bits::
 205  */
 206 #define CLOCK_SOURCE_IS_CONTINUOUS              0x01
 207 #define CLOCK_SOURCE_MUST_VERIFY                0x02
 208
 209 #define CLOCK_SOURCE_WATCHDOG                   0x10
 210 #define CLOCK_SOURCE_VALID_FOR_HRES             0x20
 211 #define CLOCK_SOURCE_UNSTABLE                   0x40
 212 #define CLOCK_SOURCE_SUSPEND_NONSTOP            0x80
 213 #define CLOCK_SOURCE_RESELECT                   0x100
 214
 215 /* simplify initialization of mask field */
 216 #define CLOCKSOURCE_MASK(bits) (cycle_t)((bits) < 64 ? ((1ULL<<(bits))-1) : -1)
 217
 218 /**
 219  * clocksource_khz2mult - calculates mult from khz and shift
 220  * @khz:                Clocksource frequency in KHz
 221  * @shift_constant:     Clocksource shift factor
 222  *
 223  * Helper functions that converts a khz counter frequency to a timsource
 224  * multiplier, given the clocksource shift value
 225  */
 226 static inline u32 clocksource_khz2mult(u32 khz, u32 shift_constant)
 227 {
 228         /*  khz = cyc/(Million ns)
 229          *  mult/2^shift  = ns/cyc
 230          *  mult = ns/cyc * 2^shift
 231          *  mult = 1Million/khz * 2^shift
 232          *  mult = 1000000 * 2^shift / khz
 233          *  mult = (1000000<<shift) / khz
 234          */
 235         u64 tmp = ((u64)1000000) << shift_constant;
 236
 237         tmp += khz/2; /* round for do_div */
 238         do_div(tmp, khz);
 239
 240         return (u32)tmp;
 241 }
 242
 243 /**
 244  * clocksource_hz2mult - calculates mult from hz and shift
 245  * @hz:                 Clocksource frequency in Hz
 246  * @shift_constant:     Clocksource shift factor
 247  *
 248  * Helper functions that converts a hz counter
 249  * frequency to a timsource multiplier, given the
 250  * clocksource shift value
 251  */
 252 static inline u32 clocksource_hz2mult(u32 hz, u32 shift_constant)
 253 {
 254         /*  hz = cyc/(Billion ns)
 255          *  mult/2^shift  = ns/cyc
 256          *  mult = ns/cyc * 2^shift
 257          *  mult = 1Billion/hz * 2^shift
 258          *  mult = 1000000000 * 2^shift / hz
 259          *  mult = (1000000000<<shift) / hz
 260          */
 261         u64 tmp = ((u64)1000000000) << shift_constant;
 262
 263         tmp += hz/2; /* round for do_div */
 264         do_div(tmp, hz);
 265
 266         return (u32)tmp;
 267 }
 268
 269 /**
 270  * clocksource_cyc2ns - converts clocksource cycles to nanoseconds
 271  * @cycles:     cycles
 272  * @mult:       cycle to nanosecond multiplier
 273  * @shift:      cycle to nanosecond divisor (power of two)
 274  *
 275  * Converts cycles to nanoseconds, using the given mult and shift.
 276  *
 277  * XXX - This could use some mult_lxl_ll() asm optimization
 278  */
 279 static inline s64 clocksource_cyc2ns(cycle_t cycles, u32 mult, u32 shift)
 280 {
 281         return ((u64) cycles * mult) >> shift;
 282 }
 283
 284
 285 extern int clocksource_register(struct clocksource*);
 286 extern int clocksource_unregister(struct clocksource*);
 287 extern void clocksource_touch_watchdog(void);
 288 extern struct clocksource* clocksource_get_next(void);
 289 extern void clocksource_change_rating(struct clocksource *cs, int rating);
 290 extern void clocksource_suspend(void);
 291 extern void clocksource_resume(void);
 292 extern struct clocksource * __init __weak clocksource_default_clock(void);
 293 extern void clocksource_mark_unstable(struct clocksource *cs);
 294
 295 extern u64
 296 clocks_calc_max_nsecs(u32 mult, u32 shift, u32 maxadj, u64 mask);
 297 extern void
 298 clocks_calc_mult_shift(u32 *mult, u32 *shift, u32 from, u32 to, u32 minsec);
 299
 300 /*
 301  * Don't call __clocksource_register_scale directly, use
 302  * clocksource_register_hz/khz
 303  */
 304 extern int
 305 __clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq);
 306 extern void
 307 __clocksource_updatefreq_scale(struct clocksource *cs, u32 scale, u32 freq);
 308
 309 static inline int clocksource_register_hz(struct clocksource *cs, u32 hz)
 310 {
 311         return __clocksource_register_scale(cs, 1, hz);
 312 }
 313
 314 static inline int clocksource_register_khz(struct clocksource *cs, u32 khz)
 315 {
 316         return __clocksource_register_scale(cs, 1000, khz);
 317 }
 318
 319 static inline void __clocksource_updatefreq_hz(struct clocksource *cs, u32 hz)
 320 {
 321         __clocksource_updatefreq_scale(cs, 1, hz);
 322 }
 323
 324 static inline void __clocksource_updatefreq_khz(struct clocksource *cs, u32 khz)
 325 {
 326         __clocksource_updatefreq_scale(cs, 1000, khz);
 327 }
 328
 329
 330 extern int timekeeping_notify(struct clocksource *clock);
 331
 332 extern cycle_t clocksource_mmio_readl_up(struct clocksource *);
 333 extern cycle_t clocksource_mmio_readl_down(struct clocksource *);
 334 extern cycle_t clocksource_mmio_readw_up(struct clocksource *);
 335 extern cycle_t clocksource_mmio_readw_down(struct clocksource *);
 336
 337 extern int clocksource_mmio_init(void __iomem *, const char *,
 338         unsigned long, int, unsigned, cycle_t (*)(struct clocksource *));
 339
 340 extern int clocksource_i8253_init(void);
 341
 342 struct device_node;
 343 typedef void(*clocksource_of_init_fn)(struct device_node *);
 344 #ifdef CONFIG_CLKSRC_OF
 345 extern void clocksource_of_init(void);
 346
 347 #define CLOCKSOURCE_OF_DECLARE(name, compat, fn)                        \
 348         static const struct of_device_id __clksrc_of_table_##name       \
 349                 __used __section(__clksrc_of_table)                     \
 350                  = { .compatible = compat,                              \
 351                      .data = (fn == (clocksource_of_init_fn)NULL) ? fn : fn }
 352 #else
 353 static inline void clocksource_of_init(void) {}
 354 #define CLOCKSOURCE_OF_DECLARE(name, compat, fn)                        \
 355         static const struct of_device_id __clksrc_of_table_##name       \
 356                 __attribute__((unused))                                 \
 357                  = { .compatible = compat,                              \
 358                      .data = (fn == (clocksource_of_init_fn)NULL) ? fn : fn }
 359 #endif
 360
 361 #endif /* _LINUX_CLOCKSOURCE_H */