kernel/time/clockevents.c

   1 /*
   2  * linux/kernel/time/clockevents.c
   3  *
   4  * This file contains functions which manage clock event devices.
   5  *
   6  * Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de>
   7  * Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar
   8  * Copyright(C) 2006-2007, Timesys Corp., Thomas Gleixner
   9  *
  10  * This code is licenced under the GPL version 2. For details see
  11  * kernel-base/COPYING.
  12  */
  13
  14 #include <linux/clockchips.h>
  15 #include <linux/hrtimer.h>
  16 #include <linux/init.h>
  17 #include <linux/module.h>
  18 #include <linux/notifier.h>
  19 #include <linux/smp.h>
  20 #include <linux/sysdev.h>
  21
  22 #include "tick-internal.h"
  23
  24 /* The registered clock event devices */
  25 static LIST_HEAD(clockevent_devices);
  26 static LIST_HEAD(clockevents_released);
  27
  28 /* Notification for clock events */
  29 static RAW_NOTIFIER_HEAD(clockevents_chain);
  30
  31 /* Protection for the above */
  32 static DEFINE_RAW_SPINLOCK(clockevents_lock);
  33
  34 /**
  35  * clockevents_delta2ns - Convert a latch value (device ticks) to nanoseconds
  36  * @latch:      value to convert
  37  * @evt:        pointer to clock event device descriptor
  38  *
  39  * Math helper, returns latch value converted to nanoseconds (bound checked)
  40  */
  41 u64 clockevent_delta2ns(unsigned long latch, struct clock_event_device *evt)
  42 {
  43         u64 clc = (u64) latch << evt->shift;
  44
  45         if (unlikely(!evt->mult)) {
  46                 evt->mult = 1;
  47                 WARN_ON(1);
  48         }
  49
  50         do_div(clc, evt->mult);
  51         if (clc < 1000)
  52                 clc = 1000;
  53         if (clc > KTIME_MAX)
  54                 clc = KTIME_MAX;
  55
  56         return clc;
  57 }
  58 EXPORT_SYMBOL_GPL(clockevent_delta2ns);
  59
  60 /**
  61  * clockevents_set_mode - set the operating mode of a clock event device
  62  * @dev:        device to modify
  63  * @mode:       new mode
  64  *
  65  * Must be called with interrupts disabled !
  66  */
  67 void clockevents_set_mode(struct clock_event_device *dev,
  68                                  enum clock_event_mode mode)
  69 {
  70         if (dev->mode != mode) {
  71                 dev->set_mode(mode, dev);
  72                 dev->mode = mode;
  73
  74                 /*
  75                  * A nsec2cyc multiplicator of 0 is invalid and we'd crash
  76                  * on it, so fix it up and emit a warning:
  77                  */
  78                 if (mode == CLOCK_EVT_MODE_ONESHOT) {
  79                         if (unlikely(!dev->mult)) {
  80                                 dev->mult = 1;
  81                                 WARN_ON(1);
  82                         }
  83                 }
  84         }
  85 }
  86
  87 /**
  88  * clockevents_shutdown - shutdown the device and clear next_event
  89  * @dev:        device to shutdown
  90  */
  91 void clockevents_shutdown(struct clock_event_device *dev)
  92 {
  93         clockevents_set_mode(dev, CLOCK_EVT_MODE_SHUTDOWN);
  94         dev->next_event.tv64 = KTIME_MAX;
  95 }
  96
  97 #ifdef CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST
  98
  99 /* Limit min_delta to a jiffie */
 100 #define MIN_DELTA_LIMIT         (NSEC_PER_SEC / HZ)
 101
 102 /**
 103  * clockevents_increase_min_delta - raise minimum delta of a clock event device
 104  * @dev:       device to increase the minimum delta
 105  *
 106  * Returns 0 on success, -ETIME when the minimum delta reached the limit.
