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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 struct module;
 25 
 26 #ifdef CONFIG_ARCH_CLOCKSOURCE_DATA
 27 #include <asm/clocksource.h>
 28 #endif
 29 
 30 /**
 31  * struct cyclecounter - hardware abstraction for a free running counter
 32  *      Provides completely state-free accessors to the underlying hardware.
 33  *      Depending on which hardware it reads, the cycle counter may wrap
 34  *      around quickly. Locking rules (if necessary) have to be defined
 35  *      by the implementor and user of specific instances of this API.
 36  *
 37  * @read:               returns the current cycle value
 38  * @mask:               bitmask for two's complement
 39  *                      subtraction of non 64 bit counters,
 40  *                      see CLOCKSOURCE_MASK() helper macro
 41  * @mult:               cycle to nanosecond multiplier
 42  * @shift:              cycle to nanosecond divisor (power of two)
 43  */
 44 struct cyclecounter {
 45         cycle_t (*read)(const struct cyclecounter *cc);
 46         cycle_t mask;
 47         u32 mult;
 48         u32 shift;
 49 };
 50 
 51 /**
 52  * struct timecounter - layer above a %struct cyclecounter which counts nanoseconds
 53  *      Contains the state needed by timecounter_read() to detect
 54  *      cycle counter wrap around. Initialize with
 55  *      timecounter_init(). Also used to convert cycle counts into the
 56  *      corresponding nanosecond counts with timecounter_cyc2time(). Users
 57  *      of this code are responsible for initializing the underlying
 58  *      cycle counter hardware, locking issues and reading the time
 59  *      more often than the cycle counter wraps around. The nanosecond
 60  *      counter will only wrap around after ~585 years.
 61  *
 62  * @cc:                 the cycle counter used by this instance
 63  * @cycle_last:         most recent cycle counter value seen by
 64  *                      timecounter_read()
 65  * @nsec:               continuously increasing count
 66  */
 67 struct timecounter {
 68         const struct cyclecounter *cc;
 69         cycle_t cycle_last;
 70         u64 nsec;
 71 };
 72 
 73 /**
 74  * cyclecounter_cyc2ns - converts cycle counter cycles to nanoseconds
 75  * @cc:         Pointer to cycle counter.
 76  * @cycles:     Cycles
 77  *
 78  * XXX - This could use some mult_lxl_ll() asm optimization. Same code
 79  * as in cyc2ns, but with unsigned result.
 80  */
 81 static inline u64 cyclecounter_cyc2ns(const struct cyclecounter *cc,
 82                                       cycle_t cycles)
 83 {
 84         u64 ret = (u64)cycles;
 85         ret = (ret * cc->mult) >> cc->shift;
 86         return ret;
 87 }
 88 
 89 /**
 90  * timecounter_init - initialize a time counter
 91  * @tc:                 Pointer to time counter which is to be initialized/reset
 92  * @cc:                 A cycle counter, ready to be used.
 93  * @start_tstamp:       Arbitrary initial time stamp.
 94  *
 95  * After this call the current cycle register (roughly) corresponds to
 96  * the initial time stamp. Every call to timecounter_read() increments
 97  * the time stamp counter by the number of elapsed nanoseconds.
 98  */
 99 extern void timecounter_init(struct timecounter *tc,
100                              const struct cyclecounter *cc,
101                              u64 start_tstamp);
102 
103 /**
104  * timecounter_read - return nanoseconds elapsed since timecounter_init()
105  *                    plus the initial time stamp
106  * @tc:          Pointer to time counter.
107  *
108  * In other words, keeps track of time since the same epoch as
109  * the function which generated the initial time stamp.
110  */
111 extern u64 timecounter_read(struct timecounter *tc);
112 
113 /**
114  * timecounter_cyc2time - convert a cycle counter to same
115  *                        time base as values returned by
116  *                        timecounter_read()
117  * @tc:         Pointer to time counter.
118  * @cycle_tstamp:       a value returned by tc->cc->read()
119  *
120  * Cycle counts that are converted correctly as long as they
121  * fall into the interval [-1/2 max cycle count, +1/2 max cycle count],
122  * with "max cycle count" == cs->mask+1.
123  *
124  * This allows conversion of cycle counter values which were generated
125  * in the past.
126  */
127 extern u64 timecounter_cyc2time(struct timecounter *tc,
128                                 cycle_t cycle_tstamp);
129 
130 /**
131  * struct clocksource - hardware abstraction for a free running counter
132  *      Provides mostly state-free accessors to the underlying hardware.
133  *      This is the structure used for system time.
