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