drivers/cpuidle/driver.c

   1 /*
   2  * driver.c - driver support
   3  *
   4  * (C) 2006-2007 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
   5  *               Shaohua Li <shaohua.li@intel.com>
   6  *               Adam Belay <abelay@novell.com>
   7  *
   8  * This code is licenced under the GPL.
   9  */
  10
  11 #include <linux/mutex.h>
  12 #include <linux/module.h>
  13 #include <linux/sched.h>
  14 #include <linux/cpuidle.h>
  15 #include <linux/cpumask.h>
  16 #include <linux/tick.h>
  17
  18 #include "cpuidle.h"
  19
  20 DEFINE_SPINLOCK(cpuidle_driver_lock);
  21
  22 #ifdef CONFIG_CPU_IDLE_MULTIPLE_DRIVERS
  23
  24 static DEFINE_PER_CPU(struct cpuidle_driver *, cpuidle_drivers);
  25
  26 /**
  27  * __cpuidle_get_cpu_driver - return the cpuidle driver tied to a CPU.
  28  * @cpu: the CPU handled by the driver
  29  *
  30  * Returns a pointer to struct cpuidle_driver or NULL if no driver has been
  31  * registered for @cpu.
  32  */
  33 static struct cpuidle_driver *__cpuidle_get_cpu_driver(int cpu)
  34 {
  35         return per_cpu(cpuidle_drivers, cpu);
  36 }
  37
  38 /**
  39  * __cpuidle_unset_driver - unset per CPU driver variables.
  40  * @drv: a valid pointer to a struct cpuidle_driver
  41  *
  42  * For each CPU in the driver's CPU mask, unset the registered driver per CPU
  43  * variable. If @drv is different from the registered driver, the corresponding
  44  * variable is not cleared.
  45  */
  46 static inline void __cpuidle_unset_driver(struct cpuidle_driver *drv)
  47 {
  48         int cpu;
  49
  50         for_each_cpu(cpu, drv->cpumask) {
  51
  52                 if (drv != __cpuidle_get_cpu_driver(cpu))
  53                         continue;
  54
  55                 per_cpu(cpuidle_drivers, cpu) = NULL;
  56         }
  57 }
  58
  59 /**
  60  * __cpuidle_set_driver - set per CPU driver variables for the given driver.
  61  * @drv: a valid pointer to a struct cpuidle_driver
  62  *
  63  * For each CPU in the driver's cpumask, unset the registered driver per CPU
  64  * to @drv.
  65  *
  66  * Returns 0 on success, -EBUSY if the CPUs have driver(s) already.
  67  */
  68 static inline int __cpuidle_set_driver(struct cpuidle_driver *drv)
  69 {
  70         int cpu;
  71
  72         for_each_cpu(cpu, drv->cpumask) {
  73
  74                 if (__cpuidle_get_cpu_driver(cpu)) {
  75                         __cpuidle_unset_driver(drv);
  76                         return -EBUSY;
  77                 }
  78
  79                 per_cpu(cpuidle_drivers, cpu) = drv;
  80         }
  81
  82         return 0;
  83 }
  84
  85 #else
  86
  87 static struct cpuidle_driver *cpuidle_curr_driver;
  88
  89 /**
  90  * __cpuidle_get_cpu_driver - return the global cpuidle driver pointer.
  91  * @cpu: ignored without the multiple driver support
  92  *
  93  * Return a pointer to a struct cpuidle_driver object or NULL if no driver was
  94  * previously registered.
  95  */
  96 static inline struct cpuidle_driver *__cpuidle_get_cpu_driver(int cpu)
  97 {
  98         return cpuidle_curr_driver;
  99 }
 100
 101 /**
 102  * __cpuidle_set_driver - assign the global cpuidle driver variable.
 103  * @drv: pointer to a struct cpuidle_driver object
 104  *
 105  * Returns 0 on success, -EBUSY if the driver is already registered.
 106  */
 107 static inline int __cpuidle_set_driver(struct cpuidle_driver *drv)
 108 {
 109         if (cpuidle_curr_driver)
 110                 return -EBUSY;
 111
 112         cpuidle_curr_driver = drv;
 113
 114         return 0;
 115 }
 116
 117 /**
 118  * __cpuidle_unset_driver - unset the global cpuidle driver variable.
 119  * @drv: a pointer to a struct cpuidle_driver
 120  *
 121  * Reset the global cpuidle variable to NULL.  If @drv does not match the
 122  * registered driver, do nothing.
