1 /*
2 * linux/kernel/time/tick-common.c
3 *
4 * This file contains the base functions to manage periodic tick
5 * related events.
6 *
7 * Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de>
8 * Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar
9 * Copyright(C) 2006-2007, Timesys Corp., Thomas Gleixner
10 *
11 * This code is licenced under the GPL version 2. For details see
12 * kernel-base/COPYING.
13 */
14 #include <linux/cpu.h>
15 #include <linux/err.h>
16 #include <linux/hrtimer.h>
17 #include <linux/irq.h>
18 #include <linux/percpu.h>
19 #include <linux/profile.h>
20 #include <linux/sched.h>
21 #include <linux/tick.h>
22
23 #include "tick-internal.h"
24
25 /*
26 * Tick devices
27 */
28 DEFINE_PER_CPU(struct tick_device, tick_cpu_device);
29 /*
30 * Tick next event: keeps track of the tick time
31 */
32 ktime_t tick_next_period;
33 ktime_t tick_period;
34 int tick_do_timer_cpu __read_mostly = -1;
35 DEFINE_RAW_SPINLOCK(tick_device_lock);
36
37 /*
38 * Debugging: see timer_list.c
39 */
40 struct tick_device *tick_get_device(int cpu)
41 {
42 return &per_cpu(tick_cpu_device, cpu);
43 }
44
45 /**
46 * tick_is_oneshot_available - check for a oneshot capable event device
47 */
48 int tick_is_oneshot_available(void)
49 {
50 struct clock_event_device *dev = __get_cpu_var(tick_cpu_device).evtdev;
51
52 return dev && (dev->features & CLOCK_EVT_FEAT_ONESHOT);
53 }
54
55 /*
56 * Periodic tick
57 */
58 static void tick_periodic(int cpu)
59 {
60 if (tick_do_timer_cpu == cpu) {
61 write_seqlock(&xtime_lock);
62
63 /* Keep track of the next tick event */
64 tick_next_period = ktime_add(tick_next_period, tick_period);
65
66 do_timer(1);
67 write_sequnlock(&xtime_lock);
68 }
69
70 update_process_times(user_mode(get_irq_regs()));
71 }
72
73 /*
74 * Event handler for periodic ticks
75 */
76 void tick_handle_periodic(struct clock_event_device *dev)
77 {
78 int cpu = smp_processor_id();
79 ktime_t next;
80
81 tick_periodic(cpu);
82
83 if (dev->mode != CLOCK_EVT_MODE_ONESHOT)
84 return;
85 /*
86 * Setup the next period for devices, which do not have
87 * periodic mode:
88 */
89 next = ktime_add(dev->next_event, tick_period);
90 for (;;) {
91 if (!clockevents_program_event(dev, next, ktime_get()))
92 return;
93 tick_periodic(cpu);
94 next = ktime_add(next, tick_period);
95 }
96 }
97
98 /*
99 * Setup the device for a periodic tick
100 */
101 void tick_setup_periodic(struct clock_event_device *dev, int broadcast)
102 {
103 tick_set_periodic_handler(dev, broadcast);
104
105 /* Broadcast setup ? */
106 if (!tick_device_is_functional(dev))
107 return;
108
109 if (dev->features & CLOCK_EVT_FEAT_PERIODIC) {
110 clockevents_set_mode(dev, CLOCK_EVT_MODE_PERIODIC);
111 } else {
112 unsigned long seq;
113 ktime_t next;
114
115 do {
116 seq = read_seqbegin(&xtime_lock);
117 next = tick_next_period;
118 } while (read_seqretry(&xtime_lock, seq));
119
120 clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
121
122 for (;;) {
123 if (!clockevents_program_event(dev, next, ktime_get()))
124 return;
125 next = ktime_add(next, tick_period);
126 }
127 }
128 }
129
130 /*
131 * Setup the tick device
132 */
133 static void tick_setup_device(struct tick_device *td,
134 struct clock_event_device *newdev, int cpu,
135 cpumask_t cpumask)
136 {
137 ktime_t next_event;
138 void (*handler)(struct clock_event_device *) = NULL;
139
140 /*
141 * First device setup ?
