206 lines
6.0 KiB
C
206 lines
6.0 KiB
C
/*
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* pm.c - Power management interface
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*
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* Copyright (C) 2000 Andrew Henroid
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*/
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#include <linux/init.h>
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#include <linux/module.h>
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#include <linux/spinlock.h>
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#include <linux/mm.h>
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#include <linux/slab.h>
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#include <linux/pm.h>
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#include <linux/pm_legacy.h>
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#include <linux/interrupt.h>
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#include <linux/mutex.h>
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/*
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* Locking notes:
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* pm_devs_lock can be a semaphore providing pm ops are not called
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* from an interrupt handler (already a bad idea so no change here). Each
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* change must be protected so that an unlink of an entry doesn't clash
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* with a pm send - which is permitted to sleep in the current architecture
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*
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* Module unloads clashing with pm events now work out safely, the module
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* unload path will block until the event has been sent. It may well block
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* until a resume but that will be fine.
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*/
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static DEFINE_MUTEX(pm_devs_lock);
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static LIST_HEAD(pm_devs);
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/**
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* pm_register - register a device with power management
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* @type: device type
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* @id: device ID
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* @callback: callback function
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*
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* Add a device to the list of devices that wish to be notified about
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* power management events. A &pm_dev structure is returned on success,
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* on failure the return is %NULL.
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*
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* The callback function will be called in process context and
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* it may sleep.
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*/
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struct pm_dev *pm_register(pm_dev_t type,
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unsigned long id,
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pm_callback callback)
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{
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struct pm_dev *dev = kzalloc(sizeof(struct pm_dev), GFP_KERNEL);
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if (dev) {
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dev->type = type;
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dev->id = id;
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dev->callback = callback;
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mutex_lock(&pm_devs_lock);
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list_add(&dev->entry, &pm_devs);
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mutex_unlock(&pm_devs_lock);
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}
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return dev;
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}
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/**
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* pm_send - send request to a single device
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* @dev: device to send to
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* @rqst: power management request
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* @data: data for the callback
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*
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* Issue a power management request to a given device. The
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* %PM_SUSPEND and %PM_RESUME events are handled specially. The
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* data field must hold the intended next state. No call is made
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* if the state matches.
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*
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* BUGS: what stops two power management requests occurring in parallel
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* and conflicting.
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*
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* WARNING: Calling pm_send directly is not generally recommended, in
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* particular there is no locking against the pm_dev going away. The
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* caller must maintain all needed locking or have 'inside knowledge'
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* on the safety. Also remember that this function is not locked against
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* pm_unregister. This means that you must handle SMP races on callback
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* execution and unload yourself.
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*/
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static int pm_send(struct pm_dev *dev, pm_request_t rqst, void *data)
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{
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int status = 0;
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unsigned long prev_state, next_state;
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if (in_interrupt())
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BUG();
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switch (rqst) {
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case PM_SUSPEND:
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case PM_RESUME:
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prev_state = dev->state;
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next_state = (unsigned long) data;
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if (prev_state != next_state) {
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if (dev->callback)
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status = (*dev->callback)(dev, rqst, data);
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if (!status) {
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dev->state = next_state;
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dev->prev_state = prev_state;
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}
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}
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else {
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dev->prev_state = prev_state;
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}
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break;
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default:
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if (dev->callback)
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status = (*dev->callback)(dev, rqst, data);
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break;
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}
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return status;
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}
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/*
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* Undo incomplete request
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*/
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static void pm_undo_all(struct pm_dev *last)
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{
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struct list_head *entry = last->entry.prev;
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while (entry != &pm_devs) {
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struct pm_dev *dev = list_entry(entry, struct pm_dev, entry);
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if (dev->state != dev->prev_state) {
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/* previous state was zero (running) resume or
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* previous state was non-zero (suspended) suspend
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*/
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pm_request_t undo = (dev->prev_state
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? PM_SUSPEND:PM_RESUME);
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pm_send(dev, undo, (void*) dev->prev_state);
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}
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entry = entry->prev;
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}
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}
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/**
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* pm_send_all - send request to all managed devices
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* @rqst: power management request
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* @data: data for the callback
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*
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* Issue a power management request to a all devices. The
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* %PM_SUSPEND events are handled specially. Any device is
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* permitted to fail a suspend by returning a non zero (error)
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* value from its callback function. If any device vetoes a
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* suspend request then all other devices that have suspended
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* during the processing of this request are restored to their
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* previous state.
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*
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* WARNING: This function takes the pm_devs_lock. The lock is not dropped until
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* the callbacks have completed. This prevents races against pm locking
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* functions, races against module unload pm_unregister code. It does
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* mean however that you must not issue pm_ functions within the callback
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* or you will deadlock and users will hate you.
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*
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* Zero is returned on success. If a suspend fails then the status
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* from the device that vetoes the suspend is returned.
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*
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* BUGS: what stops two power management requests occurring in parallel
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* and conflicting.
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*/
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int pm_send_all(pm_request_t rqst, void *data)
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{
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struct list_head *entry;
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mutex_lock(&pm_devs_lock);
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entry = pm_devs.next;
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while (entry != &pm_devs) {
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struct pm_dev *dev = list_entry(entry, struct pm_dev, entry);
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if (dev->callback) {
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int status = pm_send(dev, rqst, data);
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if (status) {
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/* return devices to previous state on
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* failed suspend request
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*/
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if (rqst == PM_SUSPEND)
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pm_undo_all(dev);
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mutex_unlock(&pm_devs_lock);
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return status;
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}
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}
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entry = entry->next;
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}
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mutex_unlock(&pm_devs_lock);
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return 0;
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}
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EXPORT_SYMBOL(pm_register);
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EXPORT_SYMBOL(pm_send_all);
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