LXR linux/arch/arm/mach-ux500/cpuidle.c

   1/*
   2 * Copyright (c) 2012 Linaro : Daniel Lezcano <daniel.lezcano@linaro.org> (IBM)
   3 *
   4 * Based on the work of Rickard Andersson <rickard.andersson@stericsson.com>
   5 * and Jonas Aaberg <jonas.aberg@stericsson.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#include <linux/module.h>
  13#include <linux/cpuidle.h>
  14#include <linux/spinlock.h>
  15#include <linux/atomic.h>
  16#include <linux/smp.h>
  17#include <linux/mfd/dbx500-prcmu.h>
  18#include <linux/platform_data/arm-ux500-pm.h>
  19
  20#include <asm/cpuidle.h>
  21#include <asm/proc-fns.h>
  22
  23#include "db8500-regs.h"
  24#include "id.h"
  25
  26static atomic_t master = ATOMIC_INIT(0);
  27static DEFINE_SPINLOCK(master_lock);
  28
  29static inline int ux500_enter_idle(struct cpuidle_device *dev,
  30                                   struct cpuidle_driver *drv, int index)
  31{
  32        int this_cpu = smp_processor_id();
  33        bool recouple = false;
  34
  35        if (atomic_inc_return(&master) == num_online_cpus()) {
  36
  37                /* With this lock, we prevent the other cpu to exit and enter
  38                 * this function again and become the master */
  39                if (!spin_trylock(&master_lock))
  40                        goto wfi;
  41
  42                /* decouple the gic from the A9 cores */
  43                if (prcmu_gic_decouple()) {
  44                        spin_unlock(&master_lock);
  45                        goto out;
  46                }
  47
  48                /* If an error occur, we will have to recouple the gic
  49                 * manually */
  50                recouple = true;
  51
  52                /* At this state, as the gic is decoupled, if the other
  53                 * cpu is in WFI, we have the guarantee it won't be wake
  54                 * up, so we can safely go to retention */
  55                if (!prcmu_is_cpu_in_wfi(this_cpu ? 0 : 1))
  56                        goto out;
  57
  58                /* The prcmu will be in charge of watching the interrupts
  59                 * and wake up the cpus */
  60                if (prcmu_copy_gic_settings())
  61                        goto out;
  62
  63                /* Check in the meantime an interrupt did
  64                 * not occur on the gic ... */
  65                if (prcmu_gic_pending_irq())
  66                        goto out;
  67
  68                /* ... and the prcmu */
  69                if (prcmu_pending_irq())
  70                        goto out;
  71
  72                /* Go to the retention state, the prcmu will wait for the
  73                 * cpu to go WFI and this is what happens after exiting this
  74                 * 'master' critical section */
  75                if (prcmu_set_power_state(PRCMU_AP_IDLE, true, true))
  76                        goto out;
  77
  78                /* When we switch to retention, the prcmu is in charge
  79                 * of recoupling the gic automatically */
  80                recouple = false;
  81
  82                spin_unlock(&master_lock);
  83        }
  84wfi:
  85        cpu_do_idle();
  86out:
  87        atomic_dec(&master);
  88
  89        if (recouple) {
  90                prcmu_gic_recouple();
  91                spin_unlock(&master_lock);
  92        }
  93
  94        return index;
  95}
  96
  97static struct cpuidle_driver ux500_idle_driver = {
  98        .name = "ux500_idle",
  99        .owner = THIS_MODULE,
 100        .states = {
 101                ARM_CPUIDLE_WFI_STATE,
 102                {
 103                        .enter            = ux500_enter_idle,
 104                        .exit_latency     = 70,
 105                        .target_residency = 260,
 106                        .flags            = CPUIDLE_FLAG_TIME_VALID |
 107                                            CPUIDLE_FLAG_TIMER_STOP,
 108                        .name             = "ApIdle",
 109                        .desc             = "ARM Retention",
 110                },
 111        },
 112        .safe_state_index = 0,
 113        .state_count = 2,
 114};
 115
 116int __init ux500_idle_init(void)
 117{
 118        if (!(cpu_is_u8500_family() || cpu_is_ux540_family()))
 119                return -ENODEV;
 120
 121        /* Configure wake up reasons */
 122        prcmu_enable_wakeups(PRCMU_WAKEUP(ARM) | PRCMU_WAKEUP(RTC) |
 123                             PRCMU_WAKEUP(ABB));
 124
 125        return cpuidle_register(&ux500_idle_driver, NULL);
 126}
 127
 128device_initcall(ux500_idle_init);
 129