xref: /openbmc/linux/arch/arm/kernel/cpuidle.c (revision 68198dca)
1 /*
2  * Copyright 2012 Linaro Ltd.
3  *
4  * The code contained herein is licensed under the GNU General Public
5  * License. You may obtain a copy of the GNU General Public License
6  * Version 2 or later at the following locations:
7  *
8  * http://www.opensource.org/licenses/gpl-license.html
9  * http://www.gnu.org/copyleft/gpl.html
10  */
11 
12 #include <linux/cpuidle.h>
13 #include <linux/of.h>
14 #include <linux/of_device.h>
15 #include <asm/cpuidle.h>
16 
17 extern struct of_cpuidle_method __cpuidle_method_of_table[];
18 
19 static const struct of_cpuidle_method __cpuidle_method_of_table_sentinel
20 	__used __section(__cpuidle_method_of_table_end);
21 
22 static struct cpuidle_ops cpuidle_ops[NR_CPUS] __ro_after_init;
23 
24 /**
25  * arm_cpuidle_simple_enter() - a wrapper to cpu_do_idle()
26  * @dev: not used
27  * @drv: not used
28  * @index: not used
29  *
30  * A trivial wrapper to allow the cpu_do_idle function to be assigned as a
31  * cpuidle callback by matching the function signature.
32  *
33  * Returns the index passed as parameter
34  */
35 int arm_cpuidle_simple_enter(struct cpuidle_device *dev,
36 		struct cpuidle_driver *drv, int index)
37 {
38 	cpu_do_idle();
39 
40 	return index;
41 }
42 
43 /**
44  * arm_cpuidle_suspend() - function to enter low power idle states
45  * @index: an integer used as an identifier for the low level PM callbacks
46  *
47  * This function calls the underlying arch specific low level PM code as
48  * registered at the init time.
49  *
50  * Returns the result of the suspend callback.
51  */
52 int arm_cpuidle_suspend(int index)
53 {
54 	int cpu = smp_processor_id();
55 
56 	return cpuidle_ops[cpu].suspend(index);
57 }
58 
59 /**
60  * arm_cpuidle_get_ops() - find a registered cpuidle_ops by name
61  * @method: the method name
62  *
63  * Search in the __cpuidle_method_of_table array the cpuidle ops matching the
64  * method name.
65  *
66  * Returns a struct cpuidle_ops pointer, NULL if not found.
67  */
68 static const struct cpuidle_ops *__init arm_cpuidle_get_ops(const char *method)
69 {
70 	struct of_cpuidle_method *m = __cpuidle_method_of_table;
71 
72 	for (; m->method; m++)
73 		if (!strcmp(m->method, method))
74 			return m->ops;
75 
76 	return NULL;
77 }
78 
79 /**
80  * arm_cpuidle_read_ops() - Initialize the cpuidle ops with the device tree
81  * @dn: a pointer to a struct device node corresponding to a cpu node
82  * @cpu: the cpu identifier
83  *
84  * Get the method name defined in the 'enable-method' property, retrieve the
85  * associated cpuidle_ops and do a struct copy. This copy is needed because all
86  * cpuidle_ops are tagged __initconst and will be unloaded after the init
87  * process.
88  *
89  * Return 0 on sucess, -ENOENT if no 'enable-method' is defined, -EOPNOTSUPP if
90  * no cpuidle_ops is registered for the 'enable-method', or if either init or
91  * suspend callback isn't defined.
92  */
93 static int __init arm_cpuidle_read_ops(struct device_node *dn, int cpu)
94 {
95 	const char *enable_method;
96 	const struct cpuidle_ops *ops;
97 
98 	enable_method = of_get_property(dn, "enable-method", NULL);
99 	if (!enable_method)
100 		return -ENOENT;
101 
102 	ops = arm_cpuidle_get_ops(enable_method);
103 	if (!ops) {
104 		pr_warn("%pOF: unsupported enable-method property: %s\n",
105 			dn, enable_method);
106 		return -EOPNOTSUPP;
107 	}
108 
109 	if (!ops->init || !ops->suspend) {
110 		pr_warn("cpuidle_ops '%s': no init or suspend callback\n",
111 			enable_method);
112 		return -EOPNOTSUPP;
113 	}
114 
115 	cpuidle_ops[cpu] = *ops; /* structure copy */
116 
117 	pr_notice("cpuidle: enable-method property '%s'"
118 		  " found operations\n", enable_method);
119 
120 	return 0;
121 }
122 
123 /**
124  * arm_cpuidle_init() - Initialize cpuidle_ops for a specific cpu
125  * @cpu: the cpu to be initialized
126  *
127  * Initialize the cpuidle ops with the device for the cpu and then call
128  * the cpu's idle initialization callback. This may fail if the underlying HW
129  * is not operational.
130  *
131  * Returns:
132  *  0 on success,
133  *  -ENODEV if it fails to find the cpu node in the device tree,
134  *  -EOPNOTSUPP if it does not find a registered and valid cpuidle_ops for
135  *  this cpu,
136  *  -ENOENT if it fails to find an 'enable-method' property,
137  *  -ENXIO if the HW reports a failure or a misconfiguration,
138  *  -ENOMEM if the HW report an memory allocation failure
139  */
140 int __init arm_cpuidle_init(int cpu)
141 {
142 	struct device_node *cpu_node = of_cpu_device_node_get(cpu);
143 	int ret;
144 
145 	if (!cpu_node)
146 		return -ENODEV;
147 
148 	ret = arm_cpuidle_read_ops(cpu_node, cpu);
149 	if (!ret)
150 		ret = cpuidle_ops[cpu].init(cpu_node, cpu);
151 
152 	of_node_put(cpu_node);
153 
154 	return ret;
155 }
156