mcfmmu.c

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/*
 * Based upon linux/arch/m68k/mm/sun3mmu.c
 * Based upon linux/arch/ppc/mm/mmu_context.c
 *
 * Implementations of mm routines specific to the Coldfire MMU.
 *
 * Copyright (c) 2008 Freescale Semiconductor, Inc.
 */

#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/mm.h>
#include <linux/init.h>
#include <linux/string.h>
#include <linux/bootmem.h>

#include <asm/setup.h>
#include <asm/page.h>
#include <asm/pgtable.h>
#include <asm/mmu_context.h>
#include <asm/mcf_pgalloc.h>
#include <asm/tlbflush.h>

#define KMAPAREA(x) ((x >= VMALLOC_START) && (x < KMAP_END))

mm_context_t next_mmu_context;
unsigned long context_map[LAST_CONTEXT / BITS_PER_LONG + 1];
atomic_t nr_free_contexts;
struct mm_struct *context_mm[LAST_CONTEXT+1];
extern unsigned long num_pages;

void free_initmem(void)
{
}

/*
 * ColdFire paging_init derived from sun3.
 */
void __init paging_init(void)
{
    pgd_t *pg_dir;
    pte_t *pg_table;
    unsigned long address, size;
    unsigned long next_pgtable, bootmem_end;
    unsigned long zones_size[MAX_NR_ZONES];
    enum zone_type zone;
    int i;

    empty_zero_page = (void *) alloc_bootmem_pages(PAGE_SIZE);
    memset((void *) empty_zero_page, 0, PAGE_SIZE);

    pg_dir = swapper_pg_dir;
    memset(swapper_pg_dir, 0, sizeof(swapper_pg_dir));

    size = num_pages * sizeof(pte_t);
    size = (size + PAGE_SIZE) & ~(PAGE_SIZE-1);
    next_pgtable = (unsigned long) alloc_bootmem_pages(size);

    bootmem_end = (next_pgtable + size + PAGE_SIZE) & PAGE_MASK;
    pg_dir += PAGE_OFFSET >> PGDIR_SHIFT;

    address = PAGE_OFFSET;
    while (address < (unsigned long)high_memory) {
        pg_table = (pte_t *) next_pgtable;
        next_pgtable += PTRS_PER_PTE * sizeof(pte_t);
        pgd_val(*pg_dir) = (unsigned long) pg_table;
        pg_dir++;

        /* now change pg_table to kernel virtual addresses */
        for (i = 0; i < PTRS_PER_PTE; ++i, ++pg_table) {
            pte_t pte = pfn_pte(virt_to_pfn(address), PAGE_INIT);
            if (address >= (unsigned long) high_memory)
                pte_val(pte) = 0;

            set_pte(pg_table, pte);
            address += PAGE_SIZE;
        }
    }

    current->mm = NULL;

    for (zone = 0; zone < MAX_NR_ZONES; zone++)
        zones_size[zone] = 0x0;
    zones_size[ZONE_DMA] = num_pages;
    free_area_init(zones_size);
}

int cf_tlb_miss(struct pt_regs *regs, int write, int dtlb, int extension_word)
{
    unsigned long flags, mmuar, mmutr;
    struct mm_struct *mm;
    pgd_t *pgd;
    pmd_t *pmd;
    pte_t *pte;
    int asid;

    local_irq_save(flags);

    mmuar = (dtlb) ? mmu_read(MMUAR) :
        regs->pc + (extension_word * sizeof(long));

    mm = (!user_mode(regs) && KMAPAREA(mmuar)) ? &init_mm : current->mm;
    if (!mm) {
        local_irq_restore(flags);
        return -1;
    }

    pgd = pgd_offset(mm, mmuar);
    if (pgd_none(*pgd))  {
        local_irq_restore(flags);
        return -1;
    }

    pmd = pmd_offset(pgd, mmuar);
    if (pmd_none(*pmd)) {
        local_irq_restore(flags);
        return -1;
    }

    pte = (KMAPAREA(mmuar)) ? pte_offset_kernel(pmd, mmuar)
                : pte_offset_map(pmd, mmuar);
    if (pte_none(*pte) || !pte_present(*pte)) {
        local_irq_restore(flags);
        return -1;
    }

    if (write) {
        if (!pte_write(*pte)) {
            local_irq_restore(flags);
            return -1;
        }
        set_pte(pte, pte_mkdirty(*pte));
    }

    set_pte(pte, pte_mkyoung(*pte));
    asid = mm->context & 0xff;
    if (!pte_dirty(*pte) && !KMAPAREA(mmuar))
        set_pte(pte, pte_wrprotect(*pte));

    mmutr = (mmuar & PAGE_MASK) | (asid << MMUTR_IDN) | MMUTR_V;
    if ((mmuar < TASK_UNMAPPED_BASE) || (mmuar >= TASK_SIZE))
        mmutr |= (pte->pte & CF_PAGE_MMUTR_MASK) >> CF_PAGE_MMUTR_SHIFT;
    mmu_write(MMUTR, mmutr);

    mmu_write(MMUDR, (pte_val(*pte) & PAGE_MASK) |
        ((pte->pte) & CF_PAGE_MMUDR_MASK) | MMUDR_SZ_8KB | MMUDR_X);

    if (dtlb)
        mmu_write(MMUOR, MMUOR_ACC | MMUOR_UAA);
    else
        mmu_write(MMUOR, MMUOR_ITLB | MMUOR_ACC | MMUOR_UAA);

    local_irq_restore(flags);
    return 0;
}

/*
 * Initialize the context management stuff.
 * The following was taken from arch/ppc/mmu_context.c
 */
void __init mmu_context_init(void)
{
    /*
     * Some processors have too few contexts to reserve one for
     * init_mm, and require using context 0 for a normal task.
     * Other processors reserve the use of context zero for the kernel.
     * This code assumes FIRST_CONTEXT < 32.
     */
    context_map[0] = (1 << FIRST_CONTEXT) - 1;
    next_mmu_context = FIRST_CONTEXT;
    atomic_set(&nr_free_contexts, LAST_CONTEXT - FIRST_CONTEXT + 1);
}

/*
 * Steal a context from a task that has one at the moment.
 * This is only used on 8xx and 4xx and we presently assume that
 * they don't do SMP.  If they do then thicfpgalloc.hs will have to check
 * whether the MM we steal is in use.
 * We also assume that this is only used on systems that don't
 * use an MMU hash table - this is true for 8xx and 4xx.
 * This isn't an LRU system, it just frees up each context in
 * turn (sort-of pseudo-random replacement :).  This would be the
 * place to implement an LRU scheme if anyone was motivated to do it.
 *  -- paulus
 */
void steal_context(void)
{
    struct mm_struct *mm;
    /*
     * free up context `next_mmu_context'
     * if we shouldn't free context 0, don't...
     */
    if (next_mmu_context < FIRST_CONTEXT)
        next_mmu_context = FIRST_CONTEXT;
    mm = context_mm[next_mmu_context];
    flush_tlb_mm(mm);
    destroy_context(mm);
}