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1/* linux/include/linux/clocksource.h
2 *
3 * This file contains the structure definitions for clocksources.
4 *
5 * If you are not a clocksource, or timekeeping code, you should
6 * not be including this file!
7 */
8#ifndef _LINUX_CLOCKSOURCE_H
9#define _LINUX_CLOCKSOURCE_H
10
11#include <linux/types.h>
12#include <linux/timex.h>
13#include <linux/time.h>
14#include <linux/list.h>
15#include <linux/cache.h>
16#include <linux/timer.h>
17#include <linux/init.h>
18#include <linux/of.h>
19#include <asm/div64.h>
20#include <asm/io.h>
21
22struct clocksource;
23struct module;
24
25#ifdef CONFIG_ARCH_CLOCKSOURCE_DATA
26#include <asm/clocksource.h>
27#endif
28
29/**
30 * struct clocksource - hardware abstraction for a free running counter
31 * Provides mostly state-free accessors to the underlying hardware.
32 * This is the structure used for system time.
33 *
34 * @name: ptr to clocksource name
35 * @list: list head for registration
36 * @rating: rating value for selection (higher is better)
37 * To avoid rating inflation the following
38 * list should give you a guide as to how
39 * to assign your clocksource a rating
40 * 1-99: Unfit for real use
41 * Only available for bootup and testing purposes.
42 * 100-199: Base level usability.
43 * Functional for real use, but not desired.
44 * 200-299: Good.
45 * A correct and usable clocksource.
46 * 300-399: Desired.
47 * A reasonably fast and accurate clocksource.
48 * 400-499: Perfect
49 * The ideal clocksource. A must-use where
50 * available.
51 * @read: returns a cycle value, passes clocksource as argument
52 * @enable: optional function to enable the clocksource
53 * @disable: optional function to disable the clocksource
54 * @mask: bitmask for two's complement
55 * subtraction of non 64 bit counters
56 * @mult: cycle to nanosecond multiplier
57 * @shift: cycle to nanosecond divisor (power of two)
58 * @max_idle_ns: max idle time permitted by the clocksource (nsecs)
59 * @maxadj: maximum adjustment value to mult (~11%)
60 * @max_cycles: maximum safe cycle value which won't overflow on multiplication
61 * @flags: flags describing special properties
62 * @archdata: arch-specific data
63 * @suspend: suspend function for the clocksource, if necessary
64 * @resume: resume function for the clocksource, if necessary
65 * @mark_unstable: Optional function to inform the clocksource driver that
66 * the watchdog marked the clocksource unstable
67 * @owner: module reference, must be set by clocksource in modules
68 *
69 * Note: This struct is not used in hotpathes of the timekeeping code
70 * because the timekeeper caches the hot path fields in its own data
71 * structure, so no line cache alignment is required,
72 *
73 * The pointer to the clocksource itself is handed to the read
74 * callback. If you need extra information there you can wrap struct
75 * clocksource into your own struct. Depending on the amount of
76 * information you need you should consider to cache line align that
77 * structure.
78 */
79struct clocksource {
80 u64 (*read)(struct clocksource *cs);
81 u64 mask;
82 u32 mult;
83 u32 shift;
84 u64 max_idle_ns;
85 u32 maxadj;
86#ifdef CONFIG_ARCH_CLOCKSOURCE_DATA
87 struct arch_clocksource_data archdata;
88#endif
89 u64 max_cycles;
90 const char *name;
91 struct list_head list;
92 int rating;
93 int (*enable)(struct clocksource *cs);
94 void (*disable)(struct clocksource *cs);
95 unsigned long flags;
96 void (*suspend)(struct clocksource *cs);
97 void (*resume)(struct clocksource *cs);
98 void (*mark_unstable)(struct clocksource *cs);
99 void (*tick_stable)(struct clocksource *cs);
100
101 /* private: */
102#ifdef CONFIG_CLOCKSOURCE_WATCHDOG
103 /* Watchdog related data, used by the framework */
104 struct list_head wd_list;
105 u64 cs_last;
106 u64 wd_last;
107#endif
108 struct module *owner;
109};
110
111/*
112 * Clock source flags bits::
113 */
114#define CLOCK_SOURCE_IS_CONTINUOUS 0x01
115#define CLOCK_SOURCE_MUST_VERIFY 0x02
116
117#define CLOCK_SOURCE_WATCHDOG 0x10
118#define CLOCK_SOURCE_VALID_FOR_HRES 0x20
119#define CLOCK_SOURCE_UNSTABLE 0x40
120#define CLOCK_SOURCE_SUSPEND_NONSTOP 0x80
121#define CLOCK_SOURCE_RESELECT 0x100
122
123/* simplify initialization of mask field */
124#define CLOCKSOURCE_MASK(bits) GENMASK_ULL((bits) - 1, 0)
125
126static inline u32 clocksource_freq2mult(u32 freq, u32 shift_constant, u64 from)
127{
128 /* freq = cyc/from
129 * mult/2^shift = ns/cyc
130 * mult = ns/cyc * 2^shift
131 * mult = from/freq * 2^shift
132 * mult = from * 2^shift / freq
