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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 <asm/div64.h>
19#include <asm/io.h>
20
21struct clocksource;
22struct module;
23
24#ifdef CONFIG_ARCH_CLOCKSOURCE_DATA
25#include <asm/clocksource.h>
26#endif
27
28/**
29 * struct clocksource - hardware abstraction for a free running counter
30 * Provides mostly state-free accessors to the underlying hardware.
31 * This is the structure used for system time.
32 *
33 * @name: ptr to clocksource name
34 * @list: list head for registration
35 * @rating: rating value for selection (higher is better)
36 * To avoid rating inflation the following
37 * list should give you a guide as to how
38 * to assign your clocksource a rating
39 * 1-99: Unfit for real use
40 * Only available for bootup and testing purposes.
41 * 100-199: Base level usability.
42 * Functional for real use, but not desired.
43 * 200-299: Good.
44 * A correct and usable clocksource.
45 * 300-399: Desired.
46 * A reasonably fast and accurate clocksource.
47 * 400-499: Perfect
48 * The ideal clocksource. A must-use where
49 * available.
50 * @read: returns a cycle value, passes clocksource as argument
51 * @enable: optional function to enable the clocksource
52 * @disable: optional function to disable the clocksource
53 * @mask: bitmask for two's complement
54 * subtraction of non 64 bit counters
55 * @mult: cycle to nanosecond multiplier
56 * @shift: cycle to nanosecond divisor (power of two)
57 * @max_idle_ns: max idle time permitted by the clocksource (nsecs)
58 * @maxadj: maximum adjustment value to mult (~11%)
59 * @flags: flags describing special properties
60 * @archdata: arch-specific data
61 * @suspend: suspend function for the clocksource, if necessary
62 * @resume: resume function for the clocksource, if necessary
63 * @owner: module reference, must be set by clocksource in modules
64 */
65struct clocksource {
66 /*
67 * Hotpath data, fits in a single cache line when the
68 * clocksource itself is cacheline aligned.
69 */
70 cycle_t (*read)(struct clocksource *cs);
71 cycle_t mask;
72 u32 mult;
73 u32 shift;
74 u64 max_idle_ns;
75 u32 maxadj;
76#ifdef CONFIG_ARCH_CLOCKSOURCE_DATA
77 struct arch_clocksource_data archdata;
78#endif
79
80 const char *name;
81 struct list_head list;
82 int rating;
83 int (*enable)(struct clocksource *cs);
84 void (*disable)(struct clocksource *cs);
85 unsigned long flags;
86 void (*suspend)(struct clocksource *cs);
87 void (*resume)(struct clocksource *cs);
88
89 /* private: */
90#ifdef CONFIG_CLOCKSOURCE_WATCHDOG
91 /* Watchdog related data, used by the framework */
92 struct list_head wd_list;
93 cycle_t cs_last;
94 cycle_t wd_last;
95#endif
96 struct module *owner;
97} ____cacheline_aligned;
98
99/*
100 * Clock source flags bits::
101 */
102#define CLOCK_SOURCE_IS_CONTINUOUS 0x01
103#define CLOCK_SOURCE_MUST_VERIFY 0x02
104
105#define CLOCK_SOURCE_WATCHDOG 0x10
106#define CLOCK_SOURCE_VALID_FOR_HRES 0x20
107#define CLOCK_SOURCE_UNSTABLE 0x40
108#define CLOCK_SOURCE_SUSPEND_NONSTOP 0x80
109#define CLOCK_SOURCE_RESELECT 0x100
110
111/* simplify initialization of mask field */
112#define CLOCKSOURCE_MASK(bits) (cycle_t)((bits) < 64 ? ((1ULL<<(bits))-1) : -1)
113
114/**
115 * clocksource_khz2mult - calculates mult from khz and shift
116 * @khz: Clocksource frequency in KHz
117 * @shift_constant: Clocksource shift factor
118 *
119 * Helper functions that converts a khz counter frequency to a timsource
120 * multiplier, given the clocksource shift value
121 */
122static inline u32 clocksource_khz2mult(u32 khz, u32 shift_constant)
123{
124 /* khz = cyc/(Million ns)
125 * mult/2^shift = ns/cyc
126 * mult = ns/cyc * 2^shift
127 * mult = 1Million/khz * 2^shift
128 * mult = 1000000 * 2^shift / khz
129 * mult = (1000000<<shift) / khz
