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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/interrupt.h>
18 #include <linux/percpu.h>
19 #include <linux/profile.h>
20 #include <linux/sched.h>
21 #include <linux/tick.h>
22
23 #include <asm/irq_regs.h>
24
25 #include "tick-internal.h"
26
27 /*
28  * Tick devices
29  */
30 DEFINE_PER_CPU(struct tick_device, tick_cpu_device);
31 /*
32  * Tick next event: keeps track of the tick time
33  */
34 ktime_t tick_next_period;
35 ktime_t tick_period;
36 int tick_do_timer_cpu __read_mostly = TICK_DO_TIMER_BOOT;
37 DEFINE_SPINLOCK(tick_device_lock);
38
39 /*
40  * Debugging: see timer_list.c
41  */
42 struct tick_device *tick_get_device(int cpu)
43 {
44         return &per_cpu(tick_cpu_device, cpu);
45 }
46
47 /**
48  * tick_is_oneshot_available - check for a oneshot capable event device
49  */
50 int tick_is_oneshot_available(void)
51 {
52         struct clock_event_device *dev = __get_cpu_var(tick_cpu_device).evtdev;
53
54         return dev && (dev->features & CLOCK_EVT_FEAT_ONESHOT);
55 }
56
57 /*
58  * Periodic tick
59  */
60 static void tick_periodic(int cpu)
61 {
62         if (tick_do_timer_cpu == cpu) {
63                 write_seqlock(&xtime_lock);
64
65                 /* Keep track of the next tick event */
66                 tick_next_period = ktime_add(tick_next_period, tick_period);
67
68                 do_timer(1);
69                 write_sequnlock(&xtime_lock);
70         }
71
72         update_process_times(user_mode(get_irq_regs()));
73         profile_tick(CPU_PROFILING);
74 }
75
76 /*
77  * Event handler for periodic ticks
78  */
79 void tick_handle_periodic(struct clock_event_device *dev)
80 {
81         int cpu = smp_processor_id();
82         ktime_t next;
83
84         tick_periodic(cpu);
85
86         if (dev->mode != CLOCK_EVT_MODE_ONESHOT)
87                 return;
88         /*
89          * Setup the next period for devices, which do not have
90          * periodic mode:
91          */
92         next = ktime_add(dev->next_event, tick_period);
93         for (;;) {
94                 if (!clockevents_program_event(dev, next, ktime_get()))
95                         return;
96                 tick_periodic(cpu);
97                 next = ktime_add(next, tick_period);
98         }
99 }
100
101 /*
102  * Setup the device for a periodic tick
103  */
104 void tick_setup_periodic(struct clock_event_device *dev, int broadcast)
105 {
106         tick_set_periodic_handler(dev, broadcast);
107
108         /* Broadcast setup ? */
109         if (!tick_device_is_functional(dev))
110                 return;
111
112         if ((dev->features & CLOCK_EVT_FEAT_PERIODIC) &&
113             !tick_broadcast_oneshot_active()) {
114                 clockevents_set_mode(dev, CLOCK_EVT_MODE_PERIODIC);
115         } else {
116                 unsigned long seq;
117                 ktime_t next;
118
119                 do {
120                         seq = read_seqbegin(&xtime_lock);
121                         next = tick_next_period;
122                 } while (read_seqretry(&xtime_lock, seq));
123
124                 clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
125
126                 for (;;) {
127                         if (!clockevents_program_event(dev, next, ktime_get()))
128                                 return;
129                         next = ktime_add(next, tick_period);
130                 }
131         }
132 }
133
134 /*
135  * Setup the tick device
136  */
137 static void tick_setup_device(struct tick_device *td,
138                               struct clock_event_device *newdev, int cpu,
139                               const struct cpumask *cpumask)
140 {
141         ktime_t next_event;
142         void (*handler)(struct clock_event_device *) = NULL;
143
144         /*
145          * First device setup ?
