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         ktime_t t1, t2;
 186         s64 diff;
 187
 188         t1 = ktime_get();
 189         local_irq_enable();
 190         while (!need_resched())
 191                 cpu_relax();
 192
 193         t2 = ktime_get();
 194         diff = ktime_to_us(ktime_sub(t2, t1));
 195         if (diff > INT_MAX)
 196                 diff = INT_MAX;
 197
 198         dev->last_residency = (int) diff;
 199
 200         return index;
 201 }
 202
 203 static void poll_idle_init(struct cpuidle_driver *drv)
 204 {
 205         struct cpuidle_state *state = &drv->states[0];
 206
 207         snprintf(state->name, CPUIDLE_NAME_LEN, "POLL");
 208         snprintf(state->desc, CPUIDLE_DESC_LEN, "CPUIDLE CORE POLL IDLE");
 209         state->exit_latency = 0;
 210         state->target_residency = 0;
 211         state->power_usage = -1;
 212         state->flags = 0;
 213         state->enter = poll_idle;
 214         state->disabled = false;
 215 }
 216 #else
 217 static void poll_idle_init(struct cpuidle_driver *drv) {}
 218 #endif /* !CONFIG_ARCH_HAS_CPU_RELAX */
 219
 220 /**
 221  * __cpuidle_register_driver: register the driver
 222  * @drv: a valid pointer to a struct cpuidle_driver
 223  *
 224  * Do some sanity checks, initialize the driver, assign the driver to the
 225  * global cpuidle driver variable(s) and set up the broadcast timer if the
 226  * cpuidle driver has some states that shut down the local timer.
 227  *
 228  * Returns 0 on success, a negative error code otherwise:
 229  *  * -EINVAL if the driver pointer is NULL or no idle states are available
 230  *  * -ENODEV if the cpuidle framework is disabled
 231  *  * -EBUSY if the driver is already assigned to the global variable(s)
 232  */
 233 static int __cpuidle_register_driver(struct cpuidle_driver *drv)
 234 {
 235         int ret;
 236
 237         if (!drv || !drv->state_count)
 238                 return -EINVAL;
 239
 240         if (cpuidle_disabled())
 241                 return -ENODEV;
 242
 243         __cpuidle_driver_init(drv);
 244
 245         ret = __cpuidle_set_driver(drv);
 246         if (ret)
 247                 return ret;
 248
 249         if (drv->bctimer)
 250                 on_each_cpu_mask(drv->cpumask, cpuidle_setup_broadcast_timer,
 251                                  (void *)CLOCK_EVT_NOTIFY_BROADCAST_ON, 1);
 252
 253         poll_idle_init(drv);
 254
 255         return 0;
 256 }
 257
 258 /**
 259  * __cpuidle_unregister_driver - unregister the driver
 260  * @drv: a valid pointer to a struct cpuidle_driver
 261  *
 262  * Check if the driver is no longer in use, reset the global cpuidle driver
 263  * variable(s) and disable the timer broadcast notification mechanism if it was
 264  * in use.
 265  *
 266  */
 267 static void __cpuidle_unregister_driver(struct cpuidle_driver *drv)
 268 {
 269         if (WARN_ON(drv->refcnt > 0))
 270                 return;
 271
 272         if (drv->bctimer) {
 273                 drv->bctimer = 0;
 274                 on_each_cpu_mask(drv->cpumask, cpuidle_setup_broadcast_timer,
 275                                  (void *)CLOCK_EVT_NOTIFY_BROADCAST_OFF, 1);
 276         }
 277
 278         __cpuidle_unset_driver(drv);
 279 }
 280
 281 /**
 282  * cpuidle_register_driver - registers a driver
 283  * @drv: a pointer to a valid struct cpuidle_driver
 284  *
 285  * Register the driver under a lock to prevent concurrent attempts to
 286  * [un]register the driver from occuring at the same time.
