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/* SPDX-License-Identifier: GPL-2.0 */
/* linux/include/linux/clocksource.h
* This file contains the structure definitions for clocksources.
* If you are not a clocksource, or timekeeping code, you should
* not be including this file!
#include <linux/types.h>
#include <linux/timex.h>
#include <linux/time.h>
#include <linux/list.h>
#include <linux/cache.h>
#include <linux/timer.h>
#include <linux/init.h>
#include <linux/of.h>
#include <asm/div64.h>
#include <asm/io.h>
struct clocksource;
struct module;
#include <asm/clocksource.h>
* struct clocksource - hardware abstraction for a free running counter
* Provides mostly state-free accessors to the underlying hardware.
* This is the structure used for system time.
* @name: ptr to clocksource name
* @list: list head for registration
* @rating: rating value for selection (higher is better)
* To avoid rating inflation the following
* list should give you a guide as to how
* to assign your clocksource a rating
* 1-99: Unfit for real use
* Only available for bootup and testing purposes.
* 100-199: Base level usability.
* Functional for real use, but not desired.
* 200-299: Good.
* A correct and usable clocksource.
* 300-399: Desired.
* A reasonably fast and accurate clocksource.
* 400-499: Perfect
* The ideal clocksource. A must-use where
* available.
* @read: returns a cycle value, passes clocksource as argument
* @enable: optional function to enable the clocksource
* @disable: optional function to disable the clocksource
* @mask: bitmask for two's complement
* subtraction of non 64 bit counters
* @mult: cycle to nanosecond multiplier
* @shift: cycle to nanosecond divisor (power of two)
* @max_idle_ns: max idle time permitted by the clocksource (nsecs)
* @maxadj: maximum adjustment value to mult (~11%)
* @max_cycles: maximum safe cycle value which won't overflow on multiplication
* @flags: flags describing special properties
* @archdata: arch-specific data
* @suspend: suspend function for the clocksource, if necessary
* @resume: resume function for the clocksource, if necessary
* @mark_unstable: Optional function to inform the clocksource driver that
* the watchdog marked the clocksource unstable
* @owner: module reference, must be set by clocksource in modules
* Note: This struct is not used in hotpathes of the timekeeping code
* because the timekeeper caches the hot path fields in its own data
* structure, so no line cache alignment is required,
* The pointer to the clocksource itself is handed to the read
* callback. If you need extra information there you can wrap struct
* clocksource into your own struct. Depending on the amount of
* information you need you should consider to cache line align that
* structure.
struct clocksource {
u64 (*read)(struct clocksource *cs);
u64 mask;
u32 mult;
u32 shift;
u64 max_idle_ns;
u32 maxadj;
struct arch_clocksource_data archdata;
u64 max_cycles;
const char *name;
struct list_head list;
int rating;
int (*enable)(struct clocksource *cs);
void (*disable)(struct clocksource *cs);
unsigned long flags;
void (*suspend)(struct clocksource *cs);
void (*resume)(struct clocksource *cs);
void (*mark_unstable)(struct clocksource *cs);
void (*tick_stable)(struct clocksource *cs);
/* private: */
/* Watchdog related data, used by the framework */
struct list_head wd_list;
u64 cs_last;
u64 wd_last;
struct module *owner;
* Clock source flags bits::
/* simplify initialization of mask field */
#define CLOCKSOURCE_MASK(bits) GENMASK_ULL((bits) - 1, 0)
static inline u32 clocksource_freq2mult(u32 freq, u32 shift_constant, u64 from)
/* freq = cyc/from
* mult/2^shift = ns/cyc
* mult = ns/cyc * 2^shift
* mult = from/freq * 2^shift
* mult = from * 2^shift / freq
* mult = (from<<shift) / freq
u64 tmp = ((u64)from) << shift_constant;
tmp += freq/2; /* round for do_div */
do_div(tmp, freq);
return (u32)tmp;
* clocksource_khz2mult - calculates mult from khz and shift
* @khz: Clocksource frequency in KHz
* @shift_constant: Clocksource shift factor
* Helper functions that converts a khz counter frequency to a timsource
* multiplier, given the clocksource shift value
static inline u32 clocksource_khz2mult(u32 khz, u32 shift_constant)
return clocksource_freq2mult(khz, shift_constant, NSEC_PER_MSEC);
* clocksource_hz2mult - calculates mult from hz and shift
* @hz: Clocksource frequency in Hz
* @shift_constant: Clocksource shift factor
* Helper functions that converts a hz counter
* frequency to a timsource multiplier, given the
* clocksource shift value
static inline u32 clocksource_hz2mult(u32 hz, u32 shift_constant)
return clocksource_freq2mult(hz, shift_constant, NSEC_PER_SEC);
* clocksource_cyc2ns - converts clocksource cycles to nanoseconds
* @cycles: cycles
* @mult: cycle to nanosecond multiplier
* @shift: cycle to nanosecond divisor (power of two)
* Converts clocksource cycles to nanoseconds, using the given @mult and @shift.