146          */
147         if (!td->evtdev) {
148                 /*
149                  * If no cpu took the do_timer update, assign it to
150                  * this cpu:
151                  */
152                 if (tick_do_timer_cpu == TICK_DO_TIMER_BOOT) {
153                         tick_do_timer_cpu = cpu;
154                         tick_next_period = ktime_get();
155                         tick_period = ktime_set(0, NSEC_PER_SEC / HZ);
156                 }
157
158                 /*
159                  * Startup in periodic mode first.
160                  */
161                 td->mode = TICKDEV_MODE_PERIODIC;
162         } else {
163                 handler = td->evtdev->event_handler;
164                 next_event = td->evtdev->next_event;
165                 td->evtdev->event_handler = clockevents_handle_noop;
166         }
167
168         td->evtdev = newdev;
169
170         /*
171          * When the device is not per cpu, pin the interrupt to the
172          * current cpu:
173          */
174         if (!cpumask_equal(newdev->cpumask, cpumask))
175                 irq_set_affinity(newdev->irq, cpumask);
176
177         /*
178          * When global broadcasting is active, check if the current
179          * device is registered as a placeholder for broadcast mode.
180          * This allows us to handle this x86 misfeature in a generic
181          * way.
182          */
183         if (tick_device_uses_broadcast(newdev, cpu))
184                 return;
185
186         if (td->mode == TICKDEV_MODE_PERIODIC)
187                 tick_setup_periodic(newdev, 0);
188         else
189                 tick_setup_oneshot(newdev, handler, next_event);
190 }
191
192 /*
193  * Check, if the new registered device should be used.
194  */
195 static int tick_check_new_device(struct clock_event_device *newdev)
196 {
197         struct clock_event_device *curdev;
198         struct tick_device *td;
199         int cpu, ret = NOTIFY_OK;
200         unsigned long flags;
201
202         spin_lock_irqsave(&tick_device_lock, flags);
203
204         cpu = smp_processor_id();
205         if (!cpumask_test_cpu(cpu, newdev->cpumask))
206                 goto out_bc;
207
208         td = &per_cpu(tick_cpu_device, cpu);
209         curdev = td->evtdev;
210
211         /* cpu local device ? */
212         if (!cpumask_equal(newdev->cpumask, cpumask_of(cpu))) {
213
214                 /*
215                  * If the cpu affinity of the device interrupt can not
216                  * be set, ignore it.
217                  */
218                 if (!irq_can_set_affinity(newdev->irq))
219                         goto out_bc;
220
221                 /*
222                  * If we have a cpu local device already, do not replace it
223                  * by a non cpu local device
224                  */
225                 if (curdev && cpumask_equal(curdev->cpumask, cpumask_of(cpu)))
226                         goto out_bc;
227         }
228
229         /*
230          * If we have an active device, then check the rating and the oneshot
231          * feature.
232          */
233         if (curdev) {
234                 /*
235                  * Prefer one shot capable devices !
236                  */
237                 if ((curdev->features & CLOCK_EVT_FEAT_ONESHOT) &&
238                     !(newdev->features & CLOCK_EVT_FEAT_ONESHOT))
239                         goto out_bc;
240                 /*
241                  * Check the rating
242                  */
243                 if (curdev->rating >= newdev->rating)
244                         goto out_bc;
245         }
246
247         /*
248          * Replace the eventually existing device by the new
249          * device. If the current device is the broadcast device, do
250          * not give it back to the clockevents layer !
251          */
252         if (tick_is_broadcast_device(curdev)) {
253                 clockevents_shutdown(curdev);
254                 curdev = NULL;
255         }
256         clockevents_exchange_device(curdev, newdev);
257         tick_setup_device(td, newdev, cpu, cpumask_of(cpu));
258         if (newdev->features & CLOCK_EVT_FEAT_ONESHOT)
259                 tick_oneshot_notify();
260
261         spin_unlock_irqrestore(&tick_device_lock, flags);
262         return NOTIFY_STOP;
263
264 out_bc:
265         /*
266          * Can the new device be used as a broadcast device ?
267          */
268         if (tick_check_broadcast_device(newdev))
269                 ret = NOTIFY_STOP;
270
271         spin_unlock_irqrestore(&tick_device_lock, flags);
272
273         return ret;
274 }
275
276 /*
277  * Shutdown an event device on a given cpu:
278  *
279  * This is called on a life CPU, when a CPU is dead. So we cannot
280  * access the hardware device itself.
