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 <asm/div64.h>
20 /* clocksource cycle base type */
25 * struct clocksource - hardware abstraction for a free running counter
26 * Provides mostly state-free accessors to the underlying hardware.
28 * @name: ptr to clocksource name
29 * @list: list head for registration
30 * @rating: rating value for selection (higher is better)
31 * To avoid rating inflation the following
32 * list should give you a guide as to how
33 * to assign your clocksource a rating
34 * 1-99: Unfit for real use
35 * Only available for bootup and testing purposes.
36 * 100-199: Base level usability.
37 * Functional for real use, but not desired.
39 * A correct and usable clocksource.
41 * A reasonably fast and accurate clocksource.
43 * The ideal clocksource. A must-use where
45 * @read: returns a cycle value
46 * @mask: bitmask for two's complement
47 * subtraction of non 64 bit counters
48 * @mult: cycle to nanosecond multiplier (adjusted by NTP)
49 * @mult_orig: cycle to nanosecond multiplier (unadjusted by NTP)
50 * @shift: cycle to nanosecond divisor (power of two)
51 * @flags: flags describing special properties
52 * @vread: vsyscall based read
53 * @resume: resume function for the clocksource, if necessary
54 * @cycle_interval: Used internally by timekeeping core, please ignore.
55 * @xtime_interval: Used internally by timekeeping core, please ignore.
59 * First part of structure is read mostly
62 struct list_head list;
64 cycle_t (*read)(void);
70 cycle_t (*vread)(void);
73 void *fsys_mmio; /* used by fsyscall asm code */
74 #define CLKSRC_FSYS_MMIO_SET(mmio, addr) ((mmio) = (addr))
76 #define CLKSRC_FSYS_MMIO_SET(mmio, addr) do { } while (0)
79 /* timekeeping specific data, ignore */
80 cycle_t cycle_interval;
83 * Second part is written at each timer interrupt
84 * Keep it in a different cache line to dirty no
85 * more than one cache line.
87 cycle_t cycle_last ____cacheline_aligned_in_smp;
91 #ifdef CONFIG_CLOCKSOURCE_WATCHDOG
92 /* Watchdog related data, used by the framework */
93 struct list_head wd_list;
98 extern struct clocksource *clock; /* current clocksource */
101 * Clock source flags bits::
103 #define CLOCK_SOURCE_IS_CONTINUOUS 0x01
104 #define CLOCK_SOURCE_MUST_VERIFY 0x02
106 #define CLOCK_SOURCE_WATCHDOG 0x10
107 #define CLOCK_SOURCE_VALID_FOR_HRES 0x20
109 /* simplify initialization of mask field */
110 #define CLOCKSOURCE_MASK(bits) (cycle_t)((bits) < 64 ? ((1ULL<<(bits))-1) : -1)
113 * clocksource_khz2mult - calculates mult from khz and shift
114 * @khz: Clocksource frequency in KHz
115 * @shift_constant: Clocksource shift factor
117 * Helper functions that converts a khz counter frequency to a timsource
118 * multiplier, given the clocksource shift value
120 static inline u32 clocksource_khz2mult(u32 khz, u32 shift_constant)
122 /* khz = cyc/(Million ns)
123 * mult/2^shift = ns/cyc
124 * mult = ns/cyc * 2^shift
125 * mult = 1Million/khz * 2^shift
126 * mult = 1000000 * 2^shift / khz
127 * mult = (1000000<<shift) / khz
129 u64 tmp = ((u64)1000000) << shift_constant;
131 tmp += khz/2; /* round for do_div */
138 * clocksource_hz2mult - calculates mult from hz and shift
139 * @hz: Clocksource frequency in Hz
140 * @shift_constant: Clocksource shift factor
142 * Helper functions that converts a hz counter
143 * frequency to a timsource multiplier, given the
144 * clocksource shift value
146 static inline u32 clocksource_hz2mult(u32 hz, u32 shift_constant)
148 /* hz = cyc/(Billion ns)
149 * mult/2^shift = ns/cyc
150 * mult = ns/cyc * 2^shift
151 * mult = 1Billion/hz * 2^shift
152 * mult = 1000000000 * 2^shift / hz
153 * mult = (1000000000<<shift) / hz
155 u64 tmp = ((u64)1000000000) << shift_constant;
157 tmp += hz/2; /* round for do_div */
164 * clocksource_read: - Access the clocksource's current cycle value
165 * @cs: pointer to clocksource being read
167 * Uses the clocksource to return the current cycle_t value
169 static inline cycle_t clocksource_read(struct clocksource *cs)
175 * cyc2ns - converts clocksource cycles to nanoseconds
176 * @cs: Pointer to clocksource
179 * Uses the clocksource and ntp ajdustment to convert cycle_ts to nanoseconds.
181 * XXX - This could use some mult_lxl_ll() asm optimization
183 static inline s64 cyc2ns(struct clocksource *cs, cycle_t cycles)
185 u64 ret = (u64)cycles;
186 ret = (ret * cs->mult) >> cs->shift;
191 * clocksource_calculate_interval - Calculates a clocksource interval struct
193 * @c: Pointer to clocksource.
194 * @length_nsec: Desired interval length in nanoseconds.
196 * Calculates a fixed cycle/nsec interval for a given clocksource/adjustment
197 * pair and interval request.
199 * Unless you're the timekeeping code, you should not be using this!
201 static inline void clocksource_calculate_interval(struct clocksource *c,
202 unsigned long length_nsec)
206 /* Do the ns -> cycle conversion first, using original mult */
209 tmp += c->mult_orig/2;
210 do_div(tmp, c->mult_orig);
212 c->cycle_interval = (cycle_t)tmp;
213 if (c->cycle_interval == 0)
214 c->cycle_interval = 1;
216 /* Go back from cycles -> shifted ns, this time use ntp adjused mult */
217 c->xtime_interval = (u64)c->cycle_interval * c->mult;
221 /* used to install a new clocksource */
222 extern int clocksource_register(struct clocksource*);
223 extern void clocksource_unregister(struct clocksource*);
224 extern void clocksource_touch_watchdog(void);
225 extern struct clocksource* clocksource_get_next(void);
226 extern void clocksource_change_rating(struct clocksource *cs, int rating);
227 extern void clocksource_resume(void);
229 #ifdef CONFIG_GENERIC_TIME_VSYSCALL
230 extern void update_vsyscall(struct timespec *ts, struct clocksource *c);
231 extern void update_vsyscall_tz(void);
233 static inline void update_vsyscall(struct timespec *ts, struct clocksource *c)
237 static inline void update_vsyscall_tz(void)
242 #endif /* _LINUX_CLOCKSOURCE_H */