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1/* SPDX-License-Identifier: GPL-2.0 */
2/* linux/include/linux/clocksource.h
3 *
4 * This file contains the structure definitions for clocksources.
5 *
6 * If you are not a clocksource, or timekeeping code, you should
7 * not be including this file!
8 */
9#ifndef _LINUX_CLOCKSOURCE_H
10#define _LINUX_CLOCKSOURCE_H
11
12#include <linux/types.h>
13#include <linux/timex.h>
14#include <linux/time.h>
15#include <linux/list.h>
16#include <linux/cache.h>
17#include <linux/timer.h>
18#include <linux/init.h>
19#include <linux/of.h>
20#include <linux/clocksource_ids.h>
21#include <asm/div64.h>
22#include <asm/io.h>
23
24struct clocksource_base;
25struct clocksource;
26struct module;
27
28#if defined(CONFIG_ARCH_CLOCKSOURCE_DATA) || \
29 defined(CONFIG_GENERIC_GETTIMEOFDAY)
30#include <asm/clocksource.h>
31#endif
32
33#include <vdso/clocksource.h>
34
35/**
36 * struct clocksource - hardware abstraction for a free running counter
37 * Provides mostly state-free accessors to the underlying hardware.
38 * This is the structure used for system time.
39 *
40 * @read: Returns a cycle value, passes clocksource as argument
41 * @mask: Bitmask for two's complement
42 * subtraction of non 64 bit counters
43 * @mult: Cycle to nanosecond multiplier
44 * @shift: Cycle to nanosecond divisor (power of two)
45 * @max_idle_ns: Maximum idle time permitted by the clocksource (nsecs)
46 * @maxadj: Maximum adjustment value to mult (~11%)
47 * @uncertainty_margin: Maximum uncertainty in nanoseconds per half second.
48 * Zero says to use default WATCHDOG_THRESHOLD.
49 * @archdata: Optional arch-specific data
50 * @max_cycles: Maximum safe cycle value which won't overflow on
51 * multiplication
52 * @max_raw_delta: Maximum safe delta value for negative motion detection
53 * @name: Pointer to clocksource name
54 * @list: List head for registration (internal)
55 * @freq_khz: Clocksource frequency in khz.
56 * @rating: Rating value for selection (higher is better)
57 * To avoid rating inflation the following
58 * list should give you a guide as to how
59 * to assign your clocksource a rating
60 * 1-99: Unfit for real use
61 * Only available for bootup and testing purposes.
62 * 100-199: Base level usability.
63 * Functional for real use, but not desired.
64 * 200-299: Good.
65 * A correct and usable clocksource.
66 * 300-399: Desired.
67 * A reasonably fast and accurate clocksource.
68 * 400-499: Perfect
69 * The ideal clocksource. A must-use where
70 * available.
71 * @id: Defaults to CSID_GENERIC. The id value is captured
72 * in certain snapshot functions to allow callers to
73 * validate the clocksource from which the snapshot was
74 * taken.
75 * @flags: Flags describing special properties
76 * @base: Hardware abstraction for clock on which a clocksource
77 * is based
78 * @enable: Optional function to enable the clocksource
79 * @disable: Optional function to disable the clocksource
80 * @suspend: Optional suspend function for the clocksource
81 * @resume: Optional resume function for the clocksource
82 * @mark_unstable: Optional function to inform the clocksource driver that
83 * the watchdog marked the clocksource unstable
84 * @tick_stable: Optional function called periodically from the watchdog
85 * code to provide stable synchronization points
86 * @wd_list: List head to enqueue into the watchdog list (internal)
87 * @cs_last: Last clocksource value for clocksource watchdog
88 * @wd_last: Last watchdog value corresponding to @cs_last
89 * @owner: Module reference, must be set by clocksource in modules
90 *
91 * Note: This struct is not used in hotpathes of the timekeeping code
92 * because the timekeeper caches the hot path fields in its own data
93 * structure, so no cache line alignment is required,
94 *
95 * The pointer to the clocksource itself is handed to the read
96 * callback. If you need extra information there you can wrap struct
97 * clocksource into your own struct. Depending on the amount of
98 * information you need you should consider to cache line align that
99 * structure.
