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 49 * @shift: cycle to nanosecond divisor (power of two) 50 * @flags: flags describing special properties 51 * @vread: vsyscall based read 52 * @resume: resume function for the clocksource, if necessary 53 * @cycle_interval: Used internally by timekeeping core, please ignore. 54 * @xtime_interval: Used internally by timekeeping core, please ignore. 55 */ 56 struct clocksource { 57 /* 58 * First part of structure is read mostly 59 */ 60 char *name; 61 struct list_head list; 62 int rating; 63 cycle_t (*read)(void); 64 cycle_t mask; 65 u32 mult; 66 u32 shift; 67 unsigned long flags; 68 cycle_t (*vread)(void); 69 void (*resume)(void); 70 #ifdef CONFIG_IA64 71 void *fsys_mmio; /* used by fsyscall asm code */ 72 #define CLKSRC_FSYS_MMIO_SET(mmio, addr) ((mmio) = (addr)) 73 #else 74 #define CLKSRC_FSYS_MMIO_SET(mmio, addr) do { } while (0) 75 #endif 76 77 /* timekeeping specific data, ignore */ 78 cycle_t cycle_interval; 79 u64 xtime_interval; 80 /* 81 * Second part is written at each timer interrupt 82 * Keep it in a different cache line to dirty no 83 * more than one cache line. 84 */ 85 cycle_t cycle_last ____cacheline_aligned_in_smp; 86 u64 xtime_nsec; 87 s64 error; 88 89 #ifdef CONFIG_CLOCKSOURCE_WATCHDOG 90 /* Watchdog related data, used by the framework */ 91 struct list_head wd_list; 92 cycle_t wd_last; 93 #endif 94 }; 95 96 extern struct clocksource *clock; /* current clocksource */ 97 98 /* 99 * Clock source flags bits:: 100 */ 101 #define CLOCK_SOURCE_IS_CONTINUOUS 0x01 102 #define CLOCK_SOURCE_MUST_VERIFY 0x02 103 104 #define CLOCK_SOURCE_WATCHDOG 0x10 105 #define CLOCK_SOURCE_VALID_FOR_HRES 0x20 106 107 /* simplify initialization of mask field */ 108 #define CLOCKSOURCE_MASK(bits) (cycle_t)((bits) < 64 ? ((1ULL<<(bits))-1) : -1) 109 110 /** 111 * clocksource_khz2mult - calculates mult from khz and shift 112 * @khz: Clocksource frequency in KHz 113 * @shift_constant: Clocksource shift factor 114 * 115 * Helper functions that converts a khz counter frequency to a timsource 116 * multiplier, given the clocksource shift value 117 */ 118 static inline u32 clocksource_khz2mult(u32 khz, u32 shift_constant) 119 { 120 /* khz = cyc/(Million ns) 121 * mult/2^shift = ns/cyc 122 * mult = ns/cyc * 2^shift 123 * mult = 1Million/khz * 2^shift 124 * mult = 1000000 * 2^shift / khz 125 * mult = (1000000<<shift) / khz 126 */ 127 u64 tmp = ((u64)1000000) << shift_constant; 128 129 tmp += khz/2; /* round for do_div */ 130 do_div(tmp, khz); 131 132 return (u32)tmp; 133 } 134 135 /** 136 * clocksource_hz2mult - calculates mult from hz and shift 137 * @hz: Clocksource frequency in Hz 138 * @shift_constant: Clocksource shift factor 139 * 140 * Helper functions that converts a hz counter 141 * frequency to a timsource multiplier, given the 142 * clocksource shift value 143 */ 144 static inline u32 clocksource_hz2mult(u32 hz, u32 shift_constant) 145 { 146 /* hz = cyc/(Billion ns) 147 * mult/2^shift = ns/cyc 148 * mult = ns/cyc * 2^shift 149 * mult = 1Billion/hz * 2^shift 150 * mult = 1000000000 * 2^shift / hz 151 * mult = (1000000000<<shift) / hz 152 */ 153 u64 tmp = ((u64)1000000000) << shift_constant; 154 155 tmp += hz/2; /* round for do_div */ 156 do_div(tmp, hz); 157 158 return (u32)tmp; 159 } 160 161 /** 162 * clocksource_read: - Access the clocksource's current cycle value 163 * @cs: pointer to clocksource being read 164 * 165 * Uses the clocksource to return the current cycle_t value 166 */ 167 static inline cycle_t clocksource_read(struct clocksource *cs) 168 { 169 return cs->read(); 170 } 171 172 /** 173 * cyc2ns - converts clocksource cycles to nanoseconds 174 * @cs: Pointer to clocksource 175 * @cycles: Cycles 176 * 177 * Uses the clocksource and ntp ajdustment to convert cycle_ts to nanoseconds. 178 * 179 * XXX - This could use some mult_lxl_ll() asm optimization 180 */ 181 static inline s64 cyc2ns(struct clocksource *cs, cycle_t cycles) 182 { 183 u64 ret = (u64)cycles; 184 ret = (ret * cs->mult) >> cs->shift; 185 return ret; 186 } 187 188 /** 189 * clocksource_calculate_interval - Calculates a clocksource interval struct 190 * 191 * @c: Pointer to clocksource. 192 * @length_nsec: Desired interval length in nanoseconds. 193 * 194 * Calculates a fixed cycle/nsec interval for a given clocksource/adjustment 195 * pair and interval request. 196 * 197 * Unless you're the timekeeping code, you should not be using this! 198 */ 199 static inline void clocksource_calculate_interval(struct clocksource *c, 200 unsigned long length_nsec) 201 { 202 u64 tmp; 203 204 /* XXX - All of this could use a whole lot of optimization */ 205 tmp = length_nsec; 206 tmp <<= c->shift; 207 tmp += c->mult/2; 208 do_div(tmp, c->mult); 209 210 c->cycle_interval = (cycle_t)tmp; 211 if (c->cycle_interval == 0) 212 c->cycle_interval = 1; 213 214 c->xtime_interval = (u64)c->cycle_interval * c->mult; 215 } 216 217 218 /* used to install a new clocksource */ 219 extern int clocksource_register(struct clocksource*); 220 extern void clocksource_unregister(struct clocksource*); 221 extern void clocksource_touch_watchdog(void); 222 extern struct clocksource* clocksource_get_next(void); 223 extern void clocksource_change_rating(struct clocksource *cs, int rating); 224 extern void clocksource_resume(void); 225 226 #ifdef CONFIG_GENERIC_TIME_VSYSCALL 227 extern void update_vsyscall(struct timespec *ts, struct clocksource *c); 228 extern void update_vsyscall_tz(void); 229 #else 230 static inline void update_vsyscall(struct timespec *ts, struct clocksource *c) 231 { 232 } 233 234 static inline void update_vsyscall_tz(void) 235 { 236 } 237 #endif 238 239 #endif /* _LINUX_CLOCKSOURCE_H */ 240