include/linux/clocksource.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 /*  linux/include/linux/clocksource.h
   3  *
   4  *  This file contains the structure definitions for clocksources.
   5  *
   6  *  If you are not a clocksource, or timekeeping code, you should
   7  *  not be including this file!
   8  */
   9 #ifndef _LINUX_CLOCKSOURCE_H
  10 #define _LINUX_CLOCKSOURCE_H
  11
  12 #include <linux/types.h>
  13 #include <linux/timex.h>
  14 #include <linux/time.h>
  15 #include <linux/list.h>
  16 #include <linux/cache.h>
  17 #include <linux/timer.h>
  18 #include <linux/init.h>
  19 #include <linux/of.h>
  20 #include <asm/div64.h>
  21 #include <asm/io.h>
  22
  23 struct clocksource;
  24 struct module;
  25
  26 #if defined(CONFIG_ARCH_CLOCKSOURCE_DATA) || \
  27     defined(CONFIG_GENERIC_GETTIMEOFDAY)
  28 #include <asm/clocksource.h>
  29 #endif
  30
  31 #include <vdso/clocksource.h>
  32
  33 /**
  34  * struct clocksource - hardware abstraction for a free running counter
  35  *      Provides mostly state-free accessors to the underlying hardware.
  36  *      This is the structure used for system time.
  37  *
  38  * @read:               Returns a cycle value, passes clocksource as argument
  39  * @mask:               Bitmask for two's complement
  40  *                      subtraction of non 64 bit counters
  41  * @mult:               Cycle to nanosecond multiplier
  42  * @shift:              Cycle to nanosecond divisor (power of two)
  43  * @max_idle_ns:        Maximum idle time permitted by the clocksource (nsecs)
  44  * @maxadj:             Maximum adjustment value to mult (~11%)
  45  * @archdata:           Optional arch-specific data
  46  * @max_cycles:         Maximum safe cycle value which won't overflow on
  47  *                      multiplication
  48  * @name:               Pointer to clocksource name
  49  * @list:               List head for registration (internal)
  50  * @rating:             Rating value for selection (higher is better)
  51  *                      To avoid rating inflation the following
  52  *                      list should give you a guide as to how
  53  *                      to assign your clocksource a rating
  54  *                      1-99: Unfit for real use
  55  *                              Only available for bootup and testing purposes.
  56  *                      100-199: Base level usability.
  57  *                              Functional for real use, but not desired.
  58  *                      200-299: Good.
  59  *                              A correct and usable clocksource.
  60  *                      300-399: Desired.
  61  *                              A reasonably fast and accurate clocksource.
  62  *                      400-499: Perfect
  63  *                              The ideal clocksource. A must-use where
  64  *                              available.
  65  * @flags:              Flags describing special properties
  66  * @enable:             Optional function to enable the clocksource
  67  * @disable:            Optional function to disable the clocksource
  68  * @suspend:            Optional suspend function for the clocksource
  69  * @resume:             Optional resume function for the clocksource
  70  * @mark_unstable:      Optional function to inform the clocksource driver that
  71  *                      the watchdog marked the clocksource unstable
  72  * @tick_stable:        Optional function called periodically from the watchdog
  73  *                      code to provide stable syncrhonization points
  74  * @wd_list:            List head to enqueue into the watchdog list (internal)
  75  * @cs_last:            Last clocksource value for clocksource watchdog
  76  * @wd_last:            Last watchdog value corresponding to @cs_last
  77  * @owner:              Module reference, must be set by clocksource in modules
  78  *
  79  * Note: This struct is not used in hotpathes of the timekeeping code
  80  * because the timekeeper caches the hot path fields in its own data
  81  * structure, so no cache line alignment is required,
  82  *
  83  * The pointer to the clocksource itself is handed to the read
  84  * callback. If you need extra information there you can wrap struct
  85  * clocksource into your own struct. Depending on the amount of
  86  * information you need you should consider to cache line align that
  87  * structure.
