| 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 | |
| 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 on a cpu |
| 134 | * @arg: a void pointer used to match the SMP cross call API |
| 135 | * |
| 136 | * If @arg is NULL broadcast is disabled otherwise enabled |
| 137 | * |
| 138 | * This function is executed per CPU by an SMP cross call. It's not |
| 139 | * supposed to be called directly. |
| 140 | */ |
| 141 | static void cpuidle_setup_broadcast_timer(void *arg) |
| 142 | { |
| 143 | if (arg) |
| 144 | tick_broadcast_enable(); |
| 145 | else |
| 146 | tick_broadcast_disable(); |
| 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 | #ifdef CONFIG_ARCH_HAS_CPU_RELAX |
| 181 | static int poll_idle(struct cpuidle_device *dev, |
| 182 | struct cpuidle_driver *drv, int index) |
| 183 | { |
| 184 | local_irq_enable(); |
| 185 | if (!current_set_polling_and_test()) { |
| 186 | while (!need_resched()) |
| 187 | cpu_relax(); |
| 188 | } |
| 189 | current_clr_polling(); |
| 190 | |
| 191 | return index; |
| 192 | } |
| 193 | |
| 194 | static void poll_idle_init(struct cpuidle_driver *drv) |
| 195 | { |
| 196 | struct cpuidle_state *state = &drv->states[0]; |
| 197 | |
| 198 | snprintf(state->name, CPUIDLE_NAME_LEN, "POLL"); |
| 199 | snprintf(state->desc, CPUIDLE_DESC_LEN, "CPUIDLE CORE POLL IDLE"); |
| 200 | state->exit_latency = 0; |
| 201 | state->target_residency = 0; |
| 202 | state->power_usage = -1; |
| 203 | state->enter = poll_idle; |
| 204 | state->disabled = false; |
| 205 | } |
| 206 | #else |
| 207 | static void poll_idle_init(struct cpuidle_driver *drv) {} |
| 208 | #endif /* !CONFIG_ARCH_HAS_CPU_RELAX */ |
| 209 | |
| 210 | /** |
| 211 | * __cpuidle_register_driver: register the driver |
| 212 | * @drv: a valid pointer to a struct cpuidle_driver |
| 213 | * |
| 214 | * Do some sanity checks, initialize the driver, assign the driver to the |
| 215 | * global cpuidle driver variable(s) and set up the broadcast timer if the |
| 216 | * cpuidle driver has some states that shut down the local timer. |
| 217 | * |
| 218 | * Returns 0 on success, a negative error code otherwise: |
| 219 | * * -EINVAL if the driver pointer is NULL or no idle states are available |
| 220 | * * -ENODEV if the cpuidle framework is disabled |
| 221 | * * -EBUSY if the driver is already assigned to the global variable(s) |
| 222 | */ |
| 223 | static int __cpuidle_register_driver(struct cpuidle_driver *drv) |
| 224 | { |
| 225 | int ret; |
| 226 | |
| 227 | if (!drv || !drv->state_count) |
| 228 | return -EINVAL; |
| 229 | |
| 230 | if (cpuidle_disabled()) |
| 231 | return -ENODEV; |
| 232 | |
| 233 | __cpuidle_driver_init(drv); |
| 234 | |
| 235 | ret = __cpuidle_set_driver(drv); |
| 236 | if (ret) |
| 237 | return ret; |
| 238 | |
| 239 | if (drv->bctimer) |
| 240 | on_each_cpu_mask(drv->cpumask, cpuidle_setup_broadcast_timer, |
| 241 | (void *)1, 1); |
| 242 | |
| 243 | poll_idle_init(drv); |
| 244 | |
| 245 | return 0; |
| 246 | } |
| 247 | |
| 248 | /** |
| 249 | * __cpuidle_unregister_driver - unregister the driver |
| 250 | * @drv: a valid pointer to a struct cpuidle_driver |
| 251 | * |
| 252 | * Check if the driver is no longer in use, reset the global cpuidle driver |
| 253 | * variable(s) and disable the timer broadcast notification mechanism if it was |
| 254 | * in use. |
| 255 | * |
| 256 | */ |
| 257 | static void __cpuidle_unregister_driver(struct cpuidle_driver *drv) |
| 258 | { |
| 259 | if (WARN_ON(drv->refcnt > 0)) |
| 260 | return; |
| 261 | |
| 262 | if (drv->bctimer) { |
| 263 | drv->bctimer = 0; |
| 264 | on_each_cpu_mask(drv->cpumask, cpuidle_setup_broadcast_timer, |
| 265 | NULL, 1); |
| 266 | } |
| 267 | |
| 268 | __cpuidle_unset_driver(drv); |
| 269 | } |
| 270 | |
| 271 | /** |
