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   1 /*
   2  * linux/kernel/time/tick-broadcast.c
   3  *
   4  * This file contains functions which emulate a local clock-event
   5  * device via a broadcast event source.
   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  * Broadcast support for broken x86 hardware, where the local apic
  27  * timer stops in C3 state.
  28  */
  29
  30 struct tick_device tick_broadcast_device;
  31 static cpumask_t tick_broadcast_mask;
  32 static DEFINE_SPINLOCK(tick_broadcast_lock);
  33
  34 /*
  35  * Start the device in periodic mode
  36  */
  37 static void tick_broadcast_start_periodic(struct clock_event_device *bc)
  38 {
  39         if (bc && bc->mode == CLOCK_EVT_MODE_SHUTDOWN)
  40                 tick_setup_periodic(bc, 1);
  41 }
  42
  43 /*
  44  * Check, if the device can be utilized as broadcast device:
  45  */
  46 int tick_check_broadcast_device(struct clock_event_device *dev)
  47 {
  48         if (tick_broadcast_device.evtdev ||
  49             (dev->features & CLOCK_EVT_FEAT_C3STOP))
  50                 return 0;
  51
  52         clockevents_exchange_device(NULL, dev);
  53         tick_broadcast_device.evtdev = dev;
  54         if (!cpus_empty(tick_broadcast_mask))
  55                 tick_broadcast_start_periodic(dev);
  56         return 1;
  57 }
  58
  59 /*
  60  * Check, if the device is the broadcast device
  61  */
  62 int tick_is_broadcast_device(struct clock_event_device *dev)
  63 {
  64         return (dev && tick_broadcast_device.evtdev == dev);
  65 }
  66
  67 /*
  68  * Check, if the device is disfunctional and a place holder, which
  69  * needs to be handled by the broadcast device.
  70  */
  71 int tick_device_uses_broadcast(struct clock_event_device *dev, int cpu)
  72 {
  73         unsigned long flags;
  74         int ret = 0;
  75
  76         spin_lock_irqsave(&tick_broadcast_lock, flags);
  77
  78         /*
  79          * Devices might be registered with both periodic and oneshot
  80          * mode disabled. This signals, that the device needs to be
  81          * operated from the broadcast device and is a placeholder for
  82          * the cpu local device.
  83          */
  84         if (!tick_device_is_functional(dev)) {
  85                 dev->event_handler = tick_handle_periodic;
  86                 cpu_set(cpu, tick_broadcast_mask);
  87                 tick_broadcast_start_periodic(tick_broadcast_device.evtdev);
  88                 ret = 1;
  89         }
  90
  91         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
  92         return ret;
  93 }
  94
  95 /*
  96  * Broadcast the event to the cpus, which are set in the mask
  97  */
  98 int tick_do_broadcast(cpumask_t mask)
  99 {
 100         int ret = 0, cpu = smp_processor_id();
 101         struct tick_device *td;
 102
 103         /*
 104          * Check, if the current cpu is in the mask
 105          */
 106         if (cpu_isset(cpu, mask)) {
 107                 cpu_clear(cpu, mask);
 108                 td = &per_cpu(tick_cpu_device, cpu);
 109                 td->evtdev->event_handler(td->evtdev);
 110                 ret = 1;
 111         }
 112
 113         if (!cpus_empty(mask)) {
 114                 /*
 115                  * It might be necessary to actually check whether the devices
 116                  * have different broadcast functions. For now, just use the
 117                  * one of the first device. This works as long as we have this
 118                  * misfeature only on x86 (lapic)
 119                  */
 120                 cpu = first_cpu(mask);
 121                 td = &per_cpu(tick_cpu_device, cpu);
