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         if (cpuidle_disabled())
 231                 return -ENODEV;
 232
 233         __cpuidle_driver_init(drv);
 234
 235         ret = __cpuidle_set_driver(drv);
 236         if (ret)
 237                 return ret;
 238
 239         if (drv->bctimer)
 240                 on_each_cpu_mask(drv->cpumask, cpuidle_setup_broadcast_timer,
 241                                  (void *)1, 1);
 242
 243         poll_idle_init(drv);
 244
 245         return 0;
 246 }
 247
 248 /**
 249  * __cpuidle_unregister_driver - unregister the driver
 250  * @drv: a valid pointer to a struct cpuidle_driver
 251  *
 252  * Check if the driver is no longer in use, reset the global cpuidle driver
 253  * variable(s) and disable the timer broadcast notification mechanism if it was
 254  * in use.
 255  *
 256  */
 257 static void __cpuidle_unregister_driver(struct cpuidle_driver *drv)
 258 {
 259         if (WARN_ON(drv->refcnt > 0))
 260                 return;
 261
 262         if (drv->bctimer) {
 263                 drv->bctimer = 0;
 264                 on_each_cpu_mask(drv->cpumask, cpuidle_setup_broadcast_timer,
 265                                  NULL, 1);
 266         }
 267
 268         __cpuidle_unset_driver(drv);
 269 }
 270
 271 /**
 272  * cpuidle_register_driver - registers a driver
 273  * @drv: a pointer to a valid struct cpuidle_driver
 274  *
 275  * Register the driver under a lock to prevent concurrent attempts to
 276  * [un]register the driver from occuring at the same time.
 277  *
 278  * Returns 0 on success, a negative error code (returned by
 279  * __cpuidle_register_driver()) otherwise.
 280  */
 281 int cpuidle_register_driver(struct cpuidle_driver *drv)
 282 {
 283         int ret;
 284
 285         spin_lock(&cpuidle_driver_lock);
 286         ret = __cpuidle_register_driver(drv);
 287         spin_unlock(&cpuidle_driver_lock);
 288
 289         return ret;
 290 }
 291 EXPORT_SYMBOL_GPL(cpuidle_register_driver);
 292
 293 /**
 294  * cpuidle_unregister_driver - unregisters a driver
 295  * @drv: a pointer to a valid struct cpuidle_driver
 296  *
 297  * Unregisters the cpuidle driver under a lock to prevent concurrent attempts
 298  * to [un]register the driver from occuring at the same time.  @drv has to
 299  * match the currently registered driver.
 300  */
 301 void cpuidle_unregister_driver(struct cpuidle_driver *drv)
 302 {
 303         spin_lock(&cpuidle_driver_lock);
 304         __cpuidle_unregister_driver(drv);
 305         spin_unlock(&cpuidle_driver_lock);
 306 }
 307 EXPORT_SYMBOL_GPL(cpuidle_unregister_driver);
 308
 309 /**
 310  * cpuidle_get_driver - return the driver tied to the current CPU.
 311  *
 312  * Returns a struct cpuidle_driver pointer, or NULL if no driver is registered.
 313  */
 314 struct cpuidle_driver *cpuidle_get_driver(void)
 315 {
 316         struct cpuidle_driver *drv;
 317         int cpu;
 318
 319         cpu = get_cpu();
 320         drv = __cpuidle_get_cpu_driver(cpu);
 321         put_cpu();
 322
 323         return drv;
 324 }
 325 EXPORT_SYMBOL_GPL(cpuidle_get_driver);
 326
 327 /**
 328  * cpuidle_get_cpu_driver - return the driver registered for a CPU.
 329  * @dev: a valid pointer to a struct cpuidle_device
 330  *
 331  * Returns a struct cpuidle_driver pointer, or NULL if no driver is registered
 332  * for the CPU associated with @dev.
 333  */
 334 struct cpuidle_driver *cpuidle_get_cpu_driver(struct cpuidle_device *dev)
 335 {
 336         if (!dev)
 337                 return NULL;
 338
 339         return __cpuidle_get_cpu_driver(dev->cpu);
 340 }
 341 EXPORT_SYMBOL_GPL(cpuidle_get_cpu_driver);
 342
 343 /**
 344  * cpuidle_driver_ref - get a reference to the driver.
 345  *
 346  * Increment the reference counter of the cpuidle driver associated with
 347  * the current CPU.
 348  *
 349  * Returns a pointer to the driver, or NULL if the current CPU has no driver.
 350  */
 351 struct cpuidle_driver *cpuidle_driver_ref(void)
 352 {
 353         struct cpuidle_driver *drv;
 354
 355         spin_lock(&cpuidle_driver_lock);
 356
 357         drv = cpuidle_get_driver();
 358         if (drv)
 359                 drv->refcnt++;
 360
 361         spin_unlock(&cpuidle_driver_lock);
 362         return drv;
 363 }
 364
 365 /**
 366  * cpuidle_driver_unref - puts down the refcount for the driver
 367  *
 368  * Decrement the reference counter of the cpuidle driver associated with
 369  * the current CPU.
 370  */
 371 void cpuidle_driver_unref(void)
 372 {
 373         struct cpuidle_driver *drv;
 374
 375         spin_lock(&cpuidle_driver_lock);
 376
 377         drv = cpuidle_get_driver();
 378         if (drv && !WARN_ON(drv->refcnt <= 0))
 379                 drv->refcnt--;
 380
 381         spin_unlock(&cpuidle_driver_lock);
 382 }