diff options
Diffstat (limited to 'drivers/base/power/qos.c')
| -rw-r--r-- | drivers/base/power/qos.c | 420 |
1 files changed, 420 insertions, 0 deletions
diff --git a/drivers/base/power/qos.c b/drivers/base/power/qos.c new file mode 100644 index 000000000000..30a94eadc200 --- /dev/null +++ b/drivers/base/power/qos.c @@ -0,0 +1,420 @@ +/* + * Devices PM QoS constraints management + * + * Copyright (C) 2011 Texas Instruments, Inc. + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License version 2 as + * published by the Free Software Foundation. + * + * + * This module exposes the interface to kernel space for specifying + * per-device PM QoS dependencies. It provides infrastructure for registration + * of: + * + * Dependents on a QoS value : register requests + * Watchers of QoS value : get notified when target QoS value changes + * + * This QoS design is best effort based. Dependents register their QoS needs. + * Watchers register to keep track of the current QoS needs of the system. + * Watchers can register different types of notification callbacks: + * . a per-device notification callback using the dev_pm_qos_*_notifier API. + * The notification chain data is stored in the per-device constraint + * data struct. + * . a system-wide notification callback using the dev_pm_qos_*_global_notifier + * API. The notification chain data is stored in a static variable. + * + * Note about the per-device constraint data struct allocation: + * . The per-device constraints data struct ptr is tored into the device + * dev_pm_info. + * . To minimize the data usage by the per-device constraints, the data struct + * is only allocated at the first call to dev_pm_qos_add_request. + * . The data is later free'd when the device is removed from the system. + * . A global mutex protects the constraints users from the data being + * allocated and free'd. + */ + +#include <linux/pm_qos.h> +#include <linux/spinlock.h> +#include <linux/slab.h> +#include <linux/device.h> +#include <linux/mutex.h> +#include <linux/export.h> + + +static DEFINE_MUTEX(dev_pm_qos_mtx); + +static BLOCKING_NOTIFIER_HEAD(dev_pm_notifiers); + +/** + * dev_pm_qos_read_value - Get PM QoS constraint for a given device. + * @dev: Device to get the PM QoS constraint value for. + */ +s32 dev_pm_qos_read_value(struct device *dev) +{ + struct pm_qos_constraints *c; + unsigned long flags; + s32 ret = 0; + + spin_lock_irqsave(&dev->power.lock, flags); + + c = dev->power.constraints; + if (c) + ret = pm_qos_read_value(c); + + spin_unlock_irqrestore(&dev->power.lock, flags); + + return ret; +} + +/* + * apply_constraint + * @req: constraint request to apply + * @action: action to perform add/update/remove, of type enum pm_qos_req_action + * @value: defines the qos request + * + * Internal function to update the constraints list using the PM QoS core + * code and if needed call the per-device and the global notification + * callbacks + */ +static int apply_constraint(struct dev_pm_qos_request *req, + enum pm_qos_req_action action, int value) +{ + int ret, curr_value; + + ret = pm_qos_update_target(req->dev->power.constraints, + &req->node, action, value); + + if (ret) { + /* Call the global callbacks if needed */ + curr_value = pm_qos_read_value(req->dev->power.constraints); + blocking_notifier_call_chain(&dev_pm_notifiers, + (unsigned long)curr_value, + req); + } + + return ret; +} + +/* + * dev_pm_qos_constraints_allocate + * @dev: device to allocate data for + * + * Called at the first call to add_request, for constraint data allocation + * Must be called with the dev_pm_qos_mtx mutex held + */ +static int dev_pm_qos_constraints_allocate(struct device *dev) +{ + struct pm_qos_constraints *c; + struct blocking_notifier_head *n; + + c = kzalloc(sizeof(*c), GFP_KERNEL); + if (!c) + return -ENOMEM; + + n = kzalloc(sizeof(*n), GFP_KERNEL); + if (!n) { + kfree(c); + return -ENOMEM; + } + BLOCKING_INIT_NOTIFIER_HEAD(n); + + plist_head_init(&c->list); + c->target_value = PM_QOS_DEV_LAT_DEFAULT_VALUE; + c->default_value = PM_QOS_DEV_LAT_DEFAULT_VALUE; + c->type = PM_QOS_MIN; + c->notifiers = n; + + spin_lock_irq(&dev->power.lock); + dev->power.constraints = c; + spin_unlock_irq(&dev->power.lock); + + return 0; +} + +/** + * dev_pm_qos_constraints_init - Initalize device's PM QoS constraints pointer. + * @dev: target device + * + * Called from the device PM subsystem during device insertion under + * device_pm_lock(). + */ +void dev_pm_qos_constraints_init(struct device *dev) +{ + mutex_lock(&dev_pm_qos_mtx); + dev->power.constraints = NULL; + dev->power.power_state = PMSG_ON; + mutex_unlock(&dev_pm_qos_mtx); +} + +/** + * dev_pm_qos_constraints_destroy + * @dev: target device + * + * Called from the device PM subsystem on device removal under device_pm_lock(). + */ +void dev_pm_qos_constraints_destroy(struct device *dev) +{ + struct dev_pm_qos_request *req, *tmp; + struct pm_qos_constraints *c; + + mutex_lock(&dev_pm_qos_mtx); + + dev->power.power_state = PMSG_INVALID; + c = dev->power.constraints; + if (!c) + goto out; + + /* Flush the constraints list for the device */ + plist_for_each_entry_safe(req, tmp, &c->list, node) { + /* + * Update constraints list and call the notification + * callbacks if needed + */ + apply_constraint(req, PM_QOS_REMOVE_REQ, PM_QOS_DEFAULT_VALUE); + memset(req, 0, sizeof(*req)); + } + + spin_lock_irq(&dev->power.lock); + dev->power.constraints = NULL; + spin_unlock_irq(&dev->power.lock); + + kfree(c->notifiers); + kfree(c); + + out: + mutex_unlock(&dev_pm_qos_mtx); +} + +/** + * dev_pm_qos_add_request - inserts new qos request into the list + * @dev: target device for the constraint + * @req: pointer to a preallocated handle + * @value: defines the qos request + * + * This function inserts a new entry in the device constraints list of + * requested qos performance characteristics. It recomputes the aggregate + * QoS expectations of parameters and initializes the dev_pm_qos_request + * handle. Caller needs to save this handle for later use in updates and + * removal. + * + * Returns 1 if the aggregated constraint value has changed, + * 0 if the aggregated constraint value has not changed, + * -EINVAL in case of wrong parameters, -ENOMEM if there's not enough memory + * to allocate for data structures, -ENODEV if the device has just been removed + * from the system. + */ +int dev_pm_qos_add_request(struct device *dev, struct dev_pm_qos_request *req, + s32 value) +{ + int ret = 0; + + if (!dev || !req) /*guard against callers passing in null */ + return -EINVAL; + + if (dev_pm_qos_request_active(req)) { + WARN(1, KERN_ERR "dev_pm_qos_add_request() called for already " + "added request\n"); + return -EINVAL; + } + + req->dev = dev; + + mutex_lock(&dev_pm_qos_mtx); + + if (!dev->power.constraints) { + if (dev->power.power_state.event == PM_EVENT_INVALID) { + /* The device has been removed from the system. */ + req->dev = NULL; + ret = -ENODEV; + goto out; + } else { + /* + * Allocate the constraints data on the first call to + * add_request, i.e. only if the data is not already + * allocated and if the device has not been removed. + */ + ret = dev_pm_qos_constraints_allocate(dev); + } + } + + if (!ret) + ret = apply_constraint(req, PM_QOS_ADD_REQ, value); + + out: + mutex_unlock(&dev_pm_qos_mtx); + + return ret; +} +EXPORT_SYMBOL_GPL(dev_pm_qos_add_request); + +/** + * dev_pm_qos_update_request - modifies an existing qos request + * @req : handle to list element holding a dev_pm_qos request to use + * @new_value: defines the qos request + * + * Updates an existing dev PM qos request along with updating the + * target value. + * + * Attempts are made to make this code callable on hot code paths. + * + * Returns 1 if the aggregated constraint value has changed, + * 0 if the aggregated constraint value has not changed, + * -EINVAL in case of wrong parameters, -ENODEV if the device has been + * removed from the system + */ +int dev_pm_qos_update_request(struct dev_pm_qos_request *req, + s32 new_value) +{ + int ret = 0; + + if (!req) /*guard against callers passing in null */ + return -EINVAL; + + if (!dev_pm_qos_request_active(req)) { + WARN(1, KERN_ERR "dev_pm_qos_update_request() called for " + "unknown object\n"); + return -EINVAL; + } + + mutex_lock(&dev_pm_qos_mtx); + + if (req->dev->power.constraints) { + if (new_value != req->node.prio) + ret = apply_constraint(req, PM_QOS_UPDATE_REQ, + new_value); + } else { + /* Return if the device has been removed */ + ret = -ENODEV; + } + + mutex_unlock(&dev_pm_qos_mtx); + return ret; +} +EXPORT_SYMBOL_GPL(dev_pm_qos_update_request); + +/** + * dev_pm_qos_remove_request - modifies an existing qos request + * @req: handle to request list element + * + * Will remove pm qos request from the list of constraints and + * recompute the current target value. Call this on slow code paths. + * + * Returns 1 if the aggregated constraint value has changed, + * 0 if the aggregated constraint value has not changed, + * -EINVAL in case of wrong parameters, -ENODEV if the device has been + * removed from the system + */ +int dev_pm_qos_remove_request(struct dev_pm_qos_request *req) +{ + int ret = 0; + + if (!req) /*guard against callers passing in null */ + return -EINVAL; + + if (!dev_pm_qos_request_active(req)) { + WARN(1, KERN_ERR "dev_pm_qos_remove_request() called for " + "unknown object\n"); + return -EINVAL; + } + + mutex_lock(&dev_pm_qos_mtx); + + if (req->dev->power.constraints) { + ret = apply_constraint(req, PM_QOS_REMOVE_REQ, + PM_QOS_DEFAULT_VALUE); + memset(req, 0, sizeof(*req)); + } else { + /* Return if the device has been removed */ + ret = -ENODEV; + } + + mutex_unlock(&dev_pm_qos_mtx); + return ret; +} +EXPORT_SYMBOL_GPL(dev_pm_qos_remove_request); + +/** + * dev_pm_qos_add_notifier - sets notification entry for changes to target value + * of per-device PM QoS constraints + * + * @dev: target device for the constraint + * @notifier: notifier block managed by caller. + * + * Will register the notifier into a notification chain that gets called + * upon changes to the target value for the device. + */ +int dev_pm_qos_add_notifier(struct device *dev, struct notifier_block *notifier) +{ + int retval = 0; + + mutex_lock(&dev_pm_qos_mtx); + + /* Silently return if the constraints object is not present. */ + if (dev->power.constraints) + retval = blocking_notifier_chain_register( + dev->power.constraints->notifiers, + notifier); + + mutex_unlock(&dev_pm_qos_mtx); + return retval; +} +EXPORT_SYMBOL_GPL(dev_pm_qos_add_notifier); + +/** + * dev_pm_qos_remove_notifier - deletes notification for changes to target value + * of per-device PM QoS constraints + * + * @dev: target device for the constraint + * @notifier: notifier block to be removed. + * + * Will remove the notifier from the notification chain that gets called + * upon changes to the target value. + */ +int dev_pm_qos_remove_notifier(struct device *dev, + struct notifier_block *notifier) +{ + int retval = 0; + + mutex_lock(&dev_pm_qos_mtx); + + /* Silently return if the constraints object is not present. */ + if (dev->power.constraints) + retval = blocking_notifier_chain_unregister( + dev->power.constraints->notifiers, + notifier); + + mutex_unlock(&dev_pm_qos_mtx); + return retval; +} +EXPORT_SYMBOL_GPL(dev_pm_qos_remove_notifier); + +/** + * dev_pm_qos_add_global_notifier - sets notification entry for changes to + * target value of the PM QoS constraints for any device + * + * @notifier: notifier block managed by caller. + * + * Will register the notifier into a notification chain that gets called + * upon changes to the target value for any device. + */ +int dev_pm_qos_add_global_notifier(struct notifier_block *notifier) +{ + return blocking_notifier_chain_register(&dev_pm_notifiers, notifier); +} +EXPORT_SYMBOL_GPL(dev_pm_qos_add_global_notifier); + +/** + * dev_pm_qos_remove_global_notifier - deletes notification for changes to + * target value of PM QoS constraints for any device + * + * @notifier: notifier block to be removed. + * + * Will remove the notifier from the notification chain that gets called + * upon changes to the target value for any device. + */ +int dev_pm_qos_remove_global_notifier(struct notifier_block *notifier) +{ + return blocking_notifier_chain_unregister(&dev_pm_notifiers, notifier); +} +EXPORT_SYMBOL_GPL(dev_pm_qos_remove_global_notifier); |