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platsmp.c

/* linux/arch/arm/mach-s5pv310/platsmp.c
 *
 * Copyright (c) 2010 Samsung Electronics Co., Ltd.
 *          http://www.samsung.com/
 *
 * Cloned from linux/arch/arm/mach-vexpress/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 <linux/io.h>

#include <asm/cacheflush.h>
#include <asm/smp_scu.h>
#include <asm/unified.h>

#include <mach/hardware.h>
#include <mach/regs-clock.h>

extern void s5pv310_secondary_startup(void);

/*
 * control for which core is the next to come out of the secondary
 * boot "holding pen"
 */

volatile int __cpuinitdata pen_release = -1;

/*
 * 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();
      __cpuc_flush_dcache_area((void *)&pen_release, sizeof(pen_release));
      outer_clean_range(__pa(&pen_release), __pa(&pen_release + 1));
}

static void __iomem *scu_base_addr(void)
{
      return (void __iomem *)(S5P_VA_SCU);
}

static DEFINE_SPINLOCK(boot_lock);

void __cpuinit platform_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 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);

      /*
       * The secondary processor is waiting to be released from
       * the holding pen - release it, then wait for it to flag
       * that it has been released by resetting pen_release.
       *
       * Note that "pen_release" is the hardware CPU ID, whereas
       * "cpu" is Linux's internal ID.
       */
      write_pen_release(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.
       */
      smp_cross_call(cpumask_of(cpu), 1);

      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;
}

/*
 * Initialise the CPU possible map early - this describes the CPUs
 * which may be present or become present in the system.
 */

void __init smp_init_cpus(void)
{
      void __iomem *scu_base = scu_base_addr();
      unsigned int i, ncores;

      ncores = scu_base ? scu_get_core_count(scu_base) : 1;

      /* sanity check */
      if (ncores > NR_CPUS) {
            printk(KERN_WARNING
                   "S5PV310: no. of cores (%d) greater than configured "
                   "maximum of %d - clipping\n",
                   ncores, NR_CPUS);
            ncores = NR_CPUS;
      }

      for (i = 0; i < ncores; i++)
            set_cpu_possible(i, true);
}

void __init platform_smp_prepare_cpus(unsigned int max_cpus)
{
      int i;

      /*
       * Initialise the present map, which describes the set of CPUs
       * actually populated at the present time.
       */
      for (i = 0; i < max_cpus; i++)
            set_cpu_present(i, true);

      scu_enable(scu_base_addr());

      /*
       * Write the address of secondary startup into the
       * system-wide flags register. The boot monitor waits
       * until it receives a soft interrupt, and then the
       * secondary CPU branches to this address.
       */
      __raw_writel(BSYM(virt_to_phys(s5pv310_secondary_startup)), S5P_VA_SYSRAM);
}

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