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