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 /*
34 * This introduces a RCU read critical section, which could be
35 * disfunctional in cpu idle. Copy RCU_NONIDLE code to let RCU know
36 * this.
37 */
38 ct_irq_enter_irqson();
39 rcu_read_lock();
40 ret = raw_notifier_call_chain(&cpu_pm_notifier.chain, event, NULL);
41 rcu_read_unlock();
42 ct_irq_exit_irqson();
43
44 return notifier_to_errno(ret);
45 }
46
cpu_pm_notify_robust(enum cpu_pm_event event_up,enum cpu_pm_event event_down)47 static int cpu_pm_notify_robust(enum cpu_pm_event event_up, enum cpu_pm_event event_down)
48 {
49 unsigned long flags;
50 int ret;
51
52 ct_irq_enter_irqson();
53 raw_spin_lock_irqsave(&cpu_pm_notifier.lock, flags);
54 ret = raw_notifier_call_chain_robust(&cpu_pm_notifier.chain, event_up, event_down, NULL);
55 raw_spin_unlock_irqrestore(&cpu_pm_notifier.lock, flags);
56 ct_irq_exit_irqson();
57
58 return notifier_to_errno(ret);
59 }
60
61 /**
62 * cpu_pm_register_notifier - register a driver with cpu_pm
63 * @nb: notifier block to register
64 *
65 * Add a driver to a list of drivers that are notified about
66 * CPU and CPU cluster low power entry and exit.
67 *
68 * This function has the same return conditions as raw_notifier_chain_register.
69 */
cpu_pm_register_notifier(struct notifier_block * nb)70 int cpu_pm_register_notifier(struct notifier_block *nb)
71 {
72 unsigned long flags;
73 int ret;
74
75 raw_spin_lock_irqsave(&cpu_pm_notifier.lock, flags);
76 ret = raw_notifier_chain_register(&cpu_pm_notifier.chain, nb);
77 raw_spin_unlock_irqrestore(&cpu_pm_notifier.lock, flags);
78 return ret;
79 }
80 EXPORT_SYMBOL_GPL(cpu_pm_register_notifier);
81
82 /**
83 * cpu_pm_unregister_notifier - unregister a driver with cpu_pm
84 * @nb: notifier block to be unregistered
85 *
86 * Remove a driver from the CPU PM notifier list.
87 *
88 * This function has the same return conditions as raw_notifier_chain_unregister.
89 */
cpu_pm_unregister_notifier(struct notifier_block * nb)90 int cpu_pm_unregister_notifier(struct notifier_block *nb)
91 {
92 unsigned long flags;
93 int ret;
94
95 raw_spin_lock_irqsave(&cpu_pm_notifier.lock, flags);
96 ret = raw_notifier_chain_unregister(&cpu_pm_notifier.chain, nb);
97 raw_spin_unlock_irqrestore(&cpu_pm_notifier.lock, flags);
98 return ret;
99 }
100 EXPORT_SYMBOL_GPL(cpu_pm_unregister_notifier);
101
102 /**
103 * cpu_pm_enter - CPU low power entry notifier
104 *
105 * Notifies listeners that a single CPU is entering a low power state that may
106 * cause some blocks in the same power domain as the cpu to reset.
107 *
108 * Must be called on the affected CPU with interrupts disabled. Platform is
109 * responsible for ensuring that cpu_pm_enter is not called twice on the same
110 * CPU before cpu_pm_exit is called. Notified drivers can include VFP
111 * co-processor, interrupt controller and its PM extensions, local CPU
112 * timers context save/restore which shouldn't be interrupted. Hence it
113 * must be called with interrupts disabled.
114 *
115 * Return conditions are same as __raw_notifier_call_chain.
116 */
cpu_pm_enter(void)117 int cpu_pm_enter(void)
118 {
119 return cpu_pm_notify_robust(CPU_PM_ENTER, CPU_PM_ENTER_FAILED);
120 }
121 EXPORT_SYMBOL_GPL(cpu_pm_enter);
122
123 /**
124 * cpu_pm_exit - CPU low power exit notifier
125 *
126 * Notifies listeners that a single CPU is exiting a low power state that may
127 * have caused some blocks in the same power domain as the cpu to reset.
128 *
129 * Notified drivers can include VFP co-processor, interrupt controller
130 * and its PM extensions, local CPU timers context save/restore which
131 * shouldn't be interrupted. Hence it must be called with interrupts disabled.
132 *
133 * Return conditions are same as __raw_notifier_call_chain.
134 */
cpu_pm_exit(void)135 int cpu_pm_exit(void)
136 {
137 return cpu_pm_notify(CPU_PM_EXIT);
138 }
139 EXPORT_SYMBOL_GPL(cpu_pm_exit);
140
141 /**
142 * cpu_cluster_pm_enter - CPU cluster low power entry notifier
143 *
144 * Notifies listeners that all cpus in a power domain are entering a low power
145 * state that may cause some blocks in the same power domain to reset.
146 *
147 * Must be called after cpu_pm_enter has been called on all cpus in the power
148 * domain, and before cpu_pm_exit has been called on any cpu in the power
149 * domain. Notified drivers can include VFP co-processor, interrupt controller
150 * and its PM extensions, local CPU timers context save/restore which
151 * shouldn't be interrupted. Hence it must be called with interrupts disabled.
152 *
153 * Must be called with interrupts disabled.
154 *
155 * Return conditions are same as __raw_notifier_call_chain.
156 */
cpu_cluster_pm_enter(void)157 int cpu_cluster_pm_enter(void)
158 {
159 return cpu_pm_notify_robust(CPU_CLUSTER_PM_ENTER, CPU_CLUSTER_PM_ENTER_FAILED);
160 }
161 EXPORT_SYMBOL_GPL(cpu_cluster_pm_enter);
162
163 /**
164 * cpu_cluster_pm_exit - CPU cluster low power exit notifier
165 *
166 * Notifies listeners that all cpus in a power domain are exiting form a
167 * low power state that may have caused some blocks in the same power domain
168 * to reset.
169 *
170 * Must be called after cpu_cluster_pm_enter has been called for the power
171 * domain, and before cpu_pm_exit has been called on any cpu in the power
172 * domain. Notified drivers can include VFP co-processor, interrupt controller
173 * and its PM extensions, local CPU timers context save/restore which
174 * shouldn't be interrupted. Hence it must be called with interrupts disabled.
175 *
176 * Return conditions are same as __raw_notifier_call_chain.
177 */
cpu_cluster_pm_exit(void)178 int cpu_cluster_pm_exit(void)
179 {
180 return cpu_pm_notify(CPU_CLUSTER_PM_EXIT);
181 }
182 EXPORT_SYMBOL_GPL(cpu_cluster_pm_exit);
183
184 #ifdef CONFIG_PM
cpu_pm_suspend(void)185 static int cpu_pm_suspend(void)
186 {
187 int ret;
188
189 ret = cpu_pm_enter();
190 if (ret)
191 return ret;
192
193 ret = cpu_cluster_pm_enter();
194 return ret;
195 }
196
cpu_pm_resume(void)197 static void cpu_pm_resume(void)
198 {
199 cpu_cluster_pm_exit();
200 cpu_pm_exit();
201 }
202
203 static struct syscore_ops cpu_pm_syscore_ops = {
204 .suspend = cpu_pm_suspend,
205 .resume = cpu_pm_resume,
206 };
207
cpu_pm_init(void)208 static int cpu_pm_init(void)
209 {
210 register_syscore_ops(&cpu_pm_syscore_ops);
211 return 0;
212 }
213 core_initcall(cpu_pm_init);
214 #endif
215
