kernel/cpu_pm.c

   1 /*
   2  * Copyright (C) 2011 Google, Inc.
   3  *
   4  * Author:
   5  *      Colin Cross <ccross@android.com>
   6  *
   7  * This software is licensed under the terms of the GNU General Public
   8  * License version 2, as published by the Free Software Foundation, and
   9  * may be copied, distributed, and modified under those terms.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  */
  17
  18 #include <linux/kernel.h>
  19 #include <linux/cpu_pm.h>
  20 #include <linux/module.h>
  21 #include <linux/notifier.h>
  22 #include <linux/spinlock.h>
  23 #include <linux/syscore_ops.h>
  24
  25 static ATOMIC_NOTIFIER_HEAD(cpu_pm_notifier_chain);
  26
  27 static int cpu_pm_notify(enum cpu_pm_event event, int nr_to_call, int *nr_calls)
  28 {
  29         int ret;
  30
  31         /*
  32          * __atomic_notifier_call_chain has a RCU read critical section, which
  33          * could be disfunctional in cpu idle. Copy RCU_NONIDLE code to let
  34          * RCU know this.
  35          */
  36         rcu_irq_enter_irqson();
  37         ret = __atomic_notifier_call_chain(&cpu_pm_notifier_chain, event, NULL,
  38                 nr_to_call, nr_calls);
  39         rcu_irq_exit_irqson();
  40
  41         return notifier_to_errno(ret);
  42 }
  43
  44 /**
  45  * cpu_pm_register_notifier - register a driver with cpu_pm
  46  * @nb: notifier block to register
  47  *
  48  * Add a driver to a list of drivers that are notified about
  49  * CPU and CPU cluster low power entry and exit.
  50  *
  51  * This function may sleep, and has the same return conditions as
  52  * raw_notifier_chain_register.
  53  */
  54 int cpu_pm_register_notifier(struct notifier_block *nb)
  55 {
  56         return atomic_notifier_chain_register(&cpu_pm_notifier_chain, nb);
  57 }
  58 EXPORT_SYMBOL_GPL(cpu_pm_register_notifier);
  59
  60 /**
  61  * cpu_pm_unregister_notifier - unregister a driver with cpu_pm
  62  * @nb: notifier block to be unregistered
  63  *
  64  * Remove a driver from the CPU PM notifier list.
  65  *
  66  * This function may sleep, and has the same return conditions as
  67  * raw_notifier_chain_unregister.
  68  */
  69 int cpu_pm_unregister_notifier(struct notifier_block *nb)
  70 {
  71         return atomic_notifier_chain_unregister(&cpu_pm_notifier_chain, nb);
  72 }
  73 EXPORT_SYMBOL_GPL(cpu_pm_unregister_notifier);
  74
  75 /**
  76  * cpu_pm_enter - CPU low power entry notifier
  77  *
  78  * Notifies listeners that a single CPU is entering a low power state that may
  79  * cause some blocks in the same power domain as the cpu to reset.
  80  *
  81  * Must be called on the affected CPU with interrupts disabled.  Platform is
  82  * responsible for ensuring that cpu_pm_enter is not called twice on the same
  83  * CPU before cpu_pm_exit is called. Notified drivers can include VFP
  84  * co-processor, interrupt controller and its PM extensions, local CPU
  85  * timers context save/restore which shouldn't be interrupted. Hence it
  86  * must be called with interrupts disabled.
  87  *
  88  * Return conditions are same as __raw_notifier_call_chain.
  89  */
  90 int cpu_pm_enter(void)
  91 {
  92         int nr_calls;
  93         int ret = 0;
  94
  95         ret = cpu_pm_notify(CPU_PM_ENTER, -1, &nr_calls);
  96         if (ret)
  97                 /*
  98                  * Inform listeners (nr_calls - 1) about failure of CPU PM
  99                  * PM entry who are notified earlier to prepare for it.
 100                  */
 101                 cpu_pm_notify(CPU_PM_ENTER_FAILED, nr_calls - 1, NULL);
 102
 103         return ret;
 104 }
 105 EXPORT_SYMBOL_GPL(cpu_pm_enter);
 106
 107 /**
 108  * cpu_pm_exit - CPU low power exit notifier
 109  *
 110  * Notifies listeners that a single CPU is exiting a low power state that may
 111  * have caused some blocks in the same power domain as the cpu to reset.
