ioremap_fixed.c

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/*
 * Re-map IO memory to kernel address space so that we can access it.
 *
 * These functions should only be used when it is necessary to map a
 * physical address space into the kernel address space before ioremap()
 * can be used, e.g. early in boot before paging_init().
 *
 * Copyright (C) 2009  Matt Fleming
 */

#include <linux/vmalloc.h>
#include <linux/ioport.h>
#include <linux/module.h>
#include <linux/mm.h>
#include <linux/io.h>
#include <linux/bootmem.h>
#include <linux/proc_fs.h>
#include <asm/fixmap.h>
#include <asm/page.h>
#include <asm/pgalloc.h>
#include <asm/addrspace.h>
#include <asm/cacheflush.h>
#include <asm/tlbflush.h>
#include <asm/mmu.h>
#include <asm/mmu_context.h>

struct ioremap_map {
    void __iomem *addr;
    unsigned long size;
    unsigned long fixmap_addr;
};

static struct ioremap_map ioremap_maps[FIX_N_IOREMAPS];

void __init ioremap_fixed_init(void)
{
    struct ioremap_map *map;
    int i;

    for (i = 0; i < FIX_N_IOREMAPS; i++) {
        map = &ioremap_maps[i];
        map->fixmap_addr = __fix_to_virt(FIX_IOREMAP_BEGIN + i);
    }
}

void __init __iomem *
ioremap_fixed(phys_addr_t phys_addr, unsigned long size, pgprot_t prot)
{
    enum fixed_addresses idx0, idx;
    struct ioremap_map *map;
    unsigned int nrpages;
    unsigned long offset;
    int i, slot;

    /*
     * Mappings have to be page-aligned
     */
    offset = phys_addr & ~PAGE_MASK;
    phys_addr &= PAGE_MASK;
    size = PAGE_ALIGN(phys_addr + size) - phys_addr;

    slot = -1;
    for (i = 0; i < FIX_N_IOREMAPS; i++) {
        map = &ioremap_maps[i];
        if (!map->addr) {
            map->size = size;
            slot = i;
            break;
        }
    }

    if (slot < 0)
        return NULL;

    /*
     * Mappings have to fit in the FIX_IOREMAP area.
     */
    nrpages = size >> PAGE_SHIFT;
    if (nrpages > FIX_N_IOREMAPS)
        return NULL;

    /*
     * Ok, go for it..
     */
    idx0 = FIX_IOREMAP_BEGIN + slot;
    idx = idx0;
    while (nrpages > 0) {
        pgprot_val(prot) |= _PAGE_WIRED;
        __set_fixmap(idx, phys_addr, prot);
        phys_addr += PAGE_SIZE;
        idx++;
        --nrpages;
    }

    map->addr = (void __iomem *)(offset + map->fixmap_addr);
    return map->addr;
}

int iounmap_fixed(void __iomem *addr)
{
    enum fixed_addresses idx;
    struct ioremap_map *map;
    unsigned int nrpages;
    int i, slot;

    slot = -1;
    for (i = 0; i < FIX_N_IOREMAPS; i++) {
        map = &ioremap_maps[i];
        if (map->addr == addr) {
            slot = i;
            break;
        }
    }

    /*
     * If we don't match, it's not for us.
     */
    if (slot < 0)
        return -EINVAL;

    nrpages = map->size >> PAGE_SHIFT;

    idx = FIX_IOREMAP_BEGIN + slot + nrpages - 1;
    while (nrpages > 0) {
        __clear_fixmap(idx, __pgprot(_PAGE_WIRED));
        --idx;
        --nrpages;
    }

    map->size = 0;
    map->addr = NULL;

    return 0;
}