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 #include <linux/cpu.h>
  18
  19 #include "cpuidle.h"
  20
  21 DEFINE_SPINLOCK(cpuidle_driver_lock);
  22
  23 #ifdef CONFIG_CPU_IDLE_MULTIPLE_DRIVERS
  24
  25 static DEFINE_PER_CPU(struct cpuidle_driver *, cpuidle_drivers);
  26
  27 /**
  28  * __cpuidle_get_cpu_driver - return the cpuidle driver tied to a CPU.
  29  * @cpu: the CPU handled by the driver
  30  *
  31  * Returns a pointer to struct cpuidle_driver or NULL if no driver has been
  32  * registered for @cpu.
  33  */
  34 static struct cpuidle_driver *__cpuidle_get_cpu_driver(int cpu)
  35 {
  36         return per_cpu(cpuidle_drivers, cpu);
  37 }
  38
  39 /**
  40  * __cpuidle_unset_driver - unset per CPU driver variables.
  41  * @drv: a valid pointer to a struct cpuidle_driver
  42  *
  43  * For each CPU in the driver's CPU mask, unset the registered driver per CPU
  44  * variable. If @drv is different from the registered driver, the corresponding
  45  * variable is not cleared.
  46  */
  47 static inline void __cpuidle_unset_driver(struct cpuidle_driver *drv)
  48 {
  49         int cpu;
  50
  51         for_each_cpu(cpu, drv->cpumask) {
  52
  53                 if (drv != __cpuidle_get_cpu_driver(cpu))
  54                         continue;
  55
  56                 per_cpu(cpuidle_drivers, cpu) = NULL;
  57         }
  58 }
  59
  60 /**
  61  * __cpuidle_set_driver - set per CPU driver variables for the given driver.
  62  * @drv: a valid pointer to a struct cpuidle_driver
  63  *
  64  * For each CPU in the driver's cpumask, unset the registered driver per CPU
  65  * to @drv.
  66  *
  67  * Returns 0 on success, -EBUSY if the CPUs have driver(s) already.
  68  */
  69 static inline int __cpuidle_set_driver(struct cpuidle_driver *drv)
  70 {
  71         int cpu;
  72
  73         for_each_cpu(cpu, drv->cpumask) {
  74
  75                 if (__cpuidle_get_cpu_driver(cpu)) {
  76                         __cpuidle_unset_driver(drv);
  77                         return -EBUSY;
  78                 }
  79
  80                 per_cpu(cpuidle_drivers, cpu) = drv;
  81         }
  82
  83         return 0;
  84 }
  85
  86 #else
  87
  88 static struct cpuidle_driver *cpuidle_curr_driver;
  89
  90 /**
  91  * __cpuidle_get_cpu_driver - return the global cpuidle driver pointer.
  92  * @cpu: ignored without the multiple driver support
  93  *
  94  * Return a pointer to a struct cpuidle_driver object or NULL if no driver was
  95  * previously registered.
  96  */
  97 static inline struct cpuidle_driver *__cpuidle_get_cpu_driver(int cpu)
  98 {
  99         return cpuidle_curr_driver;
 100 }
 101
 102 /**
 103  * __cpuidle_set_driver - assign the global cpuidle driver variable.
 104  * @drv: pointer to a struct cpuidle_driver object
 105  *
 106  * Returns 0 on success, -EBUSY if the driver is already registered.
 107  */
 108 static inline int __cpuidle_set_driver(struct cpuidle_driver *drv)
 109 {
 110         if (cpuidle_curr_driver)
 111                 return -EBUSY;
 112
 113         cpuidle_curr_driver = drv;
 114
 115         return 0;
 116 }
 117
 118 /**
 119  * __cpuidle_unset_driver - unset the global cpuidle driver variable.
 120  * @drv: a pointer to a struct cpuidle_driver
 121  *
 122  * Reset the global cpuidle variable to NULL.  If @drv does not match the
 123  * registered driver, do nothing.
 124  */
 125 static inline void __cpuidle_unset_driver(struct cpuidle_driver *drv)
 126 {
 127         if (drv == cpuidle_curr_driver)
 128                 cpuidle_curr_driver = NULL;
 129 }
 130
 131 #endif
 132
 133 /**
 134  * cpuidle_setup_broadcast_timer - enable/disable the broadcast timer on a cpu
 135  * @arg: a void pointer used to match the SMP cross call API
 136  *
 137  * If @arg is NULL broadcast is disabled otherwise enabled
 138  *
 139  * This function is executed per CPU by an SMP cross call.  It's not
 140  * supposed to be called directly.
 141  */
 142 static void cpuidle_setup_broadcast_timer(void *arg)
 143 {
 144         if (arg)
 145                 tick_broadcast_enable();
 146         else
 147                 tick_broadcast_disable();
 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 __cpuidle 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         ret = cpuidle_coupled_state_verify(drv);
 232         if (ret)
 233                 return ret;
 234
 235         if (cpuidle_disabled())
 236                 return -ENODEV;
 237
 238         __cpuidle_driver_init(drv);
 239
 240         ret = __cpuidle_set_driver(drv);
 241         if (ret)
 242                 return ret;
 243
 244         if (drv->bctimer)
 245                 on_each_cpu_mask(drv->cpumask, cpuidle_setup_broadcast_timer,
 246                                  (void *)1, 1);
 247
 248         poll_idle_init(drv);
 249
 250         return 0;
 251 }
 252
 253 /**
 254  * __cpuidle_unregister_driver - unregister the driver
 255  * @drv: a valid pointer to a struct cpuidle_driver
 256  *
 257  * Check if the driver is no longer in use, reset the global cpuidle driver
 258  * variable(s) and disable the timer broadcast notification mechanism if it was
 259  * in use.
