Release 4.11 arch/arm/plat-versatile/platsmp.c

/*
 *  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 <plat/platsmp.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 write_pen_release(int val)
{
	pen_release = val;
	smp_wmb();
	sync_cache_w(&pen_release);
}

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static DEFINE_SPINLOCK(boot_lock);



void versatile_secondary_init(unsigned int cpu)
{
	/*
         * 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);
}

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int 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.
         */
	arch_send_wakeup_ipi_mask(cpumask_of(cpu));

	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;
}
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Marc Zyngier
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Nico Pitre
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Directory: arch/arm/plat-versatile

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