smp.c

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/*
 * SMP support for Hexagon
 *
 * Copyright (c) 2010-2012, The Linux Foundation. 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 and
 * only version 2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA.
 */

#include <linux/err.h>
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/percpu.h>
#include <linux/sched.h>
#include <linux/smp.h>
#include <linux/spinlock.h>
#include <linux/cpu.h>

#include <asm/time.h>    /*  timer_interrupt  */
#include <asm/hexagon_vm.h>

#define BASE_IPI_IRQ 26

/*
 * cpu_possible_mask needs to be filled out prior to setup_per_cpu_areas
 * (which is prior to any of our smp_prepare_cpu crap), in order to set
 * up the...  per_cpu areas.
 */

struct ipi_data {
    unsigned long bits;
};

static DEFINE_PER_CPU(struct ipi_data, ipi_data);

static inline void __handle_ipi(unsigned long *ops, struct ipi_data *ipi,
                int cpu)
{
    unsigned long msg = 0;
    do {
        msg = find_next_bit(ops, BITS_PER_LONG, msg+1);

        switch (msg) {

        case IPI_TIMER:
            ipi_timer();
            break;

        case IPI_CALL_FUNC:
            generic_smp_call_function_interrupt();
            break;

        case IPI_CALL_FUNC_SINGLE:
            generic_smp_call_function_single_interrupt();
            break;

        case IPI_CPU_STOP:
            /*
             * call vmstop()
             */
            __vmstop();
            break;

        case IPI_RESCHEDULE:
            scheduler_ipi();
            break;
        }
    } while (msg < BITS_PER_LONG);
}

/*  Used for IPI call from other CPU's to unmask int  */
void smp_vm_unmask_irq(void *info)
{
    __vmintop_locen((long) info);
}


/*
 * This is based on Alpha's IPI stuff.
 * Supposed to take (int, void*) as args now.
 * Specifically, first arg is irq, second is the irq_desc.
 */

irqreturn_t handle_ipi(int irq, void *desc)
{
    int cpu = smp_processor_id();
    struct ipi_data *ipi = &per_cpu(ipi_data, cpu);
    unsigned long ops;

    while ((ops = xchg(&ipi->bits, 0)) != 0)
        __handle_ipi(&ops, ipi, cpu);
    return IRQ_HANDLED;
}

void send_ipi(const struct cpumask *cpumask, enum ipi_message_type msg)
{
    unsigned long flags;
    unsigned long cpu;
    unsigned long retval;

    local_irq_save(flags);

    for_each_cpu(cpu, cpumask) {
        struct ipi_data *ipi = &per_cpu(ipi_data, cpu);

        set_bit(msg, &ipi->bits);
        /*  Possible barrier here  */
        retval = __vmintop_post(BASE_IPI_IRQ+cpu);

        if (retval != 0) {
            printk(KERN_ERR "interrupt %ld not configured?\n",
                BASE_IPI_IRQ+cpu);
        }
    }

    local_irq_restore(flags);
}

static struct irqaction ipi_intdesc = {
    .handler = handle_ipi,
    .flags = IRQF_TRIGGER_RISING,
    .name = "ipi_handler"
};

void __init smp_prepare_boot_cpu(void)
{
}

/*
 * interrupts should already be disabled from the VM
 * SP should already be correct; need to set THREADINFO_REG
 * to point to current thread info
 */

void __cpuinit start_secondary(void)
{
    unsigned int cpu;
    unsigned long thread_ptr;

    /*  Calculate thread_info pointer from stack pointer  */
    __asm__ __volatile__(
        "%0 = SP;\n"
        : "=r" (thread_ptr)
    );

    thread_ptr = thread_ptr & ~(THREAD_SIZE-1);

    __asm__ __volatile__(
        QUOTED_THREADINFO_REG " = %0;\n"
        :
        : "r" (thread_ptr)
    );

    /*  Set the memory struct  */
    atomic_inc(&init_mm.mm_count);
    current->active_mm = &init_mm;

    cpu = smp_processor_id();

    setup_irq(BASE_IPI_IRQ + cpu, &ipi_intdesc);

    /*  Register the clock_event dummy  */
    setup_percpu_clockdev();

    printk(KERN_INFO "%s cpu %d\n", __func__, current_thread_info()->cpu);

    notify_cpu_starting(cpu);

    set_cpu_online(cpu, true);

    local_irq_enable();

    cpu_idle();
}


/*
 * called once for each present cpu
 * apparently starts up the CPU and then
 * maintains control until "cpu_online(cpu)" is set.
 */

int __cpuinit __cpu_up(unsigned int cpu, struct task_struct *idle)
{
    struct thread_info *thread = (struct thread_info *)idle->stack;
    void *stack_start;

    thread->cpu = cpu;

    /*  Boot to the head.  */
    stack_start =  ((void *) thread) + THREAD_SIZE;
    __vmstart(start_secondary, stack_start);

    while (!cpu_online(cpu))
        barrier();

    return 0;
}

void __init smp_cpus_done(unsigned int max_cpus)
{
}

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

    /*
     * should eventually have some sort of machine
     * descriptor that has this stuff
     */

    /*  Right now, let's just fake it. */
    for (i = 0; i < max_cpus; i++)
        set_cpu_present(i, true);

    /*  Also need to register the interrupts for IPI  */
    if (max_cpus > 1)
        setup_irq(BASE_IPI_IRQ, &ipi_intdesc);
}

void smp_send_reschedule(int cpu)
{
    send_ipi(cpumask_of(cpu), IPI_RESCHEDULE);
}

void smp_send_stop(void)
{
    struct cpumask targets;
    cpumask_copy(&targets, cpu_online_mask);
    cpumask_clear_cpu(smp_processor_id(), &targets);
    send_ipi(&targets, IPI_CPU_STOP);
}

void arch_send_call_function_single_ipi(int cpu)
{
    send_ipi(cpumask_of(cpu), IPI_CALL_FUNC_SINGLE);
}

void arch_send_call_function_ipi_mask(const struct cpumask *mask)
{
    send_ipi(mask, IPI_CALL_FUNC);
}

int setup_profiling_timer(unsigned int multiplier)
{
    return -EINVAL;
}

void smp_start_cpus(void)
{
    int i;

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