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d316c57f TG |
1 | /* |
2 | * linux/kernel/time/clockevents.c | |
3 | * | |
4 | * This file contains functions which manage clock event devices. | |
5 | * | |
6 | * Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de> | |
7 | * Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar | |
8 | * Copyright(C) 2006-2007, Timesys Corp., Thomas Gleixner | |
9 | * | |
10 | * This code is licenced under the GPL version 2. For details see | |
11 | * kernel-base/COPYING. | |
12 | */ | |
13 | ||
14 | #include <linux/clockchips.h> | |
15 | #include <linux/hrtimer.h> | |
16 | #include <linux/init.h> | |
17 | #include <linux/module.h> | |
18 | #include <linux/notifier.h> | |
19 | #include <linux/smp.h> | |
20 | #include <linux/sysdev.h> | |
21 | ||
22 | /* The registered clock event devices */ | |
23 | static LIST_HEAD(clockevent_devices); | |
24 | static LIST_HEAD(clockevents_released); | |
25 | ||
26 | /* Notification for clock events */ | |
27 | static RAW_NOTIFIER_HEAD(clockevents_chain); | |
28 | ||
29 | /* Protection for the above */ | |
30 | static DEFINE_SPINLOCK(clockevents_lock); | |
31 | ||
32 | /** | |
33 | * clockevents_delta2ns - Convert a latch value (device ticks) to nanoseconds | |
34 | * @latch: value to convert | |
35 | * @evt: pointer to clock event device descriptor | |
36 | * | |
37 | * Math helper, returns latch value converted to nanoseconds (bound checked) | |
38 | */ | |
39 | unsigned long clockevent_delta2ns(unsigned long latch, | |
40 | struct clock_event_device *evt) | |
41 | { | |
42 | u64 clc = ((u64) latch << evt->shift); | |
43 | ||
44 | do_div(clc, evt->mult); | |
45 | if (clc < 1000) | |
46 | clc = 1000; | |
47 | if (clc > LONG_MAX) | |
48 | clc = LONG_MAX; | |
49 | ||
50 | return (unsigned long) clc; | |
51 | } | |
52 | ||
53 | /** | |
54 | * clockevents_set_mode - set the operating mode of a clock event device | |
55 | * @dev: device to modify | |
56 | * @mode: new mode | |
57 | * | |
58 | * Must be called with interrupts disabled ! | |
59 | */ | |
60 | void clockevents_set_mode(struct clock_event_device *dev, | |
61 | enum clock_event_mode mode) | |
62 | { | |
63 | if (dev->mode != mode) { | |
64 | dev->set_mode(mode, dev); | |
65 | dev->mode = mode; | |
66 | } | |
67 | } | |
68 | ||
69 | /** | |
70 | * clockevents_program_event - Reprogram the clock event device. | |
71 | * @expires: absolute expiry time (monotonic clock) | |
72 | * | |
73 | * Returns 0 on success, -ETIME when the event is in the past. | |
74 | */ | |
75 | int clockevents_program_event(struct clock_event_device *dev, ktime_t expires, | |
76 | ktime_t now) | |
77 | { | |
78 | unsigned long long clc; | |
79 | int64_t delta; | |
80 | ||
81 | delta = ktime_to_ns(ktime_sub(expires, now)); | |
82 | ||
83 | if (delta <= 0) | |
84 | return -ETIME; | |
85 | ||
86 | dev->next_event = expires; | |
87 | ||
88 | if (dev->mode == CLOCK_EVT_MODE_SHUTDOWN) | |
89 | return 0; | |
90 | ||
91 | if (delta > dev->max_delta_ns) | |
92 | delta = dev->max_delta_ns; | |
93 | if (delta < dev->min_delta_ns) | |
94 | delta = dev->min_delta_ns; | |
95 | ||
96 | clc = delta * dev->mult; | |
97 | clc >>= dev->shift; | |
98 | ||
99 | return dev->set_next_event((unsigned long) clc, dev); | |
100 | } | |
101 | ||
102 | /** | |
103 | * clockevents_register_notifier - register a clock events change listener | |
104 | */ | |
105 | int clockevents_register_notifier(struct notifier_block *nb) | |
106 | { | |
107 | int ret; | |
108 | ||
109 | spin_lock(&clockevents_lock); | |
110 | ret = raw_notifier_chain_register(&clockevents_chain, nb); | |
111 | spin_unlock(&clockevents_lock); | |
112 | ||
113 | return ret; | |
114 | } | |
115 | ||
d316c57f TG |
