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/module.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 38 /* 39 * Debugging: see timer_list.c 40 */ 41 struct tick_device *tick_get_device(int cpu) 42 { 43 return &per_cpu(tick_cpu_device, cpu); 44 } 45 46 /** 47 * tick_is_oneshot_available - check for a oneshot capable event device 48 */ 49 int tick_is_oneshot_available(void) 50 { 51 struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev); 52 53 if (!dev || !(dev->features & CLOCK_EVT_FEAT_ONESHOT)) 54 return 0; 55 if (!(dev->features & CLOCK_EVT_FEAT_C3STOP)) 56 return 1; 57 return tick_broadcast_oneshot_available(); 58 } 59 60 /* 61 * Periodic tick 62 */ 63 static void tick_periodic(int cpu) 64 { 65 if (tick_do_timer_cpu == cpu) { 66 write_seqlock(&jiffies_lock); 67 68 /* Keep track of the next tick event */ 69 tick_next_period = ktime_add(tick_next_period, tick_period); 70 71 do_timer(1); 72 write_sequnlock(&jiffies_lock); 73 } 74 75 update_process_times(user_mode(get_irq_regs())); 76 profile_tick(CPU_PROFILING); 77 } 78 79 /* 80 * Event handler for periodic ticks 81 */ 82 void tick_handle_periodic(struct clock_event_device *dev) 83 { 84 int cpu = smp_processor_id(); 85 ktime_t next; 86 87 tick_periodic(cpu); 88 89 if (dev->mode != CLOCK_EVT_MODE_ONESHOT) 90 return; 91 /* 92 * Setup the next period for devices, which do not have 93 * periodic mode: 94 */ 95 next = ktime_add(dev->next_event, tick_period); 96 for (;;) { 97 if (!clockevents_program_event(dev, next, false)) 98 return; 99 /* 100 * Have to be careful here. If we're in oneshot mode, 101 * before we call tick_periodic() in a loop, we need 102 * to be sure we're using a real hardware clocksource. 103 * Otherwise we could get trapped in an infinite 104 * loop, as the tick_periodic() increments jiffies, 105 * when then will increment time, posibly causing 106 * the loop to trigger again and again. 107 */ 108 if (timekeeping_valid_for_hres()) 109 tick_periodic(cpu); 110 next = ktime_add(next, tick_period); 111 } 112 } 113 114 /* 115 * Setup the device for a periodic tick 116 */ 117 void tick_setup_periodic(struct clock_event_device *dev, int broadcast) 118 { 119 tick_set_periodic_handler(dev, broadcast); 120 121 /* Broadcast setup ? */ 122 if (!tick_device_is_functional(dev)) 123 return; 124 125 if ((dev->features & CLOCK_EVT_FEAT_PERIODIC) && 126 !tick_broadcast_oneshot_active()) { 127 clockevents_set_mode(dev, CLOCK_EVT_MODE_PERIODIC); 128 } else { 129 unsigned long seq; 130 ktime_t next; 131 132 do { 133 seq = read_seqbegin(&jiffies_lock); 134 next = tick_next_period; 135 } while (read_seqretry(&jiffies_lock, seq)); 136 137 clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT); 138 139 for (;;) { 140 if (!clockevents_program_event(dev, next, false)) 141 return; 142 next = ktime_add(next, tick_period); 143 } 144 } 145 } 146 147 /* 148 * Setup the tick device 149 */ 150 static void tick_setup_device(struct tick_device *td, 151 struct clock_event_device *newdev, int cpu, 152 const struct cpumask *cpumask) 153 { 154 ktime_t next_event; 155 void (*handler)(struct clock_event_device *) = NULL; 156 157 /* 158 * First device setup ? 159 */ 160 if (!td->evtdev) { 161 /* 162 * If no cpu took the do_timer update, assign it to 163 * this cpu: 164 */ 165 if (tick_do_timer_cpu == TICK_DO_TIMER_BOOT) { 166 if (!tick_nohz_full_cpu(cpu)) 167 tick_do_timer_cpu = cpu; 168 else 169 tick_do_timer_cpu = TICK_DO_TIMER_NONE; 170 tick_next_period = ktime_get(); 171 tick_period = ktime_set(0, NSEC_PER_SEC / HZ); 172 } 173 174 /* 175 * Startup in periodic mode first. 176 */ 177 td->mode = TICKDEV_MODE_PERIODIC; 178 } else { 179 handler = td->evtdev->event_handler; 180 next_event = td->evtdev->next_event; 181 td->evtdev->event_handler = clockevents_handle_noop; 182 } 183 184 td->evtdev = newdev; 185 186 /* 187 * When the device is not per cpu, pin the interrupt to the 188 * current cpu: 189 */ 190 if (!cpumask_equal(newdev->cpumask, cpumask)) 191 irq_set_affinity(newdev->irq, cpumask); 192 193 /* 194 * When global broadcasting is active, check if the current 195 * device is registered as a placeholder for broadcast mode. 196 * This allows us to handle this x86 misfeature in a generic 197 * way. This function also returns !