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 <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  * @flags:              flags describing special properties
  60  * @archdata:           arch-specific data
  61  * @suspend:            suspend function for the clocksource, if necessary
  62  * @resume:             resume function for the clocksource, if necessary
  63  * @owner:              module reference, must be set by clocksource in modules
  64  */
  65 struct clocksource {
  66         /*
  67          * Hotpath data, fits in a single cache line when the
  68          * clocksource itself is cacheline aligned.
  69          */
  70         cycle_t (*read)(struct clocksource *cs);
  71         cycle_t mask;
  72         u32 mult;
  73         u32 shift;
  74         u64 max_idle_ns;
  75         u32 maxadj;
  76 #ifdef CONFIG_ARCH_CLOCKSOURCE_DATA
  77         struct arch_clocksource_data archdata;
  78 #endif
  79
  80         const char *name;
  81         struct list_head list;
  82         int rating;
  83         int (*enable)(struct clocksource *cs);
  84         void (*disable)(struct clocksource *cs);
  85         unsigned long flags;
  86         void (*suspend)(struct clocksource *cs);
  87         void (*resume)(struct clocksource *cs);
  88
  89         /* private: */
  90 #ifdef CONFIG_CLOCKSOURCE_WATCHDOG
  91         /* Watchdog related data, used by the framework */
  92         struct list_head wd_list;
  93         cycle_t cs_last;
  94         cycle_t wd_last;
  95 #endif
  96         struct module *owner;
  97 } ____cacheline_aligned;
  98
  99 /*
 100  * Clock source flags bits::
 101  */
 102 #define CLOCK_SOURCE_IS_CONTINUOUS              0x01
 103 #define CLOCK_SOURCE_MUST_VERIFY                0x02
 104
 105 #define CLOCK_SOURCE_WATCHDOG                   0x10
 106 #define CLOCK_SOURCE_VALID_FOR_HRES             0x20
 107 #define CLOCK_SOURCE_UNSTABLE                   0x40
 108 #define CLOCK_SOURCE_SUSPEND_NONSTOP            0x80
 109 #define CLOCK_SOURCE_RESELECT                   0x100
 110
 111 /* simplify initialization of mask field */
 112 #define CLOCKSOURCE_MASK(bits) (cycle_t)((bits) < 64 ? ((1ULL<<(bits))-1) : -1)
 113
 114 /**
 115  * clocksource_khz2mult - calculates mult from khz and shift
 116  * @khz:                Clocksource frequency in KHz
 117  * @shift_constant:     Clocksource shift factor
 118  *
 119  * Helper functions that converts a khz counter frequency to a timsource
 120  * multiplier, given the clocksource shift value
 121  */
 122 static inline u32 clocksource_khz2mult(u32 khz, u32 shift_constant)
 123 {
 124         /*  khz = cyc/(Million ns)
 125          *  mult/2^shift  = ns/cyc
 126          *  mult = ns/cyc * 2^shift
 127          *  mult = 1Million/khz * 2^shift
 128          *  mult = 1000000 * 2^shift / khz
 129          *  mult = (1000000<<shift) / khz
 130          */
 131         u64 tmp = ((u64)1000000) << shift_constant;
 132
 133         tmp += khz/2; /* round for do_div */
 134         do_div(tmp, khz);
 135
 136         return (u32)tmp;
 137 }
 138
 139 /**
 140  * clocksource_hz2mult - calculates mult from hz and shift
 141  * @hz:                 Clocksource frequency in Hz
 142  * @shift_constant:     Clocksource shift factor
 143  *
 144  * Helper functions that converts a hz counter
 145  * frequency to a timsource multiplier, given the
 146  * clocksource shift value
 147  */
 148 static inline u32 clocksource_hz2mult(u32 hz, u32 shift_constant)
 149 {
 150         /*  hz = cyc/(Billion ns)
 151          *  mult/2^shift  = ns/cyc
 152          *  mult = ns/cyc * 2^shift
 153          *  mult = 1Billion/hz * 2^shift
 154          *  mult = 1000000000 * 2^shift / hz
 155          *  mult = (1000000000<<shift) / hz
 156          */
 157         u64 tmp = ((u64)1000000000) << shift_constant;
 158
 159         tmp += hz/2; /* round for do_div */
 160         do_div(tmp, hz);
 161
 162         return (u32)tmp;
 163 }
 164
 165 /**
 166  * clocksource_cyc2ns - converts clocksource cycles to nanoseconds
 167  * @cycles:     cycles
 168  * @mult:       cycle to nanosecond multiplier
 169  * @shift:      cycle to nanosecond divisor (power of two)
 170  *
 171  * Converts cycles to nanoseconds, using the given mult and shift.
