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 #include "hardware.h"
  17
  18 static atomic_t master = ATOMIC_INIT(0);
  19 static DEFINE_SPINLOCK(master_lock);
  20
  21 static int imx6q_enter_wait(struct cpuidle_device *dev,
  22                             struct cpuidle_driver *drv, int index)
  23 {
  24         if (atomic_inc_return(&master) == num_online_cpus()) {
  25                 /*
  26                  * With this lock, we prevent other cpu to exit and enter
  27                  * this function again and become the master.
  28                  */
  29                 if (!spin_trylock(&master_lock))
  30                         goto idle;
  31                 imx6q_set_lpm(WAIT_UNCLOCKED);
  32                 cpu_do_idle();
  33                 imx6q_set_lpm(WAIT_CLOCKED);
  34                 spin_unlock(&master_lock);
  35                 goto done;
  36         }
  37
  38 idle:
  39         cpu_do_idle();
  40 done:
  41         atomic_dec(&master);
  42
  43         return index;
  44 }
  45
  46 static struct cpuidle_driver imx6q_cpuidle_driver = {
  47         .name = "imx6q_cpuidle",
  48         .owner = THIS_MODULE,
  49         .states = {
  50                 /* WFI */
  51                 ARM_CPUIDLE_WFI_STATE,
  52                 /* WAIT */
  53                 {
  54                         .exit_latency = 50,
  55                         .target_residency = 75,
  56                         .flags = CPUIDLE_FLAG_TIME_VALID |
  57                                  CPUIDLE_FLAG_TIMER_STOP,
  58                         .enter = imx6q_enter_wait,
  59                         .name = "WAIT",
  60                         .desc = "Clock off",
  61                 },
  62         },
  63         .state_count = 2,
  64         .safe_state_index = 0,
  65 };
  66
  67 int __init imx6q_cpuidle_init(void)
  68 {
  69         /* Need to enable SCU standby for entering WAIT modes */
  70         if (!cpu_is_imx6sx())
  71                 imx_scu_standby_enable();
  72
  73         /* Set INT_MEM_CLK_LPM bit to get a reliable WAIT mode support */
  74         imx6q_set_int_mem_clk_lpm(true);
  75
  76         return cpuidle_register(&imx6q_cpuidle_driver, NULL);
  77 }