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