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