| 272 | * cpuidle_register_driver - registers a driver |
| 273 | * @drv: a pointer to a valid struct cpuidle_driver |
| 274 | * |
| 275 | * Register the driver under a lock to prevent concurrent attempts to |
| 276 | * [un]register the driver from occuring at the same time. |
| 277 | * |
| 278 | * Returns 0 on success, a negative error code (returned by |
| 279 | * __cpuidle_register_driver()) otherwise. |
| 280 | */ |
| 281 | int cpuidle_register_driver(struct cpuidle_driver *drv) |
| 282 | { |
| 283 | int ret; |
| 284 | |
| 285 | spin_lock(&cpuidle_driver_lock); |
| 286 | ret = __cpuidle_register_driver(drv); |
| 287 | spin_unlock(&cpuidle_driver_lock); |
| 288 | |
| 289 | return ret; |
| 290 | } |
| 291 | EXPORT_SYMBOL_GPL(cpuidle_register_driver); |
| 292 | |
| 293 | /** |
| 294 | * cpuidle_unregister_driver - unregisters a driver |
| 295 | * @drv: a pointer to a valid struct cpuidle_driver |
| 296 | * |
| 297 | * Unregisters the cpuidle driver under a lock to prevent concurrent attempts |
| 298 | * to [un]register the driver from occuring at the same time. @drv has to |
| 299 | * match the currently registered driver. |
| 300 | */ |
| 301 | void cpuidle_unregister_driver(struct cpuidle_driver *drv) |
| 302 | { |
| 303 | spin_lock(&cpuidle_driver_lock); |
| 304 | __cpuidle_unregister_driver(drv); |
| 305 | spin_unlock(&cpuidle_driver_lock); |
| 306 | } |
| 307 | EXPORT_SYMBOL_GPL(cpuidle_unregister_driver); |
| 308 | |
| 309 | /** |
| 310 | * cpuidle_get_driver - return the driver tied to the current CPU. |
| 311 | * |
| 312 | * Returns a struct cpuidle_driver pointer, or NULL if no driver is registered. |
| 313 | */ |
| 314 | struct cpuidle_driver *cpuidle_get_driver(void) |
| 315 | { |
| 316 | struct cpuidle_driver *drv; |
| 317 | int cpu; |
| 318 | |
| 319 | cpu = get_cpu(); |
| 320 | drv = __cpuidle_get_cpu_driver(cpu); |
| 321 | put_cpu(); |
| 322 | |
| 323 | return drv; |
| 324 | } |
| 325 | EXPORT_SYMBOL_GPL(cpuidle_get_driver); |
| 326 | |
| 327 | /** |
| 328 | * cpuidle_get_cpu_driver - return the driver registered for a CPU. |
| 329 | * @dev: a valid pointer to a struct cpuidle_device |
| 330 | * |
| 331 | * Returns a struct cpuidle_driver pointer, or NULL if no driver is registered |
| 332 | * for the CPU associated with @dev. |
| 333 | */ |
| 334 | struct cpuidle_driver *cpuidle_get_cpu_driver(struct cpuidle_device *dev) |
| 335 | { |
| 336 | if (!dev) |
| 337 | return NULL; |
| 338 | |
| 339 | return __cpuidle_get_cpu_driver(dev->cpu); |
| 340 | } |
| 341 | EXPORT_SYMBOL_GPL(cpuidle_get_cpu_driver); |
| 342 | |
| 343 | /** |
| 344 | * cpuidle_driver_ref - get a reference to the driver. |
| 345 | * |
| 346 | * Increment the reference counter of the cpuidle driver associated with |
| 347 | * the current CPU. |
| 348 | * |
| 349 | * Returns a pointer to the driver, or NULL if the current CPU has no driver. |
| 350 | */ |
| 351 | struct cpuidle_driver *cpuidle_driver_ref(void) |
| 352 | { |
| 353 | struct cpuidle_driver *drv; |
| 354 | |
| 355 | spin_lock(&cpuidle_driver_lock); |
| 356 | |
| 357 | drv = cpuidle_get_driver(); |
| 358 | if (drv) |
| 359 | drv->refcnt++; |
| 360 | |
| 361 | spin_unlock(&cpuidle_driver_lock); |
| 362 | return drv; |
| 363 | } |
| 364 | |
| 365 | /** |
| 366 | * cpuidle_driver_unref - puts down the refcount for the driver |
| 367 | * |
| 368 | * Decrement the reference counter of the cpuidle driver associated with |
| 369 | * the current CPU. |
| 370 | */ |
| 371 | void cpuidle_driver_unref(void) |
| 372 | { |
| 373 | struct cpuidle_driver *drv; |
| 374 | |
| 375 | spin_lock(&cpuidle_driver_lock); |
| 376 | |
| 377 | drv = cpuidle_get_driver(); |
| 378 | if (drv && !WARN_ON(drv->refcnt <= 0)) |
| 379 | drv->refcnt--; |
| 380 | |
| 381 | spin_unlock(&cpuidle_driver_lock); |
| 382 | } |