diff options
author | john stultz <johnstul@us.ibm.com> | 2006-06-26 03:25:05 -0400 |
---|---|---|
committer | Linus Torvalds <torvalds@g5.osdl.org> | 2006-06-26 12:58:20 -0400 |
commit | 734efb467b31e56c2f9430590a9aa867ecf3eea1 (patch) | |
tree | 30bf6b52d1e67128e656fb9a01cd7e6e13b7755e /include | |
parent | ade1a29e168ba08b699a418ff5e762315fa33f70 (diff) |
[PATCH] Time: Clocksource Infrastructure
This introduces the clocksource management infrastructure. A clocksource is a
driver-like architecture generic abstraction of a free-running counter. This
code defines the clocksource structure, and provides management code for
registering, selecting, accessing and scaling clocksources.
Additionally, this includes the trivial jiffies clocksource, a lowest common
denominator clocksource, provided mainly for use as an example.
[hirofumi@mail.parknet.co.jp: Don't enable IRQ too early]
Signed-off-by: John Stultz <johnstul@us.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>
Signed-off-by: John Stultz <johnstul@us.ibm.com>
Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'include')
-rw-r--r-- | include/linux/clocksource.h | 181 |
1 files changed, 181 insertions, 0 deletions
diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h new file mode 100644 index 000000000000..c4187cda0ee4 --- /dev/null +++ b/include/linux/clocksource.h | |||
@@ -0,0 +1,181 @@ | |||
1 | /* linux/include/linux/clocksource.h | ||
2 | * | ||
3 | * This file contains the structure definitions for clocksources. | ||
4 | * | ||
5 | * If you are not a clocksource, or timekeeping code, you should | ||
6 | * not be including this file! | ||
7 | */ | ||
8 | #ifndef _LINUX_CLOCKSOURCE_H | ||
9 | #define _LINUX_CLOCKSOURCE_H | ||
10 | |||
11 | #include <linux/types.h> | ||
12 | #include <linux/timex.h> | ||
13 | #include <linux/time.h> | ||
14 | #include <linux/list.h> | ||
15 | #include <asm/div64.h> | ||
16 | #include <asm/io.h> | ||
17 | |||
18 | /* clocksource cycle base type */ | ||
19 | typedef u64 cycle_t; | ||
20 | |||
21 | /** | ||
22 | * struct clocksource - hardware abstraction for a free running counter | ||
23 | * Provides mostly state-free accessors to the underlying hardware. | ||
24 | * | ||
25 | * @name: ptr to clocksource name | ||
26 | * @list: list head for registration | ||
27 | * @rating: rating value for selection (higher is better) | ||
28 | * To avoid rating inflation the following | ||
29 | * list should give you a guide as to how | ||
30 | * to assign your clocksource a rating | ||
31 | * 1-99: Unfit for real use | ||
32 | * Only available for bootup and testing purposes. | ||
33 | * 100-199: Base level usability. | ||
34 | * Functional for real use, but not desired. | ||
35 | * 200-299: Good. | ||
36 | * A correct and usable clocksource. | ||
37 | * 300-399: Desired. | ||
38 | * A reasonably fast and accurate clocksource. | ||
39 | * 400-499: Perfect | ||
40 | * The ideal clocksource. A must-use where | ||
41 | * available. | ||
42 | * @read: returns a cycle value | ||
43 | * @mask: bitmask for two's complement | ||
44 | * subtraction of non 64 bit counters | ||
45 | * @mult: cycle to nanosecond multiplier | ||
46 | * @shift: cycle to nanosecond divisor (power of two) | ||
47 | * @update_callback: called when safe to alter clocksource values | ||
48 | * @is_continuous: defines if clocksource is free-running. | ||
49 | * @interval_cycles: Used internally by timekeeping core, please ignore. | ||
50 | * @interval_snsecs: Used internally by timekeeping core, please ignore. | ||
51 | */ | ||
52 | struct clocksource { | ||
53 | char *name; | ||
54 | struct list_head list; | ||
55 | int rating; | ||
56 | cycle_t (*read)(void); | ||
57 | cycle_t mask; | ||
58 | u32 mult; | ||
59 | u32 shift; | ||
60 | int (*update_callback)(void); | ||
61 | int is_continuous; | ||
62 | |||
63 | /* timekeeping specific data, ignore */ | ||
64 | cycle_t interval_cycles; | ||
65 | u64 interval_snsecs; | ||
66 | }; | ||
67 | |||
68 | |||
69 | /** | ||
