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 <linux/of.h> 19 #include <asm/div64.h> 20 #include <asm/io.h> 21 22 struct clocksource; 23 struct module; 24 25 #ifdef CONFIG_ARCH_CLOCKSOURCE_DATA 26 #include <asm/clocksource.h> 27 #endif 28 29 /** 30 * struct clocksource - hardware abstraction for a free running counter 31 * Provides mostly state-free accessors to the underlying hardware. 32 * This is the structure used for system time. 33 * 34 * @name: ptr to clocksource name 35 * @list: list head for registration 36 * @rating: rating value for selection (higher is better) 37 * To avoid rating inflation the following 38 * list should give you a guide as to how 39 * to assign your clocksource a rating 40 * 1-99: Unfit for real use 41 * Only available for bootup and testing purposes. 42 * 100-199: Base level usability. 43 * Functional for real use, but not desired. 44 * 200-299: Good. 45 * A correct and usable clocksource. 46 * 300-399: Desired. 47 * A reasonably fast and accurate clocksource. 48 * 400-499: Perfect 49 * The ideal clocksource. A must-use where 50 * available. 51 * @read: returns a cycle value, passes clocksource as argument 52 * @enable: optional function to enable the clocksource 53 * @disable: optional function to disable the clocksource 54 * @mask: bitmask for two's complement 55 * subtraction of non 64 bit counters 56 * @mult: cycle to nanosecond multiplier 57 * @shift: cycle to nanosecond divisor (power of two) 58 * @max_idle_ns: max idle time permitted by the clocksource (nsecs) 59 * @maxadj: maximum adjustment value to mult (~11%) 60 * @max_cycles: maximum safe cycle value which won't overflow on multiplication 61 * @flags: flags describing special properties 62 * @archdata: arch-specific data 63 * @suspend: suspend function for the clocksource, if necessary 64 * @resume: resume function for the clocksource, if necessary 65 * @mark_unstable: Optional function to inform the clocksource driver that 66 * the watchdog marked the clocksource unstable 67 * @owner: module reference, must be set by clocksource in modules 68 * 69 * Note: This struct is not used in hotpathes of the timekeeping code 70 * because the timekeeper caches the hot path fields in its own data 71 * structure, so no line cache alignment is required, 72 * 73 * The pointer to the clocksource itself is handed to the read 74 * callback. If you need extra information there you can wrap struct 75 * clocksource into your own struct. Depending on the amount of 76 * information you need you should consider to cache line align that 77 * structure. 78 */ 79 struct clocksource { 80 u64 (*read)(struct clocksource *cs); 81 u64 mask; 82 u32 mult; 83 u32 shift; 84 u64 max_idle_ns; 85 u32 maxadj; 86 #ifdef CONFIG_ARCH_CLOCKSOURCE_DATA 87 struct arch_clocksource_data archdata; 88 #endif 89 u64 max_cycles; 90 const char *name; 91 struct list_head list; 92 int rating; 93 int (*enable)(struct clocksource *cs); 94 void (*disable)(struct clocksource *cs); 95 unsigned long flags; 96 void (*suspend)(struct clocksource *cs); 97 void (*resume)(struct clocksource *cs); 98 void (*mark_unstable)(struct clocksource *cs); 99 void (*tick_stable)(struct clocksource *cs); 100 101 /* private: */ 102 #ifdef CONFIG_CLOCKSOURCE_WATCHDOG 103 /* Watchdog related data, used by the framework */ 104 struct list_head wd_list; 105 u64 cs_last; 106 u64 wd_last; 107 #endif 108 struct module *owner; 109 }; 110 111 /* 112 * Clock source flags bits:: 113 */ 114 #define CLOCK_SOURCE_IS_CONTINUOUS 0x01 115 #define CLOCK_SOURCE_MUST_VERIFY 0x02 116 117 #define CLOCK_SOURCE_WATCHDOG 0x10 118 #define CLOCK_SOURCE_VALID_FOR_HRES 0x20 119 #define CLOCK_SOURCE_UNSTABLE 0x40 120 #define CLOCK_SOURCE_SUSPEND_NONSTOP 0x80 121 #define CLOCK_SOURCE_RESELECT 0x100 122 123 /* simplify initialization of mask field */ 124 #define CLOCKSOURCE_MASK(bits) GENMASK_ULL((bits) - 1, 0) 125 126 static inline u32 clocksource_freq2mult(u32 freq, u32 shift_constant, u64 from) 127 { 128 /* freq = cyc/from 129 * mult/2^shift = ns/cyc 130 * mult = ns/cyc * 2^shift 131 * mult = from/freq * 2^shift 132 * mult = from * 2^shift / freq 133 * mult = (from<<shift) / freq 134 */ 135 u64 tmp = ((u64)from) << shift_constant; 136 137 tmp += freq/2; /* round for do_div */ 138 do_div(tmp, freq); 139 140 return (u32)tmp; 141 } 142 143 /** 144 * clocksource_khz2mult - calculates mult from