  88  */
  89 struct clocksource {
  90         u64                     (*read)(struct clocksource *cs);
  91         u64                     mask;
  92         u32                     mult;
  93         u32                     shift;
  94         u64                     max_idle_ns;
  95         u32                     maxadj;
  96 #ifdef CONFIG_ARCH_CLOCKSOURCE_DATA
  97         struct arch_clocksource_data archdata;
  98 #endif
  99         u64                     max_cycles;
 100         const char              *name;
 101         struct list_head        list;
 102         int                     rating;
 103         enum vdso_clock_mode    vdso_clock_mode;
 104         unsigned long           flags;
 105
 106         int                     (*enable)(struct clocksource *cs);
 107         void                    (*disable)(struct clocksource *cs);
 108         void                    (*suspend)(struct clocksource *cs);
 109         void                    (*resume)(struct clocksource *cs);
 110         void                    (*mark_unstable)(struct clocksource *cs);
 111         void                    (*tick_stable)(struct clocksource *cs);
 112
 113         /* private: */
 114 #ifdef CONFIG_CLOCKSOURCE_WATCHDOG
 115         /* Watchdog related data, used by the framework */
 116         struct list_head        wd_list;
 117         u64                     cs_last;
 118         u64                     wd_last;
 119 #endif
 120         struct module           *owner;
 121 };
 122
 123 /*
 124  * Clock source flags bits::
 125  */
 126 #define CLOCK_SOURCE_IS_CONTINUOUS              0x01
 127 #define CLOCK_SOURCE_MUST_VERIFY                0x02
 128
 129 #define CLOCK_SOURCE_WATCHDOG                   0x10
 130 #define CLOCK_SOURCE_VALID_FOR_HRES             0x20
 131 #define CLOCK_SOURCE_UNSTABLE                   0x40
 132 #define CLOCK_SOURCE_SUSPEND_NONSTOP            0x80
 133 #define CLOCK_SOURCE_RESELECT                   0x100
 134
 135 /* simplify initialization of mask field */
 136 #define CLOCKSOURCE_MASK(bits) GENMASK_ULL((bits) - 1, 0)
 137
 138 static inline u32 clocksource_freq2mult(u32 freq, u32 shift_constant, u64 from)
 139 {
 140         /*  freq = cyc/from
 141          *  mult/2^shift  = ns/cyc
 142          *  mult = ns/cyc * 2^shift
 143          *  mult = from/freq * 2^shift
 144          *  mult = from * 2^shift / freq
 145          *  mult = (from<<shift) / freq
 146          */
 147         u64 tmp = ((u64)from) << shift_constant;
 148
 149         tmp += freq/2; /* round for do_div */
 150         do_div(tmp, freq);
 151
 152         return (u32)tmp;
 153 }
 154
 155 /**
 156  * clocksource_khz2mult - calculates mult from khz and shift
 157  * @khz:                Clocksource frequency in KHz
 158  * @shift_constant:     Clocksource shift factor
 159  *
 160  * Helper functions that converts a khz counter frequency to a timsource
 161  * multiplier, given the clocksource shift value
 162  */
 163 static inline u32 clocksource_khz2mult(u32 khz, u32 shift_constant)
 164 {
 165         return clocksource_freq2mult(khz, shift_constant, NSEC_PER_MSEC);
 166 }
 167
 168 /**
 169  * clocksource_hz2mult - calculates mult from hz and shift
 170  * @hz:                 Clocksource frequency in Hz
 171  * @shift_constant:     Clocksource shift factor
 172  *
 173  * Helper functions that converts a hz counter
 174  * frequency to a timsource multiplier, given the
 175  * clocksource shift value
 176  */
 177 static inline u32 clocksource_hz2mult(u32 hz, u32 shift_constant)
 178 {
 179         return clocksource_freq2mult(hz, shift_constant, NSEC_PER_SEC);
 180 }
 181
 182 /**
 183  * clocksource_cyc2ns - converts clocksource cycles to nanoseconds
 184  * @cycles:     cycles
 185  * @mult:       cycle to nanosecond multiplier
 186  * @shift:      cycle to nanosecond divisor (power of two)
 187  *
 188  * Converts clocksource cycles to nanoseconds, using the given @mult and @shift.
 189  * The code is optimized for performance and is not intended to work
 190  * with absolute clocksource cycles (as those will easily overflow),
 191  * but is only intended to be used with relative (delta) clocksource cycles.
