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 <asm/div64.h>
  18 #include <asm/io.h>
  19
  20 /* clocksource cycle base type */
  21 typedef u64 cycle_t;
  22 struct clocksource;
  23
  24 /**
  25  * struct clocksource - hardware abstraction for a free running counter
  26  *      Provides mostly state-free accessors to the underlying hardware.
  27  *
  28  * @name:               ptr to clocksource name
  29  * @list:               list head for registration
  30  * @rating:             rating value for selection (higher is better)
  31  *                      To avoid rating inflation the following
  32  *                      list should give you a guide as to how
  33  *                      to assign your clocksource a rating
  34  *                      1-99: Unfit for real use
  35  *                              Only available for bootup and testing purposes.
  36  *                      100-199: Base level usability.
  37  *                              Functional for real use, but not desired.
  38  *                      200-299: Good.
  39  *                              A correct and usable clocksource.
  40  *                      300-399: Desired.
  41  *                              A reasonably fast and accurate clocksource.
  42  *                      400-499: Perfect
  43  *                              The ideal clocksource. A must-use where
  44  *                              available.
  45  * @read:               returns a cycle value
  46  * @mask:               bitmask for two's complement
  47  *                      subtraction of non 64 bit counters
  48  * @mult:               cycle to nanosecond multiplier (adjusted by NTP)
  49  * @mult_orig:          cycle to nanosecond multiplier (unadjusted by NTP)
  50  * @shift:              cycle to nanosecond divisor (power of two)
  51  * @flags:              flags describing special properties
  52  * @vread:              vsyscall based read
  53  * @resume:             resume function for the clocksource, if necessary
  54  * @cycle_interval:     Used internally by timekeeping core, please ignore.
  55  * @xtime_interval:     Used internally by timekeeping core, please ignore.
  56  */
  57 struct clocksource {
  58         /*
  59          * First part of structure is read mostly
  60          */
  61         char *name;
  62         struct list_head list;
  63         int rating;
  64         cycle_t (*read)(void);
  65         cycle_t mask;
  66         u32 mult;
  67         u32 mult_orig;
  68         u32 shift;
  69         unsigned long flags;
  70         cycle_t (*vread)(void);
  71         void (*resume)(void);
  72 #ifdef CONFIG_IA64
  73         void *fsys_mmio;        /* used by fsyscall asm code */
  74 #define CLKSRC_FSYS_MMIO_SET(mmio, addr)      ((mmio) = (addr))
  75 #else
  76 #define CLKSRC_FSYS_MMIO_SET(mmio, addr)      do { } while (0)
  77 #endif
  78
  79         /* timekeeping specific data, ignore */
  80         cycle_t cycle_interval;
  81         u64     xtime_interval;
  82         u32     raw_interval;
  83         /*
  84          * Second part is written at each timer interrupt
  85          * Keep it in a different cache line to dirty no
  86          * more than one cache line.
  87          */
  88         cycle_t cycle_last ____cacheline_aligned_in_smp;
  89         u64 xtime_nsec;
  90         s64 error;
  91         struct timespec raw_time;
  92
  93 #ifdef CONFIG_CLOCKSOURCE_WATCHDOG
  94         /* Watchdog related data, used by the framework */
  95         struct list_head wd_list;
  96         cycle_t wd_last;
  97 #endif
  98 };
  99
 100 extern struct clocksource *clock;       /* current clocksource */
 101
 102 /*
 103  * Clock source flags bits::
 104  */
 105 #define CLOCK_SOURCE_IS_CONTINUOUS              0x01
 106 #define CLOCK_SOURCE_MUST_VERIFY                0x02
 107
 108 #define CLOCK_SOURCE_WATCHDOG                   0x10
 109 #define CLOCK_SOURCE_VALID_FOR_HRES             0x20
 110
 111 /* simplify initialization of mask field */
 112 #define CLOCKSOURCE_MASK(bits) (cycle_t)((bits) < 64 ? ((1ULL<<(bits))-1) : -1)
 113
 114 /**
 115  * clocksource_khz2mult - calculates mult from khz and shift
 116  * @khz:                Clocksource frequency in KHz
 117  * @shift_constant:     Clocksource shift factor
 118  *
 119  * Helper functions that converts a khz counter frequency to a timsource
