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