1 /* linux/include/linux/clocksource.h
3 * This file contains the structure definitions for clocksources.
5 * If you are not a clocksource, or timekeeping code, you should
6 * not be including this file!
8 #ifndef _LINUX_CLOCKSOURCE_H
9 #define _LINUX_CLOCKSOURCE_H
11 #include <linux/types.h>
12 #include <linux/timex.h>
13 #include <linux/time.h>
14 #include <linux/list.h>
15 #include <linux/cache.h>
16 #include <linux/timer.h>
17 #include <linux/init.h>
18 #include <asm/div64.h>
24 #ifdef CONFIG_ARCH_CLOCKSOURCE_DATA
25 #include <asm/clocksource.h>
29 * struct clocksource - hardware abstraction for a free running counter
30 * Provides mostly state-free accessors to the underlying hardware.
31 * This is the structure used for system time.
33 * @name: ptr to clocksource name
34 * @list: list head for registration
35 * @rating: rating value for selection (higher is better)
36 * To avoid rating inflation the following
37 * list should give you a guide as to how
38 * to assign your clocksource a rating
39 * 1-99: Unfit for real use
40 * Only available for bootup and testing purposes.
41 * 100-199: Base level usability.
42 * Functional for real use, but not desired.
44 * A correct and usable clocksource.
46 * A reasonably fast and accurate clocksource.
48 * The ideal clocksource. A must-use where
50 * @read: returns a cycle value, passes clocksource as argument
51 * @enable: optional function to enable the clocksource
52 * @disable: optional function to disable the clocksource
53 * @mask: bitmask for two's complement
54 * subtraction of non 64 bit counters
55 * @mult: cycle to nanosecond multiplier
56 * @shift: cycle to nanosecond divisor (power of two)
57 * @max_idle_ns: max idle time permitted by the clocksource (nsecs)
58 * @maxadj: maximum adjustment value to mult (~11%)
59 * @max_cycles: maximum safe cycle value which won't overflow on multiplication
60 * @flags: flags describing special properties
61 * @archdata: arch-specific data
62 * @suspend: suspend function for the clocksource, if necessary
63 * @resume: resume function for the clocksource, if necessary
64 * @owner: module reference, must be set by clocksource in modules
66 * Note: This struct is not used in hotpathes of the timekeeping code
67 * because the timekeeper caches the hot path fields in its own data
68 * structure, so no line cache alignment is required,
70 * The pointer to the clocksource itself is handed to the read
71 * callback. If you need extra information there you can wrap struct
72 * clocksource into your own struct. Depending on the amount of
73 * information you need you should consider to cache line align that
77 cycle_t (*read)(struct clocksource *cs);
83 #ifdef CONFIG_ARCH_CLOCKSOURCE_DATA
84 struct arch_clocksource_data archdata;
88 struct list_head list;
90 int (*enable)(struct clocksource *cs);
91 void (*disable)(struct clocksource *cs);
93 void (*suspend)(struct clocksource *cs);
94 void (*resume)(struct clocksource *cs);
97 #ifdef CONFIG_CLOCKSOURCE_WATCHDOG
98 /* Watchdog related data, used by the framework */
99 struct list_head wd_list;
103 struct module *owner;
107 * Clock source flags bits::
109 #define CLOCK_SOURCE_IS_CONTINUOUS 0x01
110 #define CLOCK_SOURCE_MUST_VERIFY 0x02
112 #define CLOCK_SOURCE_WATCHDOG 0x10
113 #define CLOCK_SOURCE_VALID_FOR_HRES 0x20
114 #define CLOCK_SOURCE_UNSTABLE 0x40
115 #define CLOCK_SOURCE_SUSPEND_NONSTOP 0x80
116 #define CLOCK_SOURCE_RESELECT 0x100
118 /* simplify initialization of mask field */
119 #define CLOCKSOURCE_MASK(bits) (cycle_t)((bits) < 64 ? ((1ULL<<(bits))-1) : -1)
122 * clocksource_khz2mult - calculates mult from khz and shift
123 * @khz: Clocksource frequency in KHz
124 * @shift_constant: Clocksource shift factor
126 * Helper functions that converts a khz counter frequency to a timsource
127 * multiplier, given the clocksource shift value
129 static inline u32 clocksource_khz2mult(u32 khz, u32 shift_constant)
131 /* khz = cyc/(Million ns)
132 * mult/2^shift = ns/cyc
133 * mult = ns/cyc * 2^shift
134 * mult = 1Million/khz * 2^shift
135 * mult = 1000000 * 2^shift / khz
136 * mult = (1000000<<shift) / khz
138 u64 tmp = ((u64)1000000) << shift_constant;
140 tmp += khz/2; /* round for do_div */
147 * clocksource_hz2mult - calculates mult from hz and shift
148 * @hz: Clocksource frequency in Hz
149 * @shift_constant: Clocksource shift factor
151 * Helper functions that converts a hz counter
152 * frequency to a timsource multiplier, given the
153 * clocksource shift value
155 static inline u32 clocksource_hz2mult(u32 hz, u32 shift_constant)
157 /* hz = cyc/(Billion ns)
158 * mult/2^shift = ns/cyc
159 * mult = ns/cyc * 2^shift
160 * mult = 1Billion/hz * 2^shift
161 * mult = 1000000000 * 2^shift / hz
162 * mult = (1000000000<<shift) / hz
164 u64 tmp = ((u64)1000000000) << shift_constant;
166 tmp += hz/2; /* round for do_div */
173 * clocksource_cyc2ns - converts clocksource cycles to nanoseconds
175 * @mult: cycle to nanosecond multiplier
176 * @shift: cycle to nanosecond divisor (power of two)
178 * Converts cycles to nanoseconds, using the given mult and shift.