142 */
143 if (!td->evtdev) {
144 /*
145 * If no cpu took the do_timer update, assign it to
146 * this cpu:
147 */
148 if (tick_do_timer_cpu == -1) {
149 tick_do_timer_cpu = cpu;
150 tick_next_period = ktime_get();
151 tick_period = ktime_set(0, NSEC_PER_SEC / HZ);
152 }
153
154 /*
155 * Startup in periodic mode first.
156 */
157 td->mode = TICKDEV_MODE_PERIODIC;
158 } else {
159 handler = td->evtdev->event_handler;
160 next_event = td->evtdev->next_event;
161 }
162
163 td->evtdev = newdev;
164
165 /*
166 * When the device is not per cpu, pin the interrupt to the
167 * current cpu:
168 */
169 if (!cpus_equal(newdev->cpumask, cpumask))
170 irq_set_affinity(newdev->irq, cpumask);
171
172 /*
173 * When global broadcasting is active, check if the current
174 * device is registered as a placeholder for broadcast mode.
175 * This allows us to handle this x86 misfeature in a generic
176 * way.
177 */
178 if (tick_device_uses_broadcast(newdev, cpu))
179 return;
180
181 if (td->mode == TICKDEV_MODE_PERIODIC)
182 tick_setup_periodic(newdev, 0);
183 else
184 tick_setup_oneshot(newdev, handler, next_event);
185 }
186
187 /*
188 * Check, if the new registered device should be used.
189 */
190 static int tick_check_new_device(struct clock_event_device *newdev)
191 {
192 struct clock_event_device *curdev;
193 struct tick_device *td;
194 int cpu, ret = NOTIFY_OK;
195 unsigned long flags;
196 cpumask_t cpumask;
197
198 spin_lock_irqsave(&tick_device_lock, flags);
199
200 cpu = smp_processor_id();
201 if (!cpu_isset(cpu, newdev->cpumask))
202 goto out_bc;
203
204 td = &per_cpu(tick_cpu_device, cpu);
205 curdev = td->evtdev;
206 cpumask = cpumask_of_cpu(cpu);
207
208 /* cpu local device ? */
209 if (!cpus_equal(newdev->cpumask, cpumask)) {
210
211 /*
212 * If the cpu affinity of the device interrupt can not
213 * be set, ignore it.
214 */
215 if (!irq_can_set_affinity(newdev->irq))
216 goto out_bc;
217
218 /*
219 * If we have a cpu local device already, do not replace it
220 * by a non cpu local device
221 */
222 if (curdev && cpus_equal(curdev->cpumask, cpumask))
223 goto out_bc;
224 }
225
226 /*
227 * If we have an active device, then check the rating and the oneshot
228 * feature.
229 */
230 if (curdev) {
231 /*
232 * Prefer one shot capable devices !
233 */
234 if ((curdev->features & CLOCK_EVT_FEAT_ONESHOT) &&
235 !(newdev->features & CLOCK_EVT_FEAT_ONESHOT))
236 goto out_bc;
237 /*
238 * Check the rating
239 */
240 if (curdev->rating >= newdev->rating)
241 goto out_bc;
242 }
243
244 /*
245 * Replace the eventually existing device by the new
246 * device. If the current device is the broadcast device, do
247 * not give it back to the clockevents layer !
248 */
249 if (tick_is_broadcast_device(curdev)) {
250 clockevents_set_mode(curdev, CLOCK_EVT_MODE_SHUTDOWN);
251 curdev = NULL;
252 }
253 clockevents_exchange_device(curdev, newdev);
254 tick_setup_device(td, newdev, cpu, cpumask);
255 if (newdev->features & CLOCK_EVT_FEAT_ONESHOT)
256 tick_oneshot_notify();
257
258 spin_unlock_irqrestore(&tick_device_lock, flags);
259 return NOTIFY_STOP;
260
261 out_bc:
262 /*
263 * Can the new device be used as a broadcast device ?
