xref: /openbmc/linux/kernel/cpu_pm.c (revision 43ffe817)
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 static ATOMIC_NOTIFIER_HEAD(cpu_pm_notifier_chain);
17 
18 static int cpu_pm_notify(enum cpu_pm_event event)
19 {
20 	int ret;
21 
22 	/*
23 	 * atomic_notifier_call_chain has a RCU read critical section, which
24 	 * could be disfunctional in cpu idle. Copy RCU_NONIDLE code to let
25 	 * RCU know this.
26 	 */
27 	rcu_irq_enter_irqson();
28 	ret = atomic_notifier_call_chain(&cpu_pm_notifier_chain, event, NULL);
29 	rcu_irq_exit_irqson();
30 
31 	return notifier_to_errno(ret);
32 }
33 
34 static int cpu_pm_notify_robust(enum cpu_pm_event event_up, enum cpu_pm_event event_down)
35 {
36 	int ret;
37 
38 	rcu_irq_enter_irqson();
39 	ret = atomic_notifier_call_chain_robust(&cpu_pm_notifier_chain, event_up, event_down, NULL);
40 	rcu_irq_exit_irqson();
41 
42 	return notifier_to_errno(ret);
43 }
44 
45 /**
46  * cpu_pm_register_notifier - register a driver with cpu_pm
47  * @nb: notifier block to register
48  *
49  * Add a driver to a list of drivers that are notified about
50  * CPU and CPU cluster low power entry and exit.
51  *
52  * This function may sleep, and has the same return conditions as
53  * raw_notifier_chain_register.
54  */
55 int cpu_pm_register_notifier(struct notifier_block *nb)
56 {
57 	return atomic_notifier_chain_register(&cpu_pm_notifier_chain, nb);
58 }
59 EXPORT_SYMBOL_GPL(cpu_pm_register_notifier);
60 
61 /**
62  * cpu_pm_unregister_notifier - unregister a driver with cpu_pm
63  * @nb: notifier block to be unregistered
64  *
65  * Remove a driver from the CPU PM notifier list.
66  *
67  * This function may sleep, and has the same return conditions as
68  * raw_notifier_chain_unregister.
69  */
70 int cpu_pm_unregister_notifier(struct notifier_block *nb)
71 {
72 	return atomic_notifier_chain_unregister(&cpu_pm_notifier_chain, nb);
73 }
74 EXPORT_SYMBOL_GPL(cpu_pm_unregister_notifier);
75 
76 /**
77  * cpu_pm_enter - CPU low power entry notifier
78  *
79  * Notifies listeners that a single CPU is entering a low power state that may
80  * cause some blocks in the same power domain as the cpu to reset.
81  *
82  * Must be called on the affected CPU with interrupts disabled.  Platform is
83  * responsible for ensuring that cpu_pm_enter is not called twice on the same
84  * CPU before cpu_pm_exit is called. Notified drivers can include VFP
85  * co-processor, interrupt controller and its PM extensions, local CPU
86  * timers context save/restore which shouldn't be interrupted. Hence it
87  * must be called with interrupts disabled.
88  *
89  * Return conditions are same as __raw_notifier_call_chain.
90  */
91 int cpu_pm_enter(void)
92 {
93 	return cpu_pm_notify_robust(CPU_PM_ENTER, CPU_PM_ENTER_FAILED);
94 }
95 EXPORT_SYMBOL_GPL(cpu_pm_enter);
96 
97 /**
98  * cpu_pm_exit - CPU low power exit notifier
99  *
100  * Notifies listeners that a single CPU is exiting a low power state that may
101  * have caused some blocks in the same power domain as the cpu to reset.
102  *
103  * Notified drivers can include VFP co-processor, interrupt controller
104  * and its PM extensions, local CPU timers context save/restore which
105  * shouldn't be interrupted. Hence it must be called with interrupts disabled.
106  *
107  * Return conditions are same as __raw_notifier_call_chain.
108  */
109 int cpu_pm_exit(void)
110 {
111 	return cpu_pm_notify(CPU_PM_EXIT);
112 }
113 EXPORT_SYMBOL_GPL(cpu_pm_exit);
114 
115 /**
116  * cpu_cluster_pm_enter - CPU cluster low power entry notifier
117  *
118  * Notifies listeners that all cpus in a power domain are entering a low power
119  * state that may cause some blocks in the same power domain to reset.
120  *
121  * Must be called after cpu_pm_enter has been called on all cpus in the power
122  * domain, and before cpu_pm_exit has been called on any cpu in the power
123  * domain. Notified drivers can include VFP co-processor, interrupt controller
124  * and its PM extensions, local CPU timers context save/restore which
125  * shouldn't be interrupted. Hence it must be called with interrupts disabled.
126  *
127  * Must be called with interrupts disabled.
128  *
129  * Return conditions are same as __raw_notifier_call_chain.
130  */
131 int cpu_cluster_pm_enter(void)
132 {
133 	return cpu_pm_notify_robust(CPU_CLUSTER_PM_ENTER, CPU_CLUSTER_PM_ENTER_FAILED);
134 }
135 EXPORT_SYMBOL_GPL(cpu_cluster_pm_enter);
136 
137 /**
138  * cpu_cluster_pm_exit - CPU cluster low power exit notifier
139  *
140  * Notifies listeners that all cpus in a power domain are exiting form a
141  * low power state that may have caused some blocks in the same power domain
142  * to reset.
143  *
144  * Must be called after cpu_cluster_pm_enter has been called for the power
145  * domain, and before cpu_pm_exit has been called on any cpu in the power
146  * domain. Notified drivers can include VFP co-processor, interrupt controller
147  * and its PM extensions, local CPU timers context save/restore which
148  * shouldn't be interrupted. Hence it must be called with interrupts disabled.
149  *
150  * Return conditions are same as __raw_notifier_call_chain.
151  */
152 int cpu_cluster_pm_exit(void)
153 {
154 	return cpu_pm_notify(CPU_CLUSTER_PM_EXIT);
155 }
156 EXPORT_SYMBOL_GPL(cpu_cluster_pm_exit);
157 
158 #ifdef CONFIG_PM
159 static int cpu_pm_suspend(void)
160 {
161 	int ret;
162 
163 	ret = cpu_pm_enter();
164 	if (ret)
165 		return ret;
166 
167 	ret = cpu_cluster_pm_enter();
168 	return ret;
169 }
170 
171 static void cpu_pm_resume(void)
172 {
173 	cpu_cluster_pm_exit();
174 	cpu_pm_exit();
175 }
176 
177 static struct syscore_ops cpu_pm_syscore_ops = {
178 	.suspend = cpu_pm_suspend,
179 	.resume = cpu_pm_resume,
180 };
181 
182 static int cpu_pm_init(void)
183 {
184 	register_syscore_ops(&cpu_pm_syscore_ops);
185 	return 0;
186 }
187 core_initcall(cpu_pm_init);
188 #endif
189