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