projects/linux·blob v4.8 · refs

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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 * @owner: module reference, must be set by clocksource in modules
66 *
67 * Note: This struct is not used in hotpathes of the timekeeping code
68 * because the timekeeper caches the hot path fields in its own data
69 * structure, so no line cache alignment is required,
70 *
71 * The pointer to the clocksource itself is handed to the read
72 * callback. If you need extra information there you can wrap struct
73 * clocksource into your own struct. Depending on the amount of
74 * information you need you should consider to cache line align that
75 * structure.
76 */
77struct clocksource {
78 cycle_t (*read)(struct clocksource *cs);
79 cycle_t mask;
80 u32 mult;
81 u32 shift;
82 u64 max_idle_ns;
83 u32 maxadj;
84#ifdef CONFIG_ARCH_CLOCKSOURCE_DATA
85 struct arch_clocksource_data archdata;
86#endif
87 u64 max_cycles;
88 const char *name;
89 struct list_head list;
90 int rating;
91 int (*enable)(struct clocksource *cs);
92 void (*disable)(struct clocksource *cs);
93 unsigned long flags;
94 void (*suspend)(struct clocksource *cs);
95 void (*resume)(struct clocksource *cs);
96
97 /* private: */
98#ifdef CONFIG_CLOCKSOURCE_WATCHDOG
99 /* Watchdog related data, used by the framework */
100 struct list_head wd_list;
101 cycle_t cs_last;
102 cycle_t wd_last;
103#endif
104 struct module *owner;
105};
106
107/*
108 * Clock source flags bits::
109 */
110#define CLOCK_SOURCE_IS_CONTINUOUS 0x01
111#define CLOCK_SOURCE_MUST_VERIFY 0x02
112
113#define CLOCK_SOURCE_WATCHDOG 0x10
114#define CLOCK_SOURCE_VALID_FOR_HRES 0x20
115#define CLOCK_SOURCE_UNSTABLE 0x40
116#define CLOCK_SOURCE_SUSPEND_NONSTOP 0x80
117#define CLOCK_SOURCE_RESELECT 0x100
118
119/* simplify initialization of mask field */
120#define CLOCKSOURCE_MASK(bits) (cycle_t)((bits) < 64 ? ((1ULL<<(bits))-1) : -1)
121
122static inline u32 clocksource_freq2mult(u32 freq, u32 shift_constant, u64 from)
123{
124 /* freq = cyc/from
125 * mult/2^shift = ns/cyc
126 * mult = ns/cyc * 2^shift
127 * mult = from/freq * 2^shift
128 * mult = from * 2^shift / freq
129 * mult = (from<<shift) / freq
130 */
131 u64 tmp = ((u64)from) << shift_constant;
132
133 tmp += freq/2; /* round for do_div */
134 do_div(tmp, freq);
135
136 return (u32)tmp;
137}
138
139/**
140 * clocksource_khz2mult - calculates mult from khz and shift
141 * @khz: Clocksource frequency in KHz
142 * @shift_constant: Clocksource shift factor
143 *
144 * Helper functions that converts a khz counter frequency to a timsource
145 * multiplier, given the clocksource shift value
146 */
147static inline u32 clocksource_khz2mult(u32 khz, u32 shift_constant)
148{
149 return clocksource_freq2mult(khz, shift_constant, NSEC_PER_MSEC);
150}
151
152/**
153 * clocksource_hz2mult - calculates mult from hz and shift
154 * @hz: Clocksource frequency in Hz
155 * @shift_constant: Clocksource shift factor
156 *
157 * Helper functions that converts a hz counter
158 * frequency to a timsource multiplier, given the
159 * clocksource shift value
160 */
161static inline u32 clocksource_hz2mult(u32 hz, u32 shift_constant)
162{
163 return clocksource_freq2mult(hz, shift_constant, NSEC_PER_SEC);
164}
165
166/**
167 * clocksource_cyc2ns - converts clocksource cycles to nanoseconds
168 * @cycles: cycles
169 * @mult: cycle to nanosecond multiplier
170 * @shift: cycle to nanosecond divisor (power of two)
171 *
172 * Converts cycles to nanoseconds, using the given mult and shift.
173 *
174 * XXX - This could use some mult_lxl_ll() asm optimization
175 */
176static inline s64 clocksource_cyc2ns(cycle_t cycles, u32 mult, u32 shift)
177{
178 return ((u64) cycles * mult) >> shift;
179}
180
181
182extern int clocksource_unregister(struct clocksource*);
183extern void clocksource_touch_watchdog(void);
184extern void clocksource_change_rating(struct clocksource *cs, int rating);
185extern void clocksource_suspend(void);
186extern void clocksource_resume(void);
187extern struct clocksource * __init clocksource_default_clock(void);
188extern void clocksource_mark_unstable(struct clocksource *cs);
189
190extern u64
191clocks_calc_max_nsecs(u32 mult, u32 shift, u32 maxadj, u64 mask, u64 *max_cycles);
192extern void
193clocks_calc_mult_shift(u32 *mult, u32 *shift, u32 from, u32 to, u32 minsec);
194
195/*
196 * Don't call __clocksource_register_scale directly, use
197 * clocksource_register_hz/khz
198 */
199extern int
200__clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq);
201extern void
202__clocksource_update_freq_scale(struct clocksource *cs, u32 scale, u32 freq);
203
204/*
205 * Don't call this unless you are a default clocksource
206 * (AKA: jiffies) and absolutely have to.
207 */
208static inline int __clocksource_register(struct clocksource *cs)
209{
210 return __clocksource_register_scale(cs, 1, 0);
211}
212
213static inline int clocksource_register_hz(struct clocksource *cs, u32 hz)
214{
215 return __clocksource_register_scale(cs, 1, hz);
216}
217
218static inline int clocksource_register_khz(struct clocksource *cs, u32 khz)
219{
220 return __clocksource_register_scale(cs, 1000, khz);
221}
222
223static inline void __clocksource_update_freq_hz(struct clocksource *cs, u32 hz)
224{
225 __clocksource_update_freq_scale(cs, 1, hz);
226}
227
228static inline void __clocksource_update_freq_khz(struct clocksource *cs, u32 khz)
229{
230 __clocksource_update_freq_scale(cs, 1000, khz);
231}
232
233
234extern int timekeeping_notify(struct clocksource *clock);
235
236extern cycle_t clocksource_mmio_readl_up(struct clocksource *);
237extern cycle_t clocksource_mmio_readl_down(struct clocksource *);
238extern cycle_t clocksource_mmio_readw_up(struct clocksource *);
239extern cycle_t clocksource_mmio_readw_down(struct clocksource *);
240
241extern int clocksource_mmio_init(void __iomem *, const char *,
242 unsigned long, int, unsigned, cycle_t (*)(struct clocksource *));
243
244extern int clocksource_i8253_init(void);
245
246#define CLOCKSOURCE_OF_DECLARE(name, compat, fn) \
247 OF_DECLARE_1_RET(clksrc, name, compat, fn)
248
249#ifdef CONFIG_CLKSRC_PROBE
250extern void clocksource_probe(void);
251#else
252static inline void clocksource_probe(void) {}
253#endif
254
255#define CLOCKSOURCE_ACPI_DECLARE(name, table_id, fn) \
256 ACPI_DECLARE_PROBE_ENTRY(clksrc, name, table_id, 0, NULL, 0, fn)
257
258#endif /* _LINUX_CLOCKSOURCE_H */