/*
 * 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;

/*
 * 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);
}