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 static int tick_do_timer_cpu = -1; 35 DEFINE_SPINLOCK(tick_device_lock); 36 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 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 */ 93 void tick_setup_periodic(struct clock_event_device *dev, int broadcast) 94 { 95 tick_set_periodic_handler(dev, broadcast); 96 97 /* Broadcast setup ? */ 98 if (!tick_device_is_functional(dev)) 99 return; 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); 163 164 /* 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; 172 173 if (td->mode == TICKDEV_MODE_PERIODIC) 174 tick_setup_periodic(newdev, 0); 175 else 176 tick_setup_oneshot(newdev, handler, next_event); 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) { 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; 229 /* 230 * Check the rating 231 */ 232 if (curdev->rating >= newdev->rating) 233 goto out_bc; 234 } 235 236 /* 237 * Replace the eventually existing device by the new 238 * device. If the current device is the broadcast device, do 239 * not give it back to the clockevents layer ! 240 */ 241 if (tick_is_broadcast_device(curdev)) { 242 clockevents_set_mode(curdev, CLOCK_EVT_MODE_SHUTDOWN); 243 curdev = NULL; 244 } 245 clockevents_exchange_device(curdev, newdev); 246 tick_setup_device(td, newdev, cpu, cpumask); 247 if (newdev->features & CLOCK_EVT_FEAT_ONESHOT) 248 tick_oneshot_notify(); 249 250 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; 259 out: 260 spin_unlock_irqrestore(&tick_device_lock, flags); 261 262 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); 302 303 case CLOCK_EVT_NOTIFY_BROADCAST_ON: 304 case CLOCK_EVT_NOTIFY_BROADCAST_OFF: 305 tick_broadcast_on_off(reason, dev); 306 break; 307 308 case CLOCK_EVT_NOTIFY_BROADCAST_ENTER: 309 case CLOCK_EVT_NOTIFY_BROADCAST_EXIT: 310 tick_broadcast_oneshot_control(reason); 311 break; 312 313 case CLOCK_EVT_NOTIFY_CPU_DEAD: 314 tick_shutdown_broadcast_oneshot(dev); 315 tick_shutdown_broadcast(dev); 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 } 339