projects/linux·blob v6.1 · refs

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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 <linux/clocksource_ids.h>
21#include <asm/div64.h>
22#include <asm/io.h>
23
24struct clocksource;
25struct module;
26
27#if defined(CONFIG_ARCH_CLOCKSOURCE_DATA) || \
28 defined(CONFIG_GENERIC_GETTIMEOFDAY)
29#include <asm/clocksource.h>
30#endif
31
32#include <vdso/clocksource.h>
33
34/**
35 * struct clocksource - hardware abstraction for a free running counter
36 * Provides mostly state-free accessors to the underlying hardware.
37 * This is the structure used for system time.
38 *
39 * @read: Returns a cycle value, passes clocksource as argument
40 * @mask: Bitmask for two's complement
41 * subtraction of non 64 bit counters
42 * @mult: Cycle to nanosecond multiplier
43 * @shift: Cycle to nanosecond divisor (power of two)
44 * @max_idle_ns: Maximum idle time permitted by the clocksource (nsecs)
45 * @maxadj: Maximum adjustment value to mult (~11%)
46 * @uncertainty_margin: Maximum uncertainty in nanoseconds per half second.
47 * Zero says to use default WATCHDOG_THRESHOLD.
48 * @archdata: Optional arch-specific data
49 * @max_cycles: Maximum safe cycle value which won't overflow on
50 * multiplication
51 * @name: Pointer to clocksource name
52 * @list: List head for registration (internal)
53 * @rating: Rating value for selection (higher is better)
54 * To avoid rating inflation the following
55 * list should give you a guide as to how
56 * to assign your clocksource a rating
57 * 1-99: Unfit for real use
58 * Only available for bootup and testing purposes.
59 * 100-199: Base level usability.
60 * Functional for real use, but not desired.
61 * 200-299: Good.
62 * A correct and usable clocksource.
63 * 300-399: Desired.
64 * A reasonably fast and accurate clocksource.
65 * 400-499: Perfect
66 * The ideal clocksource. A must-use where
67 * available.
68 * @id: Defaults to CSID_GENERIC. The id value is captured
69 * in certain snapshot functions to allow callers to
70 * validate the clocksource from which the snapshot was
71 * taken.
72 * @flags: Flags describing special properties
73 * @enable: Optional function to enable the clocksource
74 * @disable: Optional function to disable the clocksource
75 * @suspend: Optional suspend function for the clocksource
76 * @resume: Optional resume function for the clocksource
77 * @mark_unstable: Optional function to inform the clocksource driver that
78 * the watchdog marked the clocksource unstable
79 * @tick_stable: Optional function called periodically from the watchdog
80 * code to provide stable synchronization points
81 * @wd_list: List head to enqueue into the watchdog list (internal)
82 * @cs_last: Last clocksource value for clocksource watchdog
83 * @wd_last: Last watchdog value corresponding to @cs_last
84 * @owner: Module reference, must be set by clocksource in modules
85 *
86 * Note: This struct is not used in hotpathes of the timekeeping code
87 * because the timekeeper caches the hot path fields in its own data
88 * structure, so no cache line alignment is required,
89 *
90 * The pointer to the clocksource itself is handed to the read
91 * callback. If you need extra information there you can wrap struct
92 * clocksource into your own struct. Depending on the amount of
93 * information you need you should consider to cache line align that
94 * structure.
95 */
96struct clocksource {
97 u64 (*read)(struct clocksource *cs);
98 u64 mask;
99 u32 mult;
100 u32 shift;
101 u64 max_idle_ns;
102 u32 maxadj;
103 u32 uncertainty_margin;
104#ifdef CONFIG_ARCH_CLOCKSOURCE_DATA
105 struct arch_clocksource_data archdata;
106#endif
107 u64 max_cycles;
108 const char *name;
109 struct list_head list;
110 int rating;
111 enum clocksource_ids id;
112 enum vdso_clock_mode vdso_clock_mode;
113 unsigned long flags;
114
115 int (*enable)(struct clocksource *cs);
116 void (*disable)(struct clocksource *cs);
117 void (*suspend)(struct clocksource *cs);
118 void (*resume)(struct clocksource *cs);
119 void (*mark_unstable)(struct clocksource *cs);
120 void (*tick_stable)(struct clocksource *cs);
121
122 /* private: */
123#ifdef CONFIG_CLOCKSOURCE_WATCHDOG
124 /* Watchdog related data, used by the framework */
125 struct list_head wd_list;
126 u64 cs_last;
127 u64 wd_last;
128#endif
129 struct module *owner;
130};
131
132/*
133 * Clock source flags bits::
134 */
135#define CLOCK_SOURCE_IS_CONTINUOUS 0x01
136#define CLOCK_SOURCE_MUST_VERIFY 0x02
137
138#define CLOCK_SOURCE_WATCHDOG 0x10
139#define CLOCK_SOURCE_VALID_FOR_HRES 0x20
140#define CLOCK_SOURCE_UNSTABLE 0x40
141#define CLOCK_SOURCE_SUSPEND_NONSTOP 0x80
142#define CLOCK_SOURCE_RESELECT 0x100
143#define CLOCK_SOURCE_VERIFY_PERCPU 0x200
144/* simplify initialization of mask field */
145#define CLOCKSOURCE_MASK(bits) GENMASK_ULL((bits) - 1, 0)
146
147static inline u32 clocksource_freq2mult(u32 freq, u32 shift_constant, u64 from)
148{
149 /* freq = cyc/from
150 * mult/2^shift = ns/cyc
151 * mult = ns/cyc * 2^shift
152 * mult = from/freq * 2^shift
153 * mult = from * 2^shift / freq
154 * mult = (from<<shift) / freq
155 */
156 u64 tmp = ((u64)from) << shift_constant;
157
158 tmp += freq/2; /* round for do_div */
159 do_div(tmp, freq);
160
161 return (u32)tmp;
162}
163
164/**
165 * clocksource_khz2mult - calculates mult from khz and shift
166 * @khz: Clocksource frequency in KHz
167 * @shift_constant: Clocksource shift factor
168 *
169 * Helper functions that converts a khz counter frequency to a timsource
170 * multiplier, given the clocksource shift value
171 */
172static inline u32 clocksource_khz2mult(u32 khz, u32 shift_constant)
173{
174 return clocksource_freq2mult(khz, shift_constant, NSEC_PER_MSEC);
175}
176
177/**
178 * clocksource_hz2mult - calculates mult from hz and shift
179 * @hz: Clocksource frequency in Hz
180 * @shift_constant: Clocksource shift factor
181 *
182 * Helper functions that converts a hz counter
183 * frequency to a timsource multiplier, given the
184 * clocksource shift value
185 */
186static inline u32 clocksource_hz2mult(u32 hz, u32 shift_constant)
187{
188 return clocksource_freq2mult(hz, shift_constant, NSEC_PER_SEC);
189}
190
191/**
192 * clocksource_cyc2ns - converts clocksource cycles to nanoseconds
193 * @cycles: cycles
194 * @mult: cycle to nanosecond multiplier
195 * @shift: cycle to nanosecond divisor (power of two)
196 *
197 * Converts clocksource cycles to nanoseconds, using the given @mult and @shift.