 107  */
 108 static int clockevents_increase_min_delta(struct clock_event_device *dev)
 109 {
 110         /* Nothing to do if we already reached the limit */
 111         if (dev->min_delta_ns >= MIN_DELTA_LIMIT) {
 112                 printk(KERN_WARNING "CE: Reprogramming failure. Giving up\n");
 113                 dev->next_event.tv64 = KTIME_MAX;
 114                 return -ETIME;
 115         }
 116
 117         if (dev->min_delta_ns < 5000)
 118                 dev->min_delta_ns = 5000;
 119         else
 120                 dev->min_delta_ns += dev->min_delta_ns >> 1;
 121
 122         if (dev->min_delta_ns > MIN_DELTA_LIMIT)
 123                 dev->min_delta_ns = MIN_DELTA_LIMIT;
 124
 125         printk(KERN_WARNING "CE: %s increased min_delta_ns to %llu nsec\n",
 126                dev->name ? dev->name : "?",
 127                (unsigned long long) dev->min_delta_ns);
 128         return 0;
 129 }
 130
 131 /**
 132  * clockevents_program_min_delta - Set clock event device to the minimum delay.
 133  * @dev:        device to program
 134  *
 135  * Returns 0 on success, -ETIME when the retry loop failed.
 136  */
 137 static int clockevents_program_min_delta(struct clock_event_device *dev)
 138 {
 139         unsigned long long clc;
 140         int64_t delta;
 141         int i;
 142
 143         for (i = 0;;) {
 144                 delta = dev->min_delta_ns;
 145                 dev->next_event = ktime_add_ns(ktime_get(), delta);
 146
 147                 if (dev->mode == CLOCK_EVT_MODE_SHUTDOWN)
 148                         return 0;
 149
 150                 dev->retries++;
 151                 clc = ((unsigned long long) delta * dev->mult) >> dev->shift;
 152                 if (dev->set_next_event((unsigned long) clc, dev) == 0)
 153                         return 0;
 154
 155                 if (++i > 2) {
 156                         /*
 157                          * We tried 3 times to program the device with the
 158                          * given min_delta_ns. Try to increase the minimum
 159                          * delta, if that fails as well get out of here.
 160                          */
 161                         if (clockevents_increase_min_delta(dev))
 162                                 return -ETIME;
 163                         i = 0;
 164                 }
 165         }
 166 }
 167
 168 #else  /* CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST */
 169
 170 /**
 171  * clockevents_program_min_delta - Set clock event device to the minimum delay.
 172  * @dev:        device to program
 173  *
 174  * Returns 0 on success, -ETIME when the retry loop failed.
 175  */
 176 static int clockevents_program_min_delta(struct clock_event_device *dev)
 177 {
 178         unsigned long long clc;
 179         int64_t delta;
 180
 181         delta = dev->min_delta_ns;
 182         dev->next_event = ktime_add_ns(ktime_get(), delta);
 183
 184         if (dev->mode == CLOCK_EVT_MODE_SHUTDOWN)
 185                 return 0;
 186
 187         dev->retries++;
 188         clc = ((unsigned long long) delta * dev->mult) >> dev->shift;
 189         return dev->set_next_event((unsigned long) clc, dev);
 190 }
 191
 192 #endif /* CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST */
 193
 194 /**
 195  * clockevents_program_event - Reprogram the clock event device.
 196  * @dev:        device to program
 197  * @expires:    absolute expiry time (monotonic clock)
 198  * @force:      program minimum delay if expires can not be set
 199  *
 200  * Returns 0 on success, -ETIME when the event is in the past.