281  * We just set the mode and remove it from the lists.
282  */
283 static void tick_shutdown(unsigned int *cpup)
284 {
285         struct tick_device *td = &per_cpu(tick_cpu_device, *cpup);
286         struct clock_event_device *dev = td->evtdev;
287         unsigned long flags;
288
289         spin_lock_irqsave(&tick_device_lock, flags);
290         td->mode = TICKDEV_MODE_PERIODIC;
291         if (dev) {
292                 /*
293                  * Prevent that the clock events layer tries to call
294                  * the set mode function!
295                  */
296                 dev->mode = CLOCK_EVT_MODE_UNUSED;
297                 clockevents_exchange_device(dev, NULL);
298                 td->evtdev = NULL;
299         }
300         /* Transfer the do_timer job away from this cpu */
301         if (*cpup == tick_do_timer_cpu) {
302                 int cpu = cpumask_first(cpu_online_mask);
303
304                 tick_do_timer_cpu = (cpu < nr_cpu_ids) ? cpu :
305                         TICK_DO_TIMER_NONE;
306         }
307         spin_unlock_irqrestore(&tick_device_lock, flags);
308 }
309
310 static void tick_suspend(void)
311 {
312         struct tick_device *td = &__get_cpu_var(tick_cpu_device);
313         unsigned long flags;
314
315         spin_lock_irqsave(&tick_device_lock, flags);
316         clockevents_shutdown(td->evtdev);
317         spin_unlock_irqrestore(&tick_device_lock, flags);
318 }
319
320 static void tick_resume(void)
321 {
322         struct tick_device *td = &__get_cpu_var(tick_cpu_device);
323         unsigned long flags;
324         int broadcast = tick_resume_broadcast();
325
326         spin_lock_irqsave(&tick_device_lock, flags);
327         clockevents_set_mode(td->evtdev, CLOCK_EVT_MODE_RESUME);
328
329         if (!broadcast) {
330                 if (td->mode == TICKDEV_MODE_PERIODIC)
331                         tick_setup_periodic(td->evtdev, 0);
332                 else
333                         tick_resume_oneshot();
334         }
335         spin_unlock_irqrestore(&tick_device_lock, flags);
336 }
337
338 /*
339  * Notification about clock event devices
340  */
341 static int tick_notify(struct notifier_block *nb, unsigned long reason,
342                                void *dev)
343 {
344         switch (reason) {
345
346         case CLOCK_EVT_NOTIFY_ADD:
347                 return tick_check_new_device(dev);
348
349         case CLOCK_EVT_NOTIFY_BROADCAST_ON:
350         case CLOCK_EVT_NOTIFY_BROADCAST_OFF:
351         case CLOCK_EVT_NOTIFY_BROADCAST_FORCE:
352                 tick_broadcast_on_off(reason, dev);
353                 break;
354
355         case CLOCK_EVT_NOTIFY_BROADCAST_ENTER:
356         case CLOCK_EVT_NOTIFY_BROADCAST_EXIT:
357                 tick_broadcast_oneshot_control(reason);
358                 break;
359
360         case CLOCK_EVT_NOTIFY_CPU_DEAD:
361                 tick_shutdown_broadcast_oneshot(dev);
362                 tick_shutdown_broadcast(dev);
363                 tick_shutdown(dev);
364                 break;
365
366         case CLOCK_EVT_NOTIFY_SUSPEND:
367                 tick_suspend();
368                 tick_suspend_broadcast();
369                 break;
370
371         case CLOCK_EVT_NOTIFY_RESUME:
372                 tick_resume();
373                 break;
374
375         default:
376                 break;
377         }
378
379         return NOTIFY_OK;
380 }
381
382 static struct notifier_block tick_notifier = {
383         .notifier_call = tick_notify,
384 };
385
386 /**
387  * tick_init - initialize the tick control
388  *
389  * Register the notifier with the clockevents framework
390  */
391 void __init tick_init(void)
392 {
393         clockevents_register_notifier(&tick_notifier);
394 }