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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 * @max_cycles: maximum safe cycle value which won't overflow on multiplication
60 * @flags: flags describing special properties
61 * @archdata: arch-specific data
62 * @suspend: suspend function for the clocksource, if necessary
63 * @resume: resume function for the clocksource, if necessary
64 * @owner: module reference, must be set by clocksource in modules
65 *
66 * Note: This struct is not used in hotpathes of the timekeeping code
67 * because the timekeeper caches the hot path fields in its own data
68 * structure, so no line cache alignment is required,
69 *
70 * The pointer to the clocksource itself is handed to the read
71 * callback. If you need extra information there you can wrap struct
72 * clocksource into your own struct. Depending on the amount of
73 * information you need you should consider to cache line align that
74 * structure.
75 */
76struct clocksource {
77 cycle_t (*read)(struct clocksource *cs);
78 cycle_t mask;
79 u32 mult;
80 u32 shift;
81 u64 max_idle_ns;
82 u32 maxadj;
83#ifdef CONFIG_ARCH_CLOCKSOURCE_DATA
84 struct arch_clocksource_data archdata;
85#endif
86 u64 max_cycles;
87 const char *name;
88 struct list_head list;
89 int rating;
90 int (*enable)(struct clocksource *cs);
91 void (*disable)(struct clocksource *cs);
92 unsigned long flags;
93 void (*suspend)(struct clocksource *cs);
94 void (*resume)(struct clocksource *cs);
95
96 /* private: */
97#ifdef CONFIG_CLOCKSOURCE_WATCHDOG
98 /* Watchdog related data, used by the framework */
99 struct list_head wd_list;
100 cycle_t cs_last;
101 cycle_t wd_last;
102#endif
103 struct module *owner;
104};
105
106/*
107 * Clock source flags bits::
108 */
109#define CLOCK_SOURCE_IS_CONTINUOUS 0x01
110#define CLOCK_SOURCE_MUST_VERIFY 0x02
111
112#define CLOCK_SOURCE_WATCHDOG 0x10
113#define CLOCK_SOURCE_VALID_FOR_HRES 0x20
114#define CLOCK_SOURCE_UNSTABLE 0x40
115#define CLOCK_SOURCE_SUSPEND_NONSTOP 0x80
116#define CLOCK_SOURCE_RESELECT 0x100
117
118/* simplify initialization of mask field */
119#define CLOCKSOURCE_MASK(bits) (cycle_t)((bits) < 64 ? ((1ULL<<(bits))-1) : -1)
120
121static inline u32 clocksource_freq2mult(u32 freq, u32 shift_constant, u64 from)
122{
123 /* freq = cyc/from
124 * mult/2^shift = ns/cyc
125 * mult = ns/cyc * 2^shift
126 * mult = from/freq * 2^shift
127 * mult = from * 2^shift / freq
128 * mult = (from<<shift) / freq
129 */
130 u64 tmp = ((u64)from) << shift_constant;
131
132 tmp += freq/2; /* round for do_div */
133 do_div(tmp, freq);
134
135 return (u32)tmp;
136}
137
138/**
139 * clocksource_khz2mult - calculates mult from khz and shift
140 * @khz: Clocksource frequency in KHz
141 * @shift_constant: Clocksource shift factor
142 *
143 * Helper functions that converts a khz counter frequency to a timsource
144 * multiplier, given the clocksource shift value
145 */
146static inline u32 clocksource_khz2mult(u32 khz, u32 shift_constant)
147{
148 return clocksource_freq2mult(khz, shift_constant, NSEC_PER_MSEC);
149}
150
151/**
152 * clocksource_hz2mult - calculates mult from hz and shift
153 * @hz: Clocksource frequency in Hz
154 * @shift_constant: Clocksource shift factor
155 *
156 * Helper functions that converts a hz counter
157 * frequency to a timsource multiplier, given the
158 * clocksource shift value
159 */
160static inline u32 clocksource_hz2mult(u32 hz, u32 shift_constant)
161{
162 return clocksource_freq2mult(hz, shift_constant, NSEC_PER_SEC);
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_unregister(struct clocksource*);
182extern void clocksource_touch_watchdog(void);
183extern void clocksource_change_rating(struct clocksource *cs, int rating);
184extern void clocksource_suspend(void);
185extern void clocksource_resume(void);
186extern struct clocksource * __init clocksource_default_clock(void);
187extern void clocksource_mark_unstable(struct clocksource *cs);
188
189extern u64
190clocks_calc_max_nsecs(u32 mult, u32 shift, u32 maxadj, u64 mask, u64 *max_cycles);
191extern void
192clocks_calc_mult_shift(u32 *mult, u32 *shift, u32 from, u32 to, u32 minsec);
193
194/*
195 * Don't call __clocksource_register_scale directly, use
196 * clocksource_register_hz/khz
197 */
198extern int
199__clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq);
200extern void
201__clocksource_update_freq_scale(struct clocksource *cs, u32 scale, u32 freq);
202
203/*
204 * Don't call this unless you are a default clocksource
205 * (AKA: jiffies) and absolutely have to.
206 */
207static inline int __clocksource_register(struct clocksource *cs)
208{
209 return __clocksource_register_scale(cs, 1, 0);
210}
211
212static inline int clocksource_register_hz(struct clocksource *cs, u32 hz)
213{
214 return __clocksource_register_scale(cs, 1, hz);
215}
216
217static inline int clocksource_register_khz(struct clocksource *cs, u32 khz)
218{
219 return __clocksource_register_scale(cs, 1000, khz);
220}
221
222static inline void __clocksource_update_freq_hz(struct clocksource *cs, u32 hz)
223{
224 __clocksource_update_freq_scale(cs, 1, hz);
225}
226
227static inline void __clocksource_update_freq_khz(struct clocksource *cs, u32 khz)
228{
229 __clocksource_update_freq_scale(cs, 1000, khz);
230}
231
232
233extern int timekeeping_notify(struct clocksource *clock);
234
235extern cycle_t clocksource_mmio_readl_up(struct clocksource *);
236extern cycle_t clocksource_mmio_readl_down(struct clocksource *);
237extern cycle_t clocksource_mmio_readw_up(struct clocksource *);
238extern cycle_t clocksource_mmio_readw_down(struct clocksource *);
239
240extern int clocksource_mmio_init(void __iomem *, const char *,
241 unsigned long, int, unsigned, cycle_t (*)(struct clocksource *));
242
243extern int clocksource_i8253_init(void);
244
245#define CLOCKSOURCE_OF_DECLARE(name, compat, fn) \
246 OF_DECLARE_1(clksrc, name, compat, fn)
247
248#ifdef CONFIG_CLKSRC_PROBE
249extern void clocksource_probe(void);
250#else
251static inline void clocksource_probe(void) {}
252#endif
253
254#define CLOCKSOURCE_ACPI_DECLARE(name, table_id, fn) \
255 ACPI_DECLARE_PROBE_ENTRY(clksrc, name, table_id, 0, NULL, 0, fn)
256
257#endif /* _LINUX_CLOCKSOURCE_H */