100 */
101struct clocksource {
102 u64 (*read)(struct clocksource *cs);
103 u64 mask;
104 u32 mult;
105 u32 shift;
106 u64 max_idle_ns;
107 u32 maxadj;
108 u32 uncertainty_margin;
109#ifdef CONFIG_ARCH_CLOCKSOURCE_DATA
110 struct arch_clocksource_data archdata;
111#endif
112 u64 max_cycles;
113 u64 max_raw_delta;
114 const char *name;
115 struct list_head list;
116 u32 freq_khz;
117 int rating;
118 enum clocksource_ids id;
119 enum vdso_clock_mode vdso_clock_mode;
120 unsigned long flags;
121 struct clocksource_base *base;
122
123 int (*enable)(struct clocksource *cs);
124 void (*disable)(struct clocksource *cs);
125 void (*suspend)(struct clocksource *cs);
126 void (*resume)(struct clocksource *cs);
127 void (*mark_unstable)(struct clocksource *cs);
128 void (*tick_stable)(struct clocksource *cs);
129
130 /* private: */
131#ifdef CONFIG_CLOCKSOURCE_WATCHDOG
132 /* Watchdog related data, used by the framework */
133 struct list_head wd_list;
134 u64 cs_last;
135 u64 wd_last;
136#endif
137 struct module *owner;
138};
139
140/*
141 * Clock source flags bits::
142 */
143#define CLOCK_SOURCE_IS_CONTINUOUS 0x01
144#define CLOCK_SOURCE_MUST_VERIFY 0x02
145
146#define CLOCK_SOURCE_WATCHDOG 0x10
147#define CLOCK_SOURCE_VALID_FOR_HRES 0x20
148#define CLOCK_SOURCE_UNSTABLE 0x40
149#define CLOCK_SOURCE_SUSPEND_NONSTOP 0x80
150#define CLOCK_SOURCE_RESELECT 0x100
151#define CLOCK_SOURCE_VERIFY_PERCPU 0x200
152/* simplify initialization of mask field */
153#define CLOCKSOURCE_MASK(bits) GENMASK_ULL((bits) - 1, 0)
154
155static inline u32 clocksource_freq2mult(u32 freq, u32 shift_constant, u64 from)
156{
157 /* freq = cyc/from
158 * mult/2^shift = ns/cyc
159 * mult = ns/cyc * 2^shift
160 * mult = from/freq * 2^shift
161 * mult = from * 2^shift / freq
162 * mult = (from<<shift) / freq
163 */
164 u64 tmp = ((u64)from) << shift_constant;
165
166 tmp += freq/2; /* round for do_div */
167 do_div(tmp, freq);
168
169 return (u32)tmp;
170}
171
172/**
173 * clocksource_khz2mult - calculates mult from khz and shift
174 * @khz: Clocksource frequency in KHz
175 * @shift_constant: Clocksource shift factor
176 *
177 * Helper functions that converts a khz counter frequency to a timsource
178 * multiplier, given the clocksource shift value
179 */
180static inline u32 clocksource_khz2mult(u32 khz, u32 shift_constant)
181{
182 return clocksource_freq2mult(khz, shift_constant, NSEC_PER_MSEC);
183}
184
185/**
186 * clocksource_hz2mult - calculates mult from hz and shift
187 * @hz: Clocksource frequency in Hz
188 * @shift_constant: Clocksource shift factor
189 *
190 * Helper functions that converts a hz counter
191 * frequency to a timsource multiplier, given the
192 * clocksource shift value
193 */
194static inline u32 clocksource_hz2mult(u32 hz, u32 shift_constant)
195{
196 return clocksource_freq2mult(hz, shift_constant, NSEC_PER_SEC);
197}
198
199/**
200 * clocksource_cyc2ns - converts clocksource cycles to nanoseconds
201 * @cycles: cycles
202 * @mult: cycle to nanosecond multiplier
203 * @shift: cycle to nanosecond divisor (power of two)
204 *
205 * Converts clocksource cycles to nanoseconds, using the given @mult and @shift.
206 * The code is optimized for performance and is not intended to work
207 * with absolute clocksource cycles (as those will easily overflow),
208 * but is only intended to be used with relative (delta) clocksource cycles.
