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 * @resume: resume function for the clocksource, if necessary 158 */ 159 struct clocksource { 160 /* 161 * First part of structure is read mostly 162 */ 163 char *name; 164 struct list_head list; 165 int rating; 166 cycle_t (*read)(struct clocksource *cs); 167 int (*enable)(struct clocksource *cs); 168 void (*disable)(struct clocksource *cs); 169 cycle_t mask; 170 u32 mult; 171 u32 shift; 172 u64 max_idle_ns; 173 unsigned long flags; 174 cycle_t (*vread)(void); 175 void (*resume)(void); 176 #ifdef CONFIG_IA64 177 void *fsys_mmio; /* used by fsyscall asm code */ 178 #define CLKSRC_FSYS_MMIO_SET(mmio, addr) ((mmio) = (addr)) 179 #else 180 #define CLKSRC_FSYS_MMIO_SET(mmio, addr) do { } while (0) 181 #endif 182 183 /* 184 * Second part is written at each timer interrupt 185 * Keep it in a different cache line to dirty no 186 * more than one cache line. 187 */ 188 cycle_t cycle_last ____cacheline_aligned_in_smp; 189 190 #ifdef CONFIG_CLOCKSOURCE_WATCHDOG 191 /* Watchdog related data, used by the framework */ 192 struct list_head wd_list; 193 cycle_t wd_last; 194 #endif 195 }; 196 197 /* 198 * Clock source flags bits:: 199 */ 200 #define CLOCK_SOURCE_IS_CONTINUOUS 0x01 201 #define CLOCK_SOURCE_MUST_VERIFY 0x02 202 203 #define CLOCK_SOURCE_WATCHDOG 0x10 204 #define CLOCK_SOURCE_VALID_FOR_HRES 0x20 205 #define CLOCK_SOURCE_UNSTABLE 0x40 206 207 /* simplify initialization of mask field */ 208 #define CLOCKSOURCE_MASK(bits) (cycle_t)((bits) < 64 ? ((1ULL<<(bits))-1) : -1) 209 210 /** 211 * clocksource_khz2mult - calculates mult from khz and shift 212 * @khz: Clocksource frequency in KHz 213 * @shift_constant: Clocksource shift factor 214 * 215 * Helper functions that converts a khz counter frequency to a timsource 216 * multiplier, given the clocksource shift value 217 */ 218 static inline u32 clocksource_khz2mult(u32 khz, u32 shift_constant) 219 { 220 /* khz = cyc/(Million ns) 221 * mult/2^shift = ns/cyc 222 * mult = ns/cyc * 2^shift 223 * mult = 1Million/khz * 2^shift 224 * mult = 1000000 * 2^shift / khz 225 * mult = (1000000<<shift) / khz 226 */ 227 u64 tmp = ((u64)1000000) << shift_constant; 228 229 tmp += khz/2; /* round for do_div */ 230 do_div(tmp, khz); 231 232 return (u32)tmp; 233 } 234 235 /** 236 * clocksource_hz2mult - calculates mult from hz and shift 237 * @hz: Clocksource frequency in Hz 238 * @shift_constant: Clocksource shift factor 239 * 240 * Helper functions that converts a hz counter 241 * frequency to a timsource multiplier, given the 242 * clocksource shift value 243 */ 244 static inline u32 clocksource_hz2mult(u32 hz, u32 shift_constant) 245 { 246 /* hz = cyc/(Billion ns) 247 * mult/2^shift = ns/cyc 248 * mult = ns/cyc * 2^shift 249 * mult = 1Billion/hz * 2^shift 250 * mult = 1000000000 * 2^shift / hz 251 * mult = (1000000000<<shift) / hz 252 */ 253 u64 tmp = ((u64)1000000000) << shift_constant; 254 255 tmp += hz/2; /* round for do_div */ 256 do_div(tmp, hz); 257 258 return (u32)tmp; 259 } 260 261 /** 262 * clocksource_cyc2ns - converts clocksource cycles to nanoseconds 263 * 264 * Converts cycles to nanoseconds, using the given mult and shift. 265 * 266 * XXX - This could use some mult_lxl_ll() asm optimization 267 */ 268 static inline s64 clocksource_cyc2ns(cycle_t cycles, u32 mult, u32 shift) 269 { 270 return ((u64) cycles * mult) >> shift; 271 } 272 273 274 /* used to install a new clocksource */ 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_resume(void); 281 extern struct clocksource * __init __weak clocksource_default_clock(void); 282 extern void clocksource_mark_unstable(struct clocksource *cs); 283 284 extern void 285 clocks_calc_mult_shift(u32 *mult, u32 *shift, u32 from, u32 to, u32 minsec); 286 287 static inline void 288 clocksource_calc_mult_shift(struct clocksource *cs, u32 freq, u32 minsec) 289 { 290 return clocks_calc_mult_shift(&cs->mult, &cs->shift, freq, 291 NSEC_PER_SEC, minsec); 292 } 293 294 #ifdef CONFIG_GENERIC_TIME_VSYSCALL 295 extern void 296 update_vsyscall(struct timespec *ts, struct clocksource *c, u32 mult); 297 extern void update_vsyscall_tz(void); 298 #else 299 static inline void 300 update_vsyscall(struct timespec *ts, struct clocksource *c, u32 mult) 301 { 302 } 303 304 static inline void update_vsyscall_tz(void) 305 { 306 } 307 #endif 308 309 extern void timekeeping_notify(struct clocksource *clock); 310 311 #endif /* _LINUX_CLOCKSOURCE_H */ 312