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