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omap-smp.c

/*
 * OMAP4 SMP source file. It contains platform specific fucntions
 * needed for the linux smp kernel.
 *
 * Copyright (C) 2009 Texas Instruments, Inc.
 *
 * Author:
 *      Santosh Shilimkar <santosh.shilimkar@ti.com>
 *
 * Platform file needed for the OMAP4 SMP. This file is based on arm
 * realview smp platform.
 * * Copyright (c) 2002 ARM Limited.
 *
 * 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/device.h>
#include <linux/jiffies.h>
#include <linux/smp.h>
#include <linux/io.h>

#include <asm/localtimer.h>
#include <asm/smp_scu.h>
#include <mach/hardware.h>

/* Registers used for communicating startup information */
#define OMAP4_AUXCOREBOOT_REG0            (OMAP44XX_VA_WKUPGEN_BASE + 0x800)
#define OMAP4_AUXCOREBOOT_REG1            (OMAP44XX_VA_WKUPGEN_BASE + 0x804)

/* SCU base address */
static void __iomem *scu_base = OMAP44XX_VA_SCU_BASE;

/*
 * Use SCU config register to count number of cores
 */
static inline unsigned int get_core_count(void)
{
      if (scu_base)
            return scu_get_core_count(scu_base);
      return 1;
}

static DEFINE_SPINLOCK(boot_lock);

void __cpuinit platform_secondary_init(unsigned int cpu)
{
      trace_hardirqs_off();

      /*
       * 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_cpu_init(0, OMAP2_IO_ADDRESS(OMAP44XX_GIC_CPU_BASE));

      /*
       * 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);

      /*
       * Update the AuxCoreBoot1 with boot state for secondary core.
       * omap_secondary_startup() routine will hold the secondary core till
       * the AuxCoreBoot1 register is updated with cpu state
       * A barrier is added to ensure that write buffer is drained
       */
      __raw_writel(cpu, OMAP4_AUXCOREBOOT_REG1);
      smp_wmb();

      timeout = jiffies + (1 * HZ);
      while (time_before(jiffies, timeout))
            ;

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

      return 0;
}

static void __init wakeup_secondary(void)
{
      /*
       * Write the address of secondary startup routine into the
       * AuxCoreBoot0 where ROM code will jump and start executing
       * on secondary core once out of WFE
       * A barrier is added to ensure that write buffer is drained
       */
      __raw_writel(virt_to_phys(omap_secondary_startup),       \
                              OMAP4_AUXCOREBOOT_REG0);
      smp_wmb();

      /*
       * Send a 'sev' to wake the secondary core from WFE.
       */
      set_event();
      mb();
}

/*
 * 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)
{
      unsigned int i, ncores = get_core_count();

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

void __init smp_prepare_cpus(unsigned int max_cpus)
{
      unsigned int ncores = get_core_count();
      unsigned int cpu = smp_processor_id();
      int i;

      /* sanity check */
      if (ncores == 0) {
            printk(KERN_ERR
                   "OMAP4: strange core count of 0? Default to 1\n");
            ncores = 1;
      }

      if (ncores > NR_CPUS) {
            printk(KERN_WARNING
                   "OMAP4: no. of cores (%d) greater than configured "
                   "maximum of %d - clipping\n",
                   ncores, NR_CPUS);
            ncores = NR_CPUS;
      }
      smp_store_cpu_info(cpu);

      /*
       * are we trying to boot more cores than exist?
       */
      if (max_cpus > ncores)
            max_cpus = ncores;

      /*
       * 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);

      if (max_cpus > 1) {
            /*
             * Enable the local timer or broadcast device for the
             * boot CPU, but only if we have more than one CPU.
             */
            percpu_timer_setup();

            /*
             * Initialise the SCU and wake up the secondary core using
             * wakeup_secondary().
             */
            scu_enable(scu_base);
            wakeup_secondary();
      }
}

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