cpuidle.c

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/*
 * Copyright (c) 2012 Linaro : Daniel Lezcano <[email protected]> (IBM)
 *
 * Based on the work of Rickard Andersson <[email protected]>
 * and Jonas Aaberg <[email protected]>.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/module.h>
#include <linux/cpuidle.h>
#include <linux/clockchips.h>
#include <linux/spinlock.h>
#include <linux/atomic.h>
#include <linux/smp.h>
#include <linux/mfd/dbx500-prcmu.h>

#include <asm/cpuidle.h>
#include <asm/proc-fns.h>

static atomic_t master = ATOMIC_INIT(0);
static DEFINE_SPINLOCK(master_lock);
static DEFINE_PER_CPU(struct cpuidle_device, ux500_cpuidle_device);

static inline int ux500_enter_idle(struct cpuidle_device *dev,
                   struct cpuidle_driver *drv, int index)
{
    int this_cpu = smp_processor_id();
    bool recouple = false;

    clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER, &this_cpu);

    if (atomic_inc_return(&master) == num_online_cpus()) {

        /* With this lock, we prevent the other cpu to exit and enter
         * this function again and become the master */
        if (!spin_trylock(&master_lock))
            goto wfi;

        /* decouple the gic from the A9 cores */
        if (prcmu_gic_decouple())
            goto out;

        /* If an error occur, we will have to recouple the gic
         * manually */
        recouple = true;

        /* At this state, as the gic is decoupled, if the other
         * cpu is in WFI, we have the guarantee it won't be wake
         * up, so we can safely go to retention */
        if (!prcmu_is_cpu_in_wfi(this_cpu ? 0 : 1))
            goto out;

        /* The prcmu will be in charge of watching the interrupts
         * and wake up the cpus */
        if (prcmu_copy_gic_settings())
            goto out;

        /* Check in the meantime an interrupt did
         * not occur on the gic ... */
        if (prcmu_gic_pending_irq())
            goto out;

        /* ... and the prcmu */
        if (prcmu_pending_irq())
            goto out;

        /* Go to the retention state, the prcmu will wait for the
         * cpu to go WFI and this is what happens after exiting this
         * 'master' critical section */
        if (prcmu_set_power_state(PRCMU_AP_IDLE, true, true))
            goto out;

        /* When we switch to retention, the prcmu is in charge
         * of recoupling the gic automatically */
        recouple = false;

        spin_unlock(&master_lock);
    }
wfi:
    cpu_do_idle();
out:
    atomic_dec(&master);

    if (recouple) {
        prcmu_gic_recouple();
        spin_unlock(&master_lock);
    }

    clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_EXIT, &this_cpu);

    return index;
}

static struct cpuidle_driver ux500_idle_driver = {
    .name = "ux500_idle",
    .owner = THIS_MODULE,
    .en_core_tk_irqen = 1,
    .states = {
        ARM_CPUIDLE_WFI_STATE,
        {
            .enter        = ux500_enter_idle,
            .exit_latency     = 70,
            .target_residency = 260,
            .flags        = CPUIDLE_FLAG_TIME_VALID,
            .name         = "ApIdle",
            .desc         = "ARM Retention",
        },
    },
    .safe_state_index = 0,
    .state_count = 2,
};

/*
 * For each cpu, setup the broadcast timer because we will
 * need to migrate the timers for the states >= ApIdle.
 */
static void ux500_setup_broadcast_timer(void *arg)
{
    int cpu = smp_processor_id();
    clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ON, &cpu);
}

int __init ux500_idle_init(void)
{
    int ret, cpu;
    struct cpuidle_device *device;

        /* Configure wake up reasons */
    prcmu_enable_wakeups(PRCMU_WAKEUP(ARM) | PRCMU_WAKEUP(RTC) |
                 PRCMU_WAKEUP(ABB));

    /*
     * Configure the timer broadcast for each cpu, that must
     * be done from the cpu context, so we use a smp cross
     * call with 'on_each_cpu'.
     */
    on_each_cpu(ux500_setup_broadcast_timer, NULL, 1);

    ret = cpuidle_register_driver(&ux500_idle_driver);
    if (ret) {
        printk(KERN_ERR "failed to register ux500 idle driver\n");
        return ret;
    }

    for_each_online_cpu(cpu) {
        device = &per_cpu(ux500_cpuidle_device, cpu);
        device->cpu = cpu;
        ret = cpuidle_register_device(device);
        if (ret) {
            printk(KERN_ERR "Failed to register cpuidle "
                   "device for cpu%d\n", cpu);
            goto out_unregister;
        }
    }
out:
    return ret;

out_unregister:
    for_each_online_cpu(cpu) {
        device = &per_cpu(ux500_cpuidle_device, cpu);
        cpuidle_unregister_device(device);
    }

    cpuidle_unregister_driver(&ux500_idle_driver);
    goto out;
}

device_initcall(ux500_idle_init);