drivers/base/power/main.c

   1 /*
   2  * drivers/base/power/main.c - Where the driver meets power management.
   3  *
   4  * Copyright (c) 2003 Patrick Mochel
   5  * Copyright (c) 2003 Open Source Development Lab
   6  *
   7  * This file is released under the GPLv2
   8  *
   9  *
  10  * The driver model core calls device_pm_add() when a device is registered.
  11  * This will intialize the embedded device_pm_info object in the device
  12  * and add it to the list of power-controlled devices. sysfs entries for
  13  * controlling device power management will also be added.
  14  *
  15  * A different set of lists than the global subsystem list are used to
  16  * keep track of power info because we use different lists to hold
  17  * devices based on what stage of the power management process they
  18  * are in. The power domain dependencies may also differ from the
  19  * ancestral dependencies that the subsystem list maintains.
  20  */
  21
  22 #include <linux/config.h>
  23 #include <linux/device.h>
  24 #include "power.h"
  25
  26 LIST_HEAD(dpm_active);
  27 LIST_HEAD(dpm_off);
  28 LIST_HEAD(dpm_off_irq);
  29
  30 DECLARE_MUTEX(dpm_sem);
  31 DECLARE_MUTEX(dpm_list_sem);
  32
  33 /*
  34  * PM Reference Counting.
  35  */
  36
  37 static inline void device_pm_hold(struct device * dev)
  38 {
  39         if (dev)
  40                 atomic_inc(&dev->power.pm_users);
  41 }
  42
  43 static inline void device_pm_release(struct device * dev)
  44 {
  45         if (dev)
  46                 atomic_dec(&dev->power.pm_users);
  47 }
  48
  49
  50 /**
  51  *      device_pm_set_parent - Specify power dependency.
  52  *      @dev:           Device who needs power.
  53  *      @parent:        Device that supplies power.
  54  *
  55  *      This function is used to manually describe a power-dependency
  56  *      relationship. It may be used to specify a transversal relationship
  57  *      (where the power supplier is not the physical (or electrical)
  58  *      ancestor of a specific device.
  59  *      The effect of this is that the supplier will not be powered down
  60  *      before the power dependent.
  61  */
  62
  63 void device_pm_set_parent(struct device * dev, struct device * parent)
  64 {
  65         struct device * old_parent = dev->power.pm_parent;
  66         device_pm_release(old_parent);
  67         dev->power.pm_parent = parent;
  68         device_pm_hold(parent);
  69 }
  70 EXPORT_SYMBOL_GPL(device_pm_set_parent);
  71
  72 int device_pm_add(struct device * dev)
  73 {
  74         int error;
  75
  76         pr_debug("PM: Adding info for %s:%s\n",
  77                  dev->bus ? dev->bus->name : "No Bus", dev->kobj.name);
  78         atomic_set(&dev->power.pm_users, 0);
  79         down(&dpm_list_sem);
  80         list_add_tail(&dev->power.entry, &dpm_active);
  81         device_pm_set_parent(dev, dev->parent);
  82         if ((error = dpm_sysfs_add(dev)))
  83                 list_del(&dev->power.entry);
  84         up(&dpm_list_sem);
  85         return error;
  86 }
  87
  88 void device_pm_remove(struct device * dev)
  89 {
  90         pr_debug("PM: Removing info for %s:%s\n",
  91                  dev->bus ? dev->bus->name : "No Bus", dev->kobj.name);
  92         down(&dpm_list_sem);
  93         dpm_sysfs_remove(dev);
  94         device_pm_release(dev->power.pm_parent);
  95         list_del_init(&dev->power.entry);
  96         up(&dpm_list_sem);
  97 }
  98
  99