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 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("%s: unsupported enable-method property: %s\n",
 105                         dn->full_name, 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 }