180 * XXX - This could use some mult_lxl_ll() asm optimization
182 static inline s64 clocksource_cyc2ns(cycle_t cycles, u32 mult, u32 shift)
184 return ((u64) cycles * mult) >> shift;
188 extern int clocksource_unregister(struct clocksource*);
189 extern void clocksource_touch_watchdog(void);
190 extern void clocksource_change_rating(struct clocksource *cs, int rating);
191 extern void clocksource_suspend(void);
192 extern void clocksource_resume(void);
193 extern struct clocksource * __init clocksource_default_clock(void);
194 extern void clocksource_mark_unstable(struct clocksource *cs);
197 clocks_calc_max_nsecs(u32 mult, u32 shift, u32 maxadj, u64 mask, u64 *max_cycles);
199 clocks_calc_mult_shift(u32 *mult, u32 *shift, u32 from, u32 to, u32 minsec);
202 * Don't call __clocksource_register_scale directly, use
203 * clocksource_register_hz/khz
206 __clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq);
208 __clocksource_update_freq_scale(struct clocksource *cs, u32 scale, u32 freq);
211 * Don't call this unless you are a default clocksource
212 * (AKA: jiffies) and absolutely have to.
214 static inline int __clocksource_register(struct clocksource *cs)
216 return __clocksource_register_scale(cs, 1, 0);
219 static inline int clocksource_register_hz(struct clocksource *cs, u32 hz)
221 return __clocksource_register_scale(cs, 1, hz);
224 static inline int clocksource_register_khz(struct clocksource *cs, u32 khz)
226 return __clocksource_register_scale(cs, 1000, khz);
229 static inline void __clocksource_update_freq_hz(struct clocksource *cs, u32 hz)
231 __clocksource_update_freq_scale(cs, 1, hz);
234 static inline void __clocksource_update_freq_khz(struct clocksource *cs, u32 khz)
236 __clocksource_update_freq_scale(cs, 1000, khz);
240 extern int timekeeping_notify(struct clocksource *clock);
242 extern cycle_t clocksource_mmio_readl_up(struct clocksource *);
243 extern cycle_t clocksource_mmio_readl_down(struct clocksource *);
244 extern cycle_t clocksource_mmio_readw_up(struct clocksource *);
245 extern cycle_t clocksource_mmio_readw_down(struct clocksource *);
247 extern int clocksource_mmio_init(void __iomem *, const char *,
248 unsigned long, int, unsigned, cycle_t (*)(struct clocksource *));
250 extern int clocksource_i8253_init(void);
252 #define CLOCKSOURCE_OF_DECLARE(name, compat, fn) \
253 OF_DECLARE_1(clksrc, name, compat, fn)
255 #ifdef CONFIG_CLKSRC_PROBE
256 extern void clocksource_probe(void);
258 static inline void clocksource_probe(void) {}
261 #define CLOCKSOURCE_ACPI_DECLARE(name, table_id, fn) \
262 ACPI_DECLARE_PROBE_ENTRY(clksrc, name, table_id, 0, NULL, 0, fn)
264 #endif /* _LINUX_CLOCKSOURCE_H */