platsmp.c

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/*
 *  linux/arch/arm/plat-versatile/platsmp.c
 *
 *  Copyright (C) 2002 ARM Ltd.
 *  All Rights Reserved
 *
 * 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/init.h>
#include <linux/errno.h>
#include <linux/delay.h>
#include <linux/device.h>
#include <linux/jiffies.h>
#include <linux/smp.h>

#include <asm/cacheflush.h>
#include <asm/smp_plat.h>
#include <asm/hardware/gic.h>

/*
 * Write pen_release in a way that is guaranteed to be visible to all
 * observers, irrespective of whether they're taking part in coherency
 * or not.  This is necessary for the hotplug code to work reliably.
 */
static void __cpuinit write_pen_release(int val)
{
    pen_release = val;
    smp_wmb();
    __cpuc_flush_dcache_area((void *)&pen_release, sizeof(pen_release));
    outer_clean_range(__pa(&pen_release), __pa(&pen_release + 1));
}

static DEFINE_SPINLOCK(boot_lock);

void __cpuinit versatile_secondary_init(unsigned int cpu)
{
    /*
     * if any interrupts are already enabled for the primary
     * core (e.g. timer irq), then they will not have been enabled
     * for us: do so
     */
    gic_secondary_init(0);

    /*
     * let the primary processor know we're out of the
     * pen, then head off into the C entry point
     */
    write_pen_release(-1);

    /*
     * Synchronise with the boot thread.
     */
    spin_lock(&boot_lock);
    spin_unlock(&boot_lock);
}

int __cpuinit versatile_boot_secondary(unsigned int cpu, struct task_struct *idle)
{
    unsigned long timeout;

    /*
     * Set synchronisation state between this boot processor
     * and the secondary one
     */
    spin_lock(&boot_lock);

    /*
     * This is really belt and braces; we hold unintended secondary
     * CPUs in the holding pen until we're ready for them.  However,
     * since we haven't sent them a soft interrupt, they shouldn't
     * be there.
     */
    write_pen_release(cpu_logical_map(cpu));

    /*
     * Send the secondary CPU a soft interrupt, thereby causing
     * the boot monitor to read the system wide flags register,
     * and branch to the address found there.
     */
    gic_raise_softirq(cpumask_of(cpu), 0);

    timeout = jiffies + (1 * HZ);
    while (time_before(jiffies, timeout)) {
        smp_rmb();
        if (pen_release == -1)
            break;

        udelay(10);
    }

    /*
     * now the secondary core is starting up let it run its
     * calibrations, then wait for it to finish
     */
    spin_unlock(&boot_lock);

    return pen_release != -1 ? -ENOSYS : 0;
}