 120  * multiplier, given the clocksource shift value
 121  */
 122 static inline u32 clocksource_khz2mult(u32 khz, u32 shift_constant)
 123 {
 124         /*  khz = cyc/(Million ns)
 125          *  mult/2^shift  = ns/cyc
 126          *  mult = ns/cyc * 2^shift
 127          *  mult = 1Million/khz * 2^shift
 128          *  mult = 1000000 * 2^shift / khz
 129          *  mult = (1000000<<shift) / khz
 130          */
 131         u64 tmp = ((u64)1000000) << shift_constant;
 132
 133         tmp += khz/2; /* round for do_div */
 134         do_div(tmp, khz);
 135
 136         return (u32)tmp;
 137 }
 138
 139 /**
 140  * clocksource_hz2mult - calculates mult from hz and shift
 141  * @hz:                 Clocksource frequency in Hz
 142  * @shift_constant:     Clocksource shift factor
 143  *
 144  * Helper functions that converts a hz counter
 145  * frequency to a timsource multiplier, given the
 146  * clocksource shift value
 147  */
 148 static inline u32 clocksource_hz2mult(u32 hz, u32 shift_constant)
 149 {
 150         /*  hz = cyc/(Billion ns)
 151          *  mult/2^shift  = ns/cyc
 152          *  mult = ns/cyc * 2^shift
 153          *  mult = 1Billion/hz * 2^shift
 154          *  mult = 1000000000 * 2^shift / hz
 155          *  mult = (1000000000<<shift) / hz
 156          */
 157         u64 tmp = ((u64)1000000000) << shift_constant;
 158
 159         tmp += hz/2; /* round for do_div */
 160         do_div(tmp, hz);
 161
 162         return (u32)tmp;
 163 }
 164
 165 /**
 166  * clocksource_read: - Access the clocksource's current cycle value
 167  * @cs:         pointer to clocksource being read
 168  *
 169  * Uses the clocksource to return the current cycle_t value
 170  */
 171 static inline cycle_t clocksource_read(struct clocksource *cs)
 172 {
 173         return cs->read();
 174 }
 175
 176 /**
 177  * cyc2ns - converts clocksource cycles to nanoseconds
 178  * @cs:         Pointer to clocksource
 179  * @cycles:     Cycles
 180  *
 181  * Uses the clocksource and ntp ajdustment to convert cycle_ts to nanoseconds.
 182  *
 183  * XXX - This could use some mult_lxl_ll() asm optimization
 184  */
 185 static inline s64 cyc2ns(struct clocksource *cs, cycle_t cycles)
 186 {
 187         u64 ret = (u64)cycles;
 188         ret = (ret * cs->mult) >> cs->shift;
 189         return ret;
 190 }
 191
 192 /**
 193  * clocksource_calculate_interval - Calculates a clocksource interval struct
 194  *
 195  * @c:          Pointer to clocksource.
 196  * @length_nsec: Desired interval length in nanoseconds.
 197  *
 198  * Calculates a fixed cycle/nsec interval for a given clocksource/adjustment
 199  * pair and interval request.
 200  *
 201  * Unless you're the timekeeping code, you should not be using this!
 202  */
 203 static inline void clocksource_calculate_interval(struct clocksource *c,
 204                                                   unsigned long length_nsec)
 205 {
 206         u64 tmp;
 207
 208         /* Do the ns -> cycle conversion first, using original mult */
 209         tmp = length_nsec;
 210         tmp <<= c->shift;
 211         tmp += c->mult_orig/2;
 212         do_div(tmp, c->mult_orig);
 213
 214         c->cycle_interval = (cycle_t)tmp;
 215         if (c->cycle_interval == 0)
 216                 c->cycle_interval = 1;
 217
 218         /* Go back from cycles -> shifted ns, this time use ntp adjused mult */
 219         c->xtime_interval = (u64)c->cycle_interval * c->mult;
 220         c->raw_interval = ((u64)c->cycle_interval * c->mult_orig) >> c->shift;
 221 }
 222
 223
 224 /* used to install a new clocksource */
 225 extern int clocksource_register(struct clocksource*);
 226 extern void clocksource_unregister(struct clocksource*);
 227 extern void clocksource_touch_watchdog(void);
 228 extern struct clocksource* clocksource_get_next(void);
 229 extern void clocksource_change_rating(struct clocksource *cs, int rating);
 230 extern void clocksource_resume(void);
 231
 232 #ifdef CONFIG_GENERIC_TIME_VSYSCALL
 233 extern void update_vsyscall(struct timespec *ts, struct clocksource *c);
 234 extern void update_vsyscall_tz(void);
 235 #else
 236 static inline void update_vsyscall(struct timespec *ts, struct clocksource *c)
 237 {
 238 }
 239
 240 static inline void update_vsyscall_tz(void)
 241 {
 242 }
 243 #endif
 244
 245 #endif /* _LINUX_CLOCKSOURCE_H */