2 * driver.c - driver support
4 * (C) 2006-2007 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
5 * Shaohua Li <shaohua.li@intel.com>
6 * Adam Belay <abelay@novell.com>
8 * This code is licenced under the GPL.
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>
22 DEFINE_SPINLOCK(cpuidle_driver_lock);
24 #ifdef CONFIG_CPU_IDLE_MULTIPLE_DRIVERS
26 static DEFINE_PER_CPU(struct cpuidle_driver *, cpuidle_drivers);
29 * __cpuidle_get_cpu_driver - return the cpuidle driver tied to a CPU.
30 * @cpu: the CPU handled by the driver
32 * Returns a pointer to struct cpuidle_driver or NULL if no driver has been
33 * registered for @cpu.
35 static struct cpuidle_driver *__cpuidle_get_cpu_driver(int cpu)
37 return per_cpu(cpuidle_drivers, cpu);
41 * __cpuidle_unset_driver - unset per CPU driver variables.
42 * @drv: a valid pointer to a struct cpuidle_driver
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.
48 static inline void __cpuidle_unset_driver(struct cpuidle_driver *drv)
52 for_each_cpu(cpu, drv->cpumask) {
54 if (drv != __cpuidle_get_cpu_driver(cpu))
57 per_cpu(cpuidle_drivers, cpu) = NULL;
62 * __cpuidle_set_driver - set per CPU driver variables for the given driver.
63 * @drv: a valid pointer to a struct cpuidle_driver
65 * Returns 0 on success, -EBUSY if any CPU in the cpumask have a driver
66 * different from drv already.
68 static inline int __cpuidle_set_driver(struct cpuidle_driver *drv)
72 for_each_cpu(cpu, drv->cpumask) {
73 struct cpuidle_driver *old_drv;
75 old_drv = __cpuidle_get_cpu_driver(cpu);
76 if (old_drv && old_drv != drv)
80 for_each_cpu(cpu, drv->cpumask)
81 per_cpu(cpuidle_drivers, cpu) = drv;
88 static struct cpuidle_driver *cpuidle_curr_driver;
91 * __cpuidle_get_cpu_driver - return the global cpuidle driver pointer.
92 * @cpu: ignored without the multiple driver support
94 * Return a pointer to a struct cpuidle_driver object or NULL if no driver was
95 * previously registered.
97 static inline struct cpuidle_driver *__cpuidle_get_cpu_driver(int cpu)
99 return cpuidle_curr_driver;
103 * __cpuidle_set_driver - assign the global cpuidle driver variable.
104 * @drv: pointer to a struct cpuidle_driver object
106 * Returns 0 on success, -EBUSY if the driver is already registered.
108 static inline int __cpuidle_set_driver(struct cpuidle_driver *drv)
110 if (cpuidle_curr_driver)
113 cpuidle_curr_driver = drv;
119 * __cpuidle_unset_driver - unset the global cpuidle driver variable.
120 * @drv: a pointer to a struct cpuidle_driver
122 * Reset the global cpuidle variable to NULL. If @drv does not match the
123 * registered driver, do nothing.
125 static inline void __cpuidle_unset_driver(struct cpuidle_driver *drv)
127 if (drv == cpuidle_curr_driver)
128 cpuidle_curr_driver = NULL;
134 * cpuidle_setup_broadcast_timer - enable/disable the broadcast timer on a cpu
135 * @arg: a void pointer used to match the SMP cross call API
137 * If @arg is NULL broadcast is disabled otherwise enabled
139 * This function is executed per CPU by an SMP cross call. It's not
140 * supposed to be called directly.
142 static void cpuidle_setup_broadcast_timer(void *arg)
145 tick_broadcast_enable();
147 tick_broadcast_disable();
151 * __cpuidle_driver_init - initialize the driver's internal data
152 * @drv: a valid pointer to a struct cpuidle_driver
154 static void __cpuidle_driver_init(struct cpuidle_driver *drv)
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.
166 drv->cpumask = (struct cpumask *)cpu_possible_mask;
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.
173 for (i = drv->state_count - 1; i >= 0 ; i--) {
174 if (drv->states[i].flags & CPUIDLE_FLAG_TIMER_STOP) {
182 * __cpuidle_register_driver: register the driver
183 * @drv: a valid pointer to a struct cpuidle_driver
185 * Do some sanity checks, initialize the driver, assign the driver to the
186 * global cpuidle driver variable(s) and set up the broadcast timer if the
187 * cpuidle driver has some states that shut down the local timer.
