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 <asm/div64.h>
21 #include <asm/io.h>
22
23 struct clocksource;
24 struct module;
25
26 #ifdef CONFIG_ARCH_CLOCKSOURCE_DATA
27 #include <asm/clocksource.h>
28 #endif
29
30 /**
31 * struct clocksource - hardware abstraction for a free running counter
32 * Provides mostly state-free accessors to the underlying hardware.
33 * This is the structure used for system time.
34 *
35 * @name: ptr to clocksource name
36 * @list: list head for registration
37 * @rating: rating value for selection (higher is better)
38 * To avoid rating inflation the following
39 * list should give you a guide as to how
40 * to assign your clocksource a rating
41 * 1-99: Unfit for real use
42 * Only available for bootup and testing purposes.
43 * 100-199: Base level usability.
44 * Functional for real use, but not desired.
45 * 200-299: Good.
46 * A correct and usable clocksource.
47 * 300-399: Desired.
48 * A reasonably fast and accurate clocksource.
49 * 400-499: Perfect
50 * The ideal clocksource. A must-use where
51 * available.
52 * @read: returns a cycle value, passes clocksource as argument
53 * @enable: optional function to enable the clocksource
54 * @disable: optional function to disable the clocksource
55 * @mask: bitmask for two's complement
56 * subtraction of non 64 bit counters
57 * @mult: cycle to nanosecond multiplier
58 * @shift: cycle to nanosecond divisor (power of two)
59 * @max_idle_ns: max idle time permitted by the clocksource (nsecs)
60 * @maxadj: maximum adjustment value to mult (~11%)
61 * @max_cycles: maximum safe cycle value which won't overflow on multiplication
62 * @flags: flags describing special properties
63 * @archdata: arch-specific data
64 * @suspend: suspend function for the clocksource, if necessary
65 * @resume: resume function for the clocksource, if necessary
66 * @mark_unstable: Optional function to inform the clocksource driver that
67 * the watchdog marked the clocksource unstable
68 * @owner: module reference, must be set by clocksource in modules
69 *
70 * Note: This struct is not used in hotpathes of the timekeeping code
71 * because the timekeeper caches the hot path fields in its own data
72 * structure, so no line cache alignment is required,
73 *
74 * The pointer to the clocksource itself is handed to the read
75 * callback. If you need extra information there you can wrap struct
76 * clocksource into your own struct. Depending on the amount of
77 * information you need you should consider to cache line align that
78 * structure.
79 */
80 struct clocksource {
81 u64 (*read)(struct clocksource *cs);
82 u64 mask;
83 u32 mult;
84 u32 shift;
85 u64 max_idle_ns;
86 u32 maxadj;
87 #ifdef CONFIG_ARCH_CLOCKSOURCE_DATA
88 struct arch_clocksource_data archdata;
89 #endif
90 u64 max_cycles;
91 const char *name;
92 struct list_head list;
93 int rating;
94 int (*enable)(struct clocksource *cs);
95 void (*disable)(struct clocksource *cs);
96 unsigned long flags;
97 void (*suspend)(struct clocksource *cs);
98 void (*resume)(struct clocksource *cs);
99 void (*mark_unstable)(struct clocksource *cs);
100 void (*tick_stable)(struct clocksource *cs);
101
102 /* private: */
103 #ifdef CONFIG_CLOCKSOURCE_WATCHDOG
104 /* Watchdog related data, used by the framework */
105 struct list_head wd_list;
106 u64 cs_last;
107 u64 wd_last;
108 #endif
109 struct module *owner;
110 };
111
112 /*
113 * Clock source flags bits::
114 */
115 #define CLOCK_SOURCE_IS_CONTINUOUS 0x01
116 #define CLOCK_SOURCE_MUST_VERIFY 0x02
117
118 #define CLOCK_SOURCE_WATCHDOG 0x10
119 #define CLOCK_SOURCE_VALID_FOR_HRES 0x20
120 #define CLOCK_SOURCE_UNSTABLE 0x40
121 #define CLOCK_SOURCE_SUSPEND_NONSTOP 0x80
122 #define CLOCK_SOURCE_RESELECT 0x100
123
124 /* simplify initialization of mask field */
125 #define CLOCKSOURCE_MASK(bits) GENMASK_ULL((bits) - 1, 0)
126
clocksource_freq2mult(u32 freq,u32 shift_constant,u64 from)127 static inline u32 clocksource_freq2mult(u32 freq, u32 shift_constant, u64 from)
128 {
129 /* freq = cyc/from
130 * mult/2^shift = ns/cyc
131 * mult = ns/cyc * 2^shift
132 * mult = from/freq * 2^shift
133 * mult = from * 2^shift / freq
134 * mult = (from<<shift) / freq
135 */
136 u64 tmp = ((u64)from) << shift_constant;
137
138 tmp += freq/2; /* round for do_div */
139 do_div(tmp, freq);
140
141 return (u32)tmp;
142 }
143
144 /**
145 * clocksource_khz2mult - calculates mult from khz and shift
146 * @khz: Clocksource frequency in KHz
147 * @shift_constant: Clocksource shift factor
148 *
149 * Helper functions that converts a khz counter frequency to a timsource
150 * multiplier, given the clocksource shift value
151 */
clocksource_khz2mult(u32 khz,u32 shift_constant)152 static inline u32 clocksource_khz2mult(u32 khz, u32 shift_constant)
153 {
154 return clocksource_freq2mult(khz, shift_constant, NSEC_PER_MSEC);
155 }
156
157 /**
158 * clocksource_hz2mult - calculates mult from hz and shift
159 * @hz: Clocksource frequency in Hz
160 * @shift_constant: Clocksource shift factor
161 *
162 * Helper functions that converts a hz counter
163 * frequency to a timsource multiplier, given the
164 * clocksource shift value
165 */
clocksource_hz2mult(u32 hz,u32 shift_constant)166 static inline u32 clocksource_hz2mult(u32 hz, u32 shift_constant)
167 {
168 return clocksource_freq2mult(hz, shift_constant, NSEC_PER_SEC);
169 }
170
171 /**
172 * clocksource_cyc2ns - converts clocksource cycles to nanoseconds
173 * @cycles: cycles
174 * @mult: cycle to nanosecond multiplier
175 * @shift: cycle to nanosecond divisor (power of two)
176 *
177 * Converts clocksource cycles to nanoseconds, using the given @mult and @shift.
