LXR linux/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
  23struct clocksource;
  24struct 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 */
  89struct 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
 138static 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 */
 163static 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 */
 177static 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 */
 195static inline s64 clocksource_cyc2ns(u64 cycles, u32 mult, u32 shift)
 196{
 197        return ((u64) cycles * mult) >> shift;
 198}
 199
 200
 201extern int clocksource_unregister(struct clocksource*);
 202extern void clocksource_touch_watchdog(void);
 203extern void clocksource_change_rating(struct clocksource *cs, int rating);
 204extern void clocksource_suspend(void);
 205extern void clocksource_resume(void);
 206extern struct clocksource * __init clocksource_default_clock(void);
 207extern void clocksource_mark_unstable(struct clocksource *cs);
 208extern void
 209clocksource_start_suspend_timing(struct clocksource *cs, u64 start_cycles);
 210extern u64 clocksource_stop_suspend_timing(struct clocksource *cs, u64 now);
 211
 212extern u64
 213clocks_calc_max_nsecs(u32 mult, u32 shift, u32 maxadj, u64 mask, u64 *max_cycles);
 214extern void
 215clocks_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 */
 221extern int
 222__clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq);
 223extern 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 */
 230static inline int __clocksource_register(struct clocksource *cs)
 231{
 232        return __clocksource_register_scale(cs, 1, 0);
 233}
 234
 235static inline int clocksource_register_hz(struct clocksource *cs, u32 hz)
 236{
 237        return __clocksource_register_scale(cs, 1, hz);
 238}
 239
 240static inline int clocksource_register_khz(struct clocksource *cs, u32 khz)
 241{
 242        return __clocksource_register_scale(cs, 1000, khz);
 243}
 244
 245static inline void __clocksource_update_freq_hz(struct clocksource *cs, u32 hz)
 246{
 247        __clocksource_update_freq_scale(cs, 1, hz);
 248}
 249
 250static 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
 256extern void clocksource_arch_init(struct clocksource *cs);
 257#else
 258static inline void clocksource_arch_init(struct clocksource *cs) { }
 259#endif
 260
 261extern int timekeeping_notify(struct clocksource *clock);
 262
 263extern u64 clocksource_mmio_readl_up(struct clocksource *);
 264extern u64 clocksource_mmio_readl_down(struct clocksource *);
 265extern u64 clocksource_mmio_readw_up(struct clocksource *);
 266extern u64 clocksource_mmio_readw_down(struct clocksource *);
 267
 268extern int clocksource_mmio_init(void __iomem *, const char *,
 269        unsigned long, int, unsigned, u64 (*)(struct clocksource *));
 270
 271extern 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
 277extern void timer_probe(void);
 278#else
 279static 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 */
 286