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
  32 /*
  33  * PM Reference Counting.
  34  */
  35
  36 static inline void device_pm_hold(struct device * dev)
  37 {
  38         if (dev)
  39                 atomic_inc(&dev->power.pm_users);
  40 }
  41
  42 static inline void device_pm_release(struct device * dev)
  43 {
  44         if (dev)
  45                 atomic_dec(&dev->power.pm_users);
  46 }
  47
  48
  49 /**
  50  *      device_pm_set_parent - Specify power dependency.
  51  *      @dev:           Device who needs power.
  52  *      @parent:        Device that supplies power.
  53  *
  54  *      This function is used to manually describe a power-dependency
  55  *      relationship. It may be used to specify a transversal relationship
  56  *      (where the power supplier is not the physical (or electrical)
  57  *      ancestor of a specific device.
  58  *      The effect of this is that the supplier will not be powered down
  59  *      before the power dependent.
  60  */
  61
  62 void device_pm_set_parent(struct device * dev, struct device * parent)
  63 {
  64         struct device * old_parent = dev->power.pm_parent;
  65         device_pm_release(old_parent);
  66         dev->power.pm_parent = parent;
  67         device_pm_hold(parent);
  68 }
  69 EXPORT_SYMBOL(device_pm_set_parent);
  70
  71 int device_pm_add(struct device * dev)
  72 {
  73         int error;
  74
  75         pr_debug("PM: Adding info for %s:%s\n",
  76                  dev->bus ? dev->bus->name : "No Bus", dev->kobj.name);
  77         atomic_set(&dev->power.pm_users, 0);
  78         down(&dpm_sem);
  79         list_add_tail(&dev->power.entry, &dpm_active);
  80         device_pm_set_parent(dev, dev->parent);
  81         if ((error = dpm_sysfs_add(dev)))
  82                 list_del(&dev->power.entry);
  83         up(&dpm_sem);
  84         return error;
  85 }
  86
  87 void device_pm_remove(struct device * dev)
  88 {
  89         pr_debug("PM: Removing info for %s:%s\n",
  90                  dev->bus ? dev->bus->name : "No Bus", dev->kobj.name);
  91         down(&dpm_sem);
  92         dpm_sysfs_remove(dev);
  93         device_pm_release(dev->power.pm_parent);
  94         list_del(&dev->power.entry);
  95         up(&dpm_sem);
  96 }
  97
  98