smp.c

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/*
 * SMP support for BPA machines.
 *
 * Dave Engebretsen, Peter Bergner, and
 * Mike Corrigan {engebret|bergner|mikec}@us.ibm.com
 *
 * Plus various changes from other IBM teams...
 *
 *      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.
 */

#undef DEBUG

#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/smp.h>
#include <linux/interrupt.h>
#include <linux/delay.h>
#include <linux/init.h>
#include <linux/spinlock.h>
#include <linux/cache.h>
#include <linux/err.h>
#include <linux/device.h>
#include <linux/cpu.h>

#include <asm/ptrace.h>
#include <linux/atomic.h>
#include <asm/irq.h>
#include <asm/page.h>
#include <asm/pgtable.h>
#include <asm/io.h>
#include <asm/prom.h>
#include <asm/smp.h>
#include <asm/paca.h>
#include <asm/machdep.h>
#include <asm/cputable.h>
#include <asm/firmware.h>
#include <asm/rtas.h>
#include <asm/cputhreads.h>

#include "interrupt.h"
#include <asm/udbg.h>

#ifdef DEBUG
#define DBG(fmt...) udbg_printf(fmt)
#else
#define DBG(fmt...)
#endif

/*
 * The Primary thread of each non-boot processor was started from the OF client
 * interface by prom_hold_cpus and is spinning on secondary_hold_spinloop.
 */
static cpumask_t of_spin_map;

static inline int __devinit smp_startup_cpu(unsigned int lcpu)
{
    int status;
    unsigned long start_here = __pa((u32)*((unsigned long *)
                           generic_secondary_smp_init));
    unsigned int pcpu;
    int start_cpu;

    if (cpumask_test_cpu(lcpu, &of_spin_map))
        /* Already started by OF and sitting in spin loop */
        return 1;

    pcpu = get_hard_smp_processor_id(lcpu);

    /* Fixup atomic count: it exited inside IRQ handler. */
    task_thread_info(paca[lcpu].__current)->preempt_count   = 0;

    /*
     * If the RTAS start-cpu token does not exist then presume the
     * cpu is already spinning.
     */
    start_cpu = rtas_token("start-cpu");
    if (start_cpu == RTAS_UNKNOWN_SERVICE)
        return 1;

    status = rtas_call(start_cpu, 3, 1, NULL, pcpu, start_here, lcpu);
    if (status != 0) {
        printk(KERN_ERR "start-cpu failed: %i\n", status);
        return 0;
    }

    return 1;
}

static int __init smp_iic_probe(void)
{
    iic_request_IPIs();

    return cpumask_weight(cpu_possible_mask);
}

static void __devinit smp_cell_setup_cpu(int cpu)
{
    if (cpu != boot_cpuid)
        iic_setup_cpu();

    /*
     * change default DABRX to allow user watchpoints
     */
    mtspr(SPRN_DABRX, DABRX_KERNEL | DABRX_USER);
}

static int __devinit smp_cell_kick_cpu(int nr)
{
    BUG_ON(nr < 0 || nr >= NR_CPUS);

    if (!smp_startup_cpu(nr))
        return -ENOENT;

    /*
     * The processor is currently spinning, waiting for the
     * cpu_start field to become non-zero After we set cpu_start,
     * the processor will continue on to secondary_start
     */
    paca[nr].cpu_start = 1;

    return 0;
}

static int smp_cell_cpu_bootable(unsigned int nr)
{
    /* Special case - we inhibit secondary thread startup
     * during boot if the user requests it.  Odd-numbered
     * cpus are assumed to be secondary threads.
     */
    if (system_state < SYSTEM_RUNNING &&
        cpu_has_feature(CPU_FTR_SMT) &&
        !smt_enabled_at_boot && cpu_thread_in_core(nr) != 0)
        return 0;

    return 1;
}
static struct smp_ops_t bpa_iic_smp_ops = {
    .message_pass   = iic_message_pass,
    .probe      = smp_iic_probe,
    .kick_cpu   = smp_cell_kick_cpu,
    .setup_cpu  = smp_cell_setup_cpu,
    .cpu_bootable   = smp_cell_cpu_bootable,
};

/* This is called very early */
void __init smp_init_cell(void)
{
    int i;

    DBG(" -> smp_init_cell()\n");

    smp_ops = &bpa_iic_smp_ops;

    /* Mark threads which are still spinning in hold loops. */
    if (cpu_has_feature(CPU_FTR_SMT)) {
        for_each_present_cpu(i) {
            if (cpu_thread_in_core(i) == 0)
                cpumask_set_cpu(i, &of_spin_map);
        }
    } else
        cpumask_copy(&of_spin_map, cpu_present_mask);

    cpumask_clear_cpu(boot_cpuid, &of_spin_map);

    /* Non-lpar has additional take/give timebase */
    if (rtas_token("freeze-time-base") != RTAS_UNKNOWN_SERVICE) {
        smp_ops->give_timebase = rtas_give_timebase;
        smp_ops->take_timebase = rtas_take_timebase;
    }

    DBG(" <- smp_init_cell()\n");
}