 123  */
 124 static inline void __cpuidle_unset_driver(struct cpuidle_driver *drv)
 125 {
 126         if (drv == cpuidle_curr_driver)
 127                 cpuidle_curr_driver = NULL;
 128 }
 129
 130 #endif
 131
 132 /**
 133  * cpuidle_setup_broadcast_timer - enable/disable the broadcast timer on a cpu
 134  * @arg: a void pointer used to match the SMP cross call API
 135  *
 136  * If @arg is NULL broadcast is disabled otherwise enabled
 137  *
 138  * This function is executed per CPU by an SMP cross call.  It's not
 139  * supposed to be called directly.
 140  */
 141 static void cpuidle_setup_broadcast_timer(void *arg)
 142 {
 143         if (arg)
 144                 tick_broadcast_enable();
 145         else
 146                 tick_broadcast_disable();
 147 }
 148
 149 /**
 150  * __cpuidle_driver_init - initialize the driver's internal data
 151  * @drv: a valid pointer to a struct cpuidle_driver
 152  */
 153 static void __cpuidle_driver_init(struct cpuidle_driver *drv)
 154 {
 155         int i;
 156
 157         drv->refcnt = 0;
 158
 159         /*
 160          * Use all possible CPUs as the default, because if the kernel boots
 161          * with some CPUs offline and then we online one of them, the CPU
 162          * notifier has to know which driver to assign.
 163          */
 164         if (!drv->cpumask)
 165                 drv->cpumask = (struct cpumask *)cpu_possible_mask;
 166
 167         /*
 168          * Look for the timer stop flag in the different states, so that we know
 169          * if the broadcast timer has to be set up.  The loop is in the reverse
 170          * order, because usually one of the deeper states have this flag set.
 171          */
 172         for (i = drv->state_count - 1; i >= 0 ; i--) {
 173                 if (drv->states[i].flags & CPUIDLE_FLAG_TIMER_STOP) {
 174                         drv->bctimer = 1;
 175                         break;
 176                 }
 177         }
 178 }
 179
 180 #ifdef CONFIG_ARCH_HAS_CPU_RELAX
 181 static int poll_idle(struct cpuidle_device *dev,
 182                 struct cpuidle_driver *drv, int index)
 183 {
 184         local_irq_enable();
 185         if (!current_set_polling_and_test()) {
 186                 while (!need_resched())
 187                         cpu_relax();
 188         }
 189         current_clr_polling();
 190
 191         return index;
 192 }
 193
 194 static void poll_idle_init(struct cpuidle_driver *drv)
 195 {
 196         struct cpuidle_state *state = &drv->states[0];
 197
 198         snprintf(state->name, CPUIDLE_NAME_LEN, "POLL");
 199         snprintf(state->desc, CPUIDLE_DESC_LEN, "CPUIDLE CORE POLL IDLE");
 200         state->exit_latency = 0;
 201         state->target_residency = 0;
 202         state->power_usage = -1;
 203         state->enter = poll_idle;
 204         state->disabled = false;
 205 }
 206 #else
 207 static void poll_idle_init(struct cpuidle_driver *drv) {}
 208 #endif /* !CONFIG_ARCH_HAS_CPU_RELAX */
 209
 210 /**
 211  * __cpuidle_register_driver: register the driver
 212  * @drv: a valid pointer to a struct cpuidle_driver
 213  *
 214  * Do some sanity checks, initialize the driver, assign the driver to the
 215  * global cpuidle driver variable(s) and set up the broadcast timer if the
 216  * cpuidle driver has some states that shut down the local timer.
 217  *
 218  * Returns 0 on success, a negative error code otherwise:
 219  *  * -EINVAL if the driver pointer is NULL or no idle states are available
 220  *  * -ENODEV if the cpuidle framework is disabled
 221  *  * -EBUSY if the driver is already assigned to the global variable(s)
 222  */
 223 static int __cpuidle_register_driver(struct cpuidle_driver *drv)
 224 {
 225         int ret;
 226
 227         if (!drv || !drv->state_count)
 228                 return -EINVAL;
 229
 230         ret = cpuidle_coupled_state_verify(drv);
 231         if (ret)
 232                 return ret;
 233
 234         if (cpuidle_disabled())
 235                 return -ENODEV;
 236
 237         __cpuidle_driver_init(drv);
 238
 239         ret = __cpuidle_set_driver(drv);
 240         if (ret)
 241                 return ret;
 242
 243         if (drv->bctimer)
 244                 on_each_cpu_mask(drv->cpumask, cpuidle_setup_broadcast_timer,
 245                                  (void *)1, 1);
 246
 247         poll_idle_init(drv);
 248
 249         return 0;
 250 }
 251
 252 /**
 253  * __cpuidle_unregister_driver - unregister the driver
 254  * @drv: a valid pointer to a struct cpuidle_driver
 255  *
 256  * Check if the driver is no longer in use, reset the global cpuidle driver
 257  * variable(s) and disable the timer broadcast notification mechanism if it was
 258  * in use.
