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
  25 /**
  26  * struct cyclecounter - hardware abstraction for a free running counter
  27  *      Provides completely state-free accessors to the underlying hardware.
  28  *      Depending on which hardware it reads, the cycle counter may wrap
  29  *      around quickly. Locking rules (if necessary) have to be defined
  30  *      by the implementor and user of specific instances of this API.
  31  *
  32  * @read:               returns the current cycle value
  33  * @mask:               bitmask for two's complement
  34  *                      subtraction of non 64 bit counters,
  35  *                      see CLOCKSOURCE_MASK() helper macro
  36  * @mult:               cycle to nanosecond multiplier
  37  * @shift:              cycle to nanosecond divisor (power of two)
  38  */
  39 struct cyclecounter {
  40         cycle_t (*read)(const struct cyclecounter *cc);
  41         cycle_t mask;
  42         u32 mult;
  43         u32 shift;
  44 };
  45
  46 /**
  47  * struct timecounter - layer above a %struct cyclecounter which counts nanoseconds
  48  *      Contains the state needed by timecounter_read() to detect
  49  *      cycle counter wrap around. Initialize with
  50  *      timecounter_init(). Also used to convert cycle counts into the
  51  *      corresponding nanosecond counts with timecounter_cyc2time(). Users
  52  *      of this code are responsible for initializing the underlying
  53  *      cycle counter hardware, locking issues and reading the time
  54  *      more often than the cycle counter wraps around. The nanosecond
  55  *      counter will only wrap around after ~585 years.
  56  *
  57  * @cc:                 the cycle counter used by this instance
  58  * @cycle_last:         most recent cycle counter value seen by
  59  *                      timecounter_read()
  60  * @nsec:               continuously increasing count
  61  */
  62 struct timecounter {
  63         const struct cyclecounter *cc;
  64         cycle_t cycle_last;
  65         u64 nsec;
  66 };
  67
  68 /**
  69  * cyclecounter_cyc2ns - converts cycle counter cycles to nanoseconds
  70  * @tc:         Pointer to cycle counter.
  71  * @cycles:     Cycles
  72  *
  73  * XXX - This could use some mult_lxl_ll() asm optimization. Same code
  74  * as in cyc2ns, but with unsigned result.
  75  */
  76 static inline u64 cyclecounter_cyc2ns(const struct cyclecounter *cc,
  77                                       cycle_t cycles)
  78 {
  79         u64 ret = (u64)cycles;
  80         ret = (ret * cc->mult) >> cc->shift;
  81         return ret;
  82 }
  83
  84 /**
  85  * timecounter_init - initialize a time counter
  86  * @tc:                 Pointer to time counter which is to be initialized/reset
  87  * @cc:                 A cycle counter, ready to be used.
  88  * @start_tstamp:       Arbitrary initial time stamp.
  89  *
  90  * After this call the current cycle register (roughly) corresponds to
  91  * the initial time stamp. Every call to timecounter_read() increments
  92  * the time stamp counter by the number of elapsed nanoseconds.
  93  */
  94 extern void timecounter_init(struct timecounter *tc,
  95                              const struct cyclecounter *cc,
  96                              u64 start_tstamp);
  97
  98 /**
  99  * timecounter_read - return nanoseconds elapsed since timecounter_init()
 100  *                    plus the initial time stamp
 101  * @tc:          Pointer to time counter.
 102  *
 103  * In other words, keeps track of time since the same epoch as
 104  * the function which generated the initial time stamp.
 105  */
 106 extern u64 timecounter_read(struct timecounter *tc);
 107
 108 /**
 109  * timecounter_cyc2time - convert a cycle counter to same
 110  *                        time base as values returned by
 111  *                        timecounter_read()
 112  * @tc:         Pointer to time counter.
 113  * @cycle:      a value returned by tc->cc->read()
 114  *
 115  * Cycle counts that are converted correctly as long as they
 116  * fall into the interval [-1/2 max cycle count, +1/2 max cycle count],
 117  * with "max cycle count" == cs->mask+1.
 118  *
 119  * This allows conversion of cycle counter values which were generated
 120  * in the past.
 121  */
 122 extern u64 timecounter_cyc2time(struct timecounter *tc,
 123                                 cycle_t cycle_tstamp);
 124
 125 /**
 126  * struct clocksource - hardware abstraction for a free running counter
 127  *      Provides mostly state-free accessors to the underlying hardware.
 128  *      This is the structure used for system time.