133 * mult = (from<<shift) / freq
134 */
135 u64 tmp = ((u64)from) << shift_constant;
136
137 tmp += freq/2; /* round for do_div */
138 do_div(tmp, freq);
139
140 return (u32)tmp;
141}
142
143/**
144 * clocksource_khz2mult - calculates mult from khz and shift
145 * @khz: Clocksource frequency in KHz
146 * @shift_constant: Clocksource shift factor
147 *
148 * Helper functions that converts a khz counter frequency to a timsource
149 * multiplier, given the clocksource shift value
150 */
151static inline u32 clocksource_khz2mult(u32 khz, u32 shift_constant)
152{
153 return clocksource_freq2mult(khz, shift_constant, NSEC_PER_MSEC);
154}
155
156/**
157 * clocksource_hz2mult - calculates mult from hz and shift
158 * @hz: Clocksource frequency in Hz
159 * @shift_constant: Clocksource shift factor
160 *
161 * Helper functions that converts a hz counter
162 * frequency to a timsource multiplier, given the
163 * clocksource shift value
164 */
165static inline u32 clocksource_hz2mult(u32 hz, u32 shift_constant)
166{
167 return clocksource_freq2mult(hz, shift_constant, NSEC_PER_SEC);
168}
169
170/**
171 * clocksource_cyc2ns - converts clocksource cycles to nanoseconds
172 * @cycles: cycles
173 * @mult: cycle to nanosecond multiplier
174 * @shift: cycle to nanosecond divisor (power of two)
175 *
176 * Converts clocksource cycles to nanoseconds, using the given @mult and @shift.
177 * The code is optimized for performance and is not intended to work
178 * with absolute clocksource cycles (as those will easily overflow),
179 * but is only intended to be used with relative (delta) clocksource cycles.
180 *
181 * XXX - This could use some mult_lxl_ll() asm optimization
182 */
183static inline s64 clocksource_cyc2ns(u64 cycles, u32 mult, u32 shift)
184{
185 return ((u64) cycles * mult) >> shift;
186}
187
188
189extern int clocksource_unregister(struct clocksource*);
190extern void clocksource_touch_watchdog(void);
191extern void clocksource_change_rating(struct clocksource *cs, int rating);
192extern void clocksource_suspend(void);
193extern void clocksource_resume(void);
194extern struct clocksource * __init clocksource_default_clock(void);
195extern void clocksource_mark_unstable(struct clocksource *cs);
196
197extern u64
198clocks_calc_max_nsecs(u32 mult, u32 shift, u32 maxadj, u64 mask, u64 *max_cycles);
199extern void
200clocks_calc_mult_shift(u32 *mult, u32 *shift, u32 from, u32 to, u32 minsec);
201
202/*
203 * Don't call __clocksource_register_scale directly, use
204 * clocksource_register_hz/khz
205 */
206extern int
207__clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq);
208extern void
209__clocksource_update_freq_scale(struct clocksource *cs, u32 scale, u32 freq);
210
211/*
212 * Don't call this unless you are a default clocksource
213 * (AKA: jiffies) and absolutely have to.
214 */
215static inline int __clocksource_register(struct clocksource *cs)
216{
217 return __clocksource_register_scale(cs, 1, 0);
218}
219
220static inline int clocksource_register_hz(struct clocksource *cs, u32 hz)
221{
222 return __clocksource_register_scale(cs, 1, hz);
223}
224
225static inline int clocksource_register_khz(struct clocksource *cs, u32 khz)
226{
227 return __clocksource_register_scale(cs, 1000, khz);
228}
229
230static inline void __clocksource_update_freq_hz(struct clocksource *cs, u32 hz)
231{
232 __clocksource_update_freq_scale(cs, 1, hz);
233}
234
235static inline void __clocksource_update_freq_khz(struct clocksource *cs, u32 khz)
236{
237 __clocksource_update_freq_scale(cs, 1000, khz);
238}
239
240
241extern int timekeeping_notify(struct clocksource *clock);
242
243extern u64 clocksource_mmio_readl_up(struct clocksource *);
244extern u64 clocksource_mmio_readl_down(struct clocksource *);
245extern u64 clocksource_mmio_readw_up(struct clocksource *);
246extern u64 clocksource_mmio_readw_down(struct clocksource *);
247
248extern int clocksource_mmio_init(void __iomem *, const char *,
249 unsigned long, int, unsigned, u64 (*)(struct clocksource *));
250
251extern int clocksource_i8253_init(void);
252
253#define TIMER_OF_DECLARE(name, compat, fn) \
254 OF_DECLARE_1_RET(timer, name, compat, fn)
255
256#define CLOCKSOURCE_OF_DECLARE(name, compat, fn) \
257 TIMER_OF_DECLARE(name, compat, fn)
258
259#ifdef CONFIG_TIMER_PROBE
260extern void timer_probe(void);
261#else
262static inline void timer_probe(void) {}
263#endif
264
265#define TIMER_ACPI_DECLARE(name, table_id, fn) \
266 ACPI_DECLARE_PROBE_ENTRY(timer, name, table_id, 0, NULL, 0, fn)
267
268#endif /* _LINUX_CLOCKSOURCE_H */