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TOMOYO Linux Cross Reference
Linux/include/linux/clocksource.h

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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 #ifdef CONFIG_ARCH_CLOCKSOURCE_DATA
 26 #include <asm/clocksource.h>
 27 #endif
 28 
 29 /**
 30  * struct cyclecounter - hardware abstraction for a free running counter
 31  *      Provides completely state-free accessors to the underlying hardware.
 32  *      Depending on which hardware it reads, the cycle counter may wrap
 33  *      around quickly. Locking rules (if necessary) have to be defined
 34  *      by the implementor and user of specific instances of this API.
 35  *
 36  * @read:               returns the current cycle value
 37  * @mask:               bitmask for two's complement
 38  *                      subtraction of non 64 bit counters,
 39  *                      see CLOCKSOURCE_MASK() helper macro
 40  * @mult:               cycle to nanosecond multiplier
 41  * @shift:              cycle to nanosecond divisor (power of two)
 42  */
 43 struct cyclecounter {
 44         cycle_t (*read)(const struct cyclecounter *cc);
 45         cycle_t mask;
 46         u32 mult;
 47         u32 shift;
 48 };
 49 
 50 /**
 51  * struct timecounter - layer above a %struct cyclecounter which counts nanoseconds
 52  *      Contains the state needed by timecounter_read() to detect
 53  *      cycle counter wrap around. Initialize with
 54  *      timecounter_init(). Also used to convert cycle counts into the
 55  *      corresponding nanosecond counts with timecounter_cyc2time(). Users
 56  *      of this code are responsible for initializing the underlying
 57  *      cycle counter hardware, locking issues and reading the time
 58  *      more often than the cycle counter wraps around. The nanosecond
 59  *      counter will only wrap around after ~585 years.
 60  *
 61  * @cc:                 the cycle counter used by this instance
 62  * @cycle_last:         most recent cycle counter value seen by
 63  *                      timecounter_read()
 64  * @nsec:               continuously increasing count
 65  */
 66 struct timecounter {
 67         const struct cyclecounter *cc;
 68         cycle_t cycle_last;
 69         u64 nsec;
 70 };
 71 
 72 /**
 73  * cyclecounter_cyc2ns - converts cycle counter cycles to nanoseconds
 74  * @cc:         Pointer to cycle counter.
 75  * @cycles:     Cycles
 76  *
 77  * XXX - This could use some mult_lxl_ll() asm optimization. Same code
 78  * as in cyc2ns, but with unsigned result.
 79  */
 80 static inline u64 cyclecounter_cyc2ns(const struct cyclecounter *cc,
 81                                       cycle_t cycles)
 82 {
 83         u64 ret = (u64)cycles;
 84         ret = (ret * cc->mult) >> cc->shift;
 85         return ret;
 86 }
 87 
 88 /**
 89  * timecounter_init - initialize a time counter
 90  * @tc:                 Pointer to time counter which is to be initialized/reset
 91  * @cc:                 A cycle counter, ready to be used.
 92  * @start_tstamp:       Arbitrary initial time stamp.
 93  *
 94  * After this call the current cycle register (roughly) corresponds to
 95  * the initial time stamp. Every call to timecounter_read() increments
 96  * the time stamp counter by the number of elapsed nanoseconds.
 97  */
 98 extern void timecounter_init(struct timecounter *tc,
 99                              const struct cyclecounter *cc,
100                              u64 start_tstamp);
101 
102 /**
103  * timecounter_read - return nanoseconds elapsed since timecounter_init()
104  *                    plus the initial time stamp
105  * @tc:          Pointer to time counter.
106  *
107  * In other words, keeps track of time since the same epoch as
108  * the function which generated the initial time stamp.
109  */
110 extern u64 timecounter_read(struct timecounter *tc);
111 
112 /**
113  * timecounter_cyc2time - convert a cycle counter to same
114  *                        time base as values returned by
115  *                        timecounter_read()
116  * @tc:         Pointer to time counter.
117  * @cycle_tstamp:       a value returned by tc->cc->read()
118  *
119  * Cycle counts that are converted correctly as long as they
120  * fall into the interval [-1/2 max cycle count, +1/2 max cycle count],
121  * with "max cycle count" == cs->mask+1.
122  *
123  * This allows conversion of cycle counter values which were generated
124  * in the past.
125  */
126 extern u64 timecounter_cyc2time(struct timecounter *tc,
127                                 cycle_t cycle_tstamp);
128 
129 /**
130  * struct clocksource - hardware abstraction for a free running counter
131  *      Provides mostly state-free accessors to the underlying hardware.
