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 #include <linux/ftrace.h>
22
23 /* The registered clock event devices */
24 static LIST_HEAD(clockevent_devices);
25 static LIST_HEAD(clockevents_released);
26
27 /* Notification for clock events */
28 static RAW_NOTIFIER_HEAD(clockevents_chain);
29
30 /* Protection for the above */
31 static DEFINE_RAW_SPINLOCK(clockevents_lock);
32
33 /**
34 * clockevents_delta2ns - Convert a latch value (device ticks) to nanoseconds
35 * @latch: value to convert
36 * @evt: pointer to clock event device descriptor
37 *
38 * Math helper, returns latch value converted to nanoseconds (bound checked)
39 */
40 unsigned long clockevent_delta2ns(unsigned long latch,
41 struct clock_event_device *evt)
42 {
43 u64 clc = ((u64) latch << evt->shift);
44
45 if (unlikely(!evt->mult)) {
46 evt->mult = 1;
47 WARN_ON(1);
48 }
49
50 do_div(clc, evt->mult);
51 if (clc < 1000)
52 clc = 1000;
53 if (clc > LONG_MAX)
54 clc = LONG_MAX;
55
56 return (unsigned long) clc;
57 }
58
59 /**
60 * clockevents_set_mode - set the operating mode of a clock event device
61 * @dev: device to modify
62 * @mode: new mode
63 *
64 * Must be called with interrupts disabled !
65 */
66 void clockevents_set_mode(struct clock_event_device *dev,
67 enum clock_event_mode mode)
68 {
69 if (dev->mode != mode) {
70 dev->set_mode(mode, dev);
71 dev->mode = mode;
72 }
73 }
74
75 /**
76 * clockevents_program_event - Reprogram the clock event device.
77 * @expires: absolute expiry time (monotonic clock)
78 *
79 * Returns 0 on success, -ETIME when the event is in the past.
80 */
81 int clockevents_program_event(struct clock_event_device *dev, ktime_t expires,
82 ktime_t now)
83 {
84 unsigned long long clc;
85 int64_t delta;
86
87 if (unlikely(expires.tv64 < 0)) {
88 WARN_ON_ONCE(1);
89 return -ETIME;
90 }
91
92 delta = ktime_to_ns(ktime_sub(expires, now));
93
94 ftrace_event_program_event(&expires, &delta);
95
96 if (delta <= 0)
97 return -ETIME;
98
99 dev->next_event = expires;
100
101 if (dev->mode == CLOCK_EVT_MODE_SHUTDOWN)
102 return 0;
103
104 if (delta > dev->max_delta_ns)
105 delta = dev->max_delta_ns;
106 if (delta < dev->min_delta_ns)
107 delta = dev->min_delta_ns;
108
109 clc = delta * dev->mult;
110 clc >>= dev->shift;
111
112 return dev->set_next_event((unsigned long) clc, dev);
113 }
114
115 /**
116 * clockevents_register_notifier - register a clock events change listener
117 */
118 int clockevents_register_notifier(struct notifier_block *nb)
119 {
120 int ret;
121
122 spin_lock(&clockevents_lock);
123 ret = raw_notifier_chain_register(&clockevents_chain, nb);
124 spin_unlock(&clockevents_lock);
125
126 return ret;
127 }
128
129 /*
130 * Notify about a clock event change. Called with clockevents_lock
131 * held.
132 */
133 static void clockevents_do_notify(unsigned long reason, void *dev)
134 {
135 raw_notifier_call_chain(&clockevents_chain, reason, dev);
136 }
137
138 /*
139 * Called after a notify add to make devices available which were
140 * released from the notifier call.
141 */
142 static void clockevents_notify_released(void)
143 {
144 struct clock_event_device *dev;
145
146 while (!list_empty(&clockevents_released)) {
147 dev = list_entry(clockevents_released.next,
148 struct clock_event_device, list);
149 list_del(&dev->list);
150 list_add(&dev->list, &clockevent_devices);
151 clockevents_do_notify(CLOCK_EVT_NOTIFY_ADD, dev);
152 }
153 }
154
155 /**
156 * clockevents_register_device - register a clock event device
157 * @dev: device to register
158 */
159 void clockevents_register_device(struct clock_event_device *dev)
160 {
161 BUG_ON(dev->mode != CLOCK_EVT_MODE_UNUSED);
162 /*
163 * A nsec2cyc multiplicator of 0 is invalid and we'd crash
164 * on it, so fix it up and emit a warning:
165 */
166 if (unlikely(!dev->mult)) {
167 dev->mult = 1;
168 WARN_ON(1);
169 }
170
171 spin_lock(&clockevents_lock);
172
173 list_add(&dev->list, &clockevent_devices);
174 clockevents_do_notify(CLOCK_EVT_NOTIFY_ADD, dev);
175 clockevents_notify_released();
176
177 spin_unlock(&clockevents_lock);
178 }
179
180 /*
181 * Noop handler when we shut down an event device
182 */
183 static void clockevents_handle_noop(struct clock_event_device *dev)
184 {
185 }
186
187 /**
188 * clockevents_exchange_device - release and request clock devices
189 * @old: device to release (can be NULL)
190 * @new: device to request (can be NULL)
191 *
192 * Called from the notifier chain. clockevents_lock is held already
193 */
194 void clockevents_exchange_device(struct clock_event_device *old,
195 struct clock_event_device *new)
196 {
197 unsigned long flags;
198
199 local_irq_save(flags);
200 /*
201 * Caller releases a clock event device. We queue it into the
202 * released list and do a notify add later.
203 */
204 if (old) {
205 old->event_handler = clockevents_handle_noop;
206 clockevents_set_mode(old, CLOCK_EVT_MODE_UNUSED);
207 list_del(&old->list);
208 list_add(&old->list, &clockevents_released);
209 }
210
211 if (new) {
212 BUG_ON(new->mode != CLOCK_EVT_MODE_UNUSED);
213 clockevents_set_mode(new, CLOCK_EVT_MODE_SHUTDOWN);
214 }
215 local_irq_restore(flags);
216 }
217
218 #ifdef CONFIG_GENERIC_CLOCKEVENTS
219 /**
220 * clockevents_notify - notification about relevant events
221 */
222 void clockevents_notify(unsigned long reason, void *arg)
223 {
224 struct list_head *node, *tmp;
225
226 spin_lock(&clockevents_lock);
227 clockevents_do_notify(reason, arg);
228
229 switch (reason) {
230 case CLOCK_EVT_NOTIFY_CPU_DEAD:
231 /*
232 * Unregister the clock event devices which were
233 * released from the users in the notify chain.
234 */
235 list_for_each_safe(node, tmp, &clockevents_released)
236 list_del(node);
237 break;
238 default:
239 break;
240 }
241 spin_unlock(&clockevents_lock);
242 }
243 EXPORT_SYMBOL_GPL(clockevents_notify);
244 #endif
245
|
This page was automatically generated by the
LXR engine.
|