178 * The code is optimized for performance and is not intended to work
179 * with absolute clocksource cycles (as those will easily overflow),
180 * but is only intended to be used with relative (delta) clocksource cycles.
181 *
182 * XXX - This could use some mult_lxl_ll() asm optimization
183 */
clocksource_cyc2ns(u64 cycles,u32 mult,u32 shift)184 static inline s64 clocksource_cyc2ns(u64 cycles, u32 mult, u32 shift)
185 {
186 return ((u64) cycles * mult) >> shift;
187 }
188
189
190 extern int clocksource_unregister(struct clocksource*);
191 extern void clocksource_touch_watchdog(void);
192 extern void clocksource_change_rating(struct clocksource *cs, int rating);
193 extern void clocksource_suspend(void);
194 extern void clocksource_resume(void);
195 extern struct clocksource * __init clocksource_default_clock(void);
196 extern void clocksource_mark_unstable(struct clocksource *cs);
197 extern void
198 clocksource_start_suspend_timing(struct clocksource *cs, u64 start_cycles);
199 extern u64 clocksource_stop_suspend_timing(struct clocksource *cs, u64 now);
200
201 extern u64
202 clocks_calc_max_nsecs(u32 mult, u32 shift, u32 maxadj, u64 mask, u64 *max_cycles);
203 extern void
204 clocks_calc_mult_shift(u32 *mult, u32 *shift, u32 from, u32 to, u32 minsec);
205
206 /*
207 * Don't call __clocksource_register_scale directly, use
208 * clocksource_register_hz/khz
209 */
210 extern int
211 __clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq);
212 extern void
213 __clocksource_update_freq_scale(struct clocksource *cs, u32 scale, u32 freq);
214
215 /*
216 * Don't call this unless you are a default clocksource
217 * (AKA: jiffies) and absolutely have to.
218 */
__clocksource_register(struct clocksource * cs)219 static inline int __clocksource_register(struct clocksource *cs)
220 {
221 return __clocksource_register_scale(cs, 1, 0);
222 }
223
clocksource_register_hz(struct clocksource * cs,u32 hz)224 static inline int clocksource_register_hz(struct clocksource *cs, u32 hz)
225 {
226 return __clocksource_register_scale(cs, 1, hz);
227 }
228
clocksource_register_khz(struct clocksource * cs,u32 khz)229 static inline int clocksource_register_khz(struct clocksource *cs, u32 khz)
230 {
231 return __clocksource_register_scale(cs, 1000, khz);
232 }
233
__clocksource_update_freq_hz(struct clocksource * cs,u32 hz)234 static inline void __clocksource_update_freq_hz(struct clocksource *cs, u32 hz)
235 {
236 __clocksource_update_freq_scale(cs, 1, hz);
237 }
238
__clocksource_update_freq_khz(struct clocksource * cs,u32 khz)239 static inline void __clocksource_update_freq_khz(struct clocksource *cs, u32 khz)
240 {
241 __clocksource_update_freq_scale(cs, 1000, khz);
242 }
243
244
245 extern int timekeeping_notify(struct clocksource *clock);
246
247 extern u64 clocksource_mmio_readl_up(struct clocksource *);
248 extern u64 clocksource_mmio_readl_down(struct clocksource *);
249 extern u64 clocksource_mmio_readw_up(struct clocksource *);
250 extern u64 clocksource_mmio_readw_down(struct clocksource *);
251
252 extern int clocksource_mmio_init(void __iomem *, const char *,
253 unsigned long, int, unsigned, u64 (*)(struct clocksource *));
254
255 extern int clocksource_i8253_init(void);
256
257 #define TIMER_OF_DECLARE(name, compat, fn) \
258 OF_DECLARE_1_RET(timer, name, compat, fn)
259
260 #define CLOCKSOURCE_OF_DECLARE(name, compat, fn) \
261 TIMER_OF_DECLARE(name, compat, fn)
262
263 #ifdef CONFIG_TIMER_PROBE
264 extern void timer_probe(void);
265 #else
timer_probe(void)266 static inline void timer_probe(void) {}
267 #endif
268
269 #define TIMER_ACPI_DECLARE(name, table_id, fn) \
270 ACPI_DECLARE_PROBE_ENTRY(timer, name, table_id, 0, NULL, 0, fn)
271
272 #endif /* _LINUX_CLOCKSOURCE_H */
273