 122                 td->evtdev->broadcast(mask);
 123                 ret = 1;
 124         }
 125         return ret;
 126 }
 127
 128 /*
 129  * Periodic broadcast:
 130  * - invoke the broadcast handlers
 131  */
 132 static void tick_do_periodic_broadcast(void)
 133 {
 134         cpumask_t mask;
 135
 136         spin_lock(&tick_broadcast_lock);
 137
 138         cpus_and(mask, cpu_online_map, tick_broadcast_mask);
 139         tick_do_broadcast(mask);
 140
 141         spin_unlock(&tick_broadcast_lock);
 142 }
 143
 144 /*
 145  * Event handler for periodic broadcast ticks
 146  */
 147 static void tick_handle_periodic_broadcast(struct clock_event_device *dev)
 148 {
 149         dev->next_event.tv64 = KTIME_MAX;
 150
 151         tick_do_periodic_broadcast();
 152
 153         /*
 154          * The device is in periodic mode. No reprogramming necessary:
 155          */
 156         if (dev->mode == CLOCK_EVT_MODE_PERIODIC)
 157                 return;
 158
 159         /*
 160          * Setup the next period for devices, which do not have
 161          * periodic mode:
 162          */
 163         for (;;) {
 164                 ktime_t next = ktime_add(dev->next_event, tick_period);
 165
 166                 if (!clockevents_program_event(dev, next, ktime_get()))
 167                         return;
 168                 tick_do_periodic_broadcast();
 169         }
 170 }
 171
 172 /*
 173  * Powerstate information: The system enters/leaves a state, where
 174  * affected devices might stop
 175  */
 176 static void tick_do_broadcast_on_off(void *why)
 177 {
 178         struct clock_event_device *bc, *dev;
 179         struct tick_device *td;
 180         unsigned long flags, *reason = why;
 181         int cpu;
 182
 183         spin_lock_irqsave(&tick_broadcast_lock, flags);
 184
 185         cpu = smp_processor_id();
 186         td = &per_cpu(tick_cpu_device, cpu);
 187         dev = td->evtdev;
 188         bc = tick_broadcast_device.evtdev;
 189
 190         /*
 191          * Is the device in broadcast mode forever or is it not
 192          * affected by the powerstate ?
 193          */
 194         if (!dev || !tick_device_is_functional(dev) ||
 195             !(dev->features & CLOCK_EVT_FEAT_C3STOP))
 196                 goto out;
 197
 198         if (*reason == CLOCK_EVT_NOTIFY_BROADCAST_ON) {
 199                 if (!cpu_isset(cpu, tick_broadcast_mask)) {
 200                         cpu_set(cpu, tick_broadcast_mask);
 201                         if (td->mode == TICKDEV_MODE_PERIODIC)
 202                                 clockevents_set_mode(dev,
 203                                                      CLOCK_EVT_MODE_SHUTDOWN);
 204                 }
 205         } else {
 206                 if (cpu_isset(cpu, tick_broadcast_mask)) {
 207                         cpu_clear(cpu, tick_broadcast_mask);
 208                         if (td->mode == TICKDEV_MODE_PERIODIC)
 209                                 tick_setup_periodic(dev, 0);
 210                 }
 211         }
 212
 213         if (cpus_empty(tick_broadcast_mask))
 214                 clockevents_set_mode(bc, CLOCK_EVT_MODE_SHUTDOWN);
 215         else {
 216                 if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
 217                         tick_broadcast_start_periodic(bc);
 218                 else
 219                         tick_broadcast_setup_oneshot(bc);
 220         }
 221 out:
 222         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 223 }
 224
 225 /*
 226  * Powerstate information: The system enters/leaves a state, where
 227  * affected devices might stop.
