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  * @max_cycles:         maximum safe cycle value which won't overflow on multiplication
  60  * @flags:              flags describing special properties
  61  * @archdata:           arch-specific data
  62  * @suspend:            suspend function for the clocksource, if necessary
  63  * @resume:             resume function for the clocksource, if necessary
  64  * @owner:              module reference, must be set by clocksource in modules
  65  */
  66 struct clocksource {
  67         /*
  68          * Hotpath data, fits in a single cache line when the
  69          * clocksource itself is cacheline aligned.
  70          */
  71         cycle_t (*read)(struct clocksource *cs);
  72         cycle_t mask;
  73         u32 mult;
  74         u32 shift;
  75         u64 max_idle_ns;
  76         u32 maxadj;
  77 #ifdef CONFIG_ARCH_CLOCKSOURCE_DATA
  78         struct arch_clocksource_data archdata;
  79 #endif
  80         u64 max_cycles;
  81         const char *name;
  82         struct list_head list;
  83         int rating;
  84         int (*enable)(struct clocksource *cs);
  85         void (*disable)(struct clocksource *cs);
  86         unsigned long flags;
  87         void (*suspend)(struct clocksource *cs);
  88         void (*resume)(struct clocksource *cs);
  89
  90         /* private: */
  91 #ifdef CONFIG_CLOCKSOURCE_WATCHDOG
  92         /* Watchdog related data, used by the framework */
  93         struct list_head wd_list;
  94         cycle_t cs_last;
  95         cycle_t wd_last;
  96 #endif
  97         struct module *owner;
  98 } ____cacheline_aligned;
  99
 100 /*
 101  * Clock source flags bits::
 102  */
 103 #define CLOCK_SOURCE_IS_CONTINUOUS              0x01
 104 #define CLOCK_SOURCE_MUST_VERIFY                0x02
 105
 106 #define CLOCK_SOURCE_WATCHDOG                   0x10
 107 #define CLOCK_SOURCE_VALID_FOR_HRES             0x20
 108 #define CLOCK_SOURCE_UNSTABLE                   0x40
 109 #define CLOCK_SOURCE_SUSPEND_NONSTOP            0x80
 110 #define CLOCK_SOURCE_RESELECT                   0x100
 111
 112 /* simplify initialization of mask field */
 113 #define CLOCKSOURCE_MASK(bits) (cycle_t)((bits) < 64 ? ((1ULL<<(bits))-1) : -1)
 114
 115 /**
 116  * clocksource_khz2mult - calculates mult from khz and shift
 117  * @khz:                Clocksource frequency in KHz
 118  * @shift_constant:     Clocksource shift factor
 119  *
 120  * Helper functions that converts a khz counter frequency to a timsource
 121  * multiplier, given the clocksource shift value
 122  */
 123 static inline u32 clocksource_khz2mult(u32 khz, u32 shift_constant)
 124 {
 125         /*  khz = cyc/(Million ns)
 126          *  mult/2^shift  = ns/cyc
 127          *  mult = ns/cyc * 2^shift
 128          *  mult = 1Million/khz * 2^shift
 129          *  mult = 1000000 * 2^shift / khz
 130          *  mult = (1000000<<shift) / khz
 131          */
 132         u64 tmp = ((u64)1000000) << shift_constant;
 133
 134         tmp += khz/2; /* round for do_div */
 135         do_div(tmp, khz);
 136
 137         return (u32)tmp;
 138 }
 139
 140 /**
 141  * clocksource_hz2mult - calculates mult from hz and shift
 142  * @hz:                 Clocksource frequency in Hz
 143  * @shift_constant:     Clocksource shift factor
 144  *
 145  * Helper functions that converts a hz counter
 146  * frequency to a timsource multiplier, given the
 147  * clocksource shift value
 148  */
 149 static inline u32 clocksource_hz2mult(u32 hz, u32 shift_constant)
 150 {
 151         /*  hz = cyc/(Billion ns)
 152          *  mult/2^shift  = ns/cyc
 153          *  mult = ns/cyc * 2^shift
 154          *  mult = 1Billion/hz * 2^shift
 155          *  mult = 1000000000 * 2^shift / hz
 156          *  mult = (1000000000<<shift) / hz
 157          */
 158         u64 tmp = ((u64)1000000000) << shift_constant;
 159
 160         tmp += hz/2; /* round for do_div */
 161         do_div(tmp, hz);
 162
 163         return (u32)tmp;
 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(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 */