smp.c

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/*
 * Copyright 2010 Tilera Corporation. 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
 *   as published by the Free Software Foundation, version 2.
 *
 *   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, GOOD TITLE or
 *   NON INFRINGEMENT.  See the GNU General Public License for
 *   more details.
 *
 * TILE SMP support routines.
 */

#include <linux/smp.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/irq.h>
#include <linux/module.h>
#include <asm/cacheflush.h>

HV_Topology smp_topology __write_once;
EXPORT_SYMBOL(smp_topology);

#if CHIP_HAS_IPI()
static unsigned long __iomem *ipi_mappings[NR_CPUS];
#endif


/*
 * Top-level send_IPI*() functions to send messages to other cpus.
 */

/* Set by smp_send_stop() to avoid recursive panics. */
static int stopping_cpus;

static void __send_IPI_many(HV_Recipient *recip, int nrecip, int tag)
{
    int sent = 0;
    while (sent < nrecip) {
        int rc = hv_send_message(recip, nrecip,
                     (HV_VirtAddr)&tag, sizeof(tag));
        if (rc < 0) {
            if (!stopping_cpus)  /* avoid recursive panic */
                panic("hv_send_message returned %d", rc);
            break;
        }
        WARN_ONCE(rc == 0, "hv_send_message() returned zero\n");
        sent += rc;
    }
}

void send_IPI_single(int cpu, int tag)
{
    HV_Recipient recip = {
        .y = cpu / smp_width,
        .x = cpu % smp_width,
        .state = HV_TO_BE_SENT
    };
    __send_IPI_many(&recip, 1, tag);
}

void send_IPI_many(const struct cpumask *mask, int tag)
{
    HV_Recipient recip[NR_CPUS];
    int cpu;
    int nrecip = 0;
    int my_cpu = smp_processor_id();
    for_each_cpu(cpu, mask) {
        HV_Recipient *r;
        BUG_ON(cpu == my_cpu);
        r = &recip[nrecip++];
        r->y = cpu / smp_width;
        r->x = cpu % smp_width;
        r->state = HV_TO_BE_SENT;
    }
    __send_IPI_many(recip, nrecip, tag);
}

void send_IPI_allbutself(int tag)
{
    struct cpumask mask;
    cpumask_copy(&mask, cpu_online_mask);
    cpumask_clear_cpu(smp_processor_id(), &mask);
    send_IPI_many(&mask, tag);
}

/*
 * Functions related to starting/stopping cpus.
 */

/* Handler to start the current cpu. */
static void smp_start_cpu_interrupt(void)
{
    get_irq_regs()->pc = start_cpu_function_addr;
}

/* Handler to stop the current cpu. */
static void smp_stop_cpu_interrupt(void)
{
    set_cpu_online(smp_processor_id(), 0);
    arch_local_irq_disable_all();
    for (;;)
        asm("nap; nop");
}

/* This function calls the 'stop' function on all other CPUs in the system. */
void smp_send_stop(void)
{
    stopping_cpus = 1;
    send_IPI_allbutself(MSG_TAG_STOP_CPU);
}

/* On panic, just wait; we may get an smp_send_stop() later on. */
void panic_smp_self_stop(void)
{
    while (1)
        asm("nap; nop");
}

/*
 * Dispatch code called from hv_message_intr() for HV_MSG_TILE hv messages.
 */
void evaluate_message(int tag)
{
    switch (tag) {
    case MSG_TAG_START_CPU: /* Start up a cpu */
        smp_start_cpu_interrupt();
        break;

    case MSG_TAG_STOP_CPU: /* Sent to shut down slave CPU's */
        smp_stop_cpu_interrupt();
        break;

    case MSG_TAG_CALL_FUNCTION_MANY: /* Call function on cpumask */
        generic_smp_call_function_interrupt();
        break;

    case MSG_TAG_CALL_FUNCTION_SINGLE: /* Call function on one other CPU */
        generic_smp_call_function_single_interrupt();
        break;

    default:
        panic("Unknown IPI message tag %d", tag);
        break;
    }
}


/*
 * flush_icache_range() code uses smp_call_function().
 */

struct ipi_flush {
    unsigned long start;
    unsigned long end;
};

static void ipi_flush_icache_range(void *info)
{
    struct ipi_flush *flush = (struct ipi_flush *) info;
    __flush_icache_range(flush->start, flush->end);
}

void flush_icache_range(unsigned long start, unsigned long end)
{
    struct ipi_flush flush = { start, end };
    preempt_disable();
    on_each_cpu(ipi_flush_icache_range, &flush, 1);
    preempt_enable();
}


/* Called when smp_send_reschedule() triggers IRQ_RESCHEDULE. */
static irqreturn_t handle_reschedule_ipi(int irq, void *token)
{
    __get_cpu_var(irq_stat).irq_resched_count++;
    scheduler_ipi();

    return IRQ_HANDLED;
}

static struct irqaction resched_action = {
    .handler = handle_reschedule_ipi,
    .name = "resched",
    .dev_id = handle_reschedule_ipi /* unique token */,
};

void __init ipi_init(void)
{
#if CHIP_HAS_IPI()
    int cpu;
    /* Map IPI trigger MMIO addresses. */
    for_each_possible_cpu(cpu) {
        HV_Coord tile;
        HV_PTE pte;
        unsigned long offset;

        tile.x = cpu_x(cpu);
        tile.y = cpu_y(cpu);
        if (hv_get_ipi_pte(tile, KERNEL_PL, &pte) != 0)
            panic("Failed to initialize IPI for cpu %d\n", cpu);

        offset = PFN_PHYS(pte_pfn(pte));
        ipi_mappings[cpu] = ioremap_prot(offset, PAGE_SIZE, pte);
    }
#endif

    /* Bind handle_reschedule_ipi() to IRQ_RESCHEDULE. */
    tile_irq_activate(IRQ_RESCHEDULE, TILE_IRQ_PERCPU);
    BUG_ON(setup_irq(IRQ_RESCHEDULE, &resched_action));
}

#if CHIP_HAS_IPI()

void smp_send_reschedule(int cpu)
{
    WARN_ON(cpu_is_offline(cpu));

    /*
     * We just want to do an MMIO store.  The traditional writeq()
     * functions aren't really correct here, since they're always
     * directed at the PCI shim.  For now, just do a raw store,
     * casting away the __iomem attribute.
     */
    ((unsigned long __force *)ipi_mappings[cpu])[IRQ_RESCHEDULE] = 0;
}

#else

void smp_send_reschedule(int cpu)
{
    HV_Coord coord;

    WARN_ON(cpu_is_offline(cpu));

    coord.y = cpu_y(cpu);
    coord.x = cpu_x(cpu);
    hv_trigger_ipi(coord, IRQ_RESCHEDULE);
}

#endif /* CHIP_HAS_IPI() */