1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * Copyright (C) 2011 Google, Inc.
4 *
5 * Author:
6 * Colin Cross <ccross@android.com>
7 */
8
9 #include <linux/kernel.h>
10 #include <linux/cpu_pm.h>
11 #include <linux/module.h>
12 #include <linux/notifier.h>
13 #include <linux/spinlock.h>
14 #include <linux/syscore_ops.h>
15
16 /*
17 * atomic_notifiers use a spinlock_t, which can block under PREEMPT_RT.
18 * Notifications for cpu_pm will be issued by the idle task itself, which can
19 * never block, IOW it requires using a raw_spinlock_t.
20 */
21 static struct {
22 struct raw_notifier_head chain;
23 raw_spinlock_t lock;
24 } cpu_pm_notifier = {
25 .chain = RAW_NOTIFIER_INIT(cpu_pm_notifier.chain),
26 .lock = __RAW_SPIN_LOCK_UNLOCKED(cpu_pm_notifier.lock),
27 };
28
cpu_pm_notify(enum cpu_pm_event event)29 static int cpu_pm_notify(enum cpu_pm_event event)
30 {
31 int ret;
32
33 rcu_read_lock();
34 ret = raw_notifier_call_chain(&cpu_pm_notifier.chain, event, NULL);
35 rcu_read_unlock();
36
37 return notifier_to_errno(ret);
38 }
39
cpu_pm_notify_robust(enum cpu_pm_event event_up,enum cpu_pm_event event_down)40 static int cpu_pm_notify_robust(enum cpu_pm_event event_up, enum cpu_pm_event event_down)
41 {
42 unsigned long flags;
43 int ret;
44
45 raw_spin_lock_irqsave(&cpu_pm_notifier.lock, flags);
46 ret = raw_notifier_call_chain_robust(&cpu_pm_notifier.chain, event_up, event_down, NULL);
47 raw_spin_unlock_irqrestore(&cpu_pm_notifier.lock, flags);
48
49 return notifier_to_errno(ret);
50 }
51
52 /**
53 * cpu_pm_register_notifier - register a driver with cpu_pm
54 * @nb: notifier block to register
55 *
56 * Add a driver to a list of drivers that are notified about
57 * CPU and CPU cluster low power entry and exit.
58 *
59 * This function has the same return conditions as raw_notifier_chain_register.
60 */
cpu_pm_register_notifier(struct notifier_block * nb)61 int cpu_pm_register_notifier(struct notifier_block *nb)
62 {
63 unsigned long flags;
64 int ret;
65
66 raw_spin_lock_irqsave(&cpu_pm_notifier.lock, flags);
67 ret = raw_notifier_chain_register(&cpu_pm_notifier.chain, nb);
68 raw_spin_unlock_irqrestore(&cpu_pm_notifier.lock, flags);
69 return ret;
70 }
71 EXPORT_SYMBOL_GPL(cpu_pm_register_notifier);
72
73 /**
74 * cpu_pm_unregister_notifier - unregister a driver with cpu_pm
75 * @nb: notifier block to be unregistered
76 *
77 * Remove a driver from the CPU PM notifier list.
78 *
79 * This function has the same return conditions as raw_notifier_chain_unregister.
80 */
cpu_pm_unregister_notifier(struct notifier_block * nb)81 int cpu_pm_unregister_notifier(struct notifier_block *nb)
82 {
83 unsigned long flags;
84 int ret;
85
86 raw_spin_lock_irqsave(&cpu_pm_notifier.lock, flags);
87 ret = raw_notifier_chain_unregister(&cpu_pm_notifier.chain, nb);
88 raw_spin_unlock_irqrestore(&cpu_pm_notifier.lock, flags);
89 return ret;
90 }
91 EXPORT_SYMBOL_GPL(cpu_pm_unregister_notifier);
92
93 /**
94 * cpu_pm_enter - CPU low power entry notifier
95 *
96 * Notifies listeners that a single CPU is entering a low power state that may
97 * cause some blocks in the same power domain as the cpu to reset.
98 *
99 * Must be called on the affected CPU with interrupts disabled. Platform is
100 * responsible for ensuring that cpu_pm_enter is not called twice on the same
101 * CPU before cpu_pm_exit is called. Notified drivers can include VFP
102 * co-processor, interrupt controller and its PM extensions, local CPU
103 * timers context save/restore which shouldn't be interrupted. Hence it
104 * must be called with interrupts disabled.