70 | * clocksource_khz2mult - calculates mult from khz and shift | ||
71 | * @khz: Clocksource frequency in KHz | ||
72 | * @shift_constant: Clocksource shift factor | ||
73 | * | ||
74 | * Helper functions that converts a khz counter frequency to a timsource | ||
75 | * multiplier, given the clocksource shift value | ||
76 | */ | ||
77 | static inline u32 clocksource_khz2mult(u32 khz, u32 shift_constant) | ||
78 | { | ||
79 | /* khz = cyc/(Million ns) | ||
80 | * mult/2^shift = ns/cyc | ||
81 | * mult = ns/cyc * 2^shift | ||
82 | * mult = 1Million/khz * 2^shift | ||
83 | * mult = 1000000 * 2^shift / khz | ||
84 | * mult = (1000000<<shift) / khz | ||
85 | */ | ||
86 | u64 tmp = ((u64)1000000) << shift_constant; | ||
87 | |||
88 | tmp += khz/2; /* round for do_div */ | ||
89 | do_div(tmp, khz); | ||
90 | |||
91 | return (u32)tmp; | ||
92 | } | ||
93 | |||
94 | /** | ||
95 | * clocksource_hz2mult - calculates mult from hz and shift | ||
96 | * @hz: Clocksource frequency in Hz | ||
97 | * @shift_constant: Clocksource shift factor | ||
98 | * | ||
99 | * Helper functions that converts a hz counter | ||
100 | * frequency to a timsource multiplier, given the | ||
101 | * clocksource shift value | ||
102 | */ | ||
103 | static inline u32 clocksource_hz2mult(u32 hz, u32 shift_constant) | ||
104 | { | ||
105 | /* hz = cyc/(Billion ns) | ||
106 | * mult/2^shift = ns/cyc | ||
107 | * mult = ns/cyc * 2^shift | ||
108 | * mult = 1Billion/hz * 2^shift | ||
109 | * mult = 1000000000 * 2^shift / hz | ||
110 | * mult = (1000000000<<shift) / hz | ||
111 | */ | ||
112 | u64 tmp = ((u64)1000000000) << shift_constant; | ||
113 | |||
114 | tmp += hz/2; /* round for do_div */ | ||
115 | do_div(tmp, hz); | ||
116 | |||
117 | return (u32)tmp; | ||
118 | } | ||
119 | |||
120 | /** | ||
121 | * read_clocksource: - Access the clocksource's current cycle value | ||
122 | * @cs: pointer to clocksource being read | ||
123 | * | ||
124 | * Uses the clocksource to return the current cycle_t value | ||
125 | */ | ||
126 | static inline cycle_t read_clocksource(struct clocksource *cs) | ||
127 | { | ||
128 | return cs->read(); | ||
129 | } | ||
130 | |||
131 | /** | ||
132 | * cyc2ns - converts clocksource cycles to nanoseconds | ||
133 | * @cs: Pointer to clocksource | ||
134 | * @cycles: Cycles | ||
135 | * | ||
136 | * Uses the clocksource and ntp ajdustment to convert cycle_ts to nanoseconds. | ||
137 | * | ||
138 | * XXX - This could use some mult_lxl_ll() asm optimization | ||
139 | */ | ||
140 | static inline s64 cyc2ns(struct clocksource *cs, cycle_t cycles) | ||
141 | { | ||
142 | u64 ret = (u64)cycles; | ||
143 | ret = (ret * cs->mult) >> cs->shift; | ||
144 | return ret; | ||
145 | } | ||
146 | |||
147 | /** | ||
148 | * calculate_clocksource_interval - Calculates a clocksource interval struct | ||
149 | * | ||
150 | * @c: Pointer to clocksource. | ||
151 | * @length_nsec: Desired interval length in nanoseconds. | ||
152 | * | ||
153 | * Calculates a fixed cycle/nsec interval for a given clocksource/adjustment | ||
154 | * pair and interval request. | ||
155 | * | ||
156 | * Unless you're the timekeeping code, you should not be using this! | ||
157 | */ | ||
158 | static inline void calculate_clocksource_interval(struct clocksource *c, | ||
159 | unsigned long length_nsec) | ||
160 | { | ||
161 | u64 tmp; | ||
162 | |||
163 | /* XXX - All of this could use a whole lot of optimization */ | ||
164 | tmp = length_nsec; | ||
165 | tmp <<= c->shift; | ||
166 | tmp += c->mult/2; | ||
167 | do_div(tmp, c->mult); | ||
168 | |||
169 | c->interval_cycles = (cycle_t)tmp; | ||
170 | if(c->interval_cycles == 0) | ||
171 | c->interval_cycles = 1; | ||
172 | |||
173 | c->interval_snsecs = (u64)c->interval_cycles * c->mult; | ||
174 | } | ||
175 | |||
176 | /* used to install a new clocksource */ | ||
177 | int register_clocksource(struct clocksource*); | ||
178 | void reselect_clocksource(void); | ||
179 | struct clocksource* get_next_clocksource(void); | ||
180 | |||
181 | #endif /* _LINUX_CLOCKSOURCE_H */ | ||