smp.c

Go to the documentation of this file.

/*
** SMP Support
**
** Copyright (C) 1999 Walt Drummond <[email protected]>
** Copyright (C) 1999 David Mosberger-Tang <[email protected]>
** Copyright (C) 2001,2004 Grant Grundler <[email protected]>
** 
** Lots of stuff stolen from arch/alpha/kernel/smp.c
** ...and then parisc stole from arch/ia64/kernel/smp.c. Thanks David! :^)
**
** Thanks to John Curry and Ullas Ponnadi. I learned a lot from their work.
** -grant (1/12/2001)
**
**  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.
*/
#include <linux/types.h>
#include <linux/spinlock.h>

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/smp.h>
#include <linux/kernel_stat.h>
#include <linux/mm.h>
#include <linux/err.h>
#include <linux/delay.h>
#include <linux/bitops.h>
#include <linux/ftrace.h>
#include <linux/cpu.h>

#include <linux/atomic.h>
#include <asm/current.h>
#include <asm/delay.h>
#include <asm/tlbflush.h>

#include <asm/io.h>
#include <asm/irq.h>        /* for CPU_IRQ_REGION and friends */
#include <asm/mmu_context.h>
#include <asm/page.h>
#include <asm/pgtable.h>
#include <asm/pgalloc.h>
#include <asm/processor.h>
#include <asm/ptrace.h>
#include <asm/unistd.h>
#include <asm/cacheflush.h>

#undef DEBUG_SMP
#ifdef DEBUG_SMP
static int smp_debug_lvl = 0;
#define smp_debug(lvl, printargs...)        \
        if (lvl >= smp_debug_lvl)   \
            printk(printargs);
#else
#define smp_debug(lvl, ...) do { } while(0)
#endif /* DEBUG_SMP */

volatile struct task_struct *smp_init_current_idle_task;

/* track which CPU is booting */
static volatile int cpu_now_booting __cpuinitdata;

static int parisc_max_cpus __cpuinitdata = 1;

static DEFINE_PER_CPU(spinlock_t, ipi_lock);

enum ipi_message_type {
    IPI_NOP=0,
    IPI_RESCHEDULE=1,
    IPI_CALL_FUNC,
    IPI_CALL_FUNC_SINGLE,
    IPI_CPU_START,
    IPI_CPU_STOP,
    IPI_CPU_TEST
};


/********** SMP inter processor interrupt and communication routines */

#undef PER_CPU_IRQ_REGION
#ifdef PER_CPU_IRQ_REGION
/* XXX REVISIT Ignore for now.
**    *May* need this "hook" to register IPI handler
**    once we have perCPU ExtIntr switch tables.
*/
static void
ipi_init(int cpuid)
{
#error verify IRQ_OFFSET(IPI_IRQ) is ipi_interrupt() in new IRQ region

    if(cpu_online(cpuid) )
    {
        switch_to_idle_task(current);
    }

    return;
}
#endif


/*
** Yoink this CPU from the runnable list... 
**
*/
static void
halt_processor(void) 
{
    /* REVISIT : redirect I/O Interrupts to another CPU? */
    /* REVISIT : does PM *know* this CPU isn't available? */
    set_cpu_online(smp_processor_id(), false);
    local_irq_disable();
    for (;;)
        ;
}


irqreturn_t __irq_entry
ipi_interrupt(int irq, void *dev_id) 
{
    int this_cpu = smp_processor_id();
    struct cpuinfo_parisc *p = &per_cpu(cpu_data, this_cpu);
    unsigned long ops;
    unsigned long flags;

    /* Count this now; we may make a call that never returns. */
    p->ipi_count++;

    mb();   /* Order interrupt and bit testing. */

    for (;;) {
        spinlock_t *lock = &per_cpu(ipi_lock, this_cpu);
        spin_lock_irqsave(lock, flags);
        ops = p->pending_ipi;
        p->pending_ipi = 0;
        spin_unlock_irqrestore(lock, flags);

        mb(); /* Order bit clearing and data access. */

        if (!ops)
            break;

        while (ops) {
            unsigned long which = ffz(~ops);

            ops &= ~(1 << which);

            switch (which) {
            case IPI_NOP:
                smp_debug(100, KERN_DEBUG "CPU%d IPI_NOP\n", this_cpu);
                break;
                