105 *
106 * Return conditions are same as __raw_notifier_call_chain.
107 */
cpu_pm_enter(void)108 int cpu_pm_enter(void)
109 {
110 return cpu_pm_notify_robust(CPU_PM_ENTER, CPU_PM_ENTER_FAILED);
111 }
112 EXPORT_SYMBOL_GPL(cpu_pm_enter);
113
114 /**
115 * cpu_pm_exit - CPU low power exit notifier
116 *
117 * Notifies listeners that a single CPU is exiting a low power state that may
118 * have caused some blocks in the same power domain as the cpu to reset.
119 *
120 * Notified drivers can include VFP co-processor, interrupt controller
121 * and its PM extensions, local CPU timers context save/restore which
122 * shouldn't be interrupted. Hence it must be called with interrupts disabled.
123 *
124 * Return conditions are same as __raw_notifier_call_chain.
125 */
cpu_pm_exit(void)126 int cpu_pm_exit(void)
127 {
128 return cpu_pm_notify(CPU_PM_EXIT);
129 }
130 EXPORT_SYMBOL_GPL(cpu_pm_exit);
131
132 /**
133 * cpu_cluster_pm_enter - CPU cluster low power entry notifier
134 *
135 * Notifies listeners that all cpus in a power domain are entering a low power
136 * state that may cause some blocks in the same power domain to reset.
137 *
138 * Must be called after cpu_pm_enter has been called on all cpus in the power
139 * domain, and before cpu_pm_exit has been called on any cpu in the power
140 * domain. Notified drivers can include VFP co-processor, interrupt controller
141 * and its PM extensions, local CPU timers context save/restore which
142 * shouldn't be interrupted. Hence it must be called with interrupts disabled.
143 *
144 * Must be called with interrupts disabled.
145 *
146 * Return conditions are same as __raw_notifier_call_chain.
147 */
cpu_cluster_pm_enter(void)148 int cpu_cluster_pm_enter(void)
149 {
150 return cpu_pm_notify_robust(CPU_CLUSTER_PM_ENTER, CPU_CLUSTER_PM_ENTER_FAILED);
151 }
152 EXPORT_SYMBOL_GPL(cpu_cluster_pm_enter);
153
154 /**
155 * cpu_cluster_pm_exit - CPU cluster low power exit notifier
156 *
157 * Notifies listeners that all cpus in a power domain are exiting form a
158 * low power state that may have caused some blocks in the same power domain
159 * to reset.
160 *
161 * Must be called after cpu_cluster_pm_enter has been called for the power
162 * domain, and before cpu_pm_exit has been called on any cpu in the power
163 * domain. Notified drivers can include VFP co-processor, interrupt controller
164 * and its PM extensions, local CPU timers context save/restore which
165 * shouldn't be interrupted. Hence it must be called with interrupts disabled.
166 *
167 * Return conditions are same as __raw_notifier_call_chain.
168 */
cpu_cluster_pm_exit(void)169 int cpu_cluster_pm_exit(void)
170 {
171 return cpu_pm_notify(CPU_CLUSTER_PM_EXIT);
172 }
173 EXPORT_SYMBOL_GPL(cpu_cluster_pm_exit);
174
175 #ifdef CONFIG_PM
cpu_pm_suspend(void)176 static int cpu_pm_suspend(void)
177 {
178 int ret;
179
180 ret = cpu_pm_enter();
181 if (ret)
182 return ret;
183
184 ret = cpu_cluster_pm_enter();
185 return ret;
186 }
187
cpu_pm_resume(void)188 static void cpu_pm_resume(void)
189 {
190 cpu_cluster_pm_exit();
191 cpu_pm_exit();
192 }
193
194 static struct syscore_ops cpu_pm_syscore_ops = {
195 .suspend = cpu_pm_suspend,
196 .resume = cpu_pm_resume,
197 };
198
cpu_pm_init(void)199 static int cpu_pm_init(void)
200 {
201 register_syscore_ops(&cpu_pm_syscore_ops);
202 return 0;
203 }
204 core_initcall(cpu_pm_init);
205 #endif
206