xref: /openbmc/linux/kernel/cpu_pm.c (revision 924aed16)
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