134  *
135  * @name:               ptr to clocksource name
136  * @list:               list head for registration
137  * @rating:             rating value for selection (higher is better)
138  *                      To avoid rating inflation the following
139  *                      list should give you a guide as to how
140  *                      to assign your clocksource a rating
141  *                      1-99: Unfit for real use
142  *                              Only available for bootup and testing purposes.
143  *                      100-199: Base level usability.
144  *                              Functional for real use, but not desired.
145  *                      200-299: Good.
146  *                              A correct and usable clocksource.
147  *                      300-399: Desired.
148  *                              A reasonably fast and accurate clocksource.
149  *                      400-499: Perfect
150  *                              The ideal clocksource. A must-use where
151  *                              available.
152  * @read:               returns a cycle value, passes clocksource as argument
153  * @enable:             optional function to enable the clocksource
154  * @disable:            optional function to disable the clocksource
155  * @mask:               bitmask for two's complement
156  *                      subtraction of non 64 bit counters
157  * @mult:               cycle to nanosecond multiplier
158  * @shift:              cycle to nanosecond divisor (power of two)
159  * @max_idle_ns:        max idle time permitted by the clocksource (nsecs)
160  * @maxadj:             maximum adjustment value to mult (~11%)
161  * @flags:              flags describing special properties
162  * @archdata:           arch-specific data
163  * @suspend:            suspend function for the clocksource, if necessary
164  * @resume:             resume function for the clocksource, if necessary
165  * @cycle_last:         most recent cycle counter value seen by ::read()
166  * @owner:              module reference, must be set by clocksource in modules
167  */
168 struct clocksource {
169         /*
170          * Hotpath data, fits in a single cache line when the
171          * clocksource itself is cacheline aligned.
172          */
173         cycle_t (*read)(struct clocksource *cs);
174         cycle_t cycle_last;
175         cycle_t mask;
176         u32 mult;
177         u32 shift;
178         u64 max_idle_ns;
179         u32 maxadj;
180 #ifdef CONFIG_ARCH_CLOCKSOURCE_DATA
181         struct arch_clocksource_data archdata;
182 #endif
183 
184         const char *name;
185         struct list_head list;
186         int rating;
187         int (*enable)(struct clocksource *cs);
188         void (*disable)(struct clocksource *cs);
189         unsigned long flags;
190         void (*suspend)(struct clocksource *cs);
191         void (*resume)(struct clocksource *cs);
192 
193         /* private: */
194 #ifdef CONFIG_CLOCKSOURCE_WATCHDOG
195         /* Watchdog related data, used by the framework */
196         struct list_head wd_list;
197         cycle_t cs_last;
198         cycle_t wd_last;
199 #endif
200         struct module *owner;
201 } ____cacheline_aligned;
202 
203 /*
204  * Clock source flags bits::
205  */
206 #define CLOCK_SOURCE_IS_CONTINUOUS              0x01
207 #define CLOCK_SOURCE_MUST_VERIFY                0x02
208 
209 #define CLOCK_SOURCE_WATCHDOG                   0x10
210 #define CLOCK_SOURCE_VALID_FOR_HRES             0x20
211 #define CLOCK_SOURCE_UNSTABLE                   0x40
212 #define CLOCK_SOURCE_SUSPEND_NONSTOP            0x80
213 #define CLOCK_SOURCE_RESELECT                   0x100
214 
215 /* simplify initialization of mask field */
216 #define CLOCKSOURCE_MASK(bits) (cycle_t)((bits) < 64 ? ((1ULL<<(bits))-1) : -1)
217 
218 /**
219  * clocksource_khz2mult - calculates mult from khz and shift
220  * @khz:                Clocksource frequency in KHz
221  * @shift_constant:     Clocksource shift factor
222  *
223  * Helper functions that converts a khz counter frequency to a timsource
224  * multiplier, given the clocksource shift value
225  */
226 static inline u32 clocksource_khz2mult(u32 khz, u32 shift_constant)
227 {
228         /*  khz = cyc/(Million ns)
229          *  mult/2^shift  = ns/cyc
230          *  mult = ns/cyc * 2^shift
231          *  mult = 1Million/khz * 2^shift
232          *  mult = 1000000 * 2^shift / khz
233          *  mult = (1000000<<shift) / khz
234          */
235         u64 tmp = ((u64)1000000) << shift_constant;
236 
237         tmp += khz/2; /* round for do_div */
238         do_div(tmp, khz);
239 
240         return (u32)tmp;
241 }
242 
243 /**
244  * clocksource_hz2mult - calculates mult from hz and shift
245  * @hz:                 Clocksource frequency in Hz
246  * @shift_constant:     Clocksource shift factor
247  *
248  * Helper functions that converts a hz counter
249  * frequency to a timsource multiplier, given the
250  * clocksource shift value
251  */
252 static inline u32 clocksource_hz2mult(u32 hz, u32 shift_constant)
253 {
254         /*  hz = cyc/(Billion ns)
255          *  mult/2^shift  = ns/cyc
256          *  mult = ns/cyc * 2^shift
257          *  mult = 1Billion/hz * 2^shift
258          *  mult = 1000000000 * 2^shift / hz
259          *  mult = (1000000000<<shift) / hz
260          */
261         u64 tmp = ((u64)1000000000) << shift_constant;
262 
263         tmp += hz/2; /* round for do_div */
264         do_div(tmp, hz);
265 
266         return (u32)tmp;
267 }
268 
269 /**
270  * clocksource_cyc2ns - converts clocksource cycles to nanoseconds
271  * @cycles:     cycles
272  * @mult:       cycle to nanosecond multiplier
273  * @shift:      cycle to nanosecond divisor (power of two)
274  *
275  * Converts cycles to nanoseconds, using the given mult and shift.
