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ioremap.c

/*
 * 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/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;
      if (address >= end)
            BUG();
      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;
      if (address >= end)
            BUG();
      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();
      if (address >= end)
            BUG();
      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);

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