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  * @owner:              module reference, must be set by clocksource in modules
  66  *
  67  * Note: This struct is not used in hotpathes of the timekeeping code
  68  * because the timekeeper caches the hot path fields in its own data
  69  * structure, so no line cache alignment is required,
  70  *
  71  * The pointer to the clocksource itself is handed to the read
  72  * callback. If you need extra information there you can wrap struct
  73  * clocksource into your own struct. Depending on the amount of
  74  * information you need you should consider to cache line align that
  75  * structure.
  76  */
  77 struct clocksource {
  78         cycle_t (*read)(struct clocksource *cs);
  79         cycle_t mask;
  80         u32 mult;
  81         u32 shift;
  82         u64 max_idle_ns;
  83         u32 maxadj;
  84 #ifdef CONFIG_ARCH_CLOCKSOURCE_DATA
  85         struct arch_clocksource_data archdata;
  86 #endif
  87         u64 max_cycles;
  88         const char *name;
  89         struct list_head list;
  90         int rating;
  91         int (*enable)(struct clocksource *cs);
  92         void (*disable)(struct clocksource *cs);
  93         unsigned long flags;
  94         void (*suspend)(struct clocksource *cs);
  95         void (*resume)(struct clocksource *cs);
  96
  97         /* private: */
  98 #ifdef CONFIG_CLOCKSOURCE_WATCHDOG
  99         /* Watchdog related data, used by the framework */
 100         struct list_head wd_list;
 101         cycle_t cs_last;
 102         cycle_t wd_last;
 103 #endif
 104         struct module *owner;
 105 };
 106
 107 /*
 108  * Clock source flags bits::
 109  */
 110 #define CLOCK_SOURCE_IS_CONTINUOUS              0x01
 111 #define CLOCK_SOURCE_MUST_VERIFY                0x02
 112
 113 #define CLOCK_SOURCE_WATCHDOG                   0x10
 114 #define CLOCK_SOURCE_VALID_FOR_HRES             0x20
 115 #define CLOCK_SOURCE_UNSTABLE                   0x40
 116 #define CLOCK_SOURCE_SUSPEND_NONSTOP            0x80
 117 #define CLOCK_SOURCE_RESELECT                   0x100
 118
 119 /* simplify initialization of mask field */
 120 #define CLOCKSOURCE_MASK(bits) (cycle_t)((bits) < 64 ? ((1ULL<<(bits))-1) : -1)
 121
 122 static inline u32 clocksource_freq2mult(u32 freq, u32 shift_constant, u64 from)
 123 {
 124         /*  freq = cyc/from
 125          *  mult/2^shift  = ns/cyc
 126          *  mult = ns/cyc * 2^shift
 127          *  mult = from/freq * 2^shift
 128          *  mult = from * 2^shift / freq
 129          *  mult = (from<<shift) / freq
 130          */
 131         u64 tmp = ((u64)from) << shift_constant;
 132
 133         tmp += freq/2; /* round for do_div */
 134         do_div(tmp, freq);
 135
 136         return (u32)tmp;
 137 }
 138
 139 /**
 140  * clocksource_khz2mult - calculates mult from khz and shift
 141  * @khz:                Clocksource frequency in KHz
 142  * @shift_constant:     Clocksource shift factor
 143  *
 144  * Helper functions that converts a khz counter frequency to a timsource
 145  * multiplier, given the clocksource shift value
 146  */
 147 static inline u32 clocksource_khz2mult(u32 khz, u32 shift_constant)
 148 {
 149         return clocksource_freq2mult(khz, shift_constant, NSEC_PER_MSEC);
 150 }
 151
 152 /**
 153  * clocksource_hz2mult - calculates mult from hz and shift
 154  * @hz:                 Clocksource frequency in Hz
 155  * @shift_constant:     Clocksource shift factor
 156  *
 157  * Helper functions that converts a hz counter
 158  * frequency to a timsource multiplier, given the
 159  * clocksource shift value
 160  */
 161 static inline u32 clocksource_hz2mult(u32 hz, u32 shift_constant)
 162 {
 163         return clocksource_freq2mult(hz, shift_constant, NSEC_PER_SEC);
 164 }
 165
 166 /**
 167  * clocksource_cyc2ns - converts clocksource cycles to nanoseconds
 168  * @cycles:     cycles
 169  * @mult:       cycle to nanosecond multiplier
 170  * @shift:      cycle to nanosecond divisor (power of two)
 171  *
 172  * Converts cycles to nanoseconds, using the given mult and shift.
