/* * driver.c - driver support * * (C) 2006-2007 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com> * Shaohua Li <shaohua.li@intel.com> * Adam Belay <abelay@novell.com> * * This code is licenced under the GPL. */ #include <linux/mutex.h> #include <linux/module.h> #include <linux/sched.h> #include <linux/cpuidle.h> #include <linux/cpumask.h> #include <linux/tick.h> #include <linux/cpu.h> #include "cpuidle.h" DEFINE_SPINLOCK(cpuidle_driver_lock); #ifdef CONFIG_CPU_IDLE_MULTIPLE_DRIVERS static DEFINE_PER_CPU(struct cpuidle_driver *, cpuidle_drivers); /** * __cpuidle_get_cpu_driver - return the cpuidle driver tied to a CPU. * @cpu: the CPU handled by the driver * * Returns a pointer to struct cpuidle_driver or NULL if no driver has been * registered for @cpu. */ static struct cpuidle_driver *__cpuidle_get_cpu_driver(int cpu) { return per_cpu(cpuidle_drivers, cpu); } /** * __cpuidle_unset_driver - unset per CPU driver variables. * @drv: a valid pointer to a struct cpuidle_driver * * For each CPU in the driver's CPU mask, unset the registered driver per CPU * variable. If @drv is different from the registered driver, the corresponding * variable is not cleared. */ static inline void __cpuidle_unset_driver(struct cpuidle_driver *drv) { int cpu; for_each_cpu(cpu, drv->cpumask) { if (drv != __cpuidle_get_cpu_driver(cpu)) continue; per_cpu(cpuidle_drivers, cpu) = NULL; } } /** * __cpuidle_set_driver - set per CPU driver variables for the given driver. * @drv: a valid pointer to a struct cpuidle_driver * * For each CPU in the driver's cpumask, unset the registered driver per CPU * to @drv. * * Returns 0 on success, -EBUSY if the CPUs have driver(s) already. */ static inline int __cpuidle_set_driver(struct cpuidle_driver *drv) { int cpu; for_each_cpu(cpu, drv->cpumask) { if (__cpuidle_get_cpu_driver(cpu)) { __cpuidle_unset_driver(drv); return -EBUSY; } per_cpu(cpuidle_drivers, cpu) = drv; } return 0; } #else static struct cpuidle_driver *cpuidle_curr_driver; /** * __cpuidle_get_cpu_driver - return the global cpuidle driver pointer. * @cpu: ignored without the multiple driver support * * Return a pointer to a struct cpuidle_driver object or NULL if no driver was * previously registered. */ static inline struct cpuidle_driver *__cpuidle_get_cpu_driver(int cpu) { return cpuidle_curr_driver; } /** * __cpuidle_set_driver - assign the global cpuidle driver variable. * @drv: pointer to a struct cpuidle_driver object * * Returns 0 on success, -EBUSY if the driver is already registered. */ static inline int __cpuidle_set_driver(struct cpuidle_driver *drv) { if (cpuidle_curr_driver) return -EBUSY; cpuidle_curr_driver = drv; return 0; } /** * __cpuidle_unset_driver - unset the global cpuidle driver variable. * @drv: a pointer to a struct cpuidle_driver * * Reset the global cpuidle variable to NULL. If @drv does not match the * registered driver, do nothing. */ static inline void __cpuidle_unset_driver(struct cpuidle_driver *drv) { if (drv == cpuidle_curr_driver) cpuidle_curr_driver = NULL; } #endif /** * cpuidle_setup_broadcast_timer - enable/disable the broadcast timer on a cpu * @arg: a void pointer used to match the SMP cross call API * * If @arg is NULL broadcast is disabled otherwise enabled * * This function is executed per CPU by an SMP cross call. It's not * supposed to be called directly. */ static void cpuidle_setup_broadcast_timer(void *arg) { if (arg) tick_broadcast_enable(); else tick_broadcast_disable(); } /** * __cpuidle_driver_init - initialize the driver's internal data * @drv: a valid pointer to a struct cpuidle_driver */ static void __cpuidle_driver_init(struct cpuidle_driver *drv) { int i; drv->refcnt = 0; /* * Use all possible CPUs as the default, because if the kernel boots * with some CPUs offline and then we online one of them, the CPU * notifier has to know which driver to assign. */ if (!drv->cpumask) drv->cpumask = (struct cpumask *)cpu_possible_mask; /* * Look for the timer stop flag in the different states, so that we know * if the broadcast timer has to be set up. The loop is in the reverse * order, because usually one of the deeper states have this flag set. */ for (i = drv->state_count - 1; i >= 0 ; i--) { if (drv->states[i].flags & CPUIDLE_FLAG_TIMER_STOP) { drv->bctimer = 1; break; } } } #ifdef CONFIG_ARCH_HAS_CPU_RELAX static int __cpuidle poll_idle(struct cpuidle_device *dev, struct cpuidle_driver *drv, int index) { local_irq_enable(); if (!current_set_polling_and_test()) { while (!need_resched()) cpu_relax(); } current_clr_polling(); return index; } static void poll_idle_init(struct cpuidle_driver *drv) { struct