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906568c9 TG |
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 | ||
f8381cba TG |
23 | #include "tick-internal.h" |
24 | ||
906568c9 TG |
25 | /* |
26 | * Tick devices | |
27 | */ | |
f8381cba | 28 | DEFINE_PER_CPU(struct tick_device, tick_cpu_device); |
906568c9 TG |
29 | /* |
30 | * Tick next event: keeps track of the tick time | |
31 | */ | |
f8381cba TG |
32 | ktime_t tick_next_period; |
33 | ktime_t tick_period; | |
906568c9 | 34 | static int tick_do_timer_cpu = -1; |
f8381cba | 35 | DEFINE_SPINLOCK(tick_device_lock); |
906568c9 | 36 | |
79bf2bb3 TG |
37 | /** |
38 | * tick_is_oneshot_available - check for a oneshot capable event device | |
39 | */ | |
40 | int tick_is_oneshot_available(void) | |
41 | { | |
42 | struct clock_event_device *dev = __get_cpu_var(tick_cpu_device).evtdev; | |
43 | ||
44 | return dev && (dev->features & CLOCK_EVT_FEAT_ONESHOT); | |
45 | } | |
46 | ||
906568c9 TG |
47 | /* |
48 | * Periodic tick | |
49 | */ | |
50 | static void tick_periodic(int cpu) | |
51 | { | |
52 | if (tick_do_timer_cpu == cpu) { | |
53 | write_seqlock(&xtime_lock); | |
54 | ||
55 | /* Keep track of the next tick event */ | |
56 | tick_next_period = ktime_add(tick_next_period, tick_period); | |
57 | ||
58 | do_timer(1); | |
59 | write_sequnlock(&xtime_lock); | |
60 | } | |
61 | ||
62 | update_process_times(user_mode(get_irq_regs())); | |
63 | profile_tick(CPU_PROFILING); | |
64 | } | |
65 | ||
66 | /* | |
67 | * Event handler for periodic ticks | |
68 | */ | |
69 | void tick_handle_periodic(struct clock_event_device *dev) | |
70 | { | |
71 | int cpu = smp_processor_id(); | |
72 | ||
73 | tick_periodic(cpu); | |
74 | ||
75 | if (dev->mode != CLOCK_EVT_MODE_ONESHOT) | |
76 | return; | |
77 | /* | |
78 | * Setup the next period for devices, which do not have | |
79 | * periodic mode: | |
80 | */ | |
81 | for (;;) { | |
82 | ktime_t next = ktime_add(dev->next_event, tick_period); | |
83 | ||
84 | if (!clockevents_program_event(dev, next, ktime_get())) | |
85 | return; | |
86 | tick_periodic(cpu); | |
87 | } | |
88 | } | |
89 | ||
90 | /* | |
91 | * Setup the device for a periodic tick | |
92 | */ | |
f8381cba | 93 | void tick_setup_periodic(struct clock_event_device *dev, int broadcast) |
906568c9 | 94 | { |
f8381cba TG |
95 | tick_set_periodic_handler(dev, broadcast); |
96 | ||
97 | /* Broadcast setup ? */ | |
98 | if (!tick_device_is_functional(dev)) | |
99 | return; | |
906568c9 TG |
100 | |
101 | if (dev->features & CLOCK_EVT_FEAT_PERIODIC) { | |
102 | clockevents_set_mode(dev, CLOCK_EVT_MODE_PERIODIC); | |
103 | } else { | |
104 | unsigned long seq; | |
105 | ktime_t next; | |
106 | ||
107 | do { | |
108 | seq = read_seqbegin(&xtime_lock); | |
109 | next = tick_next_period; | |
110 | } while (read_seqretry(&xtime_lock, seq)); | |
111 | ||
112 | clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT); | |
113 | ||
114 | for (;;) { | |
115 | if (!clockevents_program_event(dev, next, ktime_get())) | |
116 | return; | |
117 | next = ktime_add(next, tick_period); | |
118 | } | |
119 | } | |
120 | } | |
121 | ||
122 | /* | |
123 | * Setup the tick device | |
124 | */ | |
125 | static void tick_setup_device(struct tick_device *td, | |
126 | struct clock_event_device *newdev, int cpu, | |
127 | cpumask_t cpumask) | |
128 | { | |
129 | ktime_t next_event; | |
