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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 | |
21 | /* clocksource cycle base type */ |
22 | typedef u64 cycle_t; |
23 | struct clocksource; |
24 | |
25 | /** |
26 | * struct cyclecounter - hardware abstraction for a free running counter |
27 | * Provides completely state-free accessors to the underlying hardware. |
28 | * Depending on which hardware it reads, the cycle counter may wrap |
29 | * around quickly. Locking rules (if necessary) have to be defined |
30 | * by the implementor and user of specific instances of this API. |
31 | * |
32 | * @read: returns the current cycle value |
33 | * @mask: bitmask for two's complement |
34 | * subtraction of non 64 bit counters, |
35 | * see CLOCKSOURCE_MASK() helper macro |
36 | * @mult: cycle to nanosecond multiplier |
37 | * @shift: cycle to nanosecond divisor (power of two) |
38 | */ |
39 | struct cyclecounter { |
40 | cycle_t (*read)(const struct cyclecounter *cc); |
41 | cycle_t mask; |
42 | u32 mult; |
43 | u32 shift; |
44 | }; |
45 | |
46 | /** |
47 | * struct timecounter - layer above a %struct cyclecounter which counts nanoseconds |
48 | * Contains the state needed by timecounter_read() to detect |
49 | * cycle counter wrap around. Initialize with |
50 | * timecounter_init(). Also used to convert cycle counts into the |
51 | * corresponding nanosecond counts with timecounter_cyc2time(). Users |
52 | * of this code are responsible for initializing the underlying |
53 | * cycle counter hardware, locking issues and reading the time |
54 | * more often than the cycle counter wraps around. The nanosecond |
55 | * counter will only wrap around after ~585 years. |
56 | * |
57 | * @cc: the cycle counter used by this instance |
58 | * @cycle_last: most recent cycle counter value seen by |
59 | * timecounter_read() |
60 | * @nsec: continuously increasing count |
61 | */ |
62 | struct timecounter { |
63 | const struct cyclecounter *cc; |
64 | cycle_t cycle_last; |
65 | u64 nsec; |
66 | }; |
67 | |
68 | /** |
69 | * cyclecounter_cyc2ns - converts cycle counter cycles to nanoseconds |
70 | * @tc: Pointer to cycle counter. |
71 | * @cycles: Cycles |
72 | * |
73 | * XXX - This could use some mult_lxl_ll() asm optimization. Same code |
74 | * as in cyc2ns, but with unsigned result. |
75 | */ |
76 | static inline u64 cyclecounter_cyc2ns(const struct cyclecounter *cc, |
77 | cycle_t cycles) |
78 | { |
79 | u64 ret = (u64)cycles; |
80 | ret = (ret * cc->mult) >> cc->shift; |
81 | return ret; |
82 | } |
83 | |
84 | /** |
85 | * timecounter_init - initialize a time counter |
86 | * @tc: Pointer to time counter which is to be initialized/reset |
87 | * @cc: A cycle counter, ready to be used. |
88 | * @start_tstamp: Arbitrary initial time stamp. |
89 | * |
90 | * After this call the current cycle register (roughly) corresponds to |
91 | * the initial time stamp. Every call to timecounter_read() increments |
92 | * the time stamp counter by the number of elapsed nanoseconds. |
93 | */ |
94 | extern void timecounter_init(struct timecounter *tc, |
95 | const struct cyclecounter *cc, |
96 | u64 start_tstamp); |
97 | |
98 | /** |
99 | * timecounter_read - return nanoseconds elapsed since timecounter_init() |
100 | * plus the initial time stamp |
101 | * @tc: Pointer to time counter. |
102 | * |
103 | * In other words, keeps track of time since the same epoch as |
104 | * the function which generated the initial time stamp. |
105 | */ |
106 | extern u64 timecounter_read(struct timecounter *tc); |
107 | |
108 | /** |
109 | * timecounter_cyc2time - convert a cycle counter to same |
110 | * time base as values returned by |
111 | * timecounter_read() |
112 | * @tc: Pointer to time counter. |