cpuidle_state *state = &drv->states[0]; snprintf(state->name, CPUIDLE_NAME_LEN, "POLL"); snprintf(state->desc, CPUIDLE_DESC_LEN, "CPUIDLE CORE POLL IDLE"); state->exit_latency = 0; state->target_residency = 0; state->power_usage = -1; state->enter = poll_idle; state->disabled = false; } #else static void poll_idle_init(struct cpuidle_driver *drv) {} #endif /* !CONFIG_ARCH_HAS_CPU_RELAX */ /** * __cpuidle_register_driver: register the driver * @drv: a valid pointer to a struct cpuidle_driver * * Do some sanity checks, initialize the driver, assign the driver to the * global cpuidle driver variable(s) and set up the broadcast timer if the * cpuidle driver has some states that shut down the local timer. * * Returns 0 on success, a negative error code otherwise: * * -EINVAL if the driver pointer is NULL or no idle states are available * * -ENODEV if the cpuidle framework is disabled * * -EBUSY if the driver is already assigned to the global variable(s) */ static int __cpuidle_register_driver(struct cpuidle_driver *drv) { int ret; if (!drv || !drv->state_count) return -EINVAL; ret = cpuidle_coupled_state_verify(drv); if (ret) return ret; if (cpuidle_disabled()) return -ENODEV; __cpuidle_driver_init(drv); ret = __cpuidle_set_driver(drv); if (ret) return ret; if (drv->bctimer) on_each_cpu_mask(drv->cpumask, cpuidle_setup_broadcast_timer, (void *)1, 1); poll_idle_init(drv); return 0; } /** * __cpuidle_unregister_driver - unregister the driver * @drv: a valid pointer to a struct cpuidle_driver * * Check if the driver is no longer in use, reset the global cpuidle driver * variable(s) and disable the timer broadcast notification mechanism if it was * in use. * */ static void __cpuidle_unregister_driver(struct cpuidle_driver *drv) { if (WARN_ON(drv->refcnt > 0)) return; if (drv->bctimer) { drv->bctimer = 0; on_each_cpu_mask(drv->cpumask, cpuidle_setup_broadcast_timer, NULL, 1); } __cpuidle_unset_driver(drv); } /** * cpuidle_register_driver - registers a driver * @drv: a pointer to a valid struct cpuidle_driver * * Register the driver under a lock to prevent concurrent attempts to * [un]register the driver from occuring at the same time. * * Returns 0 on success, a negative error code (returned by * __cpuidle_register_driver()) otherwise. */ int cpuidle_register_driver(struct cpuidle_driver *drv) { int ret; spin_lock(&cpuidle_driver_lock); ret = __cpuidle_register_driver(drv); spin_unlock(&cpuidle_driver_lock); return ret; } EXPORT_SYMBOL_GPL(cpuidle_register_driver); /** * cpuidle_unregister_driver - unregisters a driver * @drv: a pointer to a valid struct cpuidle_driver * * Unregisters the cpuidle driver under a lock to prevent concurrent attempts * to [un]register the driver from occuring at the same time. @drv has to * match the currently registered driver. */ void cpuidle_unregister_driver(struct cpuidle_driver *drv) { spin_lock(&cpuidle_driver_lock); __cpuidle_unregister_driver(drv); spin_unlock(&cpuidle_driver_lock); } EXPORT_SYMBOL_GPL(cpuidle_unregister_driver); /** * cpuidle_get_driver - return the driver tied to the current CPU. * * Returns a struct cpuidle_driver pointer, or NULL if no driver is registered. */ struct cpuidle_driver *cpuidle_get_driver(void) { struct cpuidle_driver *drv; int cpu; cpu = get_cpu(); drv = __cpuidle_get_cpu_driver(cpu); put_cpu(); return drv; } EXPORT_SYMBOL_GPL(cpuidle_get_driver); /** * cpuidle_get_cpu_driver - return the driver registered for a CPU. * @dev: a valid pointer to a struct cpuidle_device * * Returns a struct cpuidle_driver pointer, or NULL if no driver is registered * for the CPU associated with @dev. */ struct cpuidle_driver *cpuidle_get_cpu_driver(struct cpuidle_device *dev) { if (!dev) return NULL; return __cpuidle_get_cpu_driver(dev->cpu); } EXPORT_SYMBOL_GPL(cpuidle_get_cpu_driver); /** * cpuidle_driver_ref - get a reference to the driver. * * Increment the reference counter of the cpuidle driver associated with * the current CPU. * * Returns a pointer to the driver, or NULL if the current CPU has no driver. */ struct cpuidle_driver *cpuidle_driver_ref(void) { struct cpuidle_driver *drv; spin_lock(&cpuidle_driver_lock); drv = cpuidle_get_driver(); if (drv) drv->refcnt++; spin_unlock(&cpuidle_driver_lock); return drv; } /** * cpuidle_driver_unref - puts down the refcount for the driver * * Decrement the reference counter of the cpuidle driver associated with * the current CPU. */ void cpuidle_driver_unref(void) { struct cpuidle_driver *drv; spin_lock(&cpuidle_driver_lock); drv = cpuidle_get_driver(); if (drv && !WARN_ON(drv->refcnt <= 0)) drv->refcnt--; spin_unlock(&cpuidle_driver_lock); }