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 struct clocksource; 22 struct module; 23 24 #ifdef CONFIG_ARCH_CLOCKSOURCE_DATA 25 #include <asm/clocksource.h> 26 #endif 27 28 /** 29 * struct clocksource - hardware abstraction for a free running counter 30 * Provides mostly state-free accessors to the underlying hardware. 31 * This is the structure used for system time. 32 * 33 * @name: ptr to clocksource name 34 * @list: list head for registration 35 * @rating: rating value for selection (higher is better) 36 * To avoid rating inflation the following 37 * list should give you a guide as to how 38 * to assign your clocksource a rating 39 * 1-99: Unfit for real use 40 * Only available for bootup and testing purposes. 41 * 100-199: Base level usability. 42 * Functional for real use, but not desired. 43 * 200-299: Good. 44 * A correct and usable clocksource. 45 * 300-399: Desired. 46 * A reasonably fast and accurate clocksource. 47 * 400-499: Perfect 48 * The ideal clocksource. A must-use where 49 * available. 50 * @read: returns a cycle value, passes clocksource as argument 51 * @enable: optional function to enable the clocksource 52 * @disable: optional function to disable the clocksource 53 * @mask: bitmask for two's complement 54 * subtraction of non 64 bit counters 55 * @mult: cycle to nanosecond multiplier 56 * @shift: cycle to nanosecond divisor (power of two) 57 * @max_idle_ns: max idle time permitted by the clocksource (nsecs) 58 * @maxadj: maximum adjustment value to mult (~11%) 59 * @max_cycles: maximum safe cycle value which won't overflow on multiplication 60 * @flags: flags describing special properties 61 * @archdata: arch-specific data 62 * @suspend: suspend function for the clocksource, if necessary 63 * @resume: resume function for the clocksource, if necessary 64 * @owner: module reference, must be set by clocksource in modules 65 * 66 * Note: This struct is not used in hotpathes of the timekeeping code 67 * because the timekeeper caches the hot path fields in its own data 68 * structure, so no line cache alignment is required, 69 * 70 * The pointer to the clocksource itself is handed to the read 71 * callback. If you need extra information there you can wrap struct 72 * clocksource into your own struct. Depending on the amount of 73 * information you need you should consider to cache line align that 74 * structure. 75 */ 76 struct clocksource { 77 cycle_t (*read)(struct clocksource *cs); 78 cycle_t mask; 79 u32 mult; 80 u32 shift; 81 u64 max_idle_ns; 82 u32 maxadj; 83 #ifdef CONFIG_ARCH_CLOCKSOURCE_DATA 84 struct arch_clocksource_data archdata; 85 #endif 86 u64 max_cycles; 87 const char *name; 88 struct list_head list; 89 int rating; 90 int (*enable)(struct clocksource *cs); 91 void (*disable)(struct clocksource *cs); 92 unsigned long flags; 93 void (*suspend)(struct clocksource *cs); 94 void (*resume)(struct clocksource *cs); 95 96 /* private: */ 97 #ifdef CONFIG_CLOCKSOURCE_WATCHDOG 98 /* Watchdog related data, used by the framework */ 99 struct list_head wd_list; 100 cycle_t cs_last; 101 cycle_t wd_last; 102 #endif 103 struct module *owner; 104 }; 105 106 /* 107 * Clock source flags bits:: 108 */ 109 #define CLOCK_SOURCE_IS_CONTINUOUS 0x01 110 #define CLOCK_SOURCE_MUST_VERIFY 0x02 111 112 #define CLOCK_SOURCE_WATCHDOG 0x10 113 #define CLOCK_SOURCE_VALID_FOR_HRES 0x20 114 #define CLOCK_SOURCE_UNSTABLE 0x40 115 #define CLOCK_SOURCE_SUSPEND_NONSTOP 0x80 116 #define CLOCK_SOURCE_RESELECT 0x100 117 118 /* simplify initialization of mask field */ 119 #define CLOCKSOURCE_MASK(bits) (cycle_t)((bits) < 64 ? ((1ULL<<(bits))-1) : -1) 120 121 /** 122 * clocksource_khz2mult - calculates mult from khz and shift 123 * @khz: Clocksource frequency in KHz 124 * @shift_constant: Clocksource shift factor 125 * 126 * Helper functions that converts a khz counter frequency to a timsource 127 * multiplier, given the clocksource shift value 128 */ 129 static inline u32 clocksource_khz2mult(u32 khz, u32 shift_constant) 130 { 131 /* khz = cyc/(Million ns) 132 * mult/2^shift = ns/cyc 133 * mult = ns/cyc * 2^shift 134 * mult = 1Million/khz * 2^shift 135 * mult = 1000000 * 2^shift / khz 136 * mult = (1000000<<shift) / khz 137 */ 138 u64 tmp = ((u64)1000000) << shift_constant; 139 140 tmp += khz/2; /* round for do_div */ 141 do_div(tmp, khz); 142 143 return (u32)tmp; 144 } 145 146 /** 147 * clocksource_hz2mult - calculates mult from hz and shift 148 * @hz: Clocksource frequency in Hz 149 * @shift_constant: Clocksource shift factor 150 * 151 * Helper functions that converts a hz counter 152 * frequency to a timsource multiplier, given the 153 * clocksource shift value 154 */ 155 static inline u32 clocksource_hz2mult(u32 hz, u32 shift_constant) 156 { 157 /* hz = cyc/(Billion ns) 158 * mult/2^shift = ns/cyc 159 * mult = ns/cyc * 2^shift 160 * mult = 1Billion/hz * 2^shift 161 * mult = 1000000000 * 2^shift / hz 162 * mult = (1000000000<<shift) / hz 163 */ 164 u64 tmp = ((u64)1000000000) << shift_constant; 165 166 tmp += hz/2; /* round for do_div */ 167 do_div(tmp, hz); 168 169 return (u32)tmp; 170 } 171 172 /** 173 * clocksource_cyc2ns - converts clocksource cycles to nanoseconds 174 * @cycles: cycles 175 * @mult: cycle to nanosecond multiplier 176 * @shift: cycle to nanosecond divisor (power of two) 177 * 178 * Converts cycles to nanoseconds, using the given mult and shift. 179 * 180 * XXX - This could use some mult_lxl_ll() asm optimization 181 */ 182 static inline s64 clocksource_cyc2ns(cycle_t cycles, u32 mult, u32 shift) 183 { 184 return ((u64) cycles * mult) >> shift; 185 } 186 187 188 extern int clocksource_unregister(struct clocksource*); 189 extern void clocksource_touch_watchdog(void); 190 extern void clocksource_change_rating(struct clocksource *cs, int rating); 191 extern void clocksource_suspend(void); 192 extern void clocksource_resume(void); 193 extern struct clocksource * __init clocksource_default_clock(void); 194 extern void clocksource_mark_unstable(struct clocksource *cs); 195 196 extern u64 197 clocks_calc_max_nsecs(u32 mult, u32 shift, u32 maxadj, u64 mask, u64 *max_cycles); 198 extern void 199 clocks_calc_mult_shift(u32 *mult, u32 *shift, u32 from, u32 to, u32 minsec); 200 201 /* 202 * Don't call __clocksource_register_scale directly, use 203 * clocksource_register_hz/khz 204 */ 205 extern int 206 __clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq); 207 extern void 208 __clocksource_update_freq_scale(struct clocksource *cs, u32 scale, u32 freq); 209 210 /* 211 * Don't call this unless you are a default clocksource 212 * (AKA: jiffies) and absolutely have to. 213 */ 214 static inline int __clocksource_register(struct clocksource *cs) 215 { 216 return __clocksource_register_scale(cs, 1, 0); 217 } 218 219 static inline int clocksource_register_hz(struct clocksource *cs, u32 hz) 220 { 221 return __clocksource_register_scale(cs, 1, hz); 222 } 223 224 static inline int clocksource_register_khz(struct clocksource *cs, u32 khz) 225 { 226 return __clocksource_register_scale(cs, 1000, khz); 227 } 228 229 static inline void __clocksource_update_freq_hz(struct clocksource *cs, u32 hz) 230 { 231 __clocksource_update_freq_scale(cs, 1, hz); 232 } 233 234 static inline void __clocksource_update_freq_khz(struct clocksource *cs, u32 khz) 235 { 236 __clocksource_update_freq_scale(cs, 1000, khz); 237 } 238 239 240 extern int timekeeping_notify(struct clocksource *clock); 241 242 extern cycle_t clocksource_mmio_readl_up(struct clocksource *); 243 extern cycle_t clocksource_mmio_readl_down(struct clocksource *); 244 extern cycle_t clocksource_mmio_readw_up(struct clocksource *); 245 extern cycle_t clocksource_mmio_readw_down(struct clocksource *); 246 247 extern int clocksource_mmio_init(void __iomem *, const char *, 248 unsigned long, int, unsigned, cycle_t (*)(struct clocksource *)); 249 250 extern int clocksource_i8253_init(void); 251 252 #define CLOCKSOURCE_OF_DECLARE(name, compat, fn) \ 253 OF_DECLARE_1(clksrc, name, compat, fn) 254 255 #ifdef CONFIG_CLKSRC_PROBE 256 extern void clocksource_probe(void); 257 #else 258 static inline void clocksource_probe(void) {} 259 #endif 260 261 #define CLOCKSOURCE_ACPI_DECLARE(name, table_id, fn) \ 262 ACPI_DECLARE_PROBE_ENTRY(clksrc, name, table_id, 0, NULL, 0, fn) 263 264 #endif /* _LINUX_CLOCKSOURCE_H */ 265