            case IPI_RESCHEDULE:
                smp_debug(100, KERN_DEBUG "CPU%d IPI_RESCHEDULE\n", this_cpu);
                scheduler_ipi();
                break;

            case IPI_CALL_FUNC:
                smp_debug(100, KERN_DEBUG "CPU%d IPI_CALL_FUNC\n", this_cpu);
                generic_smp_call_function_interrupt();
                break;

            case IPI_CALL_FUNC_SINGLE:
                smp_debug(100, KERN_DEBUG "CPU%d IPI_CALL_FUNC_SINGLE\n", this_cpu);
                generic_smp_call_function_single_interrupt();
                break;

            case IPI_CPU_START:
                smp_debug(100, KERN_DEBUG "CPU%d IPI_CPU_START\n", this_cpu);
                break;

            case IPI_CPU_STOP:
                smp_debug(100, KERN_DEBUG "CPU%d IPI_CPU_STOP\n", this_cpu);
                halt_processor();
                break;

            case IPI_CPU_TEST:
                smp_debug(100, KERN_DEBUG "CPU%d is alive!\n", this_cpu);
                break;

            default:
                printk(KERN_CRIT "Unknown IPI num on CPU%d: %lu\n",
                    this_cpu, which);
                return IRQ_NONE;
            } /* Switch */
        /* let in any pending interrupts */
        local_irq_enable();
        local_irq_disable();
        } /* while (ops) */
    }
    return IRQ_HANDLED;
}


static inline void
ipi_send(int cpu, enum ipi_message_type op)
{
    struct cpuinfo_parisc *p = &per_cpu(cpu_data, cpu);
    spinlock_t *lock = &per_cpu(ipi_lock, cpu);
    unsigned long flags;

    spin_lock_irqsave(lock, flags);
    p->pending_ipi |= 1 << op;
    gsc_writel(IPI_IRQ - CPU_IRQ_BASE, p->hpa);
    spin_unlock_irqrestore(lock, flags);
}

static void
send_IPI_mask(const struct cpumask *mask, enum ipi_message_type op)
{
    int cpu;

    for_each_cpu(cpu, mask)
        ipi_send(cpu, op);
}

static inline void
send_IPI_single(int dest_cpu, enum ipi_message_type op)
{
    BUG_ON(dest_cpu == NO_PROC_ID);

    ipi_send(dest_cpu, op);
}

static inline void
send_IPI_allbutself(enum ipi_message_type op)
{
    int i;
    
    for_each_online_cpu(i) {
        if (i != smp_processor_id())
            send_IPI_single(i, op);
    }
}


inline void 
smp_send_stop(void) { send_IPI_allbutself(IPI_CPU_STOP); }

static inline void
smp_send_start(void)    { send_IPI_allbutself(IPI_CPU_START); }

void 
smp_send_reschedule(int cpu) { send_IPI_single(cpu, IPI_RESCHEDULE); }

void
smp_send_all_nop(void)
{
    send_IPI_allbutself(IPI_NOP);
}

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

void arch_send_call_function_single_ipi(int cpu)
{
    send_IPI_single(cpu, IPI_CALL_FUNC_SINGLE);
}

/*
 * Flush all other CPU's tlb and then mine.  Do this with on_each_cpu()
 * as we want to ensure all TLB's flushed before proceeding.
 */

void
smp_flush_tlb_all(void)
{
    on_each_cpu(flush_tlb_all_local, NULL, 1);
}

/*
 * Called by secondaries to update state and initialize CPU registers.
 */
static void __init
smp_cpu_init(int cpunum)
{
    extern int init_per_cpu(int);  /* arch/parisc/kernel/processor.c */
    extern void init_IRQ(void);    /* arch/parisc/kernel/irq.c */
    extern void start_cpu_itimer(void); /* arch/parisc/kernel/time.c */

    /* Set modes and Enable floating point coprocessor */
    (void) init_per_cpu(cpunum);

    disable_sr_hashing();

    mb();

    /* Well, support 2.4 linux scheme as well. */
    if (cpu_online(cpunum)) {
        extern void machine_halt(void); /* arch/parisc.../process.c */

        printk(KERN_CRIT "CPU#%d already initialized!\n", cpunum);
        machine_halt();
    }

    notify_cpu_starting(cpunum);

    set_cpu_online(cpunum, true);