=0 when we keep the 198 * current active broadcast state for this CPU. 199 */ 200 if (tick_device_uses_broadcast(newdev, cpu)) 201 return; 202 203 if (td->mode == TICKDEV_MODE_PERIODIC) 204 tick_setup_periodic(newdev, 0); 205 else 206 tick_setup_oneshot(newdev, handler, next_event); 207 } 208 209 void tick_install_replacement(struct clock_event_device *newdev) 210 { 211 struct tick_device *td = &__get_cpu_var(tick_cpu_device); 212 int cpu = smp_processor_id(); 213 214 clockevents_exchange_device(td->evtdev, newdev); 215 tick_setup_device(td, newdev, cpu, cpumask_of(cpu)); 216 if (newdev->features & CLOCK_EVT_FEAT_ONESHOT) 217 tick_oneshot_notify(); 218 } 219 220 static bool tick_check_percpu(struct clock_event_device *curdev, 221 struct clock_event_device *newdev, int cpu) 222 { 223 if (!cpumask_test_cpu(cpu, newdev->cpumask)) 224 return false; 225 if (cpumask_equal(newdev->cpumask, cpumask_of(cpu))) 226 return true; 227 /* Check if irq affinity can be set */ 228 if (newdev->irq >= 0 && !irq_can_set_affinity(newdev->irq)) 229 return false; 230 /* Prefer an existing cpu local device */ 231 if (curdev && cpumask_equal(curdev->cpumask, cpumask_of(cpu))) 232 return false; 233 return true; 234 } 235 236 static bool tick_check_preferred(struct clock_event_device *curdev, 237 struct clock_event_device *newdev) 238 { 239 /* Prefer oneshot capable device */ 240 if (!(newdev->features & CLOCK_EVT_FEAT_ONESHOT)) { 241 if (curdev && (curdev->features & CLOCK_EVT_FEAT_ONESHOT)) 242 return false; 243 if (tick_oneshot_mode_active()) 244 return false; 245 } 246 247 /* 248 * Use the higher rated one, but prefer a CPU local device with a lower 249 * rating than a non-CPU local device 250 */ 251 return !curdev || 252 newdev->rating > curdev->rating || 253 !cpumask_equal(curdev->cpumask, newdev->cpumask); 254 } 255 256 /* 257 * Check whether the new device is a better fit than curdev. curdev 258 * can be NULL ! 259 */ 260 bool tick_check_replacement(struct clock_event_device *curdev, 261 struct clock_event_device *newdev) 262 { 263 if (tick_check_percpu(curdev, newdev, smp_processor_id())) 264 return false; 265 266 return tick_check_preferred(curdev, newdev); 267 } 268 269 /* 270 * Check, if the new registered device should be used. Called with 271 * clockevents_lock held and interrupts disabled. 272 */ 273 void tick_check_new_device(struct clock_event_device *newdev) 274 { 275 struct clock_event_device *curdev; 276 struct tick_device *td; 277 int cpu; 278 279 cpu = smp_processor_id(); 280 if (!cpumask_test_cpu(cpu, newdev->cpumask)) 281 goto out_bc; 282 283 td = &per_cpu(tick_cpu_device, cpu); 284 curdev = td->evtdev; 285 286 /* cpu local device ? */ 287 if (!tick_check_percpu(curdev, newdev, cpu)) 288 goto out_bc; 289 290 /* Preference decision */ 291 if (!tick_check_preferred(curdev, newdev)) 292 goto out_bc; 293 294 if (!try_module_get(newdev->owner)) 295 return; 296 297 /* 298 * Replace the eventually existing device by the new 299 * device. If the current device is the broadcast device, do 300 * not give it back to the clockevents layer ! 301 */ 302 if (tick_is_broadcast_device(curdev)) { 303 clockevents_shutdown(curdev); 304 curdev = NULL; 305 } 306 clockevents_exchange_device(curdev, newdev); 307 tick_setup_device(td, newdev, cpu, cpumask_of(cpu)); 308 if (newdev->features & CLOCK_EVT_FEAT_ONESHOT) 309 tick_oneshot_notify(); 310 return; 311 312 out_bc: 313 /* 314 * Can the new device be used as a broadcast device ? 315 */ 316 tick_install_broadcast_device(newdev); 317 } 318 319 /* 320 * Transfer the do_timer job away from a dying cpu. 321 * 322 * Called with interrupts disabled. 323 */ 324 void tick_handover_do_timer(int *cpup) 325 { 326 if (*cpup == tick_do_timer_cpu) { 327 int cpu = cpumask_first(cpu_online_mask); 328 329 tick_do_timer_cpu = (cpu < nr_cpu_ids) ? cpu : 330 TICK_DO_TIMER_NONE; 331 } 332 } 333 334 /* 335 * Shutdown an event device on a given cpu: 336 * 337 * This is called on a life CPU, when a CPU is dead. So we cannot 338 * access the hardware device itself. 339 * We just set the mode and remove it from the lists. 340 */ 341 void tick_shutdown(unsigned int *cpup) 342 { 343 struct tick_device *td = &per_cpu(tick_cpu_device, *cpup); 344 struct clock_event_device *dev = td->evtdev; 345 346 td->mode = TICKDEV_MODE_PERIODIC; 347 if (dev) { 348 /* 349 * Prevent that the clock events layer tries to call 350 * the set mode function! 351 */ 352 dev->mode = CLOCK_EVT_MODE_UNUSED; 353 clockevents_exchange_device(dev, NULL); 354 dev->event_handler = clockevents_handle_noop; 355 td->evtdev = NULL; 356 } 357 } 358 359 void tick_suspend(void) 360 { 361 struct tick_device *td = &__get_cpu_var(tick_cpu_device); 362 363 clockevents_shutdown(td->evtdev); 364 } 365 366 void tick_resume(void) 367 { 368 struct tick_device *td = &__get_cpu_var(tick_cpu_device); 369 int broadcast = tick_resume_broadcast(); 370 371 clockevents_set_mode(td->evtdev, CLOCK_EVT_MODE_RESUME); 372 373 if (!broadcast) { 374 if (td->mode == TICKDEV_MODE_PERIODIC) 375 tick_setup_periodic(td->evtdev, 0); 376 else 377 tick_resume_oneshot(); 378 } 379 } 380 381 /** 382 * tick_init - initialize the tick control 383 */ 384 void __init tick_init(void) 385 { 386 tick_broadcast_init(); 387 } 388