projects/linux·blob v3.13 · refs

361 lines · 11.3 KiB

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 */
22typedef u64 cycle_t;
23struct clocksource;
24struct 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 */
44struct 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 */
67struct 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 */
81static 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 */
99extern 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 */
111extern 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 */
127extern 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 */
168struct 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 */
226static 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 */
252static 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 */
279static inline s64 clocksource_cyc2ns(cycle_t cycles, u32 mult, u32 shift)
280{
281 return ((u64) cycles * mult) >> shift;
282}
283
284
285extern int clocksource_register(struct clocksource*);
286extern int clocksource_unregister(struct clocksource*);
287extern void clocksource_touch_watchdog(void);
288extern struct clocksource* clocksource_get_next(void);
289extern void clocksource_change_rating(struct clocksource *cs, int rating);
290extern void clocksource_suspend(void);
291extern void clocksource_resume(void);
292extern struct clocksource * __init __weak clocksource_default_clock(void);
293extern void clocksource_mark_unstable(struct clocksource *cs);
294
295extern u64
296clocks_calc_max_nsecs(u32 mult, u32 shift, u32 maxadj, u64 mask);
297extern void
298clocks_calc_mult_shift(u32 *mult, u32 *shift, u32 from, u32 to, u32 minsec);
299
300/*
301 * Don't call __clocksource_register_scale directly, use
302 * clocksource_register_hz/khz
303 */
304extern int
305__clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq);
306extern void
307__clocksource_updatefreq_scale(struct clocksource *cs, u32 scale, u32 freq);
308
309static inline int clocksource_register_hz(struct clocksource *cs, u32 hz)
310{
311 return __clocksource_register_scale(cs, 1, hz);
312}
313
314static inline int clocksource_register_khz(struct clocksource *cs, u32 khz)
315{
316 return __clocksource_register_scale(cs, 1000, khz);
317}
318
319static inline void __clocksource_updatefreq_hz(struct clocksource *cs, u32 hz)
320{
321 __clocksource_updatefreq_scale(cs, 1, hz);
322}
323
324static inline void __clocksource_updatefreq_khz(struct clocksource *cs, u32 khz)
325{
326 __clocksource_updatefreq_scale(cs, 1000, khz);
327}
328
329
330extern int timekeeping_notify(struct clocksource *clock);
331
332extern cycle_t clocksource_mmio_readl_up(struct clocksource *);
333extern cycle_t clocksource_mmio_readl_down(struct clocksource *);
334extern cycle_t clocksource_mmio_readw_up(struct clocksource *);
335extern cycle_t clocksource_mmio_readw_down(struct clocksource *);
336
337extern int clocksource_mmio_init(void __iomem *, const char *,
338 unsigned long, int, unsigned, cycle_t (*)(struct clocksource *));
339
340extern int clocksource_i8253_init(void);
341
342struct device_node;
343typedef void(*clocksource_of_init_fn)(struct device_node *);
344#ifdef CONFIG_CLKSRC_OF
345extern void clocksource_of_init(void);
346
347#define CLOCKSOURCE_OF_DECLARE(name, compat, fn) \
348 static const struct of_device_id __clksrc_of_table_##name \
349 __used __section(__clksrc_of_table) \
350 = { .compatible = compat, \
351 .data = (fn == (clocksource_of_init_fn)NULL) ? fn : fn }
352#else
353static inline void clocksource_of_init(void) {}
354#define CLOCKSOURCE_OF_DECLARE(name, compat, fn) \
355 static const struct of_device_id __clksrc_of_table_##name \
356 __attribute__((unused)) \
357 = { .compatible = compat, \
358 .data = (fn == (clocksource_of_init_fn)NULL) ? fn : fn }
359#endif
360
361#endif /* _LINUX_CLOCKSOURCE_H */