    /* Initialise the idle task for this CPU */
    atomic_inc(&init_mm.mm_count);
    current->active_mm = &init_mm;
    BUG_ON(current->mm);
    enter_lazy_tlb(&init_mm, current);

    init_IRQ();   /* make sure no IRQs are enabled or pending */
    start_cpu_itimer();
}


/*
 * Slaves start using C here. Indirectly called from smp_slave_stext.
 * Do what start_kernel() and main() do for boot strap processor (aka monarch)
 */
void __init smp_callin(void)
{
    int slave_id = cpu_now_booting;

    smp_cpu_init(slave_id);
    preempt_disable();

    flush_cache_all_local(); /* start with known state */
    flush_tlb_all_local(NULL);

    local_irq_enable();  /* Interrupts have been off until now */

    cpu_idle();      /* Wait for timer to schedule some work */

    /* NOTREACHED */
    panic("smp_callin() AAAAaaaaahhhh....\n");
}

/*
 * Bring one cpu online.
 */
int __cpuinit smp_boot_one_cpu(int cpuid, struct task_struct *idle)
{
    const struct cpuinfo_parisc *p = &per_cpu(cpu_data, cpuid);
    long timeout;

    task_thread_info(idle)->cpu = cpuid;

    /* Let _start know what logical CPU we're booting
    ** (offset into init_tasks[],cpu_data[])
    */
    cpu_now_booting = cpuid;

    /* 
    ** boot strap code needs to know the task address since
    ** it also contains the process stack.
    */
    smp_init_current_idle_task = idle ;
    mb();

    printk(KERN_INFO "Releasing cpu %d now, hpa=%lx\n", cpuid, p->hpa);

    /*
    ** This gets PDC to release the CPU from a very tight loop.
    **
    ** From the PA-RISC 2.0 Firmware Architecture Reference Specification:
    ** "The MEM_RENDEZ vector specifies the location of OS_RENDEZ which 
    ** is executed after receiving the rendezvous signal (an interrupt to 
    ** EIR{0}). MEM_RENDEZ is valid only when it is nonzero and the 
    ** contents of memory are valid."
    */
    gsc_writel(TIMER_IRQ - CPU_IRQ_BASE, p->hpa);
    mb();

    /* 
     * OK, wait a bit for that CPU to finish staggering about. 
     * Slave will set a bit when it reaches smp_cpu_init().
     * Once the "monarch CPU" sees the bit change, it can move on.
     */
    for (timeout = 0; timeout < 10000; timeout++) {
        if(cpu_online(cpuid)) {
            /* Which implies Slave has started up */
            cpu_now_booting = 0;
            smp_init_current_idle_task = NULL;
            goto alive ;
        }
        udelay(100);
        barrier();
    }
    printk(KERN_CRIT "SMP: CPU:%d is stuck.\n", cpuid);
    return -1;

alive:
    /* Remember the Slave data */
    smp_debug(100, KERN_DEBUG "SMP: CPU:%d came alive after %ld _us\n",
        cpuid, timeout * 100);
    return 0;
}

void __init smp_prepare_boot_cpu(void)
{
    int bootstrap_processor = per_cpu(cpu_data, 0).cpuid;

    /* Setup BSP mappings */
    printk(KERN_INFO "SMP: bootstrap CPU ID is %d\n", bootstrap_processor);

    set_cpu_online(bootstrap_processor, true);
    set_cpu_present(bootstrap_processor, true);
}



/*
** inventory.c:do_inventory() hasn't yet been run and thus we
** don't 'discover' the additional CPUs until later.
*/
void __init smp_prepare_cpus(unsigned int max_cpus)
{
    int cpu;

    for_each_possible_cpu(cpu)
        spin_lock_init(&per_cpu(ipi_lock, cpu));

    init_cpu_present(cpumask_of(0));

    parisc_max_cpus = max_cpus;
    if (!max_cpus)
        printk(KERN_INFO "SMP mode deactivated.\n");
}


void smp_cpus_done(unsigned int cpu_max)
{
    return;
}


int __cpuinit __cpu_up(unsigned int cpu, struct task_struct *tidle)
{
    if (cpu != 0 && cpu < parisc_max_cpus)
        smp_boot_one_cpu(cpu, tidle);

    return cpu_online(cpu) ? 0 : -ENOSYS;
}

#ifdef CONFIG_PROC_FS
int __init
setup_profiling_timer(unsigned int multiplier)
{
    return -EINVAL;
}
#endif