276  *
277  * XXX - This could use some mult_lxl_ll() asm optimization
278  */
279 static inline s64 clocksource_cyc2ns(cycle_t cycles, u32 mult, u32 shift)
280 {
281         return ((u64) cycles * mult) >> shift;
282 }
283 
284 
285 extern int clocksource_register(struct clocksource*);
286 extern int clocksource_unregister(struct clocksource*);
287 extern void clocksource_touch_watchdog(void);
288 extern struct clocksource* clocksource_get_next(void);
289 extern void clocksource_change_rating(struct clocksource *cs, int rating);
290 extern void clocksource_suspend(void);
291 extern void clocksource_resume(void);
292 extern struct clocksource * __init __weak clocksource_default_clock(void);
293 extern void clocksource_mark_unstable(struct clocksource *cs);
294 
295 extern void
296 clocks_calc_mult_shift(u32 *mult, u32 *shift, u32 from, u32 to, u32 minsec);
297 
298 /*
299  * Don't call __clocksource_register_scale directly, use
300  * clocksource_register_hz/khz
301  */
302 extern int
303 __clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq);
304 extern void
305 __clocksource_updatefreq_scale(struct clocksource *cs, u32 scale, u32 freq);
306 
307 static inline int clocksource_register_hz(struct clocksource *cs, u32 hz)
308 {
309         return __clocksource_register_scale(cs, 1, hz);
310 }
311 
312 static inline int clocksource_register_khz(struct clocksource *cs, u32 khz)
313 {
314         return __clocksource_register_scale(cs, 1000, khz);
315 }
316 
317 static inline void __clocksource_updatefreq_hz(struct clocksource *cs, u32 hz)
318 {
319         __clocksource_updatefreq_scale(cs, 1, hz);
320 }
321 
322 static inline void __clocksource_updatefreq_khz(struct clocksource *cs, u32 khz)
323 {
324         __clocksource_updatefreq_scale(cs, 1000, khz);
325 }
326 
327 
328 extern int timekeeping_notify(struct clocksource *clock);
329 
330 extern cycle_t clocksource_mmio_readl_up(struct clocksource *);
331 extern cycle_t clocksource_mmio_readl_down(struct clocksource *);
332 extern cycle_t clocksource_mmio_readw_up(struct clocksource *);
333 extern cycle_t clocksource_mmio_readw_down(struct clocksource *);
334 
335 extern int clocksource_mmio_init(void __iomem *, const char *,
336         unsigned long, int, unsigned, cycle_t (*)(struct clocksource *));
337 
338 extern int clocksource_i8253_init(void);
339 
340 struct device_node;
341 typedef void(*clocksource_of_init_fn)(struct device_node *);
342 #ifdef CONFIG_CLKSRC_OF
343 extern void clocksource_of_init(void);
344 
345 #define CLOCKSOURCE_OF_DECLARE(name, compat, fn)                        \
346         static const struct of_device_id __clksrc_of_table_##name       \
347                 __used __section(__clksrc_of_table)                     \
348                  = { .compatible = compat,                              \
349                      .data = (fn == (clocksource_of_init_fn)NULL) ? fn : fn }
350 #else
351 static inline void clocksource_of_init(void) {}
352 #define CLOCKSOURCE_OF_DECLARE(name, compat, fn)                        \
353         static const struct of_device_id __clksrc_of_table_##name       \
354                 __attribute__((unused))                                 \
355                  = { .compatible = compat,                              \
356                      .data = (fn == (clocksource_of_init_fn)NULL) ? fn : fn }
357 #endif
358 
359 #endif /* _LINUX_CLOCKSOURCE_H */
360 

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