/* SMP TLB support routines.
 *
 * Copyright (C) 2006-2008 Panasonic 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
 * 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.
 */
#include <linux/interrupt.h>
#include <linux/spinlock.h>
#include <linux/init.h>
#include <linux/jiffies.h>
#include <linux/cpumask.h>
#include <linux/err.h>
#include <linux/kernel.h>
#include <linux/delay.h>
#include <linux/sched.h>
#include <linux/profile.h>
#include <linux/smp.h>
#include <asm/tlbflush.h>
#include <asm/bitops.h>
#include <asm/processor.h>
#include <asm/bug.h>
#include <asm/exceptions.h>
#include <asm/hardirq.h>
#include <asm/fpu.h>
#include <asm/mmu_context.h>
#include <asm/thread_info.h>
#include <asm/cpu-regs.h>
#include <asm/intctl-regs.h>

/*
 * For flush TLB
 */
#define FLUSH_ALL       0xffffffff

static cpumask_t flush_cpumask;
static struct mm_struct *flush_mm;
static unsigned long flush_va;
static DEFINE_SPINLOCK(tlbstate_lock);

DEFINE_PER_CPU_SHARED_ALIGNED(struct tlb_state, cpu_tlbstate) = {
        &init_mm, 0
};

static void flush_tlb_others(cpumask_t cpumask, struct mm_struct *mm,
                             unsigned long va);
static void do_flush_tlb_all(void *info);

/**
 * smp_flush_tlb - Callback to invalidate the TLB.
 * @unused: Callback context (ignored).
 */
void smp_flush_tlb(void *unused)
{
        unsigned long cpu_id;

        cpu_id = get_cpu();

        if (!cpumask_test_cpu(cpu_id, &flush_cpumask))
                /* This was a BUG() but until someone can quote me the line
                 * from the intel manual that guarantees an IPI to multiple
                 * CPUs is retried _only_ on the erroring CPUs its staying as a
                 * return
                 *
                 * BUG();
                 */
                goto out;

        if (flush_va == FLUSH_ALL)
                local_flush_tlb();
        else
                local_flush_tlb_page(flush_mm, flush_va);

        smp_mb__before_clear_bit();
        cpumask_clear_cpu(cpu_id, &flush_cpumask);
        smp_mb__after_clear_bit();
out:
        put_cpu();
}

/**
 * flush_tlb_others - Tell the specified CPUs to invalidate their TLBs
 * @cpumask: The list of CPUs to target.
 * @mm: The VM context to flush from (if va!=FLUSH_ALL).
 * @va: Virtual address to flush or FLUSH_ALL to flush everything.
 */
static void flush_tlb_others(cpumask_t cpumask, struct mm_struct *mm,
                             unsigned long va)
{
        cpumask_t tmp;

        /* A couple of sanity checks (to be removed):
         * - mask must not be empty
         * - current CPU must not be in mask
         * - we do not send IPIs to as-yet unbooted CPUs.
         */
        BUG_ON(!mm);
        BUG_ON(cpumask_empty(&cpumask));
        BUG_ON(cpumask_test_cpu(smp_processor_id(), &cpumask));

        cpumask_and(&tmp, &cpumask, cpu_online_mask);
        BUG_ON(!cpumask_equal(&cpumask, &tmp));

        /* I'm not happy about this global shared spinlock in the MM hot path,
         * but we'll see how contended it is.
         *
         * Temporarily this turns IRQs off, so that lockups are detected by the
         * NMI watchdog.
         */
        spin_lock(&tlbstate_lock);

        flush_mm = mm;
        flush_va = va;
#if NR_CPUS <= BITS_PER_LONG
        atomic_set_mask(cpumask.bits[0], &flush_cpumask.bits[0]);
#else
#error Not supported.
#endif

        /* FIXME: if NR_CPUS>=3, change send_IPI_mask */
        smp_call_function(smp_flush_tlb, NULL, 1);

        while (!cpumask_empty(&flush_cpumask))
                /* Lockup detection does not belong here */
                smp_mb();

        flush_mm = NULL;
        flush_va = 0;
        spin_unlock(&tlbstate_lock);
}

/**
 * flush_tlb_mm - Invalidate TLB of specified VM context
 * @mm: The VM context to invalidate.
 */
void flush_tlb_mm(struct mm_struct *mm)
{
        cpumask_t cpu_mask;

        preempt_disable();
        cpumask_copy(&cpu_mask, mm_cpumask(mm));
        cpumask_clear_cpu(smp_processor_id(), &cpu_mask);

        local_flush_tlb();
        if (!cpumask_empty(&cpu_mask))
                flush_tlb_others(cpu_mask, mm, FLUSH_ALL);

        preempt_enable();
}

/**
 * flush_tlb_current_task - Invalidate TLB of current task
 */
void flush_tlb_current_task(void)
{
        struct mm_struct *mm = current->mm;
        cpumask_t cpu_mask;

        preempt_disable();
        cpumask_copy(&cpu_mask, mm_cpumask(mm));
        cpumask_clear_cpu(smp_processor_id(), &cpu_mask);

        local_flush_tlb();
        if (!cpumask_empty(&cpu_mask))
                flush_tlb_others(cpu_mask, mm, FLUSH_ALL);

        preempt_enable();
}

/**
 * flush_tlb_page - Invalidate TLB of page
 * @vma: The VM context to invalidate the page for.
 * @va: The virtual address of the page to invalidate.
 */
void flush_tlb_page(struct vm_area_struct *vma, unsigned long va)
{
        struct mm_struct *mm = vma->vm_mm;
        cpumask_t cpu_mask;

        preempt_disable();
        cpumask_copy(&cpu_mask, mm_cpumask(mm));
        cpumask_clear_cpu(smp_processor_id(), &cpu_mask);

        local_flush_tlb_page(mm, va);
        if (!cpumask_empty(&cpu_mask))
                flush_tlb_others(cpu_mask, mm, va);

        preempt_enable();
}

/**
 * do_flush_tlb_all - Callback to completely invalidate a TLB
 * @unused: Callback context (ignored).
 */
static void do_flush_tlb_all(void *unused)
{
        local_flush_tlb_all();
}

/**
 * flush_tlb_all - Completely invalidate TLBs on all CPUs
 */
void flush_tlb_all(void)
{
        on_each_cpu(do_flush_tlb_all, 0, 1);
}