 228  */
 229 void tick_broadcast_on_off(unsigned long reason, int *oncpu)
 230 {
 231         int cpu = get_cpu();
 232
 233         if (cpu == *oncpu)
 234                 tick_do_broadcast_on_off(&reason);
 235         else
 236                 smp_call_function_single(*oncpu, tick_do_broadcast_on_off,
 237                                          &reason, 1, 1);
 238         put_cpu();
 239 }
 240
 241 /*
 242  * Set the periodic handler depending on broadcast on/off
 243  */
 244 void tick_set_periodic_handler(struct clock_event_device *dev, int broadcast)
 245 {
 246         if (!broadcast)
 247                 dev->event_handler = tick_handle_periodic;
 248         else
 249                 dev->event_handler = tick_handle_periodic_broadcast;
 250 }
 251
 252 /*
 253  * Remove a CPU from broadcasting
 254  */
 255 void tick_shutdown_broadcast(unsigned int *cpup)
 256 {
 257         struct clock_event_device *bc;
 258         unsigned long flags;
 259         unsigned int cpu = *cpup;
 260
 261         spin_lock_irqsave(&tick_broadcast_lock, flags);
 262
 263         bc = tick_broadcast_device.evtdev;
 264         cpu_clear(cpu, tick_broadcast_mask);
 265
 266         if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) {
 267                 if (bc && cpus_empty(tick_broadcast_mask))
 268                         clockevents_set_mode(bc, CLOCK_EVT_MODE_SHUTDOWN);
 269         }
 270
 271         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 272 }
 273
 274 #ifdef CONFIG_TICK_ONESHOT
 275
 276 static cpumask_t tick_broadcast_oneshot_mask;
 277
 278 static int tick_broadcast_set_event(ktime_t expires, int force)
 279 {
 280         struct clock_event_device *bc = tick_broadcast_device.evtdev;
 281         ktime_t now = ktime_get();
 282         int res;
 283
 284         for(;;) {
 285                 res = clockevents_program_event(bc, expires, now);
 286                 if (!res || !force)
 287                         return res;
 288                 now = ktime_get();
 289                 expires = ktime_add(now, ktime_set(0, bc->min_delta_ns));
 290         }
 291 }
 292
 293 /*
 294  * Reprogram the broadcast device:
 295  *
 296  * Called with tick_broadcast_lock held and interrupts disabled.
 297  */
 298 static int tick_broadcast_reprogram(void)
 299 {
 300         ktime_t expires = { .tv64 = KTIME_MAX };
 301         struct tick_device *td;
 302         int cpu;
 303
 304         /*
 305          * Find the event which expires next:
 306          */
 307         for (cpu = first_cpu(tick_broadcast_oneshot_mask); cpu != NR_CPUS;
 308              cpu = next_cpu(cpu, tick_broadcast_oneshot_mask)) {
 309                 td = &per_cpu(tick_cpu_device, cpu);
 310                 if (td->evtdev->next_event.tv64 < expires.tv64)
 311                         expires = td->evtdev->next_event;
 312         }
 313
 314         if (expires.tv64 == KTIME_MAX)
 315                 return 0;
 316
 317         return tick_broadcast_set_event(expires, 0);
 318 }
 319
 320 /*
 321  * Handle oneshot mode broadcasting
 322  */
 323 static void tick_handle_oneshot_broadcast(struct clock_event_device *dev)
 324 {
 325         struct tick_device *td;
 326         cpumask_t mask;
 327         ktime_t now;
 328         int cpu;
 329
 330         spin_lock(&tick_broadcast_lock);
 331 again:
 332         dev->next_event.tv64 = KTIME_MAX;
 333         mask = CPU_MASK_NONE;
 334         now = ktime_get();
 335         /* Find all expired events */
 336         for (cpu = first_cpu(tick_broadcast_oneshot_mask); cpu != NR_CPUS;
 337              cpu = next_cpu(cpu, tick_broadcast_oneshot_mask)) {
 338                 td = &per_cpu(tick_cpu_device, cpu);
 339                 if (td->evtdev->next_event.tv64 <= now.tv64)
 340                         cpu_set(cpu, mask);
 341         }
 342
 343         /*
 344          * Wakeup the cpus which have an expired event. The broadcast
 345          * device is reprogrammed in the return from idle code.
 346          */
 347         if (!tick_do_broadcast(mask)) {
 348                 /*
 349                  * The global event did not expire any CPU local
 350                  * events. This happens in dyntick mode, as the
 351                  * maximum PIT delta is quite small.
