drivers/cpuidle/cpuidle-arm64.c

   1 /*
   2  * ARM64 generic CPU idle driver.
   3  *
   4  * Copyright (C) 2014 ARM Ltd.
   5  * Author: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License version 2 as
   9  * published by the Free Software Foundation.
  10  */
  11
  12 #define pr_fmt(fmt) "CPUidle arm64: " fmt
  13
  14 #include <linux/cpuidle.h>
  15 #include <linux/cpumask.h>
  16 #include <linux/cpu_pm.h>
  17 #include <linux/kernel.h>
  18 #include <linux/module.h>
  19 #include <linux/of.h>
  20
  21 #include <asm/cpuidle.h>
  22 #include <asm/suspend.h>
  23
  24 #include "dt_idle_states.h"
  25
  26 /*
  27  * arm64_enter_idle_state - Programs CPU to enter the specified state
  28  *
  29  * dev: cpuidle device
  30  * drv: cpuidle driver
  31  * idx: state index
  32  *
  33  * Called from the CPUidle framework to program the device to the
  34  * specified target state selected by the governor.
  35  */
  36 static int arm64_enter_idle_state(struct cpuidle_device *dev,
  37                                   struct cpuidle_driver *drv, int idx)
  38 {
  39         int ret;
  40
  41         if (!idx) {
  42                 cpu_do_idle();
  43                 return idx;
  44         }
  45
  46         ret = cpu_pm_enter();
  47         if (!ret) {
  48                 /*
  49                  * Pass idle state index to cpu_suspend which in turn will
  50                  * call the CPU ops suspend protocol with idle index as a
  51                  * parameter.
  52                  */
  53                 ret = cpu_suspend(idx);
  54
  55                 cpu_pm_exit();
  56         }
  57
  58         return ret ? -1 : idx;
  59 }
  60
  61 static struct cpuidle_driver arm64_idle_driver = {
  62         .name = "arm64_idle",
  63         .owner = THIS_MODULE,
  64         /*
  65          * State at index 0 is standby wfi and considered standard
  66          * on all ARM platforms. If in some platforms simple wfi
  67          * can't be used as "state 0", DT bindings must be implemented
  68          * to work around this issue and allow installing a special
  69          * handler for idle state index 0.
  70          */
  71         .states[0] = {
  72                 .enter                  = arm64_enter_idle_state,
  73                 .exit_latency           = 1,
  74                 .target_residency       = 1,
  75                 .power_usage            = UINT_MAX,
  76                 .flags                  = CPUIDLE_FLAG_TIME_VALID,
  77                 .name                   = "WFI",
  78                 .desc                   = "ARM64 WFI",
  79         }
  80 };
  81
  82 static const struct of_device_id arm64_idle_state_match[] __initconst = {
  83         { .compatible = "arm,idle-state",
  84           .data = arm64_enter_idle_state },
  85         { },
  86 };
  87
  88 /*
  89  * arm64_idle_init
  90  *
  91  * Registers the arm64 specific cpuidle driver with the cpuidle
  92  * framework. It relies on core code to parse the idle states
  93  * and initialize them using driver data structures accordingly.
  94  */
  95 static int __init arm64_idle_init(void)
  96 {
  97         int cpu, ret;
  98         struct cpuidle_driver *drv = &arm64_idle_driver;
  99
 100         /*
 101          * Initialize idle states data, starting at index 1.
 102          * This driver is DT only, if no DT idle states are detected (ret == 0)
 103          * let the driver initialization fail accordingly since there is no
 104          * reason to initialize the idle driver if only wfi is supported.
 105          */
 106         ret = dt_init_idle_driver(drv, arm64_idle_state_match, 1);
 107         if (ret <= 0) {
 108                 if (ret)
 109                         pr_err("failed to initialize idle states\n");
 110                 return ret ? : -ENODEV;
 111         }
 112
 113         /*
 114          * Call arch CPU operations in order to initialize
 115          * idle states suspend back-end specific data
 116          */
 117         for_each_possible_cpu(cpu) {
 118                 ret = cpu_init_idle(cpu);
 119                 if (ret) {
 120                         pr_err("CPU %d failed to init idle CPU ops\n", cpu);
 121                         return ret;
 122                 }
 123         }
 124
 125         ret = cpuidle_register(drv, NULL);
 126         if (ret) {
 127                 pr_err("failed to register cpuidle driver\n");
 128                 return ret;
 129         }
 130
 131         return 0;
 132 }
 133 device_initcall(arm64_idle_init);