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