mmu_context.h

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/*
 * Copyright (C) 2004-2006 Atmel Corporation
 *
 * ASID handling taken from SH implementation.
 *   Copyright (C) 1999 Niibe Yutaka
 *   Copyright (C) 2003 Paul Mundt
 *
 * 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.
 */
#ifndef __ASM_AVR32_MMU_CONTEXT_H
#define __ASM_AVR32_MMU_CONTEXT_H

#include <asm/tlbflush.h>
#include <asm/sysreg.h>
#include <asm-generic/mm_hooks.h>

/*
 * The MMU "context" consists of two things:
 *    (a) TLB cache version
 *    (b) ASID (Address Space IDentifier)
 */
#define MMU_CONTEXT_ASID_MASK       0x000000ff
#define MMU_CONTEXT_VERSION_MASK    0xffffff00
#define MMU_CONTEXT_FIRST_VERSION       0x00000100
#define NO_CONTEXT          0

#define MMU_NO_ASID         0x100

/* Virtual Page Number mask */
#define MMU_VPN_MASK    0xfffff000

/* Cache of MMU context last used */
extern unsigned long mmu_context_cache;

/*
 * Get MMU context if needed
 */
static inline void
get_mmu_context(struct mm_struct *mm)
{
    unsigned long mc = mmu_context_cache;

    if (((mm->context ^ mc) & MMU_CONTEXT_VERSION_MASK) == 0)
        /* It's up to date, do nothing */
        return;

    /* It's old, we need to get new context with new version */
    mc = ++mmu_context_cache;
    if (!(mc & MMU_CONTEXT_ASID_MASK)) {
        /*
         * We have exhausted all ASIDs of this version.
         * Flush the TLB and start new cycle.
         */
        flush_tlb_all();
        /*
         * Fix version. Note that we avoid version #0
         * to distinguish NO_CONTEXT.
         */
        if (!mc)
            mmu_context_cache = mc = MMU_CONTEXT_FIRST_VERSION;
    }
    mm->context = mc;
}

/*
 * Initialize the context related info for a new mm_struct
 * instance.
 */
static inline int init_new_context(struct task_struct *tsk,
                       struct mm_struct *mm)
{
    mm->context = NO_CONTEXT;
    return 0;
}

/*
 * Destroy context related info for an mm_struct that is about
 * to be put to rest.
 */
static inline void destroy_context(struct mm_struct *mm)
{
    /* Do nothing */
}

static inline void set_asid(unsigned long asid)
{
    /* XXX: We're destroying TLBEHI[8:31] */
    sysreg_write(TLBEHI, asid & MMU_CONTEXT_ASID_MASK);
    cpu_sync_pipeline();
}

static inline unsigned long get_asid(void)
{
    unsigned long asid;

    asid = sysreg_read(TLBEHI);
    return asid & MMU_CONTEXT_ASID_MASK;
}

static inline void activate_context(struct mm_struct *mm)
{
    get_mmu_context(mm);
    set_asid(mm->context & MMU_CONTEXT_ASID_MASK);
}

static inline void switch_mm(struct mm_struct *prev,
                 struct mm_struct *next,
                 struct task_struct *tsk)
{
    if (likely(prev != next)) {
        unsigned long __pgdir = (unsigned long)next->pgd;

        sysreg_write(PTBR, __pgdir);
        activate_context(next);
    }
}

#define deactivate_mm(tsk,mm) do { } while(0)

#define activate_mm(prev, next) switch_mm((prev), (next), NULL)

static inline void
enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk)
{
}


static inline void enable_mmu(void)
{
    sysreg_write(MMUCR, (SYSREG_BIT(MMUCR_S)
                 | SYSREG_BIT(E)
                 | SYSREG_BIT(MMUCR_I)));
    nop(); nop(); nop(); nop(); nop(); nop(); nop(); nop();

    if (mmu_context_cache == NO_CONTEXT)
        mmu_context_cache = MMU_CONTEXT_FIRST_VERSION;

    set_asid(mmu_context_cache & MMU_CONTEXT_ASID_MASK);
}

static inline void disable_mmu(void)
{
    sysreg_write(MMUCR, SYSREG_BIT(MMUCR_S));
}

#endif /* __ASM_AVR32_MMU_CONTEXT_H */