idle.c

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/*
 * Idle daemon for PowerPC.  Idle daemon will handle any action
 * that needs to be taken when the system becomes idle.
 *
 * Originally written by Cort Dougan ([email protected]).
 * Subsequent 32-bit hacking by Tom Rini, Armin Kuster,
 * Paul Mackerras and others.
 *
 * iSeries supported added by Mike Corrigan <[email protected]>
 *
 * Additional shared processor, SMT, and firmware support
 *    Copyright (c) 2003 Dave Engebretsen <[email protected]>
 *
 * 32-bit and 64-bit versions merged by Paul Mackerras <[email protected]>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */

#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/smp.h>
#include <linux/cpu.h>
#include <linux/sysctl.h>
#include <linux/tick.h>

#include <asm/processor.h>
#include <asm/cputable.h>
#include <asm/time.h>
#include <asm/machdep.h>
#include <asm/runlatch.h>
#include <asm/smp.h>

#ifdef CONFIG_HOTPLUG_CPU
#define cpu_should_die()    cpu_is_offline(smp_processor_id())
#else
#define cpu_should_die()    0
#endif

unsigned long cpuidle_disable = IDLE_NO_OVERRIDE;
EXPORT_SYMBOL(cpuidle_disable);

static int __init powersave_off(char *arg)
{
    ppc_md.power_save = NULL;
    cpuidle_disable = IDLE_POWERSAVE_OFF;
    return 0;
}
__setup("powersave=off", powersave_off);

/*
 * The body of the idle task.
 */
void cpu_idle(void)
{
    if (ppc_md.idle_loop)
        ppc_md.idle_loop(); /* doesn't return */

    set_thread_flag(TIF_POLLING_NRFLAG);
    while (1) {
        tick_nohz_idle_enter();
        rcu_idle_enter();

        while (!need_resched() && !cpu_should_die()) {
            ppc64_runlatch_off();

            if (ppc_md.power_save) {
                clear_thread_flag(TIF_POLLING_NRFLAG);
                /*
                 * smp_mb is so clearing of TIF_POLLING_NRFLAG
                 * is ordered w.r.t. need_resched() test.
                 */
                smp_mb();
                local_irq_disable();

                /* Don't trace irqs off for idle */
                stop_critical_timings();

                /* check again after disabling irqs */
                if (!need_resched() && !cpu_should_die())
                    ppc_md.power_save();

                start_critical_timings();

                /* Some power_save functions return with
                 * interrupts enabled, some don't.
                 */
                if (irqs_disabled())
                    local_irq_enable();
                set_thread_flag(TIF_POLLING_NRFLAG);

            } else {
                /*
                 * Go into low thread priority and possibly
                 * low power mode.
                 */
                HMT_low();
                HMT_very_low();
            }
        }

        HMT_medium();
        ppc64_runlatch_on();
        rcu_idle_exit();
        tick_nohz_idle_exit();
        if (cpu_should_die()) {
            sched_preempt_enable_no_resched();
            cpu_die();
        }
        schedule_preempt_disabled();
    }
}

int powersave_nap;

#ifdef CONFIG_SYSCTL
/*
 * Register the sysctl to set/clear powersave_nap.
 */
static ctl_table powersave_nap_ctl_table[]={
    {
        .procname   = "powersave-nap",
        .data       = &powersave_nap,
        .maxlen     = sizeof(int),
        .mode       = 0644,
        .proc_handler   = proc_dointvec,
    },
    {}
};
static ctl_table powersave_nap_sysctl_root[] = {
    {
        .procname   = "kernel",
        .mode       = 0555,
        .child      = powersave_nap_ctl_table,
    },
    {}
};

static int __init
register_powersave_nap_sysctl(void)
{
    register_sysctl_table(powersave_nap_sysctl_root);

    return 0;
}
__initcall(register_powersave_nap_sysctl);
#endif