132  *      This is the structure used for system time.
133  *
134  * @name:               ptr to clocksource name
135  * @list:               list head for registration
136  * @rating:             rating value for selection (higher is better)
137  *                      To avoid rating inflation the following
138  *                      list should give you a guide as to how
139  *                      to assign your clocksource a rating
140  *                      1-99: Unfit for real use
141  *                              Only available for bootup and testing purposes.
142  *                      100-199: Base level usability.
143  *                              Functional for real use, but not desired.
144  *                      200-299: Good.
145  *                              A correct and usable clocksource.
146  *                      300-399: Desired.
147  *                              A reasonably fast and accurate clocksource.
148  *                      400-499: Perfect
149  *                              The ideal clocksource. A must-use where
150  *                              available.
151  * @read:               returns a cycle value, passes clocksource as argument
152  * @enable:             optional function to enable the clocksource
153  * @disable:            optional function to disable the clocksource
154  * @mask:               bitmask for two's complement
155  *                      subtraction of non 64 bit counters
156  * @mult:               cycle to nanosecond multiplier
157  * @shift:              cycle to nanosecond divisor (power of two)
158  * @max_idle_ns:        max idle time permitted by the clocksource (nsecs)
159  * @maxadj:             maximum adjustment value to mult (~11%)
160  * @flags:              flags describing special properties
161  * @archdata:           arch-specific data
162  * @suspend:            suspend function for the clocksource, if necessary
163  * @resume:             resume function for the clocksource, if necessary
164  * @cycle_last:         most recent cycle counter value seen by ::read()
165  */
166 struct clocksource {
167         /*
168          * Hotpath data, fits in a single cache line when the
169          * clocksource itself is cacheline aligned.
170          */
171         cycle_t (*read)(struct clocksource *cs);
172         cycle_t cycle_last;
173         cycle_t mask;
174         u32 mult;
175         u32 shift;
176         u64 max_idle_ns;
177         u32 maxadj;
178 #ifdef CONFIG_ARCH_CLOCKSOURCE_DATA
179         struct arch_clocksource_data archdata;
180 #endif
181 
182         const char *name;
183         struct list_head list;
184         int rating;
185         int (*enable)(struct clocksource *cs);
186         void (*disable)(struct clocksource *cs);
187         unsigned long flags;
188         void (*suspend)(struct clocksource *cs);
189         void (*resume)(struct clocksource *cs);
190 
191         /* private: */
192 #ifdef CONFIG_CLOCKSOURCE_WATCHDOG
193         /* Watchdog related data, used by the framework */
194         struct list_head wd_list;
195         cycle_t cs_last;
196         cycle_t wd_last;
197 #endif
198 } ____cacheline_aligned;
199 
200 /*
201  * Clock source flags bits::
202  */
203 #define CLOCK_SOURCE_IS_CONTINUOUS              0x01
204 #define CLOCK_SOURCE_MUST_VERIFY                0x02
205 
206 #define CLOCK_SOURCE_WATCHDOG                   0x10
207 #define CLOCK_SOURCE_VALID_FOR_HRES             0x20
208 #define CLOCK_SOURCE_UNSTABLE                   0x40
209 
210 /* simplify initialization of mask field */
211 #define CLOCKSOURCE_MASK(bits) (cycle_t)((bits) < 64 ? ((1ULL<<(bits))-1) : -1)
212 
213 /**
214  * clocksource_khz2mult - calculates mult from khz and shift
215  * @khz:                Clocksource frequency in KHz
216  * @shift_constant:     Clocksource shift factor
217  *
218  * Helper functions that converts a khz counter frequency to a timsource
219  * multiplier, given the clocksource shift value
220  */
221 static inline u32 clocksource_khz2mult(u32 khz, u32 shift_constant)
222 {
223         /*  khz = cyc/(Million ns)
224          *  mult/2^shift  = ns/cyc
225          *  mult = ns/cyc * 2^shift
226          *  mult = 1Million/khz * 2^shift
227          *  mult = 1000000 * 2^shift / khz
228          *  mult = (1000000<<shift) / khz
229          */
230         u64 tmp = ((u64)1000000) << shift_constant;
231 
232         tmp += khz/2; /* round for do_div */
233         do_div(tmp, khz);
234 
235         return (u32)tmp;
236 }
237 
238 /**
239  * clocksource_hz2mult - calculates mult from hz and shift
240  * @hz:                 Clocksource frequency in Hz
241  * @shift_constant:     Clocksource shift factor
242  *
243  * Helper functions that converts a hz counter
244  * frequency to a timsource multiplier, given the
245  * clocksource shift value
246  */
247 static inline u32 clocksource_hz2mult(u32 hz, u32 shift_constant)
248 {
249         /*  hz = cyc/(Billion ns)
250          *  mult/2^shift  = ns/cyc
251          *  mult = ns/cyc * 2^shift
252          *  mult = 1Billion/hz * 2^shift
253          *  mult = 1000000000 * 2^shift / hz
254          *  mult = (1000000000<<shift) / hz
255          */
256         u64 tmp = ((u64)1000000000) << shift_constant;
257 
258         tmp += hz/2; /* round for do_div */
259         do_div(tmp, hz);
260 
261         return (u32)tmp;
262 }
263 
264 /**
265  * clocksource_cyc2ns - converts clocksource cycles to nanoseconds
266  * @cycles:     cycles
267  * @mult:       cycle to nanosecond multiplier
268  * @shift:      cycle to nanosecond divisor (power of two)
269  *
270  * Converts cycles to nanoseconds, using the given mult and shift.
