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
  17 static atomic_t master = ATOMIC_INIT(0);
  18 static DEFINE_SPINLOCK(master_lock);
  19
  20 static 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
  37 idle:
  38         cpu_do_idle();
  39 done:
  40         atomic_dec(&master);
  41
  42         return index;
  43 }
  44
  45 static 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
  66 int __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 }