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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 <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 */