khz and shift 145 * @khz: Clocksource frequency in KHz 146 * @shift_constant: Clocksource shift factor 147 * 148 * Helper functions that converts a khz counter frequency to a timsource 149 * multiplier, given the clocksource shift value 150 */ 151 static inline u32 clocksource_khz2mult(u32 khz, u32 shift_constant) 152 { 153 return clocksource_freq2mult(khz, shift_constant, NSEC_PER_MSEC); 154 } 155 156 /** 157 * clocksource_hz2mult - calculates mult from hz and shift 158 * @hz: Clocksource frequency in Hz 159 * @shift_constant: Clocksource shift factor 160 * 161 * Helper functions that converts a hz counter 162 * frequency to a timsource multiplier, given the 163 * clocksource shift value 164 */ 165 static inline u32 clocksource_hz2mult(u32 hz, u32 shift_constant) 166 { 167 return clocksource_freq2mult(hz, shift_constant, NSEC_PER_SEC); 168 } 169 170 /** 171 * clocksource_cyc2ns - converts clocksource cycles to nanoseconds 172 * @cycles: cycles 173 * @mult: cycle to nanosecond multiplier 174 * @shift: cycle to nanosecond divisor (power of two) 175 * 176 * Converts clocksource cycles to nanoseconds, using the given @mult and @shift. 177 * The code is optimized for performance and is not intended to work 178 * with absolute clocksource cycles (as those will easily overflow), 179 * but is only intended to be used with relative (delta) clocksource cycles. 180 * 181 * XXX - This could use some mult_lxl_ll() asm optimization 182 */ 183 static inline s64 clocksource_cyc2ns(u64 cycles, u32 mult, u32 shift) 184 { 185 return ((u64) cycles * mult) >> shift; 186 } 187 188 189 extern int clocksource_unregister(struct clocksource*); 190 extern void clocksource_touch_watchdog(void); 191 extern void clocksource_change_rating(struct clocksource *cs, int rating); 192 extern void clocksource_suspend(void); 193 extern void clocksource_resume(void); 194 extern struct clocksource * __init clocksource_default_clock(void); 195 extern void clocksource_mark_unstable(struct clocksource *cs); 196 197 extern u64 198 clocks_calc_max_nsecs(u32 mult, u32 shift, u32 maxadj, u64 mask, u64 *max_cycles); 199 extern void 200 clocks_calc_mult_shift(u32 *mult, u32 *shift, u32 from, u32 to, u32 minsec); 201 202 /* 203 * Don't call __clocksource_register_scale directly, use 204 * clocksource_register_hz/khz 205 */ 206 extern int 207 __clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq); 208 extern void 209 __clocksource_update_freq_scale(struct clocksource *cs, u32 scale, u32 freq); 210 211 /* 212 * Don't call this unless you are a default clocksource 213 * (AKA: jiffies) and absolutely have to. 214 */ 215 static inline int __clocksource_register(struct clocksource *cs) 216 { 217 return __clocksource_register_scale(cs, 1, 0); 218 } 219 220 static inline int clocksource_register_hz(struct clocksource *cs, u32 hz) 221 { 222 return __clocksource_register_scale(cs, 1, hz); 223 } 224 225 static inline int clocksource_register_khz(struct clocksource *cs, u32 khz) 226 { 227 return __clocksource_register_scale(cs, 1000, khz); 228 } 229 230 static inline void __clocksource_update_freq_hz(struct clocksource *cs, u32 hz) 231 { 232 __clocksource_update_freq_scale(cs, 1, hz); 233 } 234 235 static inline void __clocksource_update_freq_khz(struct clocksource *cs, u32 khz) 236 { 237 __clocksource_update_freq_scale(cs, 1000, khz); 238 } 239 240 241 extern int timekeeping_notify(struct clocksource *clock); 242 243 extern u64 clocksource_mmio_readl_up(struct clocksource *); 244 extern u64 clocksource_mmio_readl_down(struct clocksource *); 245 extern u64 clocksource_mmio_readw_up(struct clocksource *); 246 extern u64 clocksource_mmio_readw_down(struct clocksource *); 247 248 extern int clocksource_mmio_init(void __iomem *, const char *, 249 unsigned long, int, unsigned, u64 (*)(struct clocksource *)); 250 251 extern int clocksource_i8253_init(void); 252 253 #define TIMER_OF_DECLARE(name, compat, fn) \ 254 OF_DECLARE_1_RET(timer, name, compat, fn) 255 256 #define CLOCKSOURCE_OF_DECLARE(name, compat, fn) \ 257 TIMER_OF_DECLARE(name, compat, fn) 258 259 #ifdef CONFIG_TIMER_PROBE 260 extern void timer_probe(void); 261 #else 262 static inline void timer_probe(void) {} 263 #endif 264 265 #define TIMER_ACPI_DECLARE(name, table_id, fn) \ 266 ACPI_DECLARE_PROBE_ENTRY(timer, name, table_id, 0, NULL, 0, fn) 267 268 #endif /* _LINUX_CLOCKSOURCE_H */ 269