xref: /openbmc/linux/kernel/time/clockevents.c (revision 22246614)
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 	if (unlikely(!evt->mult)) {
45 		evt->mult = 1;
46 		WARN_ON(1);
47 	}
48 
49 	do_div(clc, evt->mult);
50 	if (clc < 1000)
51 		clc = 1000;
52 	if (clc > LONG_MAX)
53 		clc = LONG_MAX;
54 
55 	return (unsigned long) clc;
56 }
57 
58 /**
59  * clockevents_set_mode - set the operating mode of a clock event device
60  * @dev:	device to modify
61  * @mode:	new mode
62  *
63  * Must be called with interrupts disabled !
64  */
65 void clockevents_set_mode(struct clock_event_device *dev,
66 				 enum clock_event_mode mode)
67 {
68 	if (dev->mode != mode) {
69 		dev->set_mode(mode, dev);
70 		dev->mode = mode;
71 	}
72 }
73 
74 /**
75  * clockevents_program_event - Reprogram the clock event device.
76  * @expires:	absolute expiry time (monotonic clock)
77  *
78  * Returns 0 on success, -ETIME when the event is in the past.
79  */
80 int clockevents_program_event(struct clock_event_device *dev, ktime_t expires,
81 			      ktime_t now)
82 {
83 	unsigned long long clc;
84 	int64_t delta;
85 
86 	if (unlikely(expires.tv64 < 0)) {
87 		WARN_ON_ONCE(1);
88 		return -ETIME;
89 	}
90 
91 	delta = ktime_to_ns(ktime_sub(expires, now));
92 
93 	if (delta <= 0)
94 		return -ETIME;
95 
96 	dev->next_event = expires;
97 
98 	if (dev->mode == CLOCK_EVT_MODE_SHUTDOWN)
99 		return 0;
100 
101 	if (delta > dev->max_delta_ns)
102 		delta = dev->max_delta_ns;
103 	if (delta < dev->min_delta_ns)
104 		delta = dev->min_delta_ns;
105 
106 	clc = delta * dev->mult;
107 	clc >>= dev->shift;
108 
109 	return dev->set_next_event((unsigned long) clc, dev);
110 }
111 
112 /**
113  * clockevents_register_notifier - register a clock events change listener
114  */
115 int clockevents_register_notifier(struct notifier_block *nb)
116 {
117 	int ret;
118 
119 	spin_lock(&clockevents_lock);
120 	ret = raw_notifier_chain_register(&clockevents_chain, nb);
121 	spin_unlock(&clockevents_lock);
122 
123 	return ret;
124 }
125 
126 /*
127  * Notify about a clock event change. Called with clockevents_lock
128  * held.
129  */
130 static void clockevents_do_notify(unsigned long reason, void *dev)
131 {
132 	raw_notifier_call_chain(&clockevents_chain, reason, dev);
133 }
134 
135 /*
136  * Called after a notify add to make devices available which were
137  * released from the notifier call.
138  */
139 static void clockevents_notify_released(void)
140 {
141 	struct clock_event_device *dev;
142 
143 	while (!list_empty(&clockevents_released)) {
144 		dev = list_entry(clockevents_released.next,
145 				 struct clock_event_device, list);
146 		list_del(&dev->list);
147 		list_add(&dev->list, &clockevent_devices);
148 		clockevents_do_notify(CLOCK_EVT_NOTIFY_ADD, dev);
149 	}
150 }
151 
152 /**
153  * clockevents_register_device - register a clock event device
154  * @dev:	device to register
155  */
156 void clockevents_register_device(struct clock_event_device *dev)
157 {
158 	BUG_ON(dev->mode != CLOCK_EVT_MODE_UNUSED);
159 	/*
160 	 * A nsec2cyc multiplicator of 0 is invalid and we'd crash
161 	 * on it, so fix it up and emit a warning:
162 	 */
163 	if (unlikely(!dev->mult)) {
164 		dev->mult = 1;
165 		WARN_ON(1);
166 	}
167 
168 	spin_lock(&clockevents_lock);
169 
170 	list_add(&dev->list, &clockevent_devices);
171 	clockevents_do_notify(CLOCK_EVT_NOTIFY_ADD, dev);
172 	clockevents_notify_released();
173 
174 	spin_unlock(&clockevents_lock);
175 }
176 
177 /*
178  * Noop handler when we shut down an event device
179  */
180 static void clockevents_handle_noop(struct clock_event_device *dev)
181 {
182 }
183 
184 /**
185  * clockevents_exchange_device - release and request clock devices
186  * @old:	device to release (can be NULL)
187  * @new:	device to request (can be NULL)
188  *
189  * Called from the notifier chain. clockevents_lock is held already
190  */
191 void clockevents_exchange_device(struct clock_event_device *old,
192 				 struct clock_event_device *new)
193 {
194 	unsigned long flags;
195 
196 	local_irq_save(flags);
197 	/*
198 	 * Caller releases a clock event device. We queue it into the
199 	 * released list and do a notify add later.
200 	 */
201 	if (old) {
202 		old->event_handler = clockevents_handle_noop;
203 		clockevents_set_mode(old, CLOCK_EVT_MODE_UNUSED);
204 		list_del(&old->list);
205 		list_add(&old->list, &clockevents_released);
206 	}
207 
208 	if (new) {
209 		BUG_ON(new->mode != CLOCK_EVT_MODE_UNUSED);
210 		clockevents_set_mode(new, CLOCK_EVT_MODE_SHUTDOWN);
211 	}
212 	local_irq_restore(flags);
213 }
214 
215 #ifdef CONFIG_GENERIC_CLOCKEVENTS
216 /**
217  * clockevents_notify - notification about relevant events
218  */
219 void clockevents_notify(unsigned long reason, void *arg)
220 {
221 	struct list_head *node, *tmp;
222 
223 	spin_lock(&clockevents_lock);
224 	clockevents_do_notify(reason, arg);
225 
226 	switch (reason) {
227 	case CLOCK_EVT_NOTIFY_CPU_DEAD:
228 		/*
229 		 * Unregister the clock event devices which were
230 		 * released from the users in the notify chain.
231 		 */
232 		list_for_each_safe(node, tmp, &clockevents_released)
233 			list_del(node);
234 		break;
235 	default:
236 		break;
237 	}
238 	spin_unlock(&clockevents_lock);
239 }
240 EXPORT_SYMBOL_GPL(clockevents_notify);
241 #endif
242