 352                  */
 353                 if (tick_broadcast_reprogram())
 354                         goto again;
 355         }
 356         spin_unlock(&tick_broadcast_lock);
 357 }
 358
 359 /*
 360  * Powerstate information: The system enters/leaves a state, where
 361  * affected devices might stop
 362  */
 363 void tick_broadcast_oneshot_control(unsigned long reason)
 364 {
 365         struct clock_event_device *bc, *dev;
 366         struct tick_device *td;
 367         unsigned long flags;
 368         int cpu;
 369
 370         spin_lock_irqsave(&tick_broadcast_lock, flags);
 371
 372         /*
 373          * Periodic mode does not care about the enter/exit of power
 374          * states
 375          */
 376         if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
 377                 goto out;
 378
 379         bc = tick_broadcast_device.evtdev;
 380         cpu = smp_processor_id();
 381         td = &per_cpu(tick_cpu_device, cpu);
 382         dev = td->evtdev;
 383
 384         if (!(dev->features & CLOCK_EVT_FEAT_C3STOP))
 385                 goto out;
 386
 387         if (reason == CLOCK_EVT_NOTIFY_BROADCAST_ENTER) {
 388                 if (!cpu_isset(cpu, tick_broadcast_oneshot_mask)) {
 389                         cpu_set(cpu, tick_broadcast_oneshot_mask);
 390                         clockevents_set_mode(dev, CLOCK_EVT_MODE_SHUTDOWN);
 391                         if (dev->next_event.tv64 < bc->next_event.tv64)
 392                                 tick_broadcast_set_event(dev->next_event, 1);
 393                 }
 394         } else {
 395                 if (cpu_isset(cpu, tick_broadcast_oneshot_mask)) {
 396                         cpu_clear(cpu, tick_broadcast_oneshot_mask);
 397                         clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
 398                         if (dev->next_event.tv64 != KTIME_MAX)
 399                                 tick_program_event(dev->next_event, 1);
 400                 }
 401         }
 402
 403 out:
 404         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 405 }
 406
 407 /**
 408  * tick_broadcast_setup_highres - setup the broadcast device for highres
 409  */
 410 void tick_broadcast_setup_oneshot(struct clock_event_device *bc)
 411 {
 412         if (bc->mode != CLOCK_EVT_MODE_ONESHOT) {
 413                 bc->event_handler = tick_handle_oneshot_broadcast;
 414                 clockevents_set_mode(bc, CLOCK_EVT_MODE_ONESHOT);
 415                 bc->next_event.tv64 = KTIME_MAX;
 416         }
 417 }
 418
 419 /*
 420  * Select oneshot operating mode for the broadcast device
 421  */
 422 void tick_broadcast_switch_to_oneshot(void)
 423 {
 424         struct clock_event_device *bc;
 425         unsigned long flags;
 426
 427         spin_lock_irqsave(&tick_broadcast_lock, flags);
 428
 429         tick_broadcast_device.mode = TICKDEV_MODE_ONESHOT;
 430         bc = tick_broadcast_device.evtdev;
 431         if (bc)
 432                 tick_broadcast_setup_oneshot(bc);
 433         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 434 }
 435
 436
 437 /*
 438  * Remove a dead CPU from broadcasting
 439  */
 440 void tick_shutdown_broadcast_oneshot(unsigned int *cpup)
 441 {
 442         struct clock_event_device *bc;
 443         unsigned long flags;
 444         unsigned int cpu = *cpup;
 445
 446         spin_lock_irqsave(&tick_broadcast_lock, flags);
 447
 448         bc = tick_broadcast_device.evtdev;
 449         cpu_clear(cpu, tick_broadcast_oneshot_mask);
 450
 451         if (tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT) {
 452                 if (bc && cpus_empty(tick_broadcast_oneshot_mask))
 453                         clockevents_set_mode(bc, CLOCK_EVT_MODE_SHUTDOWN);
 454         }
 455
 456         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 457 }
 458
 459 #endif