1 /* linux/include/linux/clocksource.h
3 * This file contains the structure definitions for clocksources.
5 * If you are not a clocksource, or timekeeping code, you should
6 * not be including this file!
8 #ifndef _LINUX_CLOCKSOURCE_H
9 #define _LINUX_CLOCKSOURCE_H
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>
21 /* clocksource cycle base type */
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.
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)
40 cycle_t (*read)(const struct cyclecounter *cc);
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.
57 * @cc: the cycle counter used by this instance
58 * @cycle_last: most recent cycle counter value seen by
60 * @nsec: continuously increasing count
63 const struct cyclecounter *cc;
69 * cyclecounter_cyc2ns - converts cycle counter cycles to nanoseconds
70 * @tc: Pointer to cycle counter.
73 * XXX - This could use some mult_lxl_ll() asm optimization. Same code
74 * as in cyc2ns, but with unsigned result.
76 static inline u64 cyclecounter_cyc2ns(const struct cyclecounter *cc,
79 u64 ret = (u64)cycles;
80 ret = (ret * cc->mult) >> cc->shift;
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.
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.
94 extern void timecounter_init(struct timecounter *tc,
95 const struct cyclecounter *cc,
99 * timecounter_read - return nanoseconds elapsed since timecounter_init()
100 * plus the initial time stamp
101 * @tc: Pointer to time counter.
103 * In other words, keeps track of time since the same epoch as
104 * the function which generated the initial time stamp.
106 extern u64 timecounter_read(struct timecounter *tc);
109 * timecounter_cyc2time - convert a cycle counter to same
110 * time base as values returned by
112 * @tc: Pointer to time counter.
113 * @cycle: a value returned by tc->cc->read()
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.
119 * This allows conversion of cycle counter values which were generated
122 extern u64 timecounter_cyc2time(struct timecounter *tc,
123 cycle_t cycle_tstamp);
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.
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.
141 * A correct and usable clocksource.
143 * A reasonably fast and accurate clocksource.
145 * The ideal clocksource. A must-use where
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 (adjusted by NTP)
153 * @mult_orig: cycle to nanosecond multiplier (unadjusted by NTP)
154 * @shift: cycle to nanosecond divisor (power of two)
155 * @flags: flags describing special properties
156 * @vread: vsyscall based read
157 * @resume: resume function for the clocksource, if necessary
158 * @cycle_interval: Used internally by timekeeping core, please ignore.
159 * @xtime_interval: Used internally by timekeeping core, please ignore.
163 * First part of structure is read mostly
166 struct list_head list;
168 cycle_t (*read)(struct clocksource *cs);
169 int (*enable)(struct clocksource *cs);
170 void (*disable)(struct clocksource *cs);
176 cycle_t (*vread)(void);
177 void (*resume)(void);
179 void *fsys_mmio; /* used by fsyscall asm code */
180 #define CLKSRC_FSYS_MMIO_SET(mmio, addr) ((mmio) = (addr))
182 #define CLKSRC_FSYS_MMIO_SET(mmio, addr) do { } while (0)
185 /* timekeeping specific data, ignore */
186 cycle_t cycle_interval;
190 * Second part is written at each timer interrupt
191 * Keep it in a different cache line to dirty no
192 * more than one cache line.