113 | * @cycle: a value returned by tc->cc->read() |
114 | * |
115 | * Cycle counts that are converted correctly as long as they |
116 | * fall into the interval [-1/2 max cycle count, +1/2 max cycle count], |
117 | * with "max cycle count" == cs->mask+1. |
118 | * |
119 | * This allows conversion of cycle counter values which were generated |
120 | * in the past. |
121 | */ |
122 | extern u64 timecounter_cyc2time(struct timecounter *tc, |
123 | cycle_t cycle_tstamp); |
124 | |
125 | /** |
126 | * struct clocksource - hardware abstraction for a free running counter |
127 | * Provides mostly state-free accessors to the underlying hardware. |
128 | * This is the structure used for system time. |
129 | * |
130 | * @name: ptr to clocksource name |
131 | * @list: list head for registration |
132 | * @rating: rating value for selection (higher is better) |
133 | * To avoid rating inflation the following |
134 | * list should give you a guide as to how |
135 | * to assign your clocksource a rating |
136 | * 1-99: Unfit for real use |
137 | * Only available for bootup and testing purposes. |
138 | * 100-199: Base level usability. |
139 | * Functional for real use, but not desired. |
140 | * 200-299: Good. |
141 | * A correct and usable clocksource. |
142 | * 300-399: Desired. |
143 | * A reasonably fast and accurate clocksource. |
144 | * 400-499: Perfect |
145 | * The ideal clocksource. A must-use where |
146 | * available. |
147 | * @read: returns a cycle value, passes clocksource as argument |
148 | * @enable: optional function to enable the clocksource |
149 | * @disable: optional function to disable the clocksource |
150 | * @mask: bitmask for two's complement |
151 | * subtraction of non 64 bit counters |
152 | * @mult: cycle to nanosecond multiplier |
153 | * @shift: cycle to nanosecond divisor (power of two) |
154 | * @max_idle_ns: max idle time permitted by the clocksource (nsecs) |
155 | * @flags: flags describing special properties |
156 | * @vread: vsyscall based read |
157 | * @suspend: suspend function for the clocksource, if necessary |
158 | * @resume: resume function for the clocksource, if necessary |
159 | */ |
160 | struct clocksource { |
161 | /* |
162 | * First part of structure is read mostly |
163 | */ |
164 | char *name; |
165 | struct list_head list; |
166 | int rating; |
167 | cycle_t (*read)(struct clocksource *cs); |
168 | int (*enable)(struct clocksource *cs); |
169 | void (*disable)(struct clocksource *cs); |
170 | cycle_t mask; |
171 | u32 mult; |
172 | u32 shift; |
173 | u64 max_idle_ns; |
174 | unsigned long flags; |
175 | cycle_t (*vread)(void); |
176 | void (*suspend)(struct clocksource *cs); |
177 | void (*resume)(struct clocksource *cs); |
178 | #ifdef CONFIG_IA64 |
179 | void *fsys_mmio; /* used by fsyscall asm code */ |
180 | #define CLKSRC_FSYS_MMIO_SET(mmio, addr) ((mmio) = (addr)) |
181 | #else |
182 | #define CLKSRC_FSYS_MMIO_SET(mmio, addr) do { } while (0) |
183 | #endif |
184 | |
185 | /* |
186 | * Second part is written at each timer interrupt |
187 | * Keep it in a different cache line to dirty no |
188 | * more than one cache line. |
189 | */ |
190 | cycle_t cycle_last ____cacheline_aligned_in_smp; |
191 | |
192 | #ifdef CONFIG_CLOCKSOURCE_WATCHDOG |
193 | /* Watchdog related data, used by the framework */ |
194 | struct list_head wd_list; |
195 | cycle_t wd_last; |
196 | #endif |
197 | }; |
198 | |
199 | /* |
200 | * Clock source flags bits:: |
201 | */ |
202 | #define CLOCK_SOURCE_IS_CONTINUOUS 0x01 |
203 | #define CLOCK_SOURCE_MUST_VERIFY 0x02 |
204 | |
205 | #define CLOCK_SOURCE_WATCHDOG 0x10 |
206 | #define CLOCK_SOURCE_VALID_FOR_HRES 0x20 |
207 | #define CLOCK_SOURCE_UNSTABLE 0x40 |
208 | |
209 | /* simplify initialization of mask field */ |
