include/linux/clocksource.h

   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 */