209 *
210 * XXX - This could use some mult_lxl_ll() asm optimization
211 */
212static inline s64 clocksource_cyc2ns(u64 cycles, u32 mult, u32 shift)
213{
214 return ((u64) cycles * mult) >> shift;
215}
216
217
218extern int clocksource_unregister(struct clocksource*);
219extern void clocksource_touch_watchdog(void);
220extern void clocksource_suspend(void);
221extern void clocksource_resume(void);
222extern struct clocksource * __init clocksource_default_clock(void);
223extern void clocksource_mark_unstable(struct clocksource *cs);
224extern void
225clocksource_start_suspend_timing(struct clocksource *cs, u64 start_cycles);
226extern u64 clocksource_stop_suspend_timing(struct clocksource *cs, u64 now);
227
228extern u64
229clocks_calc_max_nsecs(u32 mult, u32 shift, u32 maxadj, u64 mask, u64 *max_cycles);
230extern void
231clocks_calc_mult_shift(u32 *mult, u32 *shift, u32 from, u32 to, u32 minsec);
232
233/*
234 * Don't call __clocksource_register_scale directly, use
235 * clocksource_register_hz/khz
236 */
237extern int
238__clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq);
239extern void
240__clocksource_update_freq_scale(struct clocksource *cs, u32 scale, u32 freq);
241
242/*
243 * Don't call this unless you are a default clocksource
244 * (AKA: jiffies) and absolutely have to.
245 */
246static inline int __clocksource_register(struct clocksource *cs)
247{
248 return __clocksource_register_scale(cs, 1, 0);
249}
250
251static inline int clocksource_register_hz(struct clocksource *cs, u32 hz)
252{
253 return __clocksource_register_scale(cs, 1, hz);
254}
255
256static inline int clocksource_register_khz(struct clocksource *cs, u32 khz)
257{
258 return __clocksource_register_scale(cs, 1000, khz);
259}
260
261static inline void __clocksource_update_freq_hz(struct clocksource *cs, u32 hz)
262{
263 __clocksource_update_freq_scale(cs, 1, hz);
264}
265
266static inline void __clocksource_update_freq_khz(struct clocksource *cs, u32 khz)
267{
268 __clocksource_update_freq_scale(cs, 1000, khz);
269}
270
271#ifdef CONFIG_ARCH_CLOCKSOURCE_INIT
272extern void clocksource_arch_init(struct clocksource *cs);
273#else
274static inline void clocksource_arch_init(struct clocksource *cs) { }
275#endif
276
277extern int timekeeping_notify(struct clocksource *clock);
278
279extern u64 clocksource_mmio_readl_up(struct clocksource *);
280extern u64 clocksource_mmio_readl_down(struct clocksource *);
281extern u64 clocksource_mmio_readw_up(struct clocksource *);
282extern u64 clocksource_mmio_readw_down(struct clocksource *);
283
284extern int clocksource_mmio_init(void __iomem *, const char *,
285 unsigned long, int, unsigned, u64 (*)(struct clocksource *));
286
287extern int clocksource_i8253_init(void);
288
289#define TIMER_OF_DECLARE(name, compat, fn) \
290 OF_DECLARE_1_RET(timer, name, compat, fn)
291
292#ifdef CONFIG_TIMER_PROBE
293extern void timer_probe(void);
294#else
295static inline void timer_probe(void) {}
296#endif
297
298#define TIMER_ACPI_DECLARE(name, table_id, fn) \
299 ACPI_DECLARE_PROBE_ENTRY(timer, name, table_id, 0, NULL, 0, fn)
300
301static inline unsigned int clocksource_get_max_watchdog_retry(void)
302{
303 /*
304 * When system is in the boot phase or under heavy workload, there
305 * can be random big latencies during the clocksource/watchdog
306 * read, so allow retries to filter the noise latency. As the
307 * latency's frequency and maximum value goes up with the number of
308 * CPUs, scale the number of retries with the number of online
309 * CPUs.
310 */
311 return (ilog2(num_online_cpus()) / 2) + 1;
312}
313
314void clocksource_verify_percpu(struct clocksource *cs);
315
316/**
317 * struct clocksource_base - hardware abstraction for clock on which a clocksource
318 * is based
319 * @id: Defaults to CSID_GENERIC. The id value is used for conversion
320 * functions which require that the current clocksource is based
321 * on a clocksource_base with a particular ID in certain snapshot
322 * functions to allow callers to validate the clocksource from
323 * which the snapshot was taken.
324 * @freq_khz: Nominal frequency of the base clock in kHz
325 * @offset: Offset between the base clock and the clocksource
326 * @numerator: Numerator of the clock ratio between base clock and the clocksource
327 * @denominator: Denominator of the clock ratio between base clock and the clocksource
328 */
329struct clocksource_base {
330 enum clocksource_ids id;
331 u32 freq_khz;
332 u64 offset;
333 u32 numerator;
334 u32 denominator;
335};
336
337#endif /* _LINUX_CLOCKSOURCE_H */