130 | void (*handler)(struct clock_event_device *) = NULL; | |
131 | ||
132 | /* | |
133 | * First device setup ? | |
134 | */ | |
135 | if (!td->evtdev) { | |
136 | /* | |
137 | * If no cpu took the do_timer update, assign it to | |
138 | * this cpu: | |
139 | */ | |
140 | if (tick_do_timer_cpu == -1) { | |
141 | tick_do_timer_cpu = cpu; | |
142 | tick_next_period = ktime_get(); | |
143 | tick_period = ktime_set(0, NSEC_PER_SEC / HZ); | |
144 | } | |
145 | ||
146 | /* | |
147 | * Startup in periodic mode first. | |
148 | */ | |
149 | td->mode = TICKDEV_MODE_PERIODIC; | |
150 | } else { | |
151 | handler = td->evtdev->event_handler; | |
152 | next_event = td->evtdev->next_event; | |
153 | } | |
154 | ||
155 | td->evtdev = newdev; | |
156 | ||
157 | /* | |
158 | * When the device is not per cpu, pin the interrupt to the | |
159 | * current cpu: | |
160 | */ | |
161 | if (!cpus_equal(newdev->cpumask, cpumask)) | |
162 | irq_set_affinity(newdev->irq, cpumask); | |
163 | ||
f8381cba TG |
164 | /* |
165 | * When global broadcasting is active, check if the current | |
166 | * device is registered as a placeholder for broadcast mode. | |
167 | * This allows us to handle this x86 misfeature in a generic | |
168 | * way. | |
169 | */ | |
170 | if (tick_device_uses_broadcast(newdev, cpu)) | |
171 | return; | |
172 | ||
906568c9 TG |
173 | if (td->mode == TICKDEV_MODE_PERIODIC) |
174 | tick_setup_periodic(newdev, 0); | |
79bf2bb3 TG |
175 | else |
176 | tick_setup_oneshot(newdev, handler, next_event); | |
906568c9 TG |
177 | } |
178 | ||
179 | /* | |
180 | * Check, if the new registered device should be used. | |
181 | */ | |
182 | static int tick_check_new_device(struct clock_event_device *newdev) | |
183 | { | |
184 | struct clock_event_device *curdev; | |
185 | struct tick_device *td; | |
186 | int cpu, ret = NOTIFY_OK; | |
187 | unsigned long flags; | |
188 | cpumask_t cpumask; | |
189 | ||
190 | spin_lock_irqsave(&tick_device_lock, flags); | |
191 | ||
192 | cpu = smp_processor_id(); | |
193 | if (!cpu_isset(cpu, newdev->cpumask)) | |
194 | goto out; | |
195 | ||
196 | td = &per_cpu(tick_cpu_device, cpu); | |
197 | curdev = td->evtdev; | |
198 | cpumask = cpumask_of_cpu(cpu); | |
199 | ||
200 | /* cpu local device ? */ | |
201 | if (!cpus_equal(newdev->cpumask, cpumask)) { | |
202 | ||
203 | /* | |
204 | * If the cpu affinity of the device interrupt can not | |
205 | * be set, ignore it. | |
206 | */ | |
207 | if (!irq_can_set_affinity(newdev->irq)) | |
208 | goto out_bc; | |
209 | ||
210 | /* | |
211 | * If we have a cpu local device already, do not replace it | |
212 | * by a non cpu local device | |
213 | */ | |
214 | if (curdev && cpus_equal(curdev->cpumask, cpumask)) | |
215 | goto out_bc; | |
216 | } | |
217 | ||
218 | /* | |
219 | * If we have an active device, then check the rating and the oneshot | |
220 | * feature. | |
221 | */ | |
222 | if (curdev) { | |
79bf2bb3 TG |
223 | /* |
224 | * Prefer one shot capable devices ! | |
225 | */ | |
226 | if ((curdev->features & CLOCK_EVT_FEAT_ONESHOT) && | |
227 | !(newdev->features & CLOCK_EVT_FEAT_ONESHOT)) | |
228 | goto out_bc; | |
906568c9 TG |
229 | /* |
230 | * Check the rating | |
231 | */ | |
232 | if (curdev->rating >= newdev->rating) | |
f8381cba | 233 | goto out_bc; |
906568c9 TG |
234 | } |
235 | ||
236 | /* | |
237 | * Replace the eventually existing device by the new | |
f8381cba TG |