 129  *
 130  * @name:               ptr to clocksource name
 131  * @list:               list head for registration
 132  * @rating:             rating value for selection (higher is better)
 133  *                      To avoid rating inflation the following
 134  *                      list should give you a guide as to how
 135  *                      to assign your clocksource a rating
 136  *                      1-99: Unfit for real use
 137  *                              Only available for bootup and testing purposes.
 138  *                      100-199: Base level usability.
 139  *                              Functional for real use, but not desired.
 140  *                      200-299: Good.
 141  *                              A correct and usable clocksource.
 142  *                      300-399: Desired.
 143  *                              A reasonably fast and accurate clocksource.
 144  *                      400-499: Perfect
 145  *                              The ideal clocksource. A must-use where
 146  *                              available.
 147  * @read:               returns a cycle value, passes clocksource as argument
 148  * @enable:             optional function to enable the clocksource
 149  * @disable:            optional function to disable the clocksource
 150  * @mask:               bitmask for two's complement
 151  *                      subtraction of non 64 bit counters
 152  * @mult:               cycle to nanosecond multiplier
 153  * @shift:              cycle to nanosecond divisor (power of two)
 154  * @max_idle_ns:        max idle time permitted by the clocksource (nsecs)
 155  * @flags:              flags describing special properties
 156  * @vread:              vsyscall based read
 157  * @suspend:            suspend function for the clocksource, if necessary
 158  * @resume:             resume function for the clocksource, if necessary
 159  */
 160 struct clocksource {
 161         /*
 162          * Hotpath data, fits in a single cache line when the
 163          * clocksource itself is cacheline aligned.
 164          */
 165         cycle_t (*read)(struct clocksource *cs);
 166         cycle_t cycle_last;
 167         cycle_t mask;
 168         u32 mult;
 169         u32 shift;
 170         u64 max_idle_ns;
 171
 172 #ifdef CONFIG_IA64
 173         void *fsys_mmio;        /* used by fsyscall asm code */
 174 #define CLKSRC_FSYS_MMIO_SET(mmio, addr)      ((mmio) = (addr))
 175 #else
 176 #define CLKSRC_FSYS_MMIO_SET(mmio, addr)      do { } while (0)
 177 #endif
 178         const char *name;
 179         struct list_head list;
 180         int rating;
 181         cycle_t (*vread)(void);
 182         int (*enable)(struct clocksource *cs);
 183         void (*disable)(struct clocksource *cs);
 184         unsigned long flags;
 185         void (*suspend)(struct clocksource *cs);
 186         void (*resume)(struct clocksource *cs);
 187
 188 #ifdef CONFIG_CLOCKSOURCE_WATCHDOG
 189         /* Watchdog related data, used by the framework */
 190         struct list_head wd_list;
 191         cycle_t cs_last;
 192         cycle_t wd_last;
 193 #endif
 194 } ____cacheline_aligned;
 195
 196 /*
 197  * Clock source flags bits::
 198  */
 199 #define CLOCK_SOURCE_IS_CONTINUOUS              0x01
 200 #define CLOCK_SOURCE_MUST_VERIFY                0x02
 201
 202 #define CLOCK_SOURCE_WATCHDOG                   0x10
 203 #define CLOCK_SOURCE_VALID_FOR_HRES             0x20
 204 #define CLOCK_SOURCE_UNSTABLE                   0x40
 205
 206 /* simplify initialization of mask field */
 207 #define CLOCKSOURCE_MASK(bits) (cycle_t)((bits) < 64 ? ((1ULL<<(bits))-1) : -1)
 208
 209 /**
 210  * clocksource_khz2mult - calculates mult from khz and shift
 211  * @khz:                Clocksource frequency in KHz
 212  * @shift_constant:     Clocksource shift factor
 213  *
 214  * Helper functions that converts a khz counter frequency to a timsource
 215  * multiplier, given the clocksource shift value
 216  */
 217 static inline u32 clocksource_khz2mult(u32 khz, u32 shift_constant)
 218 {
 219         /*  khz = cyc/(Million ns)
 220          *  mult/2^shift  = ns/cyc
 221          *  mult = ns/cyc * 2^shift
 222          *  mult = 1Million/khz * 2^shift
 223          *  mult = 1000000 * 2^shift / khz
 224          *  mult = (1000000<<shift) / khz
 225          */
 226         u64 tmp = ((u64)1000000) << shift_constant;
 227
 228         tmp += khz/2; /* round for do_div */
 229         do_div(tmp, khz);
 230
 231         return (u32)tmp;
 232 }
 233
 234 /**
 235  * clocksource_hz2mult - calculates mult from hz and shift
 236  * @hz:                 Clocksource frequency in Hz
 237  * @shift_constant:     Clocksource shift factor
 238  *
 239  * Helper functions that converts a hz counter
 240  * frequency to a timsource multiplier, given the
 241  * clocksource shift value
 242  */
 243 static inline u32 clocksource_hz2mult(u32 hz, u32 shift_constant)
 244 {
 245         /*  hz = cyc/(Billion ns)
 246          *  mult/2^shift  = ns/cyc
 247          *  mult = ns/cyc * 2^shift
 248          *  mult = 1Billion/hz * 2^shift
 249          *  mult = 1000000000 * 2^shift / hz
 250          *  mult = (1000000000<<shift) / hz
 251          */
 252         u64 tmp = ((u64)1000000000) << shift_constant;
 253
 254         tmp += hz/2; /* round for do_div */
 255         do_div(tmp, hz);
 256
 257         return (u32)tmp;
 258 }
 259
 260 /**
 261  * clocksource_cyc2ns - converts clocksource cycles to nanoseconds
 262  *
 263  * Converts cycles to nanoseconds, using the given mult and shift.