264 */
265 if (tick_check_broadcast_device(newdev))
266 ret = NOTIFY_STOP;
267
268 spin_unlock_irqrestore(&tick_device_lock, flags);
269
270 return ret;
271 }
272
273 /*
274 * Shutdown an event device on a given cpu:
275 *
276 * This is called on a life CPU, when a CPU is dead. So we cannot
277 * access the hardware device itself.
278 * We just set the mode and remove it from the lists.
279 */
280 static void tick_shutdown(unsigned int *cpup)
281 {
282 struct tick_device *td = &per_cpu(tick_cpu_device, *cpup);
283 struct clock_event_device *dev = td->evtdev;
284 unsigned long flags;
285
286 spin_lock_irqsave(&tick_device_lock, flags);
287 td->mode = TICKDEV_MODE_PERIODIC;
288 if (dev) {
289 /*
290 * Prevent that the clock events layer tries to call
291 * the set mode function!
292 */
293 dev->mode = CLOCK_EVT_MODE_UNUSED;
294 clockevents_exchange_device(dev, NULL);
295 td->evtdev = NULL;
296 }
297 /* Transfer the do_timer job away from this cpu */
298 if (*cpup == tick_do_timer_cpu) {
299 int cpu = first_cpu(cpu_online_map);
300
301 tick_do_timer_cpu = (cpu != NR_CPUS) ? cpu : -1;
302 }
303 spin_unlock_irqrestore(&tick_device_lock, flags);
304 }
305
306 static void tick_suspend(void)
307 {
308 struct tick_device *td = &__get_cpu_var(tick_cpu_device);
309 unsigned long flags;
310
311 spin_lock_irqsave(&tick_device_lock, flags);
312 clockevents_set_mode(td->evtdev, CLOCK_EVT_MODE_SHUTDOWN);
313 spin_unlock_irqrestore(&tick_device_lock, flags);
314 }
315
316 static void tick_resume(void)
317 {
318 struct tick_device *td = &__get_cpu_var(tick_cpu_device);
319 unsigned long flags;
320 int broadcast = tick_resume_broadcast();
321
322 spin_lock_irqsave(&tick_device_lock, flags);
323 clockevents_set_mode(td->evtdev, CLOCK_EVT_MODE_RESUME);
324
325 if (!broadcast) {
326 if (td->mode == TICKDEV_MODE_PERIODIC)
327 tick_setup_periodic(td->evtdev, 0);
328 else
329 tick_resume_oneshot();
330 }
331 spin_unlock_irqrestore(&tick_device_lock, flags);
332 }
333
334 /*
335 * Notification about clock event devices
336 */
337 static int tick_notify(struct notifier_block *nb, unsigned long reason,
338 void *dev)
339 {
340 switch (reason) {
341
342 case CLOCK_EVT_NOTIFY_ADD:
343 return tick_check_new_device(dev);
344
345 case CLOCK_EVT_NOTIFY_BROADCAST_ON:
346 case CLOCK_EVT_NOTIFY_BROADCAST_OFF:
347 case CLOCK_EVT_NOTIFY_BROADCAST_FORCE:
348 tick_broadcast_on_off(reason, dev);
349 break;
350
351 case CLOCK_EVT_NOTIFY_BROADCAST_ENTER:
352 case CLOCK_EVT_NOTIFY_BROADCAST_EXIT:
353 tick_broadcast_oneshot_control(reason);
354 break;
355
356 case CLOCK_EVT_NOTIFY_CPU_DEAD:
357 tick_shutdown_broadcast_oneshot(dev);
358 tick_shutdown_broadcast(dev);
359 tick_shutdown(dev);
360 break;
361
362 case CLOCK_EVT_NOTIFY_SUSPEND:
363 tick_suspend();
364 tick_suspend_broadcast();
365 break;
366
367 case CLOCK_EVT_NOTIFY_RESUME:
368 tick_resume();
369 break;
370
371 default:
372 break;
373 }
374
375 return NOTIFY_OK;
376 }
377
378 static struct notifier_block tick_notifier = {
379 .notifier_call = tick_notify,
380 };
381
382 /**
383 * tick_init - initialize the tick control
384 *
385 * Register the notifier with the clockevents framework
386 */
387 void __init tick_init(void)
388 {
389 clockevents_register_notifier(&tick_notifier);
390 }
391
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