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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 <asm/div64.h>
18#include <asm/io.h>
19
20/* clocksource cycle base type */
21typedef u64 cycle_t;
22struct clocksource;
23
24/**
25 * struct clocksource - hardware abstraction for a free running counter
26 * Provides mostly state-free accessors to the underlying hardware.
27 *
28 * @name: ptr to clocksource name
29 * @list: list head for registration
30 * @rating: rating value for selection (higher is better)
31 * To avoid rating inflation the following
32 * list should give you a guide as to how
33 * to assign your clocksource a rating
34 * 1-99: Unfit for real use
35 * Only available for bootup and testing purposes.
36 * 100-199: Base level usability.
37 * Functional for real use, but not desired.
38 * 200-299: Good.
39 * A correct and usable clocksource.
40 * 300-399: Desired.
41 * A reasonably fast and accurate clocksource.
42 * 400-499: Perfect
43 * The ideal clocksource. A must-use where
44 * available.
45 * @read: returns a cycle value
46 * @mask: bitmask for two's complement
47 * subtraction of non 64 bit counters
48 * @mult: cycle to nanosecond multiplier
49 * @shift: cycle to nanosecond divisor (power of two)
50 * @flags: flags describing special properties
51 * @vread: vsyscall based read
52 * @resume: resume function for the clocksource, if necessary
53 * @cycle_interval: Used internally by timekeeping core, please ignore.
54 * @xtime_interval: Used internally by timekeeping core, please ignore.
55 */
56struct clocksource {
57 /*
58 * First part of structure is read mostly
59 */
60 char *name;
61 struct list_head list;
62 int rating;
63 cycle_t (*read)(void);
64 cycle_t mask;
65 u32 mult;
66 u32 shift;
67 unsigned long flags;
68 cycle_t (*vread)(void);
69 void (*resume)(void);
70#ifdef CONFIG_IA64
71 void *fsys_mmio; /* used by fsyscall asm code */
72#define CLKSRC_FSYS_MMIO_SET(mmio, addr) ((mmio) = (addr))
73#else
74#define CLKSRC_FSYS_MMIO_SET(mmio, addr) do { } while (0)
75#endif
76
77 /* timekeeping specific data, ignore */
78 cycle_t cycle_interval;
79 u64 xtime_interval;
80 /*
81 * Second part is written at each timer interrupt
82 * Keep it in a different cache line to dirty no
83 * more than one cache line.
84 */
85 cycle_t cycle_last ____cacheline_aligned_in_smp;
86 u64 xtime_nsec;
87 s64 error;
88
89#ifdef CONFIG_CLOCKSOURCE_WATCHDOG
90 /* Watchdog related data, used by the framework */
91 struct list_head wd_list;
92 cycle_t wd_last;
93#endif
94};
95
96/*
97 * Clock source flags bits::
98 */
99#define CLOCK_SOURCE_IS_CONTINUOUS 0x01
100#define CLOCK_SOURCE_MUST_VERIFY 0x02
101
102#define CLOCK_SOURCE_WATCHDOG 0x10
103#define CLOCK_SOURCE_VALID_FOR_HRES 0x20
104
105/* simplify initialization of mask field */
106#define CLOCKSOURCE_MASK(bits) (cycle_t)(bits<64 ? ((1ULL<<bits)-1) : -1)
107
108/**
109 * clocksource_khz2mult - calculates mult from khz and shift
110 * @khz: Clocksource frequency in KHz
111 * @shift_constant: Clocksource shift factor
112 *
113 * Helper functions that converts a khz counter frequency to a timsource
114 * multiplier, given the clocksource shift value
115 */
116static inline u32 clocksource_khz2mult(u32 khz, u32 shift_constant)
117{
118 /* khz = cyc/(Million ns)
119 * mult/2^shift = ns/cyc
120 * mult = ns/cyc * 2^shift
121 * mult = 1Million/khz * 2^shift
122 * mult = 1000000 * 2^shift / khz
123 * mult = (1000000<<shift) / khz
124 */
125 u64 tmp = ((u64)1000000) << shift_constant;
126
127 tmp += khz/2; /* round for do_div */
128 do_div(tmp, khz);
129
130 return (u32)tmp;
131}
132
133/**
134 * clocksource_hz2mult - calculates mult from hz and shift
135 * @hz: Clocksource frequency in Hz
136 * @shift_constant: Clocksource shift factor
137 *
138 * Helper functions that converts a hz counter
139 * frequency to a timsource multiplier, given the
140 * clocksource shift value
141 */
142static inline u32 clocksource_hz2mult(u32 hz, u32 shift_constant)
143{
144 /* hz = cyc/(Billion ns)
145 * mult/2^shift = ns/cyc
146 * mult = ns/cyc * 2^shift
147 * mult = 1Billion/hz * 2^shift
148 * mult = 1000000000 * 2^shift / hz
149 * mult = (1000000000<<shift) / hz
150 */
151 u64 tmp = ((u64)1000000000) << shift_constant;
152
153 tmp += hz/2; /* round for do_div */
154 do_div(tmp, hz);
155
156 return (u32)tmp;
157}
158
159/**
160 * clocksource_read: - Access the clocksource's current cycle value
161 * @cs: pointer to clocksource being read
162 *
163 * Uses the clocksource to return the current cycle_t value
164 */
165static inline cycle_t clocksource_read(struct clocksource *cs)
166{
167 return cs->read();
168}
169
170/**
171 * cyc2ns - converts clocksource cycles to nanoseconds
172 * @cs: Pointer to clocksource
173 * @cycles: Cycles
174 *
175 * Uses the clocksource and ntp ajdustment to convert cycle_ts to nanoseconds.
176 *
177 * XXX - This could use some mult_lxl_ll() asm optimization
178 */
179static inline s64 cyc2ns(struct clocksource *cs, cycle_t cycles)
180{
181 u64 ret = (u64)cycles;
182 ret = (ret * cs->mult) >> cs->shift;
183 return ret;
184}
185
186/**
187 * clocksource_calculate_interval - Calculates a clocksource interval struct
188 *
189 * @c: Pointer to clocksource.
190 * @length_nsec: Desired interval length in nanoseconds.
191 *
192 * Calculates a fixed cycle/nsec interval for a given clocksource/adjustment
193 * pair and interval request.
194 *
195 * Unless you're the timekeeping code, you should not be using this!
196 */
197static inline void clocksource_calculate_interval(struct clocksource *c,
198 unsigned long length_nsec)
199{
200 u64 tmp;
201
202 /* XXX - All of this could use a whole lot of optimization */
203 tmp = length_nsec;
204 tmp <<= c->shift;
205 tmp += c->mult/2;
206 do_div(tmp, c->mult);
207
208 c->cycle_interval = (cycle_t)tmp;
209 if (c->cycle_interval == 0)
210 c->cycle_interval = 1;
211
212 c->xtime_interval = (u64)c->cycle_interval * c->mult;
213}
214
215
216/* used to install a new clocksource */
217extern int clocksource_register(struct clocksource*);
218extern struct clocksource* clocksource_get_next(void);
219extern void clocksource_change_rating(struct clocksource *cs, int rating);
220extern void clocksource_resume(void);
221
222#ifdef CONFIG_GENERIC_TIME_VSYSCALL
223extern void update_vsyscall(struct timespec *ts, struct clocksource *c);
224#else
225static inline void update_vsyscall(struct timespec *ts, struct clocksource *c)
226{
227}
228#endif
229
230#endif /* _LINUX_CLOCKSOURCE_H */