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/clockchips.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
 134  * @arg: a void pointer used to match the SMP cross call API
 135  *
 136  * @arg is used as a value of type 'long' with one of the two values:
 137  * - CLOCK_EVT_NOTIFY_BROADCAST_ON
 138  * - CLOCK_EVT_NOTIFY_BROADCAST_OFF
 139  *
 140  * Set the broadcast timer notification for the current CPU.  This function
 141  * is executed per CPU by an SMP cross call.  It not supposed to be called
 142  * directly.
 143  */
 144 static void cpuidle_setup_broadcast_timer(void *arg)
 145 {
 146         int cpu = smp_processor_id();
 147         clockevents_notify((long)(arg), &cpu);
 148 }
 149
 150 /**
 151  * __cpuidle_driver_init - initialize the driver's internal data
 152  * @drv: a valid pointer to a struct cpuidle_driver
 153  */
 154 static void __cpuidle_driver_init(struct cpuidle_driver *drv)
 155 {
 156         int i;
 157
 158         drv->refcnt = 0;
 159
 160         /*
 161          * Use all possible CPUs as the default, because if the kernel boots
 162          * with some CPUs offline and then we online one of them, the CPU
 163          * notifier has to know which driver to assign.
 164          */
 165         if (!drv->cpumask)
 166                 drv->cpumask = (struct cpumask *)cpu_possible_mask;
 167
 168         /*
 169          * Look for the timer stop flag in the different states, so that we know
 170          * if the broadcast timer has to be set up.  The loop is in the reverse
 171          * order, because usually one of the deeper states have this flag set.
 172          */
 173         for (i = drv->state_count - 1; i >= 0 ; i--) {
 174                 if (drv->states[i].flags & CPUIDLE_FLAG_TIMER_STOP) {
 175                         drv->bctimer = 1;
 176                         break;
 177                 }
 178         }
 179 }
 180
 181 #ifdef CONFIG_ARCH_HAS_CPU_RELAX
 182 static int poll_idle(struct cpuidle_device *dev,
 183                 struct cpuidle_driver *drv, int index)
 184 {
 185         local_irq_enable();
 186         if (!current_set_polling_and_test()) {
 187                 while (!need_resched())
 188                         cpu_relax();
 189         }
 190         current_clr_polling();
 191
 192         return index;
 193 }
 194
 195 static void poll_idle_init(struct cpuidle_driver *drv)
 196 {
 197         struct cpuidle_state *state = &drv->states[0];
 198
 199         snprintf(state->name, CPUIDLE_NAME_LEN, "POLL");
 200         snprintf(state->desc, CPUIDLE_DESC_LEN, "CPUIDLE CORE POLL IDLE");
 201         state->exit_latency = 0;
 202         state->target_residency = 0;
 203         state->power_usage = -1;
 204         state->enter = poll_idle;
 205         state->disabled = false;
 206 }
 207 #else
 208 static void poll_idle_init(struct cpuidle_driver *drv) {}
 209 #endif /* !CONFIG_ARCH_HAS_CPU_RELAX */
 210
 211 /**
 212  * __cpuidle_register_driver: register the driver
 213  * @drv: a valid pointer to a struct cpuidle_driver
 214  *
 215  * Do some sanity checks, initialize the driver, assign the driver to the
 216  * global cpuidle driver variable(s) and set up the broadcast timer if the
 217  * cpuidle driver has some states that shut down the local timer.
 218  *
 219  * Returns 0 on success, a negative error code otherwise:
 220  *  * -EINVAL if the driver pointer is NULL or no idle states are available
 221  *  * -ENODEV if the cpuidle framework is disabled
 222  *  * -EBUSY if the driver is already assigned to the global variable(s)
 223  */
 224 static int __cpuidle_register_driver(struct cpuidle_driver *drv)
 225 {
 226         int ret;
 227
 228         if (!drv || !drv->state_count)
 229                 return -EINVAL;
 230
 231         if (cpuidle_disabled())
 232                 return -ENODEV;
 233
 234         __cpuidle_driver_init(drv);
 235
 236         ret = __cpuidle_set_driver(drv);
 237         if (ret)
 238                 return ret;
 239
 240         if (drv->bctimer)
 241                 on_each_cpu_mask(drv->cpumask, cpuidle_setup_broadcast_timer,
 242                                  (void *)CLOCK_EVT_NOTIFY_BROADCAST_ON, 1);
 243
 244         poll_idle_init(drv);
 245
 246         return 0;
 247 }
 248
 249 /**
 250  * __cpuidle_unregister_driver - unregister the driver
 251  * @drv: a valid pointer to a struct cpuidle_driver
 252  *
 253  * Check if the driver is no longer in use, reset the global cpuidle driver
 254  * variable(s) and disable the timer broadcast notification mechanism if it was
 255  * in use.
