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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
100 /* private: */
101#ifdef CONFIG_CLOCKSOURCE_WATCHDOG
102 /* Watchdog related data, used by the framework */
103 struct list_head wd_list;
104 u64 cs_last;
105 u64 wd_last;
106#endif
107 struct module *owner;
108};
109
110/*
111 * Clock source flags bits::
112 */
113#define CLOCK_SOURCE_IS_CONTINUOUS 0x01
114#define CLOCK_SOURCE_MUST_VERIFY 0x02
115
116#define CLOCK_SOURCE_WATCHDOG 0x10
117#define CLOCK_SOURCE_VALID_FOR_HRES 0x20
118#define CLOCK_SOURCE_UNSTABLE 0x40
119#define CLOCK_SOURCE_SUSPEND_NONSTOP 0x80
120#define CLOCK_SOURCE_RESELECT 0x100
121
122/* simplify initialization of mask field */
123#define CLOCKSOURCE_MASK(bits) GENMASK_ULL((bits) - 1, 0)
124
125static inline u32 clocksource_freq2mult(u32 freq, u32 shift_constant, u64 from)
126{
127 /* freq = cyc/from
128 * mult/2^shift = ns/cyc
129 * mult = ns/cyc * 2^shift
130 * mult = from/freq * 2^shift
131 * mult = from * 2^shift / freq
132 * mult = (from<<shift) / freq
133 */
134 u64 tmp = ((u64)from) << shift_constant;
135
136 tmp += freq/2; /* round for do_div */
137 do_div(tmp, freq);
138
139 return (u32)tmp;
140}
141
142/**
143 * clocksource_khz2mult - calculates mult from khz and shift
144 * @khz: Clocksource frequency in KHz
145 * @shift_constant: Clocksource shift factor
146 *
147 * Helper functions that converts a khz counter frequency to a timsource
148 * multiplier, given the clocksource shift value
149 */
150static inline u32 clocksource_khz2mult(u32 khz, u32 shift_constant)
151{
152 return clocksource_freq2mult(khz, shift_constant, NSEC_PER_MSEC);
153}
154
155/**
156 * clocksource_hz2mult - calculates mult from hz and shift
157 * @hz: Clocksource frequency in Hz
158 * @shift_constant: Clocksource shift factor
159 *
160 * Helper functions that converts a hz counter
161 * frequency to a timsource multiplier, given the
162 * clocksource shift value
163 */
164static inline u32 clocksource_hz2mult(u32 hz, u32 shift_constant)
165{
166 return clocksource_freq2mult(hz, shift_constant, NSEC_PER_SEC);
167}
168
169/**
170 * clocksource_cyc2ns - converts clocksource cycles to nanoseconds
171 * @cycles: cycles
172 * @mult: cycle to nanosecond multiplier
173 * @shift: cycle to nanosecond divisor (power of two)
174 *
175 * Converts clocksource cycles to nanoseconds, using the given @mult and @shift.
176 * The code is optimized for performance and is not intended to work
177 * with absolute clocksource cycles (as those will easily overflow),
178 * but is only intended to be used with relative (delta) clocksource cycles.
179 *
180 * XXX - This could use some mult_lxl_ll() asm optimization
181 */
182static inline s64 clocksource_cyc2ns(u64 cycles, u32 mult, u32 shift)
183{
184 return ((u64) cycles * mult) >> shift;
185}
186
187
188extern int clocksource_unregister(struct clocksource*);
189extern void clocksource_touch_watchdog(void);
190extern void clocksource_change_rating(struct clocksource *cs, int rating);
191extern void clocksource_suspend(void);
192extern void clocksource_resume(void);
193extern struct clocksource * __init clocksource_default_clock(void);
194extern void clocksource_mark_unstable(struct clocksource *cs);
195
196extern u64
197clocks_calc_max_nsecs(u32 mult, u32 shift, u32 maxadj, u64 mask, u64 *max_cycles);
198extern void
199clocks_calc_mult_shift(u32 *mult, u32 *shift, u32 from, u32 to, u32 minsec);
200
201/*
202 * Don't call __clocksource_register_scale directly, use
203 * clocksource_register_hz/khz
204 */
205extern int
206__clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq);
207extern void
208__clocksource_update_freq_scale(struct clocksource *cs, u32 scale, u32 freq);
209
210/*
211 * Don't call this unless you are a default clocksource
212 * (AKA: jiffies) and absolutely have to.
213 */
214static inline int __clocksource_register(struct clocksource *cs)
215{
216 return __clocksource_register_scale(cs, 1, 0);
217}
218
219static inline int clocksource_register_hz(struct clocksource *cs, u32 hz)
220{
221 return __clocksource_register_scale(cs, 1, hz);
222}
223
224static inline int clocksource_register_khz(struct clocksource *cs, u32 khz)
225{
226 return __clocksource_register_scale(cs, 1000, khz);
227}
228
229static inline void __clocksource_update_freq_hz(struct clocksource *cs, u32 hz)
230{
231 __clocksource_update_freq_scale(cs, 1, hz);
232}
233
234static inline void __clocksource_update_freq_khz(struct clocksource *cs, u32 khz)
235{
236 __clocksource_update_freq_scale(cs, 1000, khz);
237}
238
239
240extern int timekeeping_notify(struct clocksource *clock);
241
242extern u64 clocksource_mmio_readl_up(struct clocksource *);
243extern u64 clocksource_mmio_readl_down(struct clocksource *);
244extern u64 clocksource_mmio_readw_up(struct clocksource *);
245extern u64 clocksource_mmio_readw_down(struct clocksource *);
246
247extern int clocksource_mmio_init(void __iomem *, const char *,
248 unsigned long, int, unsigned, u64 (*)(struct clocksource *));
249
250extern int clocksource_i8253_init(void);
251
252#define CLOCKSOURCE_OF_DECLARE(name, compat, fn) \
253 OF_DECLARE_1_RET(clksrc, name, compat, fn)
254
255#ifdef CONFIG_CLKSRC_PROBE
256extern void clocksource_probe(void);
257#else
258static inline void clocksource_probe(void) {}
259#endif
260
261#define CLOCKSOURCE_ACPI_DECLARE(name, table_id, fn) \
262 ACPI_DECLARE_PROBE_ENTRY(clksrc, name, table_id, 0, NULL, 0, fn)
263
264#endif /* _LINUX_CLOCKSOURCE_H */