* The code is optimized for performance and is not intended to work
* with absolute clocksource cycles (as those will easily overflow),
* but is only intended to be used with relative (delta) clocksource cycles.
* XXX - This could use some mult_lxl_ll() asm optimization
static inline s64 clocksource_cyc2ns(u64 cycles, u32 mult, u32 shift)
return ((u64) cycles * mult) >> shift;
extern int clocksource_unregister(struct clocksource*);
extern void clocksource_touch_watchdog(void);
extern void clocksource_change_rating(struct clocksource *cs, int rating);
extern void clocksource_suspend(void);
extern void clocksource_resume(void);
extern struct clocksource * __init clocksource_default_clock(void);
extern void clocksource_mark_unstable(struct clocksource *cs);
extern void
clocksource_start_suspend_timing(struct clocksource *cs, u64 start_cycles);
extern u64 clocksource_stop_suspend_timing(struct clocksource *cs, u64 now);
extern u64
clocks_calc_max_nsecs(u32 mult, u32 shift, u32 maxadj, u64 mask, u64 *max_cycles);
extern void
clocks_calc_mult_shift(u32 *mult, u32 *shift, u32 from, u32 to, u32 minsec);
* Don't call __clocksource_register_scale directly, use
* clocksource_register_hz/khz
extern int
__clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq);
extern void
__clocksource_update_freq_scale(struct clocksource *cs, u32 scale, u32 freq);
* Don't call this unless you are a default clocksource
* (AKA: jiffies) and absolutely have to.
static inline int __clocksource_register(struct clocksource *cs)
return __clocksource_register_scale(cs, 1, 0);
static inline int clocksource_register_hz(struct clocksource *cs, u32 hz)
return __clocksource_register_scale(cs, 1, hz);
static inline int clocksource_register_khz(struct clocksource *cs, u32 khz)
return __clocksource_register_scale(cs, 1000, khz);
static inline void __clocksource_update_freq_hz(struct clocksource *cs, u32 hz)
__clocksource_update_freq_scale(cs, 1, hz);
static inline void __clocksource_update_freq_khz(struct clocksource *cs, u32 khz)
__clocksource_update_freq_scale(cs, 1000, khz);
extern int timekeeping_notify(struct clocksource *clock);
extern u64 clocksource_mmio_readl_up(struct clocksource *);
extern u64 clocksource_mmio_readl_down(struct clocksource *);
extern u64 clocksource_mmio_readw_up(struct clocksource *);
extern u64 clocksource_mmio_readw_down(struct clocksource *);
extern int clocksource_mmio_init(void __iomem *, const char *,
unsigned long, int, unsigned, u64 (*)(struct clocksource *));
extern int clocksource_i8253_init(void);
#define TIMER_OF_DECLARE(name, compat, fn) \
OF_DECLARE_1_RET(timer, name, compat, fn)
#define CLOCKSOURCE_OF_DECLARE(name, compat, fn) \
TIMER_OF_DECLARE(name, compat, fn)
extern void timer_probe(void);
static inline void timer_probe(void) {}
#define TIMER_ACPI_DECLARE(name, table_id, fn) \
ACPI_DECLARE_PROBE_ENTRY(timer, name, table_id, 0, NULL, 0, fn)