130 */
131 u64 tmp = ((u64)1000000) << shift_constant;
132
133 tmp += khz/2; /* round for do_div */
134 do_div(tmp, khz);
135
136 return (u32)tmp;
137}
138
139/**
140 * clocksource_hz2mult - calculates mult from hz and shift
141 * @hz: Clocksource frequency in Hz
142 * @shift_constant: Clocksource shift factor
143 *
144 * Helper functions that converts a hz counter
145 * frequency to a timsource multiplier, given the
146 * clocksource shift value
147 */
148static inline u32 clocksource_hz2mult(u32 hz, u32 shift_constant)
149{
150 /* hz = cyc/(Billion ns)
151 * mult/2^shift = ns/cyc
152 * mult = ns/cyc * 2^shift
153 * mult = 1Billion/hz * 2^shift
154 * mult = 1000000000 * 2^shift / hz
155 * mult = (1000000000<<shift) / hz
156 */
157 u64 tmp = ((u64)1000000000) << shift_constant;
158
159 tmp += hz/2; /* round for do_div */
160 do_div(tmp, hz);
161
162 return (u32)tmp;
163}
164
165/**
166 * clocksource_cyc2ns - converts clocksource cycles to nanoseconds
167 * @cycles: cycles
168 * @mult: cycle to nanosecond multiplier
169 * @shift: cycle to nanosecond divisor (power of two)
170 *
171 * Converts cycles to nanoseconds, using the given mult and shift.
172 *
173 * XXX - This could use some mult_lxl_ll() asm optimization
174 */
175static inline s64 clocksource_cyc2ns(cycle_t cycles, u32 mult, u32 shift)
176{
177 return ((u64) cycles * mult) >> shift;
178}
179
180
181extern int clocksource_register(struct clocksource*);
182extern int clocksource_unregister(struct clocksource*);
183extern void clocksource_touch_watchdog(void);
184extern struct clocksource* clocksource_get_next(void);
185extern void clocksource_change_rating(struct clocksource *cs, int rating);
186extern void clocksource_suspend(void);
187extern void clocksource_resume(void);
188extern struct clocksource * __init clocksource_default_clock(void);
189extern void clocksource_mark_unstable(struct clocksource *cs);
190
191extern u64
192clocks_calc_max_nsecs(u32 mult, u32 shift, u32 maxadj, u64 mask);
193extern void
194clocks_calc_mult_shift(u32 *mult, u32 *shift, u32 from, u32 to, u32 minsec);
195
196/*
197 * Don't call __clocksource_register_scale directly, use
198 * clocksource_register_hz/khz
199 */
200extern int
201__clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq);
202extern void
203__clocksource_updatefreq_scale(struct clocksource *cs, u32 scale, u32 freq);
204
205static inline int clocksource_register_hz(struct clocksource *cs, u32 hz)
206{
207 return __clocksource_register_scale(cs, 1, hz);
208}
209
210static inline int clocksource_register_khz(struct clocksource *cs, u32 khz)
211{
212 return __clocksource_register_scale(cs, 1000, khz);
213}
214
215static inline void __clocksource_updatefreq_hz(struct clocksource *cs, u32 hz)
216{
217 __clocksource_updatefreq_scale(cs, 1, hz);
218}
219
220static inline void __clocksource_updatefreq_khz(struct clocksource *cs, u32 khz)
221{
222 __clocksource_updatefreq_scale(cs, 1000, khz);
223}
224
225
226extern int timekeeping_notify(struct clocksource *clock);
227
228extern cycle_t clocksource_mmio_readl_up(struct clocksource *);
229extern cycle_t clocksource_mmio_readl_down(struct clocksource *);
230extern cycle_t clocksource_mmio_readw_up(struct clocksource *);
231extern cycle_t clocksource_mmio_readw_down(struct clocksource *);
232
233extern int clocksource_mmio_init(void __iomem *, const char *,
234 unsigned long, int, unsigned, cycle_t (*)(struct clocksource *));
235
236extern int clocksource_i8253_init(void);
237
238#define CLOCKSOURCE_OF_DECLARE(name, compat, fn) \
239 OF_DECLARE_1(clksrc, name, compat, fn)
240
241#ifdef CONFIG_CLKSRC_OF
242extern void clocksource_of_init(void);
243#else
244static inline void clocksource_of_init(void) {}
245#endif
246
247#endif /* _LINUX_CLOCKSOURCE_H */