LXR linux/arch/arm/mach-imx/cpuidle-imx6q.c

   1/*
   2 * Copyright (C) 2012 Freescale Semiconductor, Inc.
   3 *
   4 * This program is free software; you can redistribute it and/or modify
   5 * it under the terms of the GNU General Public License version 2 as
   6 * published by the Free Software Foundation.
   7 */
   8
   9#include <linux/cpuidle.h>
  10#include <linux/module.h>
  11#include <asm/cpuidle.h>
  12#include <asm/proc-fns.h>
  13
  14#include "common.h"
  15#include "cpuidle.h"
  16
  17static atomic_t master = ATOMIC_INIT(0);
  18static DEFINE_SPINLOCK(master_lock);
  19
  20static int imx6q_enter_wait(struct cpuidle_device *dev,
  21                            struct cpuidle_driver *drv, int index)
  22{
  23        if (atomic_inc_return(&master) == num_online_cpus()) {
  24                /*
  25                 * With this lock, we prevent other cpu to exit and enter
  26                 * this function again and become the master.
  27                 */
  28                if (!spin_trylock(&master_lock))
  29                        goto idle;
  30                imx6q_set_lpm(WAIT_UNCLOCKED);
  31                cpu_do_idle();
  32                imx6q_set_lpm(WAIT_CLOCKED);
  33                spin_unlock(&master_lock);
  34                goto done;
  35        }
  36
  37idle:
  38        cpu_do_idle();
  39done:
  40        atomic_dec(&master);
  41
  42        return index;
  43}
  44
  45static struct cpuidle_driver imx6q_cpuidle_driver = {
  46        .name = "imx6q_cpuidle",
  47        .owner = THIS_MODULE,
  48        .states = {
  49                /* WFI */
  50                ARM_CPUIDLE_WFI_STATE,
  51                /* WAIT */
  52                {
  53                        .exit_latency = 50,
  54                        .target_residency = 75,
  55                        .flags = CPUIDLE_FLAG_TIME_VALID |
  56                                 CPUIDLE_FLAG_TIMER_STOP,
  57                        .enter = imx6q_enter_wait,
  58                        .name = "WAIT",
  59                        .desc = "Clock off",
  60                },
  61        },
  62        .state_count = 2,
  63        .safe_state_index = 0,
  64};
  65
  66int __init imx6q_cpuidle_init(void)
  67{
  68        /* Need to enable SCU standby for entering WAIT modes */
  69        imx_scu_standby_enable();
  70
  71        /* Set chicken bit to get a reliable WAIT mode support */
  72        imx6q_set_chicken_bit();
  73
  74        return cpuidle_register(&imx6q_cpuidle_driver, NULL);
  75}
  76