ioremap.c

Go to the documentation of this file.

/*
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 *
 * (C) Copyright 1995 1996 Linus Torvalds
 * (C) Copyright 2001, 2002 Ralf Baechle
 */
#include <linux/module.h>
#include <asm/addrspace.h>
#include <asm/byteorder.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <asm/cacheflush.h>
#include <asm/io.h>
#include <asm/tlbflush.h>

static inline void remap_area_pte(pte_t * pte, unsigned long address,
    phys_t size, phys_t phys_addr, unsigned long flags)
{
    phys_t end;
    unsigned long pfn;
    pgprot_t pgprot = __pgprot(_PAGE_GLOBAL | _PAGE_PRESENT | __READABLE
                               | __WRITEABLE | flags);

    address &= ~PMD_MASK;
    end = address + size;
    if (end > PMD_SIZE)
        end = PMD_SIZE;
    BUG_ON(address >= end);
    pfn = phys_addr >> PAGE_SHIFT;
    do {
        if (!pte_none(*pte)) {
            printk("remap_area_pte: page already exists\n");
            BUG();
        }
        set_pte(pte, pfn_pte(pfn, pgprot));
        address += PAGE_SIZE;
        pfn++;
        pte++;
    } while (address && (address < end));
}

static inline int remap_area_pmd(pmd_t * pmd, unsigned long address,
    phys_t size, phys_t phys_addr, unsigned long flags)
{
    phys_t end;

    address &= ~PGDIR_MASK;
    end = address + size;
    if (end > PGDIR_SIZE)
        end = PGDIR_SIZE;
    phys_addr -= address;
    BUG_ON(address >= end);
    do {
        pte_t * pte = pte_alloc_kernel(pmd, address);
        if (!pte)
            return -ENOMEM;
        remap_area_pte(pte, address, end - address, address + phys_addr, flags);
        address = (address + PMD_SIZE) & PMD_MASK;
        pmd++;
    } while (address && (address < end));
    return 0;
}

static int remap_area_pages(unsigned long address, phys_t phys_addr,
    phys_t size, unsigned long flags)
{
    int error;
    pgd_t * dir;
    unsigned long end = address + size;

    phys_addr -= address;
    dir = pgd_offset(&init_mm, address);
    flush_cache_all();
    BUG_ON(address >= end);
    do {
        pud_t *pud;
        pmd_t *pmd;

        error = -ENOMEM;
        pud = pud_alloc(&init_mm, dir, address);
        if (!pud)
            break;
        pmd = pmd_alloc(&init_mm, pud, address);
        if (!pmd)
            break;
        if (remap_area_pmd(pmd, address, end - address,
                     phys_addr + address, flags))
            break;
        error = 0;
        address = (address + PGDIR_SIZE) & PGDIR_MASK;
        dir++;
    } while (address && (address < end));
    flush_tlb_all();
    return error;
}

/*
 * Generic mapping function (not visible outside):
 */

/*
 * Remap an arbitrary physical address space into the kernel virtual
 * address space. Needed when the kernel wants to access high addresses
 * directly.
 *
 * NOTE! We need to allow non-page-aligned mappings too: we will obviously
 * have to convert them into an offset in a page-aligned mapping, but the
 * caller shouldn't need to know that small detail.
 */

#define IS_LOW512(addr) (!((phys_t)(addr) & (phys_t) ~0x1fffffffULL))

void __iomem * __ioremap(phys_t phys_addr, phys_t size, unsigned long flags)
{
    struct vm_struct * area;
    unsigned long offset;
    phys_t last_addr;
    void * addr;

    phys_addr = fixup_bigphys_addr(phys_addr, size);

    /* Don't allow wraparound or zero size */
    last_addr = phys_addr + size - 1;
    if (!size || last_addr < phys_addr)
        return NULL;

    /*
     * Map uncached objects in the low 512mb of address space using KSEG1,
     * otherwise map using page tables.
     */
    if (IS_LOW512(phys_addr) && IS_LOW512(last_addr) &&
        flags == _CACHE_UNCACHED)
        return (void __iomem *) CKSEG1ADDR(phys_addr);

    /*
     * Don't allow anybody to remap normal RAM that we're using..
     */
    if (phys_addr < virt_to_phys(high_memory)) {
        char *t_addr, *t_end;
        struct page *page;

        t_addr = __va(phys_addr);
        t_end = t_addr + (size - 1);

        for(page = virt_to_page(t_addr); page <= virt_to_page(t_end); page++)
            if(!PageReserved(page))
                return NULL;
    }

    /*
     * Mappings have to be page-aligned
     */
    offset = phys_addr & ~PAGE_MASK;
    phys_addr &= PAGE_MASK;
    size = PAGE_ALIGN(last_addr + 1) - phys_addr;

    /*
     * Ok, go for it..
     */
    area = get_vm_area(size, VM_IOREMAP);
    if (!area)
        return NULL;
    addr = area->addr;
    if (remap_area_pages((unsigned long) addr, phys_addr, size, flags)) {
        vunmap(addr);
        return NULL;
    }

    return (void __iomem *) (offset + (char *)addr);
}

#define IS_KSEG1(addr) (((unsigned long)(addr) & ~0x1fffffffUL) == CKSEG1)

void __iounmap(const volatile void __iomem *addr)
{
    struct vm_struct *p;

    if (IS_KSEG1(addr))
        return;

    p = remove_vm_area((void *) (PAGE_MASK & (unsigned long __force) addr));
    if (!p)
        printk(KERN_ERR "iounmap: bad address %p\n", addr);

        kfree(p);
}

EXPORT_SYMBOL(__ioremap);
EXPORT_SYMBOL(__iounmap);