271  *
272  * XXX - This could use some mult_lxl_ll() asm optimization
273  */
274 static inline s64 clocksource_cyc2ns(cycle_t cycles, u32 mult, u32 shift)
275 {
276         return ((u64) cycles * mult) >> shift;
277 }
278 
279 
280 extern int clocksource_register(struct clocksource*);
281 extern void clocksource_unregister(struct clocksource*);
282 extern void clocksource_touch_watchdog(void);
283 extern struct clocksource* clocksource_get_next(void);
284 extern void clocksource_change_rating(struct clocksource *cs, int rating);
285 extern void clocksource_suspend(void);
286 extern void clocksource_resume(void);
287 extern struct clocksource * __init __weak clocksource_default_clock(void);
288 extern void clocksource_mark_unstable(struct clocksource *cs);
289 
290 extern void
291 clocks_calc_mult_shift(u32 *mult, u32 *shift, u32 from, u32 to, u32 minsec);
292 
293 /*
294  * Don't call __clocksource_register_scale directly, use
295  * clocksource_register_hz/khz
296  */
297 extern int
298 __clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq);
299 extern void
300 __clocksource_updatefreq_scale(struct clocksource *cs, u32 scale, u32 freq);
301 
302 static inline int clocksource_register_hz(struct clocksource *cs, u32 hz)
303 {
304         return __clocksource_register_scale(cs, 1, hz);
305 }
306 
307 static inline int clocksource_register_khz(struct clocksource *cs, u32 khz)
308 {
309         return __clocksource_register_scale(cs, 1000, khz);
310 }
311 
312 static inline void __clocksource_updatefreq_hz(struct clocksource *cs, u32 hz)
313 {
314         __clocksource_updatefreq_scale(cs, 1, hz);
315 }
316 
317 static inline void __clocksource_updatefreq_khz(struct clocksource *cs, u32 khz)
318 {
319         __clocksource_updatefreq_scale(cs, 1000, khz);
320 }
321 
322 #ifdef CONFIG_GENERIC_TIME_VSYSCALL
323 extern void
324 update_vsyscall(struct timespec *ts, struct timespec *wtm,
325                         struct clocksource *c, u32 mult);
326 extern void update_vsyscall_tz(void);
327 #else
328 static inline void
329 update_vsyscall(struct timespec *ts, struct timespec *wtm,
330                         struct clocksource *c, u32 mult)
331 {
332 }
333 
334 static inline void update_vsyscall_tz(void)
335 {
336 }
337 #endif
338 
339 extern void timekeeping_notify(struct clocksource *clock);
340 
341 extern cycle_t clocksource_mmio_readl_up(struct clocksource *);
342 extern cycle_t clocksource_mmio_readl_down(struct clocksource *);
343 extern cycle_t clocksource_mmio_readw_up(struct clocksource *);
344 extern cycle_t clocksource_mmio_readw_down(struct clocksource *);
345 
346 extern int clocksource_mmio_init(void __iomem *, const char *,
347         unsigned long, int, unsigned, cycle_t (*)(struct clocksource *));
348 
349 extern int clocksource_i8253_init(void);
350 
351 #endif /* _LINUX_CLOCKSOURCE_H */
352 

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