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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/timer.h>
16#include <asm/div64.h>
17#include <asm/io.h>
18
19/* clocksource cycle base type */
20typedef u64 cycle_t;
21struct clocksource;
22
23/**
24 * struct clocksource - hardware abstraction for a free running counter
25 * Provides mostly state-free accessors to the underlying hardware.
26 *
27 * @name: ptr to clocksource name
28 * @list: list head for registration
29 * @rating: rating value for selection (higher is better)
30 * To avoid rating inflation the following
31 * list should give you a guide as to how
32 * to assign your clocksource a rating
33 * 1-99: Unfit for real use
34 * Only available for bootup and testing purposes.
35 * 100-199: Base level usability.
36 * Functional for real use, but not desired.
37 * 200-299: Good.
38 * A correct and usable clocksource.
39 * 300-399: Desired.
40 * A reasonably fast and accurate clocksource.
41 * 400-499: Perfect
42 * The ideal clocksource. A must-use where
43 * available.
44 * @read: returns a cycle value
45 * @mask: bitmask for two's complement
46 * subtraction of non 64 bit counters
47 * @mult: cycle to nanosecond multiplier
48 * @shift: cycle to nanosecond divisor (power of two)
49 * @flags: flags describing special properties
50 * @vread: vsyscall based read
51 * @cycle_interval: Used internally by timekeeping core, please ignore.
52 * @xtime_interval: Used internally by timekeeping core, please ignore.
53 */
54struct clocksource {
55 char *name;
56 struct list_head list;
57 int rating;
58 cycle_t (*read)(void);
59 cycle_t mask;
60 u32 mult;
61 u32 shift;
62 unsigned long flags;
63 cycle_t (*vread)(void);
64
65 /* timekeeping specific data, ignore */
66 cycle_t cycle_last, cycle_interval;
67 u64 xtime_nsec, xtime_interval;
68 s64 error;
69
70#ifdef CONFIG_CLOCKSOURCE_WATCHDOG
71 /* Watchdog related data, used by the framework */
72 struct list_head wd_list;
73 cycle_t wd_last;
74#endif
75};
76
77/*
78 * Clock source flags bits::
79 */
80#define CLOCK_SOURCE_IS_CONTINUOUS 0x01
81#define CLOCK_SOURCE_MUST_VERIFY 0x02
82
83#define CLOCK_SOURCE_WATCHDOG 0x10
84#define CLOCK_SOURCE_VALID_FOR_HRES 0x20
85
86/* simplify initialization of mask field */
87#define CLOCKSOURCE_MASK(bits) (cycle_t)(bits<64 ? ((1ULL<<bits)-1) : -1)
88
89/**
90 * clocksource_khz2mult - calculates mult from khz and shift
91 * @khz: Clocksource frequency in KHz
92 * @shift_constant: Clocksource shift factor
93 *
94 * Helper functions that converts a khz counter frequency to a timsource
95 * multiplier, given the clocksource shift value
96 */
97static inline u32 clocksource_khz2mult(u32 khz, u32 shift_constant)
98{
99 /* khz = cyc/(Million ns)
100 * mult/2^shift = ns/cyc
101 * mult = ns/cyc * 2^shift
102 * mult = 1Million/khz * 2^shift
103 * mult = 1000000 * 2^shift / khz
104 * mult = (1000000<<shift) / khz
105 */
106 u64 tmp = ((u64)1000000) << shift_constant;
107
108 tmp += khz/2; /* round for do_div */
109 do_div(tmp, khz);
110
111 return (u32)tmp;
112}
113
114/**
115 * clocksource_hz2mult - calculates mult from hz and shift
116 * @hz: Clocksource frequency in Hz
117 * @shift_constant: Clocksource shift factor
118 *
119 * Helper functions that converts a hz counter
120 * frequency to a timsource multiplier, given the
121 * clocksource shift value
122 */
123static inline u32 clocksource_hz2mult(u32 hz, u32 shift_constant)
124{
125 /* hz = cyc/(Billion ns)
126 * mult/2^shift = ns/cyc
127 * mult = ns/cyc * 2^shift
128 * mult = 1Billion/hz * 2^shift
129 * mult = 1000000000 * 2^shift / hz
130 * mult = (1000000000<<shift) / hz
131 */
132 u64 tmp = ((u64)1000000000) << shift_constant;
133
134 tmp += hz/2; /* round for do_div */
135 do_div(tmp, hz);
136
137 return (u32)tmp;
138}
139
140/**
141 * clocksource_read: - Access the clocksource's current cycle value
142 * @cs: pointer to clocksource being read
143 *
144 * Uses the clocksource to return the current cycle_t value
145 */
146static inline cycle_t clocksource_read(struct clocksource *cs)
147{
148 return cs->read();
149}
150
151/**
152 * cyc2ns - converts clocksource cycles to nanoseconds
153 * @cs: Pointer to clocksource
154 * @cycles: Cycles
155 *
156 * Uses the clocksource and ntp ajdustment to convert cycle_ts to nanoseconds.
157 *
158 * XXX - This could use some mult_lxl_ll() asm optimization
159 */
160static inline s64 cyc2ns(struct clocksource *cs, cycle_t cycles)
161{
162 u64 ret = (u64)cycles;
163 ret = (ret * cs->mult) >> cs->shift;
164 return ret;
165}
166
167/**
168 * clocksource_calculate_interval - Calculates a clocksource interval struct
169 *
170 * @c: Pointer to clocksource.
171 * @length_nsec: Desired interval length in nanoseconds.
172 *
173 * Calculates a fixed cycle/nsec interval for a given clocksource/adjustment
174 * pair and interval request.
175 *
176 * Unless you're the timekeeping code, you should not be using this!
177 */
178static inline void clocksource_calculate_interval(struct clocksource *c,
179 unsigned long length_nsec)
180{
181 u64 tmp;
182
183 /* XXX - All of this could use a whole lot of optimization */
184 tmp = length_nsec;
185 tmp <<= c->shift;
186 tmp += c->mult/2;
187 do_div(tmp, c->mult);
188
189 c->cycle_interval = (cycle_t)tmp;
190 if (c->cycle_interval == 0)
191 c->cycle_interval = 1;
192
193 c->xtime_interval = (u64)c->cycle_interval * c->mult;
194}
195
196
197/* used to install a new clocksource */
198extern int clocksource_register(struct clocksource*);
199extern struct clocksource* clocksource_get_next(void);
200extern void clocksource_change_rating(struct clocksource *cs, int rating);
201
202#ifdef CONFIG_GENERIC_TIME_VSYSCALL
203extern void update_vsyscall(struct timespec *ts, struct clocksource *c);
204#else
205static inline void update_vsyscall(struct timespec *ts, struct clocksource *c)
206{
207}
208#endif
209
210#endif /* _LINUX_CLOCKSOURCE_H */