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
 100         /* private: */
 101 #ifdef CONFIG_CLOCKSOURCE_WATCHDOG
 102         /* Watchdog related data, used by the framework */
 103         struct list_head wd_list;
 104         u64 cs_last;
 105         u64 wd_last;
 106 #endif
 107         struct module *owner;
 108 };
 109
 110 /*
 111  * Clock source flags bits::
 112  */
 113 #define CLOCK_SOURCE_IS_CONTINUOUS              0x01
 114 #define CLOCK_SOURCE_MUST_VERIFY                0x02
 115
 116 #define CLOCK_SOURCE_WATCHDOG                   0x10
 117 #define CLOCK_SOURCE_VALID_FOR_HRES             0x20
 118 #define CLOCK_SOURCE_UNSTABLE                   0x40
 119 #define CLOCK_SOURCE_SUSPEND_NONSTOP            0x80
 120 #define CLOCK_SOURCE_RESELECT                   0x100
 121
 122 /* simplify initialization of mask field */
 123 #define CLOCKSOURCE_MASK(bits) (u64)((bits) < 64 ? ((1ULL<<(bits))-1) : -1)
 124
 125 static inline u32 clocksource_freq2mult(u32 freq, u32 shift_constant, u64 from)
 126 {
 127         /*  freq = cyc/from
 128          *  mult/2^shift  = ns/cyc
 129          *  mult = ns/cyc * 2^shift
 130          *  mult = from/freq * 2^shift
 131          *  mult = from * 2^shift / freq
 132          *  mult = (from<<shift) / freq
 133          */
 134         u64 tmp = ((u64)from) << shift_constant;
 135
 136         tmp += freq/2; /* round for do_div */
 137         do_div(tmp, freq);
 138
 139         return (u32)tmp;
 140 }
 141
 142 /**
 143  * clocksource_khz2mult - calculates mult from khz and shift
 144  * @khz:                Clocksource frequency in KHz
 145  * @shift_constant:     Clocksource shift factor
 146  *
 147  * Helper functions that converts a khz counter frequency to a timsource
 148  * multiplier, given the clocksource shift value
 149  */
 150 static inline u32 clocksource_khz2mult(u32 khz, u32 shift_constant)
 151 {
 152         return clocksource_freq2mult(khz, shift_constant, NSEC_PER_MSEC);
 153 }
 154
 155 /**
 156  * clocksource_hz2mult - calculates mult from hz and shift
 157  * @hz:                 Clocksource frequency in Hz
 158  * @shift_constant:     Clocksource shift factor
 159  *
 160  * Helper functions that converts a hz counter
 161  * frequency to a timsource multiplier, given the
 162  * clocksource shift value
 163  */
 164 static inline u32 clocksource_hz2mult(u32 hz, u32 shift_constant)
 165 {
 166         return clocksource_freq2mult(hz, shift_constant, NSEC_PER_SEC);
 167 }
 168
 169 /**
 170  * clocksource_cyc2ns - converts clocksource cycles to nanoseconds
 171  * @cycles:     cycles
 172  * @mult:       cycle to nanosecond multiplier
 173  * @shift:      cycle to nanosecond divisor (power of two)
 174  *
 175  * Converts clocksource cycles to nanoseconds, using the given @mult and @shift.
 176  * The code is optimized for performance and is not intended to work
 177  * with absolute clocksource cycles (as those will easily overflow),
 178  * but is only intended to be used with relative (delta) clocksource cycles.
 179  *
 180  * XXX - This could use some mult_lxl_ll() asm optimization
 181  */
 182 static inline s64 clocksource_cyc2ns(u64 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 u64 clocksource_mmio_readl_up(struct clocksource *);
 243 extern u64 clocksource_mmio_readl_down(struct clocksource *);
 244 extern u64 clocksource_mmio_readw_up(struct clocksource *);
 245 extern u64 clocksource_mmio_readw_down(struct clocksource *);
 246
 247 extern int clocksource_mmio_init(void __iomem *, const char *,
 248         unsigned long, int, unsigned, u64 (*)(struct clocksource *));
 249
 250 extern int clocksource_i8253_init(void);
 251
 252 #define CLOCKSOURCE_OF_DECLARE(name, compat, fn) \
 253         OF_DECLARE_1_RET(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 */