arch/arm/kernel/cpuidle.c

   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];
  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 -EOPNOTSUPP if no suspend callback is defined, the result of the
  51  * callback otherwise.
  52  */
  53 int arm_cpuidle_suspend(int index)
  54 {
  55         int ret = -EOPNOTSUPP;
  56         int cpu = smp_processor_id();
  57
  58         if (cpuidle_ops[cpu].suspend)
  59                 ret = cpuidle_ops[cpu].suspend(index);
  60
  61         return ret;
  62 }
  63
  64 /**
  65  * arm_cpuidle_get_ops() - find a registered cpuidle_ops by name
  66  * @method: the method name
  67  *
  68  * Search in the __cpuidle_method_of_table array the cpuidle ops matching the
  69  * method name.
  70  *
  71  * Returns a struct cpuidle_ops pointer, NULL if not found.
  72  */
  73 static struct cpuidle_ops *__init arm_cpuidle_get_ops(const char *method)
  74 {
  75         struct of_cpuidle_method *m = __cpuidle_method_of_table;
  76
  77         for (; m->method; m++)
  78                 if (!strcmp(m->method, method))
  79                         return m->ops;
  80
  81         return NULL;
  82 }
  83
  84 /**
  85  * arm_cpuidle_read_ops() - Initialize the cpuidle ops with the device tree
  86  * @dn: a pointer to a struct device node corresponding to a cpu node
  87  * @cpu: the cpu identifier
  88  *
  89  * Get the method name defined in the 'enable-method' property, retrieve the
  90  * associated cpuidle_ops and do a struct copy. This copy is needed because all
  91  * cpuidle_ops are tagged __initdata and will be unloaded after the init
  92  * process.
  93  *
  94  * Return 0 on sucess, -ENOENT if no 'enable-method' is defined, -EOPNOTSUPP if
  95  * no cpuidle_ops is registered for the 'enable-method'.
  96  */
  97 static int __init arm_cpuidle_read_ops(struct device_node *dn, int cpu)
  98 {
  99         const char *enable_method;
 100         struct cpuidle_ops *ops;
 101
 102         enable_method = of_get_property(dn, "enable-method", NULL);
 103         if (!enable_method)
 104                 return -ENOENT;
 105
 106         ops = arm_cpuidle_get_ops(enable_method);
 107         if (!ops) {
 108                 pr_warn("%s: unsupported enable-method property: %s\n",
 109                         dn->full_name, enable_method);
 110                 return -EOPNOTSUPP;
 111         }
 112
 113         cpuidle_ops[cpu] = *ops; /* structure copy */
 114
 115         pr_notice("cpuidle: enable-method property '%s'"
 116                   " found operations\n", enable_method);
 117
 118         return 0;
 119 }
 120
 121 /**
 122  * arm_cpuidle_init() - Initialize cpuidle_ops for a specific cpu
 123  * @cpu: the cpu to be initialized
 124  *
 125  * Initialize the cpuidle ops with the device for the cpu and then call
 126  * the cpu's idle initialization callback. This may fail if the underlying HW
 127  * is not operational.
 128  *
 129  * Returns:
 130  *  0 on success,
 131  *  -ENODEV if it fails to find the cpu node in the device tree,
 132  *  -EOPNOTSUPP if it does not find a registered cpuidle_ops for this cpu,
 133  *  -ENOENT if it fails to find an 'enable-method' property,
 134  *  -ENXIO if the HW reports a failure or a misconfiguration,
 135  *  -ENOMEM if the HW report an memory allocation failure
 136  */
 137 int __init arm_cpuidle_init(int cpu)
 138 {
 139         struct device_node *cpu_node = of_cpu_device_node_get(cpu);
 140         int ret;
 141
 142         if (!cpu_node)
 143                 return -ENODEV;
 144
 145         ret = arm_cpuidle_read_ops(cpu_node, cpu);
 146         if (!ret && cpuidle_ops[cpu].init)
 147                 ret = cpuidle_ops[cpu].init(cpu_node, cpu);
 148
 149         of_node_put(cpu_node);
 150
 151         return ret;
 152 }