 172  *
 173  * XXX - This could use some mult_lxl_ll() asm optimization
 174  */
 175 static inline s64 clocksource_cyc2ns(cycle_t cycles, u32 mult, u32 shift)
 176 {
 177         return ((u64) cycles * mult) >> shift;
 178 }
 179
 180
 181 extern int clocksource_register(struct clocksource*);
 182 extern int clocksource_unregister(struct clocksource*);
 183 extern void clocksource_touch_watchdog(void);
 184 extern struct clocksource* clocksource_get_next(void);
 185 extern void clocksource_change_rating(struct clocksource *cs, int rating);
 186 extern void clocksource_suspend(void);
 187 extern void clocksource_resume(void);
 188 extern struct clocksource * __init clocksource_default_clock(void);
 189 extern void clocksource_mark_unstable(struct clocksource *cs);
 190
 191 extern u64
 192 clocks_calc_max_nsecs(u32 mult, u32 shift, u32 maxadj, u64 mask);
 193 extern void
 194 clocks_calc_mult_shift(u32 *mult, u32 *shift, u32 from, u32 to, u32 minsec);
 195
 196 /*
 197  * Don't call __clocksource_register_scale directly, use
 198  * clocksource_register_hz/khz
 199  */
 200 extern int
 201 __clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq);
 202 extern void
 203 __clocksource_updatefreq_scale(struct clocksource *cs, u32 scale, u32 freq);
 204
 205 static inline int clocksource_register_hz(struct clocksource *cs, u32 hz)
 206 {
 207         return __clocksource_register_scale(cs, 1, hz);
 208 }
 209
 210 static inline int clocksource_register_khz(struct clocksource *cs, u32 khz)
 211 {
 212         return __clocksource_register_scale(cs, 1000, khz);
 213 }
 214
 215 static inline void __clocksource_updatefreq_hz(struct clocksource *cs, u32 hz)
 216 {
 217         __clocksource_updatefreq_scale(cs, 1, hz);
 218 }
 219
 220 static inline void __clocksource_updatefreq_khz(struct clocksource *cs, u32 khz)
 221 {
 222         __clocksource_updatefreq_scale(cs, 1000, khz);
 223 }
 224
 225
 226 extern int timekeeping_notify(struct clocksource *clock);
 227
 228 extern cycle_t clocksource_mmio_readl_up(struct clocksource *);
 229 extern cycle_t clocksource_mmio_readl_down(struct clocksource *);
 230 extern cycle_t clocksource_mmio_readw_up(struct clocksource *);
 231 extern cycle_t clocksource_mmio_readw_down(struct clocksource *);
 232
 233 extern int clocksource_mmio_init(void __iomem *, const char *,
 234         unsigned long, int, unsigned, cycle_t (*)(struct clocksource *));
 235
 236 extern int clocksource_i8253_init(void);
 237
 238 #define CLOCKSOURCE_OF_DECLARE(name, compat, fn) \
 239         OF_DECLARE_1(clksrc, name, compat, fn)
 240
 241 #ifdef CONFIG_CLKSRC_OF
 242 extern void clocksource_of_init(void);
 243 #else
 244 static inline void clocksource_of_init(void) {}
 245 #endif
 246
 247 #endif /* _LINUX_CLOCKSOURCE_H */