198 * The code is optimized for performance and is not intended to work
199 * with absolute clocksource cycles (as those will easily overflow),
200 * but is only intended to be used with relative (delta) clocksource cycles.
201 *
202 * XXX - This could use some mult_lxl_ll() asm optimization
203 */
204static inline s64 clocksource_cyc2ns(u64 cycles, u32 mult, u32 shift)
205{
206 return ((u64) cycles * mult) >> shift;
207}
208
209
210extern int clocksource_unregister(struct clocksource*);
211extern void clocksource_touch_watchdog(void);
212extern void clocksource_change_rating(struct clocksource *cs, int rating);
213extern void clocksource_suspend(void);
214extern void clocksource_resume(void);
215extern struct clocksource * __init clocksource_default_clock(void);
216extern void clocksource_mark_unstable(struct clocksource *cs);
217extern void
218clocksource_start_suspend_timing(struct clocksource *cs, u64 start_cycles);
219extern u64 clocksource_stop_suspend_timing(struct clocksource *cs, u64 now);
220
221extern u64
222clocks_calc_max_nsecs(u32 mult, u32 shift, u32 maxadj, u64 mask, u64 *max_cycles);
223extern void
224clocks_calc_mult_shift(u32 *mult, u32 *shift, u32 from, u32 to, u32 minsec);
225
226/*
227 * Don't call __clocksource_register_scale directly, use
228 * clocksource_register_hz/khz
229 */
230extern int
231__clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq);
232extern void
233__clocksource_update_freq_scale(struct clocksource *cs, u32 scale, u32 freq);
234
235/*
236 * Don't call this unless you are a default clocksource
237 * (AKA: jiffies) and absolutely have to.
238 */
239static inline int __clocksource_register(struct clocksource *cs)
240{
241 return __clocksource_register_scale(cs, 1, 0);
242}
243
244static inline int clocksource_register_hz(struct clocksource *cs, u32 hz)
245{
246 return __clocksource_register_scale(cs, 1, hz);
247}
248
249static inline int clocksource_register_khz(struct clocksource *cs, u32 khz)
250{
251 return __clocksource_register_scale(cs, 1000, khz);
252}
253
254static inline void __clocksource_update_freq_hz(struct clocksource *cs, u32 hz)
255{
256 __clocksource_update_freq_scale(cs, 1, hz);
257}
258
259static inline void __clocksource_update_freq_khz(struct clocksource *cs, u32 khz)
260{
261 __clocksource_update_freq_scale(cs, 1000, khz);
262}
263
264#ifdef CONFIG_ARCH_CLOCKSOURCE_INIT
265extern void clocksource_arch_init(struct clocksource *cs);
266#else
267static inline void clocksource_arch_init(struct clocksource *cs) { }
268#endif
269
270extern int timekeeping_notify(struct clocksource *clock);
271
272extern u64 clocksource_mmio_readl_up(struct clocksource *);
273extern u64 clocksource_mmio_readl_down(struct clocksource *);
274extern u64 clocksource_mmio_readw_up(struct clocksource *);
275extern u64 clocksource_mmio_readw_down(struct clocksource *);
276
277extern int clocksource_mmio_init(void __iomem *, const char *,
278 unsigned long, int, unsigned, u64 (*)(struct clocksource *));
279
280extern int clocksource_i8253_init(void);
281
282#define TIMER_OF_DECLARE(name, compat, fn) \
283 OF_DECLARE_1_RET(timer, name, compat, fn)
284
285#ifdef CONFIG_TIMER_PROBE
286extern void timer_probe(void);
287#else
288static inline void timer_probe(void) {}
289#endif
290
291#define TIMER_ACPI_DECLARE(name, table_id, fn) \
292 ACPI_DECLARE_PROBE_ENTRY(timer, name, table_id, 0, NULL, 0, fn)
293
294extern ulong max_cswd_read_retries;
295void clocksource_verify_percpu(struct clocksource *cs);
296
297#endif /* _LINUX_CLOCKSOURCE_H */