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734efb46 | 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> | |
329c8d84 | 15 | #include <linux/cache.h> |
5d8b34fd | 16 | #include <linux/timer.h> |
f1b82746 | 17 | #include <linux/init.h> |
734efb46 | 18 | #include <asm/div64.h> |
19 | #include <asm/io.h> | |
20 | ||
21 | /* clocksource cycle base type */ | |
22 | typedef u64 cycle_t; | |
5d8b34fd | 23 | struct clocksource; |
734efb46 | 24 | |
a038a353 PO |
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 | ||
734efb46 | 125 | /** |
126 | * struct clocksource - hardware abstraction for a free running counter | |
127 | * Provides mostly state-free accessors to the underlying hardware. | |
a038a353 | 128 | * This is the structure used for system time. |
734efb46 | 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. | |
8e19608e | 147 | * @read: returns a cycle value, passes clocksource as argument |
4614e6ad MD |
148 | * @enable: optional function to enable the clocksource |
149 | * @disable: optional function to disable the clocksource | |
734efb46 | 150 | * @mask: bitmask for two's complement |
151 | * subtraction of non 64 bit counters | |
0a544198 | 152 | * @mult: cycle to nanosecond multiplier |
734efb46 | 153 | * @shift: cycle to nanosecond divisor (power of two) |
73b08d2a | 154 | * @flags: flags describing special properties |
acc9a9dc | 155 | * @vread: vsyscall based read |
b52f52a0 | 156 | * @resume: resume function for the clocksource, if necessary |
734efb46 | 157 | */ |
158 | struct clocksource { | |
329c8d84 ED |
159 | /* |
160 | * First part of structure is read mostly | |
161 | */ | |
734efb46 | 162 | char *name; |
163 | struct list_head list; | |
164 | int rating; | |
8e19608e | 165 | cycle_t (*read)(struct clocksource *cs); |
4614e6ad MD |
166 | int (*enable)(struct clocksource *cs); |
167 | void (*disable)(struct clocksource *cs); | |
734efb46 | 168 | cycle_t mask; |
169 | u32 mult; | |
170 | u32 shift; | |
73b08d2a | 171 | unsigned long flags; |
acc9a9dc | 172 | cycle_t (*vread)(void); |
b52f52a0 | 173 | void (*resume)(void); |
0aa366f3 TL |
174 | #ifdef CONFIG_IA64 |
175 | void *fsys_mmio; /* used by fsyscall asm code */ | |
176 | #define CLKSRC_FSYS_MMIO_SET(mmio, addr) ((mmio) = (addr)) | |
177 | #else | |
178 | #define CLKSRC_FSYS_MMIO_SET(mmio, addr) do { } while (0) | |
179 | #endif | |
734efb46 | 180 | |
329c8d84 ED |
181 | /* |
182 | * Second part is written at each timer interrupt | |
183 | * Keep it in a different cache line to dirty no | |
184 | * more than one cache line. | |
185 | */ | |
186 | cycle_t cycle_last ____cacheline_aligned_in_smp; | |
5d8b34fd TG |
187 | |
188 | #ifdef CONFIG_CLOCKSOURCE_WATCHDOG | |
189 | /* Watchdog related data, used by the framework */ | |
190 | struct list_head wd_list; | |
191 | cycle_t wd_last; | |
192 | #endif | |
734efb46 | 193 | }; |
194 | ||
73b08d2a TG |
195 | /* |
196 | * Clock source flags bits:: | |
197 | */ | |
5d8b34fd TG |
198 | #define CLOCK_SOURCE_IS_CONTINUOUS 0x01 |
199 | #define CLOCK_SOURCE_MUST_VERIFY 0x02 | |
200 | ||
201 | #define CLOCK_SOURCE_WATCHDOG 0x10 | |
202 | #define CLOCK_SOURCE_VALID_FOR_HRES 0x20 | |
c55c87c8 | 203 | #define CLOCK_SOURCE_UNSTABLE 0x40 |
73b08d2a | 204 | |
7f9f303a | 205 | /* simplify initialization of mask field */ |
1d76c262 | 206 | #define CLOCKSOURCE_MASK(bits) (cycle_t)((bits) < 64 ? ((1ULL<<(bits))-1) : -1) |
734efb46 | 207 | |
208 | /** | |
209 | * clocksource_khz2mult - calculates mult from khz and shift | |
210 | * @khz: Clocksource frequency in KHz | |