189 * Returns 0 on success, a negative error code otherwise:
190 * * -EINVAL if the driver pointer is NULL or no idle states are available
191 * * -ENODEV if the cpuidle framework is disabled
192 * * -EBUSY if the driver is already assigned to the global variable(s)
194 static int __cpuidle_register_driver(struct cpuidle_driver *drv)
198 if (!drv || !drv->state_count)
201 ret = cpuidle_coupled_state_verify(drv);
205 if (cpuidle_disabled())
208 __cpuidle_driver_init(drv);
210 ret = __cpuidle_set_driver(drv);
215 on_each_cpu_mask(drv->cpumask, cpuidle_setup_broadcast_timer,
222 * __cpuidle_unregister_driver - unregister the driver
223 * @drv: a valid pointer to a struct cpuidle_driver
225 * Check if the driver is no longer in use, reset the global cpuidle driver
226 * variable(s) and disable the timer broadcast notification mechanism if it was
230 static void __cpuidle_unregister_driver(struct cpuidle_driver *drv)
232 if (WARN_ON(drv->refcnt > 0))
237 on_each_cpu_mask(drv->cpumask, cpuidle_setup_broadcast_timer,
241 __cpuidle_unset_driver(drv);
245 * cpuidle_register_driver - registers a driver
246 * @drv: a pointer to a valid struct cpuidle_driver
248 * Register the driver under a lock to prevent concurrent attempts to
249 * [un]register the driver from occuring at the same time.
251 * Returns 0 on success, a negative error code (returned by
252 * __cpuidle_register_driver()) otherwise.
254 int cpuidle_register_driver(struct cpuidle_driver *drv)
256 struct cpuidle_governor *gov;
259 spin_lock(&cpuidle_driver_lock);
260 ret = __cpuidle_register_driver(drv);
261 spin_unlock(&cpuidle_driver_lock);
263 if (!ret && !strlen(param_governor) && drv->governor &&
264 (cpuidle_get_driver() == drv)) {
265 mutex_lock(&cpuidle_lock);
266 gov = cpuidle_find_governor(drv->governor);
268 cpuidle_prev_governor = cpuidle_curr_governor;
269 if (cpuidle_switch_governor(gov) < 0)
270 cpuidle_prev_governor = NULL;
272 mutex_unlock(&cpuidle_lock);
277 EXPORT_SYMBOL_GPL(cpuidle_register_driver);
280 * cpuidle_unregister_driver - unregisters a driver
281 * @drv: a pointer to a valid struct cpuidle_driver
283 * Unregisters the cpuidle driver under a lock to prevent concurrent attempts
284 * to [un]register the driver from occuring at the same time. @drv has to
285 * match the currently registered driver.
287 void cpuidle_unregister_driver(struct cpuidle_driver *drv)
289 bool enabled = (cpuidle_get_driver() == drv);
291 spin_lock(&cpuidle_driver_lock);
292 __cpuidle_unregister_driver(drv);
293 spin_unlock(&cpuidle_driver_lock);
298 mutex_lock(&cpuidle_lock);
299 if (cpuidle_prev_governor) {
300 if (!cpuidle_switch_governor(cpuidle_prev_governor))
301 cpuidle_prev_governor = NULL;
303 mutex_unlock(&cpuidle_lock);
305 EXPORT_SYMBOL_GPL(cpuidle_unregister_driver);
308 * cpuidle_get_driver - return the driver tied to the current CPU.
310 * Returns a struct cpuidle_driver pointer, or NULL if no driver is registered.
312 struct cpuidle_driver *cpuidle_get_driver(void)
314 struct cpuidle_driver *drv;
318 drv = __cpuidle_get_cpu_driver(cpu);
323 EXPORT_SYMBOL_GPL(cpuidle_get_driver);
326 * cpuidle_get_cpu_driver - return the driver registered for a CPU.
327 * @dev: a valid pointer to a struct cpuidle_device
329 * Returns a struct cpuidle_driver pointer, or NULL if no driver is registered
330 * for the CPU associated with @dev.
332 struct cpuidle_driver *cpuidle_get_cpu_driver(struct cpuidle_device *dev)
337 return __cpuidle_get_cpu_driver(dev->cpu);
339 EXPORT_SYMBOL_GPL(cpuidle_get_cpu_driver);
342 * cpuidle_driver_ref - get a reference to the driver.
344 * Increment the reference counter of the cpuidle driver associated with
347 * Returns a pointer to the driver, or NULL if the current CPU has no driver.
349 struct cpuidle_driver *cpuidle_driver_ref(void)
351 struct cpuidle_driver *drv;
353 spin_lock(&cpuidle_driver_lock);
355 drv = cpuidle_get_driver();
359 spin_unlock(&cpuidle_driver_lock);
364 * cpuidle_driver_unref - puts down the refcount for the driver
366 * Decrement the reference counter of the cpuidle driver associated with
369 void cpuidle_driver_unref(void)
371 struct cpuidle_driver *drv;
373 spin_lock(&cpuidle_driver_lock);
375 drv = cpuidle_get_driver();
376 if (drv && !WARN_ON(drv->refcnt <= 0))
379 spin_unlock(&cpuidle_driver_lock);