 201  */
 202 int clockevents_program_event(struct clock_event_device *dev, ktime_t expires,
 203                               bool force)
 204 {
 205         unsigned long long clc;
 206         int64_t delta;
 207         int rc;
 208
 209         if (unlikely(expires.tv64 < 0)) {
 210                 WARN_ON_ONCE(1);
 211                 return -ETIME;
 212         }
 213
 214         dev->next_event = expires;
 215
 216         if (dev->mode == CLOCK_EVT_MODE_SHUTDOWN)
 217                 return 0;
 218
 219         /* Shortcut for clockevent devices that can deal with ktime. */
 220         if (dev->features & CLOCK_EVT_FEAT_KTIME)
 221                 return dev->set_next_ktime(expires, dev);
 222
 223         delta = ktime_to_ns(ktime_sub(expires, ktime_get()));
 224         if (delta <= 0)
 225                 return force ? clockevents_program_min_delta(dev) : -ETIME;
 226
 227         delta = min(delta, (int64_t) dev->max_delta_ns);
 228         delta = max(delta, (int64_t) dev->min_delta_ns);
 229
 230         clc = ((unsigned long long) delta * dev->mult) >> dev->shift;
 231         rc = dev->set_next_event((unsigned long) clc, dev);
 232
 233         return (rc && force) ? clockevents_program_min_delta(dev) : rc;
 234 }
 235
 236 /**
 237  * clockevents_register_notifier - register a clock events change listener
 238  */
 239 int clockevents_register_notifier(struct notifier_block *nb)
 240 {
 241         unsigned long flags;
 242         int ret;
 243
 244         raw_spin_lock_irqsave(&clockevents_lock, flags);
 245         ret = raw_notifier_chain_register(&clockevents_chain, nb);
 246         raw_spin_unlock_irqrestore(&clockevents_lock, flags);
 247
 248         return ret;
 249 }
 250
 251 /*
 252  * Notify about a clock event change. Called with clockevents_lock
 253  * held.
 254  */
 255 static void clockevents_do_notify(unsigned long reason, void *dev)
 256 {
 257         raw_notifier_call_chain(&clockevents_chain, reason, dev);
 258 }
 259
 260 /*
 261  * Called after a notify add to make devices available which were
 262  * released from the notifier call.
 263  */
 264 static void clockevents_notify_released(void)
 265 {
 266         struct clock_event_device *dev;
 267
 268         while (!list_empty(&clockevents_released)) {
 269                 dev = list_entry(clockevents_released.next,
 270                                  struct clock_event_device, list);
 271                 list_del(&dev->list);
 272                 list_add(&dev->list, &clockevent_devices);
 273                 clockevents_do_notify(CLOCK_EVT_NOTIFY_ADD, dev);
 274         }
 275 }
 276
 277 /**
 278  * clockevents_register_device - register a clock event device
 279  * @dev:        device to register
 280  */
 281 void clockevents_register_device(struct clock_event_device *dev)
 282 {
 283         unsigned long flags;
 284
 285         BUG_ON(dev->mode != CLOCK_EVT_MODE_UNUSED);
 286         if (!dev->cpumask) {
 287                 WARN_ON(num_possible_cpus() > 1);
 288                 dev->cpumask = cpumask_of(smp_processor_id());
 289         }
 290
 291         raw_spin_lock_irqsave(&clockevents_lock, flags);
 292
 293         list_add(&dev->list, &clockevent_devices);
 294         clockevents_do_notify(CLOCK_EVT_NOTIFY_ADD, dev);
 295         clockevents_notify_released();
 296
 297         raw_spin_unlock_irqrestore(&clockevents_lock, flags);
 298 }
 299 EXPORT_SYMBOL_GPL(clockevents_register_device);
 300
 301 static void clockevents_config(struct clock_event_device *dev,
 302                                u32 freq)
 303 {
 304         u64 sec;
 305
 306         if (!(dev->features & CLOCK_EVT_FEAT_ONESHOT))
 307                 return;
 308
 309         /*
 310          * Calculate the maximum number of seconds we can sleep. Limit
 311          * to 10 minutes for hardware which can program more than
 312          * 32bit ticks so we still get reasonable conversion values.
 313          */
 314         sec = dev->max_delta_ticks;
 315         do_div(sec, freq);
 316         if (!sec)
 317                 sec = 1;
 318         else if (sec > 600 && dev->max_delta_ticks > UINT_MAX)
 319                 sec = 600;
 320
 321         clockevents_calc_mult_shift(dev, freq, sec);
 322         dev->min_delta_ns = clockevent_delta2ns(dev->min_delta_ticks, dev);
 323         dev->max_delta_ns = clockevent_delta2ns(dev->max_delta_ticks, dev);
 324 }
 325
 326 /**
 327  * clockevents_config_and_register - Configure and register a clock event device
 328  * @dev:        device to register
 329  * @freq:       The clock frequency
 330  * @min_delta:  The minimum clock ticks to program in oneshot mode
 331  * @max_delta:  The maximum clock ticks to program in oneshot mode
 332  *
 333  * min/max_delta can be 0 for devices which do not support oneshot mode.
