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 * @cc: 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_tstamp: 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 * @cycle_last: most recent cycle counter value seen by ::read() 165 */ 166 struct clocksource { 167 /* 168 * Hotpath data, fits in a single cache line when the 169 * clocksource itself is cacheline aligned. 170 */ 171 cycle_t (*read)(struct clocksource *cs); 172 cycle_t cycle_last; 173 cycle_t mask; 174 u32 mult; 175 u32 shift; 176 u64 max_idle_ns; 177 u32 maxadj; 178 #ifdef CONFIG_ARCH_CLOCKSOURCE_DATA 179 struct arch_clocksource_data archdata; 180 #endif 181 182 const char *name; 183 struct list_head list; 184 int rating; 185 int (*enable)(struct clocksource *cs); 186 void (*disable)(struct clocksource *cs); 187 unsigned long flags; 188 void (*suspend)(struct clocksource *cs); 189 void (*resume)(struct clocksource *cs); 190 191 /* private: */ 192 #ifdef CONFIG_CLOCKSOURCE_WATCHDOG 193 /* Watchdog related data, used by the framework */ 194 struct list_head wd_list; 195 cycle_t cs_last; 196 cycle_t wd_last; 197 #endif 198 } ____cacheline_aligned; 199 200 /* 201 * Clock source flags bits:: 202 */ 203 #define CLOCK_SOURCE_IS_CONTINUOUS 0x01 204 #define CLOCK_SOURCE_MUST_VERIFY 0x02 205 206 #define CLOCK_SOURCE_WATCHDOG 0x10 207 #define CLOCK_SOURCE_VALID_FOR_HRES 0x20 208 #define CLOCK_SOURCE_UNSTABLE 0x40 209 #define CLOCK_SOURCE_SUSPEND_NONSTOP 0x80 210 211 /* simplify initialization of mask field */ 212 #define CLOCKSOURCE_MASK(bits) (cycle_t)((bits) < 64 ? ((1ULL<<(bits))-1) : -1) 213 214 /** 215 * clocksource_khz2mult - calculates mult from khz and shift 216 * @khz: Clocksource frequency in KHz 217 * @shift_constant: Clocksource shift factor 218 * 219 * Helper functions that converts a khz counter frequency to a timsource 220 * multiplier, given the clocksource shift value 221 */ 222 static inline u32 clocksource_khz2mult(u32 khz, u32 shift_constant) 223 { 224 /* khz = cyc/(Million ns) 225 * mult/2^shift = ns/cyc 226 * mult = ns/cyc * 2^shift 227 * mult = 1Million/khz * 2^shift 228 * mult = 1000000 * 2^shift / khz 229 * mult = (1000000<<shift) / khz 230 */ 231 u64 tmp = ((u64)1000000) << shift_constant; 232 233 tmp += khz/2; /* round for do_div */ 234 do_div(tmp, khz); 235 236 return (u32)tmp; 237 } 238 239 /** 240 * clocksource_hz2mult - calculates mult from hz and shift 241 * @hz: Clocksource frequency in Hz 242 * @shift_constant: Clocksource shift factor 243 * 244 * Helper functions that converts a hz counter 245 * frequency to a timsource multiplier, given the 246 * clocksource shift value 247 */ 248 static inline u32 clocksource_hz2mult(u32 hz, u32 shift_constant) 249 { 250 /* hz = cyc/(Billion ns) 251 * mult/2^shift = ns/cyc 252 * mult = ns/cyc * 2^shift 253 * mult = 1Billion/hz * 2^shift 254 * mult = 1000000000 * 2^shift / hz 255 * mult = (1000000000<<shift) / hz 256 */ 257 u64 tmp = ((u64)1000000000) << shift_constant; 258 259 tmp += hz/2; /* round for do_div */ 260 do_div(tmp, hz); 261 262 return (u32)tmp; 263 } 264 265 /** 266 * clocksource_cyc2ns - converts clocksource cycles to nanoseconds 267 * @cycles: cycles 268 * @mult: cycle to nanosecond multiplier 269 * @shift: cycle to nanosecond divisor (power of two) 270 * 271 * Converts cycles to nanoseconds, using the given mult and shift. 272 * 273 * XXX - This could use some mult_lxl_ll() asm optimization 274 */ 275 static inline s64 clocksource_cyc2ns(cycle_t cycles, u32 mult, u32 shift) 276 { 277 return ((u64) cycles * mult) >> shift; 278 } 279 280 281 extern int clocksource_register(struct clocksource*); 282 extern void clocksource_unregister(struct clocksource*); 283 extern void clocksource_touch_watchdog(void); 284 extern struct clocksource* clocksource_get_next(void); 285 extern void clocksource_change_rating(struct clocksource *cs, int rating); 286 extern void clocksource_suspend(void); 287 extern void clocksource_resume(void); 288 extern struct clocksource * __init __weak clocksource_default_clock(void); 289 extern void clocksource_mark_unstable(struct clocksource *cs); 290 291 extern void 292 clocks_calc_mult_shift(u32 *mult, u32 *shift, u32 from, u32 to, u32 minsec); 293 294 /* 295 * Don't call __clocksource_register_scale directly, use 296 * clocksource_register_hz/khz 297 */ 298 extern int 299 __clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq); 300 extern void 301 __clocksource_updatefreq_scale(struct clocksource *cs, u32 scale, u32 freq); 302 303 static inline int clocksource_register_hz(struct clocksource *cs, u32 hz) 304 { 305 return __clocksource_register_scale(cs, 1, hz); 306 } 307 308 static inline int clocksource_register_khz(struct clocksource *cs, u32 khz) 309 { 310 return __clocksource_register_scale(cs, 1000, khz); 311 } 312 313 static inline void __clocksource_updatefreq_hz(struct clocksource *cs, u32 hz) 314 { 315 __clocksource_updatefreq_scale(cs, 1, hz); 316 } 317 318 static inline void __clocksource_updatefreq_khz(struct clocksource *cs, u32 khz) 319 { 320 __clocksource_updatefreq_scale(cs, 1000, khz); 321 } 322 323 324 extern void timekeeping_notify(struct clocksource *clock); 325 326 extern cycle_t clocksource_mmio_readl_up(struct clocksource *); 327 extern cycle_t clocksource_mmio_readl_down(struct clocksource *); 328 extern cycle_t clocksource_mmio_readw_up(struct clocksource *); 329 extern cycle_t clocksource_mmio_readw_down(struct clocksource *); 330 331 extern int clocksource_mmio_init(void __iomem *, const char *, 332 unsigned long, int, unsigned, cycle_t (*)(struct clocksource *)); 333 334 extern int clocksource_i8253_init(void); 335 336 struct device_node; 337 typedef void(*clocksource_of_init_fn)(struct device_node *); 338 #ifdef CONFIG_CLKSRC_OF 339 extern void clocksource_of_init(void); 340 341 #define CLOCKSOURCE_OF_DECLARE(name, compat, fn) \ 342 static const struct of_device_id __clksrc_of_table_##name \ 343 __used __section(__clksrc_of_table) \ 344 = { .compatible = compat, \ 345 .data = (fn == (clocksource_of_init_fn)NULL) ? fn : fn } 346 #else 347 static inline void clocksource_of_init(void) {} 348 #define CLOCKSOURCE_OF_DECLARE(name, compat, fn) \ 349 static const struct of_device_id __clksrc_of_table_##name \ 350 __attribute__((unused)) \ 351 = { .compatible = compat, \ 352 .data = (fn == (clocksource_of_init_fn)NULL) ? fn : fn } 353 #endif 354 355 #endif /* _LINUX_CLOCKSOURCE_H */ 356