 264  *
 265  * XXX - This could use some mult_lxl_ll() asm optimization
 266  */
 267 static inline s64 clocksource_cyc2ns(cycle_t cycles, u32 mult, u32 shift)
 268 {
 269         return ((u64) cycles * mult) >> shift;
 270 }
 271
 272
 273 extern int clocksource_register(struct clocksource*);
 274 extern void clocksource_unregister(struct clocksource*);
 275 extern void clocksource_touch_watchdog(void);
 276 extern struct clocksource* clocksource_get_next(void);
 277 extern void clocksource_change_rating(struct clocksource *cs, int rating);
 278 extern void clocksource_suspend(void);
 279 extern void clocksource_resume(void);
 280 extern struct clocksource * __init __weak clocksource_default_clock(void);
 281 extern void clocksource_mark_unstable(struct clocksource *cs);
 282
 283 extern void
 284 clocks_calc_mult_shift(u32 *mult, u32 *shift, u32 from, u32 to, u32 minsec);
 285
 286 /*
 287  * Don't call __clocksource_register_scale directly, use
 288  * clocksource_register_hz/khz
 289  */
 290 extern int
 291 __clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq);
 292 extern void
 293 __clocksource_updatefreq_scale(struct clocksource *cs, u32 scale, u32 freq);
 294
 295 static inline int clocksource_register_hz(struct clocksource *cs, u32 hz)
 296 {
 297         return __clocksource_register_scale(cs, 1, hz);
 298 }
 299
 300 static inline int clocksource_register_khz(struct clocksource *cs, u32 khz)
 301 {
 302         return __clocksource_register_scale(cs, 1000, khz);
 303 }
 304
 305 static inline void __clocksource_updatefreq_hz(struct clocksource *cs, u32 hz)
 306 {
 307         __clocksource_updatefreq_scale(cs, 1, hz);
 308 }
 309
 310 static inline void __clocksource_updatefreq_khz(struct clocksource *cs, u32 khz)
 311 {
 312         __clocksource_updatefreq_scale(cs, 1000, khz);
 313 }
 314
 315 static inline void
 316 clocksource_calc_mult_shift(struct clocksource *cs, u32 freq, u32 minsec)
 317 {
 318         return clocks_calc_mult_shift(&cs->mult, &cs->shift, freq,
 319                                       NSEC_PER_SEC, minsec);
 320 }
 321
 322 #ifdef CONFIG_GENERIC_TIME_VSYSCALL
 323 extern void
 324 update_vsyscall(struct timespec *ts, struct timespec *wtm,
 325                         struct clocksource *c, u32 mult);
 326 extern void update_vsyscall_tz(void);
 327 #else
 328 static inline void
 329 update_vsyscall(struct timespec *ts, struct timespec *wtm,
 330                         struct clocksource *c, u32 mult)
 331 {
 332 }
 333
 334 static inline void update_vsyscall_tz(void)
 335 {
 336 }
 337 #endif
 338
 339 extern void timekeeping_notify(struct clocksource *clock);
 340
 341 extern cycle_t clocksource_mmio_readl_up(struct clocksource *);
 342 extern cycle_t clocksource_mmio_readl_down(struct clocksource *);
 343 extern cycle_t clocksource_mmio_readw_up(struct clocksource *);
 344 extern cycle_t clocksource_mmio_readw_down(struct clocksource *);
 345
 346 extern int clocksource_mmio_init(void __iomem *, const char *,
 347         unsigned long, int, unsigned, cycle_t (*)(struct clocksource *));
 348
 349 extern int clocksource_i8253_init(void);
 350
 351 #endif /* _LINUX_CLOCKSOURCE_H */