Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
tjh.dev
kernel
os
linux
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;
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 */
43struct 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 */
66struct 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 * @tc: 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 */
80static 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 */
98extern 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 */
110extern 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: 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 */
126extern 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 */
165struct clocksource {
166 /*
167 * Hotpath data, fits in a single cache line when the
168 * clocksource itself is cacheline aligned.
169 */
170 cycle_t (*read)(struct clocksource *cs);
171 cycle_t cycle_last;
172 cycle_t mask;
173 u32 mult;
174 u32 shift;
175 u64 max_idle_ns;
176 u32 maxadj;
177#ifdef CONFIG_ARCH_CLOCKSOURCE_DATA
178 struct arch_clocksource_data archdata;
179#endif
180
181 const char *name;
182 struct list_head list;
183 int rating;
184 int (*enable)(struct clocksource *cs);
185 void (*disable)(struct clocksource *cs);
186 unsigned long flags;
187 void (*suspend)(struct clocksource *cs);
188 void (*resume)(struct clocksource *cs);
189
190#ifdef CONFIG_CLOCKSOURCE_WATCHDOG
191 /* Watchdog related data, used by the framework */
192 struct list_head wd_list;
193 cycle_t cs_last;
194 cycle_t wd_last;
195#endif
196} ____cacheline_aligned;
197
198/*
199 * Clock source flags bits::
200 */
201#define CLOCK_SOURCE_IS_CONTINUOUS 0x01
202#define CLOCK_SOURCE_MUST_VERIFY 0x02
203
204#define CLOCK_SOURCE_WATCHDOG 0x10
205#define CLOCK_SOURCE_VALID_FOR_HRES 0x20
206#define CLOCK_SOURCE_UNSTABLE 0x40
207
208/* simplify initialization of mask field */
209#define CLOCKSOURCE_MASK(bits) (cycle_t)((bits) < 64 ? ((1ULL<<(bits))-1) : -1)
210
211/**
212 * clocksource_khz2mult - calculates mult from khz and shift
213 * @khz: Clocksource frequency in KHz
214 * @shift_constant: Clocksource shift factor
215 *
216 * Helper functions that converts a khz counter frequency to a timsource
217 * multiplier, given the clocksource shift value
218 */
219static inline u32 clocksource_khz2mult(u32 khz, u32 shift_constant)
220{
221 /* khz = cyc/(Million ns)
222 * mult/2^shift = ns/cyc
223 * mult = ns/cyc * 2^shift
224 * mult = 1Million/khz * 2^shift
225 * mult = 1000000 * 2^shift / khz
226 * mult = (1000000<<shift) / khz
227 */
228 u64 tmp = ((u64)1000000) << shift_constant;
229
230 tmp += khz/2; /* round for do_div */
231 do_div(tmp, khz);
232
233 return (u32)tmp;
234}
235
236/**
237 * clocksource_hz2mult - calculates mult from hz and shift
238 * @hz: Clocksource frequency in Hz
239 * @shift_constant: Clocksource shift factor
240 *
241 * Helper functions that converts a hz counter
242 * frequency to a timsource multiplier, given the
243 * clocksource shift value
244 */
245static inline u32 clocksource_hz2mult(u32 hz, u32 shift_constant)
246{
247 /* hz = cyc/(Billion ns)
248 * mult/2^shift = ns/cyc
249 * mult = ns/cyc * 2^shift
250 * mult = 1Billion/hz * 2^shift
251 * mult = 1000000000 * 2^shift / hz
252 * mult = (1000000000<<shift) / hz
253 */
254 u64 tmp = ((u64)1000000000) << shift_constant;
255
256 tmp += hz/2; /* round for do_div */
257 do_div(tmp, hz);
258
259 return (u32)tmp;
260}
261
262/**
263 * clocksource_cyc2ns - converts clocksource cycles to nanoseconds
264 *
265 * Converts cycles to nanoseconds, using the given mult and shift.
266 *
267 * XXX - This could use some mult_lxl_ll() asm optimization
268 */
269static inline s64 clocksource_cyc2ns(cycle_t cycles, u32 mult, u32 shift)
270{
271 return ((u64) cycles * mult) >> shift;
272}
273
274
275extern int clocksource_register(struct clocksource*);
276extern void clocksource_unregister(struct clocksource*);
277extern void clocksource_touch_watchdog(void);
278extern struct clocksource* clocksource_get_next(void);
279extern void clocksource_change_rating(struct clocksource *cs, int rating);
280extern void clocksource_suspend(void);
281extern void clocksource_resume(void);
282extern struct clocksource * __init __weak clocksource_default_clock(void);
283extern void clocksource_mark_unstable(struct clocksource *cs);
284
285extern void
286clocks_calc_mult_shift(u32 *mult, u32 *shift, u32 from, u32 to, u32 minsec);
287
288/*
289 * Don't call __clocksource_register_scale directly, use
290 * clocksource_register_hz/khz
291 */
292extern int
293__clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq);
294extern void
295__clocksource_updatefreq_scale(struct clocksource *cs, u32 scale, u32 freq);
296
297static inline int clocksource_register_hz(struct clocksource *cs, u32 hz)
298{
299 return __clocksource_register_scale(cs, 1, hz);
300}
301
302static inline int clocksource_register_khz(struct clocksource *cs, u32 khz)
303{
304 return __clocksource_register_scale(cs, 1000, khz);
305}
306
307static inline void __clocksource_updatefreq_hz(struct clocksource *cs, u32 hz)
308{
309 __clocksource_updatefreq_scale(cs, 1, hz);
310}
311
312static inline void __clocksource_updatefreq_khz(struct clocksource *cs, u32 khz)
313{
314 __clocksource_updatefreq_scale(cs, 1000, khz);
315}
316
317static inline void
318clocksource_calc_mult_shift(struct clocksource *cs, u32 freq, u32 minsec)
319{
320 return clocks_calc_mult_shift(&cs->mult, &cs->shift, freq,
321 NSEC_PER_SEC, minsec);
322}
323
324#ifdef CONFIG_GENERIC_TIME_VSYSCALL
325extern void
326update_vsyscall(struct timespec *ts, struct timespec *wtm,
327 struct clocksource *c, u32 mult);
328extern void update_vsyscall_tz(void);
329#else
330static inline void
331update_vsyscall(struct timespec *ts, struct timespec *wtm,
332 struct clocksource *c, u32 mult)
333{
334}
335
336static inline void update_vsyscall_tz(void)
337{
338}
339#endif
340
341extern void timekeeping_notify(struct clocksource *clock);
342
343extern cycle_t clocksource_mmio_readl_up(struct clocksource *);
344extern cycle_t clocksource_mmio_readl_down(struct clocksource *);
345extern cycle_t clocksource_mmio_readw_up(struct clocksource *);
346extern cycle_t clocksource_mmio_readw_down(struct clocksource *);
347
348extern int clocksource_mmio_init(void __iomem *, const char *,
349 unsigned long, int, unsigned, cycle_t (*)(struct clocksource *));
350
351extern int clocksource_i8253_init(void);
352
353#endif /* _LINUX_CLOCKSOURCE_H */