211 | * @shift_constant: Clocksource shift factor | |
212 | * | |
213 | * Helper functions that converts a khz counter frequency to a timsource | |
214 | * multiplier, given the clocksource shift value | |
215 | */ | |
216 | static inline u32 clocksource_khz2mult(u32 khz, u32 shift_constant) | |
217 | { | |
218 | /* khz = cyc/(Million ns) | |
219 | * mult/2^shift = ns/cyc | |
220 | * mult = ns/cyc * 2^shift | |
221 | * mult = 1Million/khz * 2^shift | |
222 | * mult = 1000000 * 2^shift / khz | |
223 | * mult = (1000000<<shift) / khz | |
224 | */ | |
225 | u64 tmp = ((u64)1000000) << shift_constant; | |
226 | ||
227 | tmp += khz/2; /* round for do_div */ | |
228 | do_div(tmp, khz); | |
229 | ||
230 | return (u32)tmp; | |
231 | } | |
232 | ||
233 | /** | |
234 | * clocksource_hz2mult - calculates mult from hz and shift | |
235 | * @hz: Clocksource frequency in Hz | |
236 | * @shift_constant: Clocksource shift factor | |
237 | * | |
238 | * Helper functions that converts a hz counter | |
239 | * frequency to a timsource multiplier, given the | |
240 | * clocksource shift value | |
241 | */ | |
242 | static inline u32 clocksource_hz2mult(u32 hz, u32 shift_constant) | |
243 | { | |
244 | /* hz = cyc/(Billion ns) | |
245 | * mult/2^shift = ns/cyc | |
246 | * mult = ns/cyc * 2^shift | |
247 | * mult = 1Billion/hz * 2^shift | |
248 | * mult = 1000000000 * 2^shift / hz | |
249 | * mult = (1000000000<<shift) / hz | |
250 | */ | |
251 | u64 tmp = ((u64)1000000000) << shift_constant; | |
252 | ||
253 | tmp += hz/2; /* round for do_div */ | |
254 | do_div(tmp, hz); | |
255 | ||
256 | return (u32)tmp; | |
257 | } | |
258 | ||
734efb46 | 259 | /** |
155ec602 | 260 | * clocksource_cyc2ns - converts clocksource cycles to nanoseconds |
734efb46 | 261 | * |
155ec602 | 262 | * Converts cycles to nanoseconds, using the given mult and shift. |
734efb46 | 263 | * |
264 | * XXX - This could use some mult_lxl_ll() asm optimization | |
265 | */ | |
155ec602 | 266 | static inline s64 clocksource_cyc2ns(cycle_t cycles, u32 mult, u32 shift) |
734efb46 | 267 | { |
155ec602 | 268 | return ((u64) cycles * mult) >> shift; |
5eb6d205 | 269 | } |
270 | ||
271 | ||
734efb46 | 272 | /* used to install a new clocksource */ |
92c7e002 | 273 | extern int clocksource_register(struct clocksource*); |
4713e22c | 274 | extern void clocksource_unregister(struct clocksource*); |
7c3078b6 | 275 | extern void clocksource_touch_watchdog(void); |
92c7e002 TG |
276 | extern struct clocksource* clocksource_get_next(void); |
277 | extern void clocksource_change_rating(struct clocksource *cs, int rating); | |
b52f52a0 | 278 | extern void clocksource_resume(void); |
f1b82746 | 279 | extern struct clocksource * __init __weak clocksource_default_clock(void); |
7285dd7f | 280 | extern void clocksource_mark_unstable(struct clocksource *cs); |
734efb46 | 281 | |
acc9a9dc | 282 | #ifdef CONFIG_GENERIC_TIME_VSYSCALL |
0696b711 LM |
283 | extern void |
284 | update_vsyscall(struct timespec *ts, struct clocksource *c, u32 mult); | |
2c622148 | 285 | extern void update_vsyscall_tz(void); |
acc9a9dc | 286 | #else |
0696b711 LM |
287 | static inline void |
288 | update_vsyscall(struct timespec *ts, struct clocksource *c, u32 mult) | |
acc9a9dc | 289 | { |
290 | } | |
2c622148 TB |
291 | |
292 | static inline void update_vsyscall_tz(void) | |
293 | { | |
294 | } | |
acc9a9dc | 295 | #endif |
296 | ||
75c5158f MS |
297 | extern void timekeeping_notify(struct clocksource *clock); |
298 | ||
734efb46 | 299 | #endif /* _LINUX_CLOCKSOURCE_H */ |