194 cycle_t cycle_last ____cacheline_aligned_in_smp;
197 struct timespec raw_time;
199 #ifdef CONFIG_CLOCKSOURCE_WATCHDOG
200 /* Watchdog related data, used by the framework */
201 struct list_head wd_list;
206 extern struct clocksource *clock; /* current clocksource */
209 * Clock source flags bits::
211 #define CLOCK_SOURCE_IS_CONTINUOUS 0x01
212 #define CLOCK_SOURCE_MUST_VERIFY 0x02
214 #define CLOCK_SOURCE_WATCHDOG 0x10
215 #define CLOCK_SOURCE_VALID_FOR_HRES 0x20
217 /* simplify initialization of mask field */
218 #define CLOCKSOURCE_MASK(bits) (cycle_t)((bits) < 64 ? ((1ULL<<(bits))-1) : -1)
221 * clocksource_khz2mult - calculates mult from khz and shift
222 * @khz: Clocksource frequency in KHz
223 * @shift_constant: Clocksource shift factor
225 * Helper functions that converts a khz counter frequency to a timsource
226 * multiplier, given the clocksource shift value
228 static inline u32 clocksource_khz2mult(u32 khz, u32 shift_constant)
230 /* khz = cyc/(Million ns)
231 * mult/2^shift = ns/cyc
232 * mult = ns/cyc * 2^shift
233 * mult = 1Million/khz * 2^shift
234 * mult = 1000000 * 2^shift / khz
235 * mult = (1000000<<shift) / khz
237 u64 tmp = ((u64)1000000) << shift_constant;
239 tmp += khz/2; /* round for do_div */
246 * clocksource_hz2mult - calculates mult from hz and shift
247 * @hz: Clocksource frequency in Hz
248 * @shift_constant: Clocksource shift factor
250 * Helper functions that converts a hz counter
251 * frequency to a timsource multiplier, given the
252 * clocksource shift value
254 static inline u32 clocksource_hz2mult(u32 hz, u32 shift_constant)
256 /* hz = cyc/(Billion ns)
257 * mult/2^shift = ns/cyc
258 * mult = ns/cyc * 2^shift
259 * mult = 1Billion/hz * 2^shift
260 * mult = 1000000000 * 2^shift / hz
261 * mult = (1000000000<<shift) / hz
263 u64 tmp = ((u64)1000000000) << shift_constant;
265 tmp += hz/2; /* round for do_div */
272 * cyc2ns - converts clocksource cycles to nanoseconds
273 * @cs: Pointer to clocksource
276 * Uses the clocksource and ntp ajdustment to convert cycle_ts to nanoseconds.
278 * XXX - This could use some mult_lxl_ll() asm optimization
280 static inline s64 cyc2ns(struct clocksource *cs, cycle_t cycles)
282 u64 ret = (u64)cycles;
283 ret = (ret * cs->mult) >> cs->shift;
288 * clocksource_calculate_interval - Calculates a clocksource interval struct
290 * @c: Pointer to clocksource.
291 * @length_nsec: Desired interval length in nanoseconds.
293 * Calculates a fixed cycle/nsec interval for a given clocksource/adjustment
294 * pair and interval request.
296 * Unless you're the timekeeping code, you should not be using this!
298 static inline void clocksource_calculate_interval(struct clocksource *c,
299 unsigned long length_nsec)
303 /* Do the ns -> cycle conversion first, using original mult */
306 tmp += c->mult_orig/2;
307 do_div(tmp, c->mult_orig);
309 c->cycle_interval = (cycle_t)tmp;
310 if (c->cycle_interval == 0)
311 c->cycle_interval = 1;
313 /* Go back from cycles -> shifted ns, this time use ntp adjused mult */
314 c->xtime_interval = (u64)c->cycle_interval * c->mult;
315 c->raw_interval = ((u64)c->cycle_interval * c->mult_orig) >> c->shift;
319 /* used to install a new clocksource */
320 extern int clocksource_register(struct clocksource*);
321 extern void clocksource_unregister(struct clocksource*);
322 extern void clocksource_touch_watchdog(void);
323 extern struct clocksource* clocksource_get_next(void);
324 extern void clocksource_change_rating(struct clocksource *cs, int rating);
325 extern void clocksource_resume(void);
326 extern struct clocksource * __init __weak clocksource_default_clock(void);
328 #ifdef CONFIG_GENERIC_TIME_VSYSCALL
329 extern void update_vsyscall(struct timespec *ts, struct clocksource *c);
330 extern void update_vsyscall_tz(void);
332 static inline void update_vsyscall(struct timespec *ts, struct clocksource *c)
336 static inline void update_vsyscall_tz(void)
341 #endif /* _LINUX_CLOCKSOURCE_H */