 256  *
 257  */
 258 static void __cpuidle_unregister_driver(struct cpuidle_driver *drv)
 259 {
 260         if (WARN_ON(drv->refcnt > 0))
 261                 return;
 262
 263         if (drv->bctimer) {
 264                 drv->bctimer = 0;
 265                 on_each_cpu_mask(drv->cpumask, cpuidle_setup_broadcast_timer,
 266                                  (void *)CLOCK_EVT_NOTIFY_BROADCAST_OFF, 1);
 267         }
 268
 269         __cpuidle_unset_driver(drv);
 270 }
 271
 272 /**
 273  * cpuidle_register_driver - registers a driver
 274  * @drv: a pointer to a valid struct cpuidle_driver
 275  *
 276  * Register the driver under a lock to prevent concurrent attempts to
 277  * [un]register the driver from occuring at the same time.
 278  *
 279  * Returns 0 on success, a negative error code (returned by
 280  * __cpuidle_register_driver()) otherwise.
 281  */
 282 int cpuidle_register_driver(struct cpuidle_driver *drv)
 283 {
 284         int ret;
 285
 286         spin_lock(&cpuidle_driver_lock);
 287         ret = __cpuidle_register_driver(drv);
 288         spin_unlock(&cpuidle_driver_lock);
 289
 290         return ret;
 291 }
 292 EXPORT_SYMBOL_GPL(cpuidle_register_driver);
 293
 294 /**
 295  * cpuidle_unregister_driver - unregisters a driver
 296  * @drv: a pointer to a valid struct cpuidle_driver
 297  *
 298  * Unregisters the cpuidle driver under a lock to prevent concurrent attempts
 299  * to [un]register the driver from occuring at the same time.  @drv has to
 300  * match the currently registered driver.
 301  */
 302 void cpuidle_unregister_driver(struct cpuidle_driver *drv)
 303 {
 304         spin_lock(&cpuidle_driver_lock);
 305         __cpuidle_unregister_driver(drv);
 306         spin_unlock(&cpuidle_driver_lock);
 307 }
 308 EXPORT_SYMBOL_GPL(cpuidle_unregister_driver);
 309
 310 /**
 311  * cpuidle_get_driver - return the driver tied to the current CPU.
 312  *
 313  * Returns a struct cpuidle_driver pointer, or NULL if no driver is registered.
 314  */
 315 struct cpuidle_driver *cpuidle_get_driver(void)
 316 {
 317         struct cpuidle_driver *drv;
 318         int cpu;
 319
 320         cpu = get_cpu();
 321         drv = __cpuidle_get_cpu_driver(cpu);
 322         put_cpu();
 323
 324         return drv;
 325 }
 326 EXPORT_SYMBOL_GPL(cpuidle_get_driver);
 327
 328 /**
 329  * cpuidle_get_cpu_driver - return the driver registered for a CPU.
 330  * @dev: a valid pointer to a struct cpuidle_device
 331  *
 332  * Returns a struct cpuidle_driver pointer, or NULL if no driver is registered
 333  * for the CPU associated with @dev.
 334  */
 335 struct cpuidle_driver *cpuidle_get_cpu_driver(struct cpuidle_device *dev)
 336 {
 337         if (!dev)
 338                 return NULL;
 339
 340         return __cpuidle_get_cpu_driver(dev->cpu);
 341 }
 342 EXPORT_SYMBOL_GPL(cpuidle_get_cpu_driver);
 343
 344 /**
 345  * cpuidle_driver_ref - get a reference to the driver.
 346  *
 347  * Increment the reference counter of the cpuidle driver associated with
 348  * the current CPU.
 349  *
 350  * Returns a pointer to the driver, or NULL if the current CPU has no driver.
 351  */
 352 struct cpuidle_driver *cpuidle_driver_ref(void)
 353 {
 354         struct cpuidle_driver *drv;
 355
 356         spin_lock(&cpuidle_driver_lock);
 357
 358         drv = cpuidle_get_driver();
 359         if (drv)
 360                 drv->refcnt++;
 361
 362         spin_unlock(&cpuidle_driver_lock);
 363         return drv;
 364 }
 365
 366 /**
 367  * cpuidle_driver_unref - puts down the refcount for the driver
 368  *
 369  * Decrement the reference counter of the cpuidle driver associated with
 370  * the current CPU.
 371  */
 372 void cpuidle_driver_unref(void)
 373 {
 374         struct cpuidle_driver *drv;
 375
 376         spin_lock(&cpuidle_driver_lock);
 377
 378         drv = cpuidle_get_driver();
 379         if (drv && !WARN_ON(drv->refcnt <= 0))
 380                 drv->refcnt--;
 381
 382         spin_unlock(&cpuidle_driver_lock);
 383 }