 173  *
 174  * XXX - This could use some mult_lxl_ll() asm optimization
 175  */
 176 static inline s64 clocksource_cyc2ns(cycle_t cycles, u32 mult, u32 shift)
 177 {
 178         return ((u64) cycles * mult) >> shift;
 179 }
 180
 181
 182 extern int clocksource_unregister(struct clocksource*);
 183 extern void clocksource_touch_watchdog(void);
 184 extern void clocksource_change_rating(struct clocksource *cs, int rating);
 185 extern void clocksource_suspend(void);
 186 extern void clocksource_resume(void);
 187 extern struct clocksource * __init clocksource_default_clock(void);
 188 extern void clocksource_mark_unstable(struct clocksource *cs);
 189
 190 extern u64
 191 clocks_calc_max_nsecs(u32 mult, u32 shift, u32 maxadj, u64 mask, u64 *max_cycles);
 192 extern void
 193 clocks_calc_mult_shift(u32 *mult, u32 *shift, u32 from, u32 to, u32 minsec);
 194
 195 /*
 196  * Don't call __clocksource_register_scale directly, use
 197  * clocksource_register_hz/khz
 198  */
 199 extern int
 200 __clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq);
 201 extern void
 202 __clocksource_update_freq_scale(struct clocksource *cs, u32 scale, u32 freq);
 203
 204 /*
 205  * Don't call this unless you are a default clocksource
 206  * (AKA: jiffies) and absolutely have to.
 207  */
 208 static inline int __clocksource_register(struct clocksource *cs)
 209 {
 210         return __clocksource_register_scale(cs, 1, 0);
 211 }
 212
 213 static inline int clocksource_register_hz(struct clocksource *cs, u32 hz)
 214 {
 215         return __clocksource_register_scale(cs, 1, hz);
 216 }
 217
 218 static inline int clocksource_register_khz(struct clocksource *cs, u32 khz)
 219 {
 220         return __clocksource_register_scale(cs, 1000, khz);
 221 }
 222
 223 static inline void __clocksource_update_freq_hz(struct clocksource *cs, u32 hz)
 224 {
 225         __clocksource_update_freq_scale(cs, 1, hz);
 226 }
 227
 228 static inline void __clocksource_update_freq_khz(struct clocksource *cs, u32 khz)
 229 {
 230         __clocksource_update_freq_scale(cs, 1000, khz);
 231 }
 232
 233
 234 extern int timekeeping_notify(struct clocksource *clock);
 235
 236 extern cycle_t clocksource_mmio_readl_up(struct clocksource *);
 237 extern cycle_t clocksource_mmio_readl_down(struct clocksource *);
 238 extern cycle_t clocksource_mmio_readw_up(struct clocksource *);
 239 extern cycle_t clocksource_mmio_readw_down(struct clocksource *);
 240
 241 extern int clocksource_mmio_init(void __iomem *, const char *,
 242         unsigned long, int, unsigned, cycle_t (*)(struct clocksource *));
 243
 244 extern int clocksource_i8253_init(void);
 245
 246 #define CLOCKSOURCE_OF_DECLARE(name, compat, fn) \
 247         OF_DECLARE_1_RET(clksrc, name, compat, fn)
 248
 249 #ifdef CONFIG_CLKSRC_PROBE
 250 extern void clocksource_probe(void);
 251 #else
 252 static inline void clocksource_probe(void) {}
 253 #endif
 254
 255 #define CLOCKSOURCE_ACPI_DECLARE(name, table_id, fn)            \
 256         ACPI_DECLARE_PROBE_ENTRY(clksrc, name, table_id, 0, NULL, 0, fn)
 257
 258 #endif /* _LINUX_CLOCKSOURCE_H */