arch/i386/mm/ioremap.c

   1 /*
   2  * arch/i386/mm/ioremap.c
   3  *
   4  * Re-map IO memory to kernel address space so that we can access it.
   5  * This is needed for high PCI addresses that aren't mapped in the
   6  * 640k-1MB IO memory area on PC's
   7  *
   8  * (C) Copyright 1995 1996 Linus Torvalds
   9  */
  10
  11 #include <linux/vmalloc.h>
  12 #include <asm/io.h>
  13
  14 static inline void remap_area_pte(pte_t * pte, unsigned long address, unsigned long size,
  15         unsigned long phys_addr, unsigned long flags)
  16 {
  17         unsigned long end;
  18
  19         address &= ~PMD_MASK;
  20         end = address + size;
  21         if (end > PMD_SIZE)
  22                 end = PMD_SIZE;
  23         do {
  24                 if (!pte_none(*pte))
  25                         printk("remap_area_pte: page already exists\n");
  26                 set_pte(pte, mk_pte_phys(phys_addr, __pgprot(_PAGE_PRESENT | _PAGE_RW |
  27                                         _PAGE_DIRTY | _PAGE_ACCESSED | flags)));
  28                 address += PAGE_SIZE;
  29                 phys_addr += PAGE_SIZE;
  30                 pte++;
  31         } while (address < end);
  32 }
  33
  34 static inline int remap_area_pmd(pmd_t * pmd, unsigned long address, unsigned long size,
  35         unsigned long phys_addr, unsigned long flags)
  36 {
  37         unsigned long end;
  38
  39         address &= ~PGDIR_MASK;
  40         end = address + size;
  41         if (end > PGDIR_SIZE)
  42                 end = PGDIR_SIZE;
  43         phys_addr -= address;
  44         do {
  45                 pte_t * pte = pte_alloc_kernel(pmd, address);
  46                 if (!pte)
  47                         return -ENOMEM;
  48                 remap_area_pte(pte, address, end - address, address + phys_addr, flags);
  49                 address = (address + PMD_SIZE) & PMD_MASK;
  50                 pmd++;
  51         } while (address < end);
  52         return 0;
  53 }
  54
  55 static int remap_area_pages(unsigned long address, unsigned long phys_addr,
  56                                  unsigned long size, unsigned long flags)
  57 {
  58         pgd_t * dir;
  59         unsigned long end = address + size;
  60
  61         phys_addr -= address;
  62         dir = pgd_offset(&init_mm, address);
  63         flush_cache_all();
  64         while (address < end) {
  65                 pmd_t *pmd = pmd_alloc_kernel(dir, address);
  66                 if (!pmd)
  67                         return -ENOMEM;
  68                 if (remap_area_pmd(pmd, address, end - address,
  69                                          phys_addr + address, flags))
  70                         return -ENOMEM;
  71                 set_pgdir(address, *dir);
  72                 address = (address + PGDIR_SIZE) & PGDIR_MASK;
  73                 dir++;
  74         }
  75         flush_tlb_all();
  76         return 0;
  77 }
  78
  79 /*
  80  * Generic mapping function (not visible outside):
  81  */
  82
  83 /*
  84  * Remap an arbitrary physical address space into the kernel virtual
  85  * address space. Needed when the kernel wants to access high addresses
  86  * directly.
  87  *
  88  * NOTE! We need to allow non-page-aligned mappings too: we will obviously
  89  * have to convert them into an offset in a page-aligned mapping, but the
  90  * caller shouldn't need to know that small detail.
  91  */
  92 void * __ioremap(unsigned long phys_addr, unsigned long size, unsigned long flags)
  93 {
  94         void * addr;
  95         struct vm_struct * area;
  96         unsigned long offset;
  97
  98         /*
  99          * Don't remap the low PCI/ISA area, it's always mapped..
 100          */
 101         if (phys_addr >= 0xA0000 && (phys_addr+size) <= 0x100000)
 102                 return phys_to_virt(phys_addr);
 103
 104         /*
 105          * Don't allow anybody to remap normal RAM that we're using..
 106          */
 107         if (phys_addr < virt_to_phys(high_memory))
 108                 return NULL;
 109
 110         /*
 111          * Mappings have to be page-aligned
 112          */
 113         offset = phys_addr & ~PAGE_MASK;
 114         phys_addr &= PAGE_MASK;
 115         size = PAGE_ALIGN(size + offset);
 116
 117         /*
 118          * Don't allow mappings that wrap..
 119          */
 120         if (!size || size > phys_addr + size)
 121                 return NULL;
 122
 123         /*
 124          * Ok, go for it..
 125          */
 126         area = get_vm_area(size);
 127         if (!area)
 128                 return NULL;
 129         addr = area->addr;
 130         if (remap_area_pages(VMALLOC_VMADDR(addr), phys_addr, size, flags)) {
 131                 vfree(addr);
 132                 return NULL;
 133         }
 134         return (void *) (offset + (char *)addr);
 135 }
 136
 137 void iounmap(void *addr)
 138 {
 139         if (addr > high_memory)
 140                 return vfree((void *) (PAGE_MASK & (unsigned long) addr));
 141 }