 287  *
 288  * Returns 0 on success, a negative error code (returned by
 289  * __cpuidle_register_driver()) otherwise.
 290  */
 291 int cpuidle_register_driver(struct cpuidle_driver *drv)
 292 {
 293         int ret;
 294
 295         spin_lock(&cpuidle_driver_lock);
 296         ret = __cpuidle_register_driver(drv);
 297         spin_unlock(&cpuidle_driver_lock);
 298
 299         return ret;
 300 }
 301 EXPORT_SYMBOL_GPL(cpuidle_register_driver);
 302
 303 /**
 304  * cpuidle_unregister_driver - unregisters a driver
 305  * @drv: a pointer to a valid struct cpuidle_driver
 306  *
 307  * Unregisters the cpuidle driver under a lock to prevent concurrent attempts
 308  * to [un]register the driver from occuring at the same time.  @drv has to
 309  * match the currently registered driver.
 310  */
 311 void cpuidle_unregister_driver(struct cpuidle_driver *drv)
 312 {
 313         spin_lock(&cpuidle_driver_lock);
 314         __cpuidle_unregister_driver(drv);
 315         spin_unlock(&cpuidle_driver_lock);
 316 }
 317 EXPORT_SYMBOL_GPL(cpuidle_unregister_driver);
 318
 319 /**
 320  * cpuidle_get_driver - return the driver tied to the current CPU.
 321  *
 322  * Returns a struct cpuidle_driver pointer, or NULL if no driver is registered.
 323  */
 324 struct cpuidle_driver *cpuidle_get_driver(void)
 325 {
 326         struct cpuidle_driver *drv;
 327         int cpu;
 328
 329         cpu = get_cpu();
 330         drv = __cpuidle_get_cpu_driver(cpu);
 331         put_cpu();
 332
 333         return drv;
 334 }
 335 EXPORT_SYMBOL_GPL(cpuidle_get_driver);
 336
 337 /**
 338  * cpuidle_get_cpu_driver - return the driver registered for a CPU.
 339  * @dev: a valid pointer to a struct cpuidle_device
 340  *
 341  * Returns a struct cpuidle_driver pointer, or NULL if no driver is registered
 342  * for the CPU associated with @dev.
 343  */
 344 struct cpuidle_driver *cpuidle_get_cpu_driver(struct cpuidle_device *dev)
 345 {
 346         if (!dev)
 347                 return NULL;
 348
 349         return __cpuidle_get_cpu_driver(dev->cpu);
 350 }
 351 EXPORT_SYMBOL_GPL(cpuidle_get_cpu_driver);
 352
 353 /**
 354  * cpuidle_driver_ref - get a reference to the driver.
 355  *
 356  * Increment the reference counter of the cpuidle driver associated with
 357  * the current CPU.
 358  *
 359  * Returns a pointer to the driver, or NULL if the current CPU has no driver.
 360  */
 361 struct cpuidle_driver *cpuidle_driver_ref(void)
 362 {
 363         struct cpuidle_driver *drv;
 364
 365         spin_lock(&cpuidle_driver_lock);
 366
 367         drv = cpuidle_get_driver();
 368         if (drv)
 369                 drv->refcnt++;
 370
 371         spin_unlock(&cpuidle_driver_lock);
 372         return drv;
 373 }
 374
 375 /**
 376  * cpuidle_driver_unref - puts down the refcount for the driver
 377  *
 378  * Decrement the reference counter of the cpuidle driver associated with
 379  * the current CPU.
 380  */
 381 void cpuidle_driver_unref(void)
 382 {
 383         struct cpuidle_driver *drv;
 384
 385         spin_lock(&cpuidle_driver_lock);
 386
 387         drv = cpuidle_get_driver();
 388         if (drv && !WARN_ON(drv->refcnt <= 0))
 389                 drv->refcnt--;
 390
 391         spin_unlock(&cpuidle_driver_lock);
 392 }