 192  *
 193  * XXX - This could use some mult_lxl_ll() asm optimization
 194  */
 195 static inline s64 clocksource_cyc2ns(u64 cycles, u32 mult, u32 shift)
 196 {
 197         return ((u64) cycles * mult) >> shift;
 198 }
 199
 200
 201 extern int clocksource_unregister(struct clocksource*);
 202 extern void clocksource_touch_watchdog(void);
 203 extern void clocksource_change_rating(struct clocksource *cs, int rating);
 204 extern void clocksource_suspend(void);
 205 extern void clocksource_resume(void);
 206 extern struct clocksource * __init clocksource_default_clock(void);
 207 extern void clocksource_mark_unstable(struct clocksource *cs);
 208 extern void
 209 clocksource_start_suspend_timing(struct clocksource *cs, u64 start_cycles);
 210 extern u64 clocksource_stop_suspend_timing(struct clocksource *cs, u64 now);
 211
 212 extern u64
 213 clocks_calc_max_nsecs(u32 mult, u32 shift, u32 maxadj, u64 mask, u64 *max_cycles);
 214 extern void
 215 clocks_calc_mult_shift(u32 *mult, u32 *shift, u32 from, u32 to, u32 minsec);
 216
 217 /*
 218  * Don't call __clocksource_register_scale directly, use
 219  * clocksource_register_hz/khz
 220  */
 221 extern int
 222 __clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq);
 223 extern void
 224 __clocksource_update_freq_scale(struct clocksource *cs, u32 scale, u32 freq);
 225
 226 /*
 227  * Don't call this unless you are a default clocksource
 228  * (AKA: jiffies) and absolutely have to.
 229  */
 230 static inline int __clocksource_register(struct clocksource *cs)
 231 {
 232         return __clocksource_register_scale(cs, 1, 0);
 233 }
 234
 235 static inline int clocksource_register_hz(struct clocksource *cs, u32 hz)
 236 {
 237         return __clocksource_register_scale(cs, 1, hz);
 238 }
 239
 240 static inline int clocksource_register_khz(struct clocksource *cs, u32 khz)
 241 {
 242         return __clocksource_register_scale(cs, 1000, khz);
 243 }
 244
 245 static inline void __clocksource_update_freq_hz(struct clocksource *cs, u32 hz)
 246 {
 247         __clocksource_update_freq_scale(cs, 1, hz);
 248 }
 249
 250 static inline void __clocksource_update_freq_khz(struct clocksource *cs, u32 khz)
 251 {
 252         __clocksource_update_freq_scale(cs, 1000, khz);
 253 }
 254
 255 #ifdef CONFIG_ARCH_CLOCKSOURCE_INIT
 256 extern void clocksource_arch_init(struct clocksource *cs);
 257 #else
 258 static inline void clocksource_arch_init(struct clocksource *cs) { }
 259 #endif
 260
 261 extern int timekeeping_notify(struct clocksource *clock);
 262
 263 extern u64 clocksource_mmio_readl_up(struct clocksource *);
 264 extern u64 clocksource_mmio_readl_down(struct clocksource *);
 265 extern u64 clocksource_mmio_readw_up(struct clocksource *);
 266 extern u64 clocksource_mmio_readw_down(struct clocksource *);
 267
 268 extern int clocksource_mmio_init(void __iomem *, const char *,
 269         unsigned long, int, unsigned, u64 (*)(struct clocksource *));
 270
 271 extern int clocksource_i8253_init(void);
 272
 273 #define TIMER_OF_DECLARE(name, compat, fn) \
 274         OF_DECLARE_1_RET(timer, name, compat, fn)
 275
 276 #ifdef CONFIG_TIMER_PROBE
 277 extern void timer_probe(void);
 278 #else
 279 static inline void timer_probe(void) {}
 280 #endif
 281
 282 #define TIMER_ACPI_DECLARE(name, table_id, fn)          \
 283         ACPI_DECLARE_PROBE_ENTRY(timer, name, table_id, 0, NULL, 0, fn)
 284
 285 #endif /* _LINUX_CLOCKSOURCE_H */