238 | * device. If the current device is the broadcast device, do |
239 | * not give it back to the clockevents layer ! | |
906568c9 | 240 | */ |
f8381cba TG |
241 | if (tick_is_broadcast_device(curdev)) { |
242 | clockevents_set_mode(curdev, CLOCK_EVT_MODE_SHUTDOWN); | |
243 | curdev = NULL; | |
244 | } | |
906568c9 TG |
245 | clockevents_exchange_device(curdev, newdev); |
246 | tick_setup_device(td, newdev, cpu, cpumask); | |
79bf2bb3 TG |
247 | if (newdev->features & CLOCK_EVT_FEAT_ONESHOT) |
248 | tick_oneshot_notify(); | |
906568c9 | 249 | |
f8381cba TG |
250 | spin_unlock_irqrestore(&tick_device_lock, flags); |
251 | return NOTIFY_STOP; | |
252 | ||
253 | out_bc: | |
254 | /* | |
255 | * Can the new device be used as a broadcast device ? | |
256 | */ | |
257 | if (tick_check_broadcast_device(newdev)) | |
258 | ret = NOTIFY_STOP; | |
906568c9 TG |
259 | out: |
260 | spin_unlock_irqrestore(&tick_device_lock, flags); | |
f8381cba | 261 | |
906568c9 TG |
262 | return ret; |
263 | } | |
264 | ||
265 | /* | |
266 | * Shutdown an event device on a given cpu: | |
267 | * | |
268 | * This is called on a life CPU, when a CPU is dead. So we cannot | |
269 | * access the hardware device itself. | |
270 | * We just set the mode and remove it from the lists. | |
271 | */ | |
272 | static void tick_shutdown(unsigned int *cpup) | |
273 | { | |
274 | struct tick_device *td = &per_cpu(tick_cpu_device, *cpup); | |
275 | struct clock_event_device *dev = td->evtdev; | |
276 | unsigned long flags; | |
277 | ||
278 | spin_lock_irqsave(&tick_device_lock, flags); | |
279 | td->mode = TICKDEV_MODE_PERIODIC; | |
280 | if (dev) { | |
281 | /* | |
282 | * Prevent that the clock events layer tries to call | |
283 | * the set mode function! | |
284 | */ | |
285 | dev->mode = CLOCK_EVT_MODE_UNUSED; | |
286 | clockevents_exchange_device(dev, NULL); | |
287 | td->evtdev = NULL; | |
288 | } | |
289 | spin_unlock_irqrestore(&tick_device_lock, flags); | |
290 | } | |
291 | ||
292 | /* | |
293 | * Notification about clock event devices | |
294 | */ | |
295 | static int tick_notify(struct notifier_block *nb, unsigned long reason, | |
296 | void *dev) | |
297 | { | |
298 | switch (reason) { | |
299 | ||
300 | case CLOCK_EVT_NOTIFY_ADD: | |
301 | return tick_check_new_device(dev); | |
302 | ||
f8381cba TG |
303 | case CLOCK_EVT_NOTIFY_BROADCAST_ON: |
304 | case CLOCK_EVT_NOTIFY_BROADCAST_OFF: | |
305 | tick_broadcast_on_off(reason, dev); | |
306 | break; | |
307 | ||
79bf2bb3 TG |
308 | case CLOCK_EVT_NOTIFY_BROADCAST_ENTER: |
309 | case CLOCK_EVT_NOTIFY_BROADCAST_EXIT: | |
310 | tick_broadcast_oneshot_control(reason); | |
311 | break; | |
312 | ||
906568c9 | 313 | case CLOCK_EVT_NOTIFY_CPU_DEAD: |
79bf2bb3 | 314 | tick_shutdown_broadcast_oneshot(dev); |
f8381cba | 315 | tick_shutdown_broadcast(dev); |
906568c9 TG |
316 | tick_shutdown(dev); |
317 | break; | |
318 | ||
319 | default: | |
320 | break; | |
321 | } | |
322 | ||
323 | return NOTIFY_OK; | |
324 | } | |
325 | ||
326 | static struct notifier_block tick_notifier = { | |
327 | .notifier_call = tick_notify, | |
328 | }; | |
329 | ||
330 | /** | |
331 | * tick_init - initialize the tick control | |
332 | * | |
333 | * Register the notifier with the clockevents framework | |
334 | */ | |
335 | void __init tick_init(void) | |
336 | { | |
337 | clockevents_register_notifier(&tick_notifier); | |
338 | } |