210 | #define CLOCKSOURCE_MASK(bits) (cycle_t)((bits) < 64 ? ((1ULL<<(bits))-1) : -1) |
211 | |
212 | /** |
213 | * clocksource_khz2mult - calculates mult from khz and shift |
214 | * @khz: Clocksource frequency in KHz |
215 | * @shift_constant: Clocksource shift factor |
216 | * |
217 | * Helper functions that converts a khz counter frequency to a timsource |
218 | * multiplier, given the clocksource shift value |
219 | */ |
220 | static inline u32 clocksource_khz2mult(u32 khz, u32 shift_constant) |
221 | { |
222 | /* khz = cyc/(Million ns) |
223 | * mult/2^shift = ns/cyc |
224 | * mult = ns/cyc * 2^shift |
225 | * mult = 1Million/khz * 2^shift |
226 | * mult = 1000000 * 2^shift / khz |
227 | * mult = (1000000<<shift) / khz |
228 | */ |
229 | u64 tmp = ((u64)1000000) << shift_constant; |
230 | |
231 | tmp += khz/2; /* round for do_div */ |
232 | do_div(tmp, khz); |
233 | |
234 | return (u32)tmp; |
235 | } |
236 | |
237 | /** |
238 | * clocksource_hz2mult - calculates mult from hz and shift |
239 | * @hz: Clocksource frequency in Hz |
240 | * @shift_constant: Clocksource shift factor |
241 | * |
242 | * Helper functions that converts a hz counter |
243 | * frequency to a timsource multiplier, given the |
244 | * clocksource shift value |
245 | */ |
246 | static inline u32 clocksource_hz2mult(u32 hz, u32 shift_constant) |
247 | { |
248 | /* hz = cyc/(Billion ns) |
249 | * mult/2^shift = ns/cyc |
250 | * mult = ns/cyc * 2^shift |
251 | * mult = 1Billion/hz * 2^shift |
252 | * mult = 1000000000 * 2^shift / hz |
253 | * mult = (1000000000<<shift) / hz |
254 | */ |
255 | u64 tmp = ((u64)1000000000) << shift_constant; |
256 | |
257 | tmp += hz/2; /* round for do_div */ |
258 | do_div(tmp, hz); |
259 | |
260 | return (u32)tmp; |
261 | } |
262 | |
263 | /** |
264 | * clocksource_cyc2ns - converts clocksource cycles to nanoseconds |
265 | * |
266 | * Converts cycles to nanoseconds, using the given mult and shift. |
267 | * |
268 | * XXX - This could use some mult_lxl_ll() asm optimization |
269 | */ |
270 | static inline s64 clocksource_cyc2ns(cycle_t cycles, u32 mult, u32 shift) |
271 | { |
272 | return ((u64) cycles * mult) >> shift; |
273 | } |
274 | |
275 | |
276 | /* used to install a new clocksource */ |
277 | extern int clocksource_register(struct clocksource*); |
278 | extern void clocksource_unregister(struct clocksource*); |
279 | extern void clocksource_touch_watchdog(void); |
280 | extern struct clocksource* clocksource_get_next(void); |
281 | extern void clocksource_change_rating(struct clocksource *cs, int rating); |
282 | extern void clocksource_suspend(void); |
283 | extern void clocksource_resume(void); |
284 | extern struct clocksource * __init __weak clocksource_default_clock(void); |
285 | extern void clocksource_mark_unstable(struct clocksource *cs); |
286 | |
287 | extern void |
288 | clocks_calc_mult_shift(u32 *mult, u32 *shift, u32 from, u32 to, u32 minsec); |
289 | |
290 | static inline void |
291 | clocksource_calc_mult_shift(struct clocksource *cs, u32 freq, u32 minsec) |
292 | { |
293 | return clocks_calc_mult_shift(&cs->mult, &cs->shift, freq, |
294 | NSEC_PER_SEC, minsec); |
295 | } |
296 | |
297 | #ifdef CONFIG_GENERIC_TIME_VSYSCALL |
298 | extern void |
299 | update_vsyscall(struct timespec *ts, struct clocksource *c, u32 mult); |
300 | extern void update_vsyscall_tz(void); |
301 | #else |
302 | static inline void |
303 | update_vsyscall(struct timespec *ts, struct clocksource *c, u32 mult) |
304 | { |
305 | } |
306 | |
307 | static inline void update_vsyscall_tz(void) |
308 | { |
309 | } |
310 | #endif |
311 | |
312 | extern void timekeeping_notify(struct clocksource *clock); |
313 | |
314 | #endif /* _LINUX_CLOCKSOURCE_H */ |
315 |
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