 334  */
 335 void clockevents_config_and_register(struct clock_event_device *dev,
 336                                      u32 freq, unsigned long min_delta,
 337                                      unsigned long max_delta)
 338 {
 339         dev->min_delta_ticks = min_delta;
 340         dev->max_delta_ticks = max_delta;
 341         clockevents_config(dev, freq);
 342         clockevents_register_device(dev);
 343 }
 344
 345 /**
 346  * clockevents_update_freq - Update frequency and reprogram a clock event device.
 347  * @dev:        device to modify
 348  * @freq:       new device frequency
 349  *
 350  * Reconfigure and reprogram a clock event device in oneshot
 351  * mode. Must be called on the cpu for which the device delivers per
 352  * cpu timer events with interrupts disabled!  Returns 0 on success,
 353  * -ETIME when the event is in the past.
 354  */
 355 int clockevents_update_freq(struct clock_event_device *dev, u32 freq)
 356 {
 357         clockevents_config(dev, freq);
 358
 359         if (dev->mode != CLOCK_EVT_MODE_ONESHOT)
 360                 return 0;
 361
 362         return clockevents_program_event(dev, dev->next_event, false);
 363 }
 364
 365 /*
 366  * Noop handler when we shut down an event device
 367  */
 368 void clockevents_handle_noop(struct clock_event_device *dev)
 369 {
 370 }
 371
 372 /**
 373  * clockevents_exchange_device - release and request clock devices
 374  * @old:        device to release (can be NULL)
 375  * @new:        device to request (can be NULL)
 376  *
 377  * Called from the notifier chain. clockevents_lock is held already
 378  */
 379 void clockevents_exchange_device(struct clock_event_device *old,
 380                                  struct clock_event_device *new)
 381 {
 382         unsigned long flags;
 383
 384         local_irq_save(flags);
 385         /*
 386          * Caller releases a clock event device. We queue it into the
 387          * released list and do a notify add later.
 388          */
 389         if (old) {
 390                 old->event_handler = clockevents_handle_noop;
 391                 clockevents_set_mode(old, CLOCK_EVT_MODE_UNUSED);
 392                 list_del(&old->list);
 393                 list_add(&old->list, &clockevents_released);
 394         }
 395
 396         if (new) {
 397                 BUG_ON(new->mode != CLOCK_EVT_MODE_UNUSED);
 398                 clockevents_shutdown(new);
 399         }
 400         local_irq_restore(flags);
 401 }
 402
 403 #ifdef CONFIG_GENERIC_CLOCKEVENTS
 404 /**
 405  * clockevents_notify - notification about relevant events
 406  */
 407 void clockevents_notify(unsigned long reason, void *arg)
 408 {
 409         struct clock_event_device *dev, *tmp;
 410         unsigned long flags;
 411         int cpu;
 412
 413         raw_spin_lock_irqsave(&clockevents_lock, flags);
 414         clockevents_do_notify(reason, arg);
 415
 416         switch (reason) {
 417         case CLOCK_EVT_NOTIFY_CPU_DEAD:
 418                 /*
 419                  * Unregister the clock event devices which were
 420                  * released from the users in the notify chain.
 421                  */
 422                 list_for_each_entry_safe(dev, tmp, &clockevents_released, list)
 423                         list_del(&dev->list);
 424                 /*
 425                  * Now check whether the CPU has left unused per cpu devices
 426                  */
 427                 cpu = *((int *)arg);
 428                 list_for_each_entry_safe(dev, tmp, &clockevent_devices, list) {
 429                         if (cpumask_test_cpu(cpu, dev->cpumask) &&
 430                             cpumask_weight(dev->cpumask) == 1 &&
 431                             !tick_is_broadcast_device(dev)) {
 432                                 BUG_ON(dev->mode != CLOCK_EVT_MODE_UNUSED);
 433                                 list_del(&dev->list);
 434                         }
 435                 }
 436                 break;
 437         default:
 438                 break;
 439         }
 440         raw_spin_unlock_irqrestore(&clockevents_lock, flags);
 441 }
 442 EXPORT_SYMBOL_GPL(clockevents_notify);
 443 #endif