 260  *
 261  */
 262 static void __cpuidle_unregister_driver(struct cpuidle_driver *drv)
 263 {
 264         if (WARN_ON(drv->refcnt > 0))
 265                 return;
 266
 267         if (drv->bctimer) {
 268                 drv->bctimer = 0;
 269                 on_each_cpu_mask(drv->cpumask, cpuidle_setup_broadcast_timer,
 270                                  NULL, 1);
 271         }
 272
 273         __cpuidle_unset_driver(drv);
 274 }
 275
 276 /**
 277  * cpuidle_register_driver - registers a driver
 278  * @drv: a pointer to a valid struct cpuidle_driver
 279  *
 280  * Register the driver under a lock to prevent concurrent attempts to
 281  * [un]register the driver from occuring at the same time.
 282  *
 283  * Returns 0 on success, a negative error code (returned by
 284  * __cpuidle_register_driver()) otherwise.
 285  */
 286 int cpuidle_register_driver(struct cpuidle_driver *drv)
 287 {
 288         int ret;
 289
 290         spin_lock(&cpuidle_driver_lock);
 291         ret = __cpuidle_register_driver(drv);
 292         spin_unlock(&cpuidle_driver_lock);
 293
 294         return ret;
 295 }
 296 EXPORT_SYMBOL_GPL(cpuidle_register_driver);
 297
 298 /**
 299  * cpuidle_unregister_driver - unregisters a driver
 300  * @drv: a pointer to a valid struct cpuidle_driver
 301  *
 302  * Unregisters the cpuidle driver under a lock to prevent concurrent attempts
 303  * to [un]register the driver from occuring at the same time.  @drv has to
 304  * match the currently registered driver.
 305  */
 306 void cpuidle_unregister_driver(struct cpuidle_driver *drv)
 307 {
 308         spin_lock(&cpuidle_driver_lock);
 309         __cpuidle_unregister_driver(drv);
 310         spin_unlock(&cpuidle_driver_lock);
 311 }
 312 EXPORT_SYMBOL_GPL(cpuidle_unregister_driver);
 313
 314 /**
 315  * cpuidle_get_driver - return the driver tied to the current CPU.
 316  *
 317  * Returns a struct cpuidle_driver pointer, or NULL if no driver is registered.
 318  */
 319 struct cpuidle_driver *cpuidle_get_driver(void)
 320 {
 321         struct cpuidle_driver *drv;
 322         int cpu;
 323
 324         cpu = get_cpu();
 325         drv = __cpuidle_get_cpu_driver(cpu);
 326         put_cpu();
 327
 328         return drv;
 329 }
 330 EXPORT_SYMBOL_GPL(cpuidle_get_driver);
 331
 332 /**
 333  * cpuidle_get_cpu_driver - return the driver registered for a CPU.
 334  * @dev: a valid pointer to a struct cpuidle_device
 335  *
 336  * Returns a struct cpuidle_driver pointer, or NULL if no driver is registered
 337  * for the CPU associated with @dev.
 338  */
 339 struct cpuidle_driver *cpuidle_get_cpu_driver(struct cpuidle_device *dev)
 340 {
 341         if (!dev)
 342                 return NULL;
 343
 344         return __cpuidle_get_cpu_driver(dev->cpu);
 345 }
 346 EXPORT_SYMBOL_GPL(cpuidle_get_cpu_driver);
 347
 348 /**
 349  * cpuidle_driver_ref - get a reference to the driver.
 350  *
 351  * Increment the reference counter of the cpuidle driver associated with
 352  * the current CPU.
 353  *
 354  * Returns a pointer to the driver, or NULL if the current CPU has no driver.
 355  */
 356 struct cpuidle_driver *cpuidle_driver_ref(void)
 357 {
 358         struct cpuidle_driver *drv;
 359
 360         spin_lock(&cpuidle_driver_lock);
 361
 362         drv = cpuidle_get_driver();
 363         if (drv)
 364                 drv->refcnt++;
 365
 366         spin_unlock(&cpuidle_driver_lock);
 367         return drv;
 368 }
 369
 370 /**
 371  * cpuidle_driver_unref - puts down the refcount for the driver
 372  *
 373  * Decrement the reference counter of the cpuidle driver associated with
 374  * the current CPU.
 375  */
 376 void cpuidle_driver_unref(void)
 377 {
 378         struct cpuidle_driver *drv;
 379
 380         spin_lock(&cpuidle_driver_lock);
 381
 382         drv = cpuidle_get_driver();
 383         if (drv && !WARN_ON(drv->refcnt <= 0))
 384                 drv->refcnt--;
 385
 386         spin_unlock(&cpuidle_driver_lock);
 387 }