 112  *
 113  * Notified drivers can include VFP co-processor, interrupt controller
 114  * and its PM extensions, local CPU timers context save/restore which
 115  * shouldn't be interrupted. Hence it must be called with interrupts disabled.
 116  *
 117  * Return conditions are same as __raw_notifier_call_chain.
 118  */
 119 int cpu_pm_exit(void)
 120 {
 121         return cpu_pm_notify(CPU_PM_EXIT, -1, NULL);
 122 }
 123 EXPORT_SYMBOL_GPL(cpu_pm_exit);
 124
 125 /**
 126  * cpu_cluster_pm_enter - CPU cluster low power entry notifier
 127  *
 128  * Notifies listeners that all cpus in a power domain are entering a low power
 129  * state that may cause some blocks in the same power domain to reset.
 130  *
 131  * Must be called after cpu_pm_enter has been called on all cpus in the power
 132  * domain, and before cpu_pm_exit has been called on any cpu in the power
 133  * domain. Notified drivers can include VFP co-processor, interrupt controller
 134  * and its PM extensions, local CPU timers context save/restore which
 135  * shouldn't be interrupted. Hence it must be called with interrupts disabled.
 136  *
 137  * Must be called with interrupts disabled.
 138  *
 139  * Return conditions are same as __raw_notifier_call_chain.
 140  */
 141 int cpu_cluster_pm_enter(void)
 142 {
 143         int nr_calls;
 144         int ret = 0;
 145
 146         ret = cpu_pm_notify(CPU_CLUSTER_PM_ENTER, -1, &nr_calls);
 147         if (ret)
 148                 /*
 149                  * Inform listeners (nr_calls - 1) about failure of CPU cluster
 150                  * PM entry who are notified earlier to prepare for it.
 151                  */
 152                 cpu_pm_notify(CPU_CLUSTER_PM_ENTER_FAILED, nr_calls - 1, NULL);
 153
 154         return ret;
 155 }
 156 EXPORT_SYMBOL_GPL(cpu_cluster_pm_enter);
 157
 158 /**
 159  * cpu_cluster_pm_exit - CPU cluster low power exit notifier
 160  *
 161  * Notifies listeners that all cpus in a power domain are exiting form a
 162  * low power state that may have caused some blocks in the same power domain
 163  * to reset.
 164  *
 165  * Must be called after cpu_cluster_pm_enter has been called for the power
 166  * domain, and before cpu_pm_exit has been called on any cpu in the power
 167  * domain. Notified drivers can include VFP co-processor, interrupt controller
 168  * and its PM extensions, local CPU timers context save/restore which
 169  * shouldn't be interrupted. Hence it must be called with interrupts disabled.
 170  *
 171  * Return conditions are same as __raw_notifier_call_chain.
 172  */
 173 int cpu_cluster_pm_exit(void)
 174 {
 175         return cpu_pm_notify(CPU_CLUSTER_PM_EXIT, -1, NULL);
 176 }
 177 EXPORT_SYMBOL_GPL(cpu_cluster_pm_exit);
 178
 179 #ifdef CONFIG_PM
 180 static int cpu_pm_suspend(void)
 181 {
 182         int ret;
 183
 184         ret = cpu_pm_enter();
 185         if (ret)
 186                 return ret;
 187
 188         ret = cpu_cluster_pm_enter();
 189         return ret;
 190 }
 191
 192 static void cpu_pm_resume(void)
 193 {
 194         cpu_cluster_pm_exit();
 195         cpu_pm_exit();
 196 }
 197
 198 static struct syscore_ops cpu_pm_syscore_ops = {
 199         .suspend = cpu_pm_suspend,
 200         .resume = cpu_pm_resume,
 201 };
 202
 203 static int cpu_pm_init(void)
 204 {
 205         register_syscore_ops(&cpu_pm_syscore_ops);
 206         return 0;
 207 }
 208 core_initcall(cpu_pm_init);
 209 #endif