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Linux/include/linux/clocksource.h

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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 <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 
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  */
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  */
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  */
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  */
219 static inline int __clocksource_register(struct clocksource *cs)
220 {
221         return __clocksource_register_scale(cs, 1, 0);
222 }
223 
224 static inline int clocksource_register_hz(struct clocksource *cs, u32 hz)
225 {
226         return __clocksource_register_scale(cs, 1, hz);
227 }
228 
229 static inline int clocksource_register_khz(struct clocksource *cs, u32 khz)
230 {
231         return __clocksource_register_scale(cs, 1000, khz);
232 }
233 
234 static inline void __clocksource_update_freq_hz(struct clocksource *cs, u32 hz)
235 {
236         __clocksource_update_freq_scale(cs, 1, hz);
237 }
238 
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 #ifdef CONFIG_ARCH_CLOCKSOURCE_INIT
245 extern void clocksource_arch_init(struct clocksource *cs);
246 #else
247 static inline void clocksource_arch_init(struct clocksource *cs) { }
248 #endif
249 
250 extern int timekeeping_notify(struct clocksource *clock);
251 
252 extern u64 clocksource_mmio_readl_up(struct clocksource *);
253 extern u64 clocksource_mmio_readl_down(struct clocksource *);
254 extern u64 clocksource_mmio_readw_up(struct clocksource *);
255 extern u64 clocksource_mmio_readw_down(struct clocksource *);
256 
257 extern int clocksource_mmio_init(void __iomem *, const char *,
258         unsigned long, int, unsigned, u64 (*)(struct clocksource *));
259 
260 extern int clocksource_i8253_init(void);
261 
262 #define TIMER_OF_DECLARE(name, compat, fn) \
263         OF_DECLARE_1_RET(timer, name, compat, fn)
264 
265 #ifdef CONFIG_TIMER_PROBE
266 extern void timer_probe(void);
267 #else
268 static inline void timer_probe(void) {}
269 #endif
270 
271 #define TIMER_ACPI_DECLARE(name, table_id, fn)          \
272         ACPI_DECLARE_PROBE_ENTRY(timer, name, table_id, 0, NULL, 0, fn)
273 
274 #endif /* _LINUX_CLOCKSOURCE_H */
275 

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