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Linux/arch/arm/kernel/cpuidle.c

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  1 // SPDX-License-Identifier: GPL-2.0-or-later
  2 /*
  3  * Copyright 2012 Linaro Ltd.
  4  */
  5 
  6 #include <linux/cpuidle.h>
  7 #include <linux/of.h>
  8 #include <linux/of_device.h>
  9 #include <asm/cpuidle.h>
 10 
 11 extern struct of_cpuidle_method __cpuidle_method_of_table[];
 12 
 13 static const struct of_cpuidle_method __cpuidle_method_of_table_sentinel
 14         __used __section("__cpuidle_method_of_table_end");
 15 
 16 static struct cpuidle_ops cpuidle_ops[NR_CPUS] __ro_after_init;
 17 
 18 /**
 19  * arm_cpuidle_simple_enter() - a wrapper to cpu_do_idle()
 20  * @dev: not used
 21  * @drv: not used
 22  * @index: not used
 23  *
 24  * A trivial wrapper to allow the cpu_do_idle function to be assigned as a
 25  * cpuidle callback by matching the function signature.
 26  *
 27  * Returns the index passed as parameter
 28  */
 29 int arm_cpuidle_simple_enter(struct cpuidle_device *dev,
 30                 struct cpuidle_driver *drv, int index)
 31 {
 32         cpu_do_idle();
 33 
 34         return index;
 35 }
 36 
 37 /**
 38  * arm_cpuidle_suspend() - function to enter low power idle states
 39  * @index: an integer used as an identifier for the low level PM callbacks
 40  *
 41  * This function calls the underlying arch specific low level PM code as
 42  * registered at the init time.
 43  *
 44  * Returns the result of the suspend callback.
 45  */
 46 int arm_cpuidle_suspend(int index)
 47 {
 48         int cpu = smp_processor_id();
 49 
 50         return cpuidle_ops[cpu].suspend(index);
 51 }
 52 
 53 /**
 54  * arm_cpuidle_get_ops() - find a registered cpuidle_ops by name
 55  * @method: the method name
 56  *
 57  * Search in the __cpuidle_method_of_table array the cpuidle ops matching the
 58  * method name.
 59  *
 60  * Returns a struct cpuidle_ops pointer, NULL if not found.
 61  */
 62 static const struct cpuidle_ops *__init arm_cpuidle_get_ops(const char *method)
 63 {
 64         struct of_cpuidle_method *m = __cpuidle_method_of_table;
 65 
 66         for (; m->method; m++)
 67                 if (!strcmp(m->method, method))
 68                         return m->ops;
 69 
 70         return NULL;
 71 }
 72 
 73 /**
 74  * arm_cpuidle_read_ops() - Initialize the cpuidle ops with the device tree
 75  * @dn: a pointer to a struct device node corresponding to a cpu node
 76  * @cpu: the cpu identifier
 77  *
 78  * Get the method name defined in the 'enable-method' property, retrieve the
 79  * associated cpuidle_ops and do a struct copy. This copy is needed because all
 80  * cpuidle_ops are tagged __initconst and will be unloaded after the init
 81  * process.
 82  *
 83  * Return 0 on sucess, -ENOENT if no 'enable-method' is defined, -EOPNOTSUPP if
 84  * no cpuidle_ops is registered for the 'enable-method', or if either init or
 85  * suspend callback isn't defined.
 86  */
 87 static int __init arm_cpuidle_read_ops(struct device_node *dn, int cpu)
 88 {
 89         const char *enable_method;
 90         const struct cpuidle_ops *ops;
 91 
 92         enable_method = of_get_property(dn, "enable-method", NULL);
 93         if (!enable_method)
 94                 return -ENOENT;
 95 
 96         ops = arm_cpuidle_get_ops(enable_method);
 97         if (!ops) {
 98                 pr_warn("%pOF: unsupported enable-method property: %s\n",
 99                         dn, enable_method);
100                 return -EOPNOTSUPP;
101         }
102 
103         if (!ops->init || !ops->suspend) {
104                 pr_warn("cpuidle_ops '%s': no init or suspend callback\n",
105                         enable_method);
106                 return -EOPNOTSUPP;
107         }
108 
109         cpuidle_ops[cpu] = *ops; /* structure copy */
110 
111         pr_notice("cpuidle: enable-method property '%s'"
112                   " found operations\n", enable_method);
113 
114         return 0;
115 }
116 
117 /**
118  * arm_cpuidle_init() - Initialize cpuidle_ops for a specific cpu
119  * @cpu: the cpu to be initialized
120  *
121  * Initialize the cpuidle ops with the device for the cpu and then call
122  * the cpu's idle initialization callback. This may fail if the underlying HW
123  * is not operational.
124  *
125  * Returns:
126  *  0 on success,
127  *  -ENODEV if it fails to find the cpu node in the device tree,
128  *  -EOPNOTSUPP if it does not find a registered and valid cpuidle_ops for
129  *  this cpu,
130  *  -ENOENT if it fails to find an 'enable-method' property,
131  *  -ENXIO if the HW reports a failure or a misconfiguration,
132  *  -ENOMEM if the HW report an memory allocation failure 
133  */
134 int __init arm_cpuidle_init(int cpu)
135 {
136         struct device_node *cpu_node = of_cpu_device_node_get(cpu);
137         int ret;
138 
139         if (!cpu_node)
140                 return -ENODEV;
141 
142         ret = arm_cpuidle_read_ops(cpu_node, cpu);
143         if (!ret)
144                 ret = cpuidle_ops[cpu].init(cpu_node, cpu);
145 
146         of_node_put(cpu_node);
147 
148         return ret;
149 }
150 

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