 259  *
 260  */
 261 static void __cpuidle_unregister_driver(struct cpuidle_driver *drv)
 262 {
 263         if (WARN_ON(drv->refcnt > 0))
 264                 return;
 265
 266         if (drv->bctimer) {
 267                 drv->bctimer = 0;
 268                 on_each_cpu_mask(drv->cpumask, cpuidle_setup_broadcast_timer,
 269                                  NULL, 1);
 270         }
 271
 272         __cpuidle_unset_driver(drv);
 273 }
 274
 275 /**
 276  * cpuidle_register_driver - registers a driver
 277  * @drv: a pointer to a valid struct cpuidle_driver
 278  *
 279  * Register the driver under a lock to prevent concurrent attempts to
 280  * [un]register the driver from occuring at the same time.
 281  *
 282  * Returns 0 on success, a negative error code (returned by
 283  * __cpuidle_register_driver()) otherwise.
 284  */
 285 int cpuidle_register_driver(struct cpuidle_driver *drv)
 286 {
 287         int ret;
 288
 289         spin_lock(&cpuidle_driver_lock);
 290         ret = __cpuidle_register_driver(drv);
 291         spin_unlock(&cpuidle_driver_lock);
 292
 293         return ret;
 294 }
 295 EXPORT_SYMBOL_GPL(cpuidle_register_driver);
 296
 297 /**
 298  * cpuidle_unregister_driver - unregisters a driver
 299  * @drv: a pointer to a valid struct cpuidle_driver
 300  *
 301  * Unregisters the cpuidle driver under a lock to prevent concurrent attempts
 302  * to [un]register the driver from occuring at the same time.  @drv has to
 303  * match the currently registered driver.
 304  */
 305 void cpuidle_unregister_driver(struct cpuidle_driver *drv)
 306 {
 307         spin_lock(&cpuidle_driver_lock);
 308         __cpuidle_unregister_driver(drv);
 309         spin_unlock(&cpuidle_driver_lock);
 310 }
 311 EXPORT_SYMBOL_GPL(cpuidle_unregister_driver);
 312
 313 /**
 314  * cpuidle_get_driver - return the driver tied to the current CPU.
 315  *
 316  * Returns a struct cpuidle_driver pointer, or NULL if no driver is registered.
 317  */
 318 struct cpuidle_driver *cpuidle_get_driver(void)
 319 {
 320         struct cpuidle_driver *drv;
 321         int cpu;
 322
 323         cpu = get_cpu();
 324         drv = __cpuidle_get_cpu_driver(cpu);
 325         put_cpu();
 326
 327         return drv;
 328 }
 329 EXPORT_SYMBOL_GPL(cpuidle_get_driver);
 330
 331 /**
 332  * cpuidle_get_cpu_driver - return the driver registered for a CPU.
 333  * @dev: a valid pointer to a struct cpuidle_device
 334  *
 335  * Returns a struct cpuidle_driver pointer, or NULL if no driver is registered
 336  * for the CPU associated with @dev.
 337  */
 338 struct cpuidle_driver *cpuidle_get_cpu_driver(struct cpuidle_device *dev)
 339 {
 340         if (!dev)
 341                 return NULL;
 342
 343         return __cpuidle_get_cpu_driver(dev->cpu);
 344 }
 345 EXPORT_SYMBOL_GPL(cpuidle_get_cpu_driver);
 346
 347 /**
 348  * cpuidle_driver_ref - get a reference to the driver.
 349  *
 350  * Increment the reference counter of the cpuidle driver associated with
 351  * the current CPU.
 352  *
 353  * Returns a pointer to the driver, or NULL if the current CPU has no driver.
 354  */
 355 struct cpuidle_driver *cpuidle_driver_ref(void)
 356 {
 357         struct cpuidle_driver *drv;
 358
 359         spin_lock(&cpuidle_driver_lock);
 360
 361         drv = cpuidle_get_driver();
 362         if (drv)
 363                 drv->refcnt++;
 364
 365         spin_unlock(&cpuidle_driver_lock);
 366         return drv;
 367 }
 368
 369 /**
 370  * cpuidle_driver_unref - puts down the refcount for the driver
 371  *
 372  * Decrement the reference counter of the cpuidle driver associated with
 373  * the current CPU.
 374  */
 375 void cpuidle_driver_unref(void)
 376 {
 377         struct cpuidle_driver *drv;
 378
 379         spin_lock(&cpuidle_driver_lock);
 380
 381         drv = cpuidle_get_driver();
 382         if (drv && !WARN_ON(drv->refcnt <= 0))
 383                 drv->refcnt--;
 384
 385         spin_unlock(&cpuidle_driver_lock);
 386 }