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