116 | /* |
117 | * Notify about a clock event change. Called with clockevents_lock | |
118 | * held. | |
119 | */ | |
120 | static void clockevents_do_notify(unsigned long reason, void *dev) | |
121 | { | |
122 | raw_notifier_call_chain(&clockevents_chain, reason, dev); | |
123 | } | |
124 | ||
125 | /* | |
126 | * Called after a notify add to make devices availble which were | |
127 | * released from the notifier call. | |
128 | */ | |
129 | static void clockevents_notify_released(void) | |
130 | { | |
131 | struct clock_event_device *dev; | |
132 | ||
133 | while (!list_empty(&clockevents_released)) { | |
134 | dev = list_entry(clockevents_released.next, | |
135 | struct clock_event_device, list); | |
136 | list_del(&dev->list); | |
137 | list_add(&dev->list, &clockevent_devices); | |
138 | clockevents_do_notify(CLOCK_EVT_NOTIFY_ADD, dev); | |
139 | } | |
140 | } | |
141 | ||
142 | /** | |
143 | * clockevents_register_device - register a clock event device | |
144 | * @dev: device to register | |
145 | */ | |
146 | void clockevents_register_device(struct clock_event_device *dev) | |
147 | { | |
148 | BUG_ON(dev->mode != CLOCK_EVT_MODE_UNUSED); | |
149 | ||
150 | spin_lock(&clockevents_lock); | |
151 | ||
152 | list_add(&dev->list, &clockevent_devices); | |
153 | clockevents_do_notify(CLOCK_EVT_NOTIFY_ADD, dev); | |
154 | clockevents_notify_released(); | |
155 | ||
156 | spin_unlock(&clockevents_lock); | |
157 | } | |
158 | ||
159 | /* | |
160 | * Noop handler when we shut down an event device | |
161 | */ | |
162 | static void clockevents_handle_noop(struct clock_event_device *dev) | |
163 | { | |
164 | } | |
165 | ||
166 | /** | |
167 | * clockevents_exchange_device - release and request clock devices | |
168 | * @old: device to release (can be NULL) | |
169 | * @new: device to request (can be NULL) | |
170 | * | |
171 | * Called from the notifier chain. clockevents_lock is held already | |
172 | */ | |
173 | void clockevents_exchange_device(struct clock_event_device *old, | |
174 | struct clock_event_device *new) | |
175 | { | |
176 | unsigned long flags; | |
177 | ||
178 | local_irq_save(flags); | |
179 | /* | |
180 | * Caller releases a clock event device. We queue it into the | |
181 | * released list and do a notify add later. | |
182 | */ | |
183 | if (old) { | |
184 | old->event_handler = clockevents_handle_noop; | |
185 | clockevents_set_mode(old, CLOCK_EVT_MODE_UNUSED); | |
186 | list_del(&old->list); | |
187 | list_add(&old->list, &clockevents_released); | |
188 | } | |
189 | ||
190 | if (new) { | |
191 | BUG_ON(new->mode != CLOCK_EVT_MODE_UNUSED); | |
192 | clockevents_set_mode(new, CLOCK_EVT_MODE_SHUTDOWN); | |
193 | } | |
194 | local_irq_restore(flags); | |
195 | } | |
196 | ||
de68d9b1 | 197 | #ifdef CONFIG_GENERIC_CLOCKEVENTS |
d316c57f TG |
198 | /** |
199 | * clockevents_notify - notification about relevant events | |
200 | */ | |
201 | void clockevents_notify(unsigned long reason, void *arg) | |
202 | { | |
203 | spin_lock(&clockevents_lock); | |
204 | clockevents_do_notify(reason, arg); | |
205 | ||
206 | switch (reason) { | |
207 | case CLOCK_EVT_NOTIFY_CPU_DEAD: | |
208 | /* | |
209 | * Unregister the clock event devices which were | |
210 | * released from the users in the notify chain. | |
211 | */ | |
212 | while (!list_empty(&clockevents_released)) { | |
213 | struct clock_event_device *dev; | |
214 | ||
215 | dev = list_entry(clockevents_released.next, | |
216 | struct clock_event_device, list); | |
217 | list_del(&dev->list); | |
218 | } | |
219 | break; | |
220 | default: | |
221 | break; | |
222 | } | |
223 | spin_unlock(&clockevents_lock); | |
224 | } | |
225 | EXPORT_SYMBOL_GPL(clockevents_notify); | |
de68d9b1 | 226 | #endif |