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 #include <asm/pgalloc.h>
  14
  15 static inline void remap_area_pte(pte_t * pte, unsigned long address, unsigned long size,
  16         unsigned long phys_addr, unsigned long flags)
  17 {
  18         unsigned long end;
  19
  20         address &= ~PMD_MASK;
  21         end = address + size;
  22         if (end > PMD_SIZE)
  23                 end = PMD_SIZE;
  24         if (address >= end)
  25                 BUG();
  26         do {
  27                 if (!pte_none(*pte)) {
  28                         printk("remap_area_pte: page already exists\n");
  29                         BUG();
  30                 }
  31                 set_pte(pte, mk_pte_phys(phys_addr, __pgprot(_PAGE_PRESENT | _PAGE_RW |
  32                                         _PAGE_DIRTY | _PAGE_ACCESSED | flags)));
  33                 address += PAGE_SIZE;
  34                 phys_addr += PAGE_SIZE;
  35                 pte++;
  36         } while (address && (address < end));
  37 }
  38
  39 static inline int remap_area_pmd(pmd_t * pmd, unsigned long address, unsigned long size,
  40         unsigned long phys_addr, unsigned long flags)
  41 {
  42         unsigned long end;
  43
  44         address &= ~PGDIR_MASK;
  45         end = address + size;
  46         if (end > PGDIR_SIZE)
  47                 end = PGDIR_SIZE;
  48         phys_addr -= address;
  49         if (address >= end)
  50                 BUG();
  51         do {
  52                 pte_t * pte = pte_alloc_kernel(pmd, address);
  53                 if (!pte)
  54                         return -ENOMEM;
  55                 remap_area_pte(pte, address, end - address, address + phys_addr, flags);
  56                 address = (address + PMD_SIZE) & PMD_MASK;
  57                 pmd++;
  58         } while (address && (address < end));
  59         return 0;
  60 }
  61
  62 static int remap_area_pages(unsigned long address, unsigned long phys_addr,
  63                                  unsigned long size, unsigned long flags)
  64 {
  65         pgd_t * dir;
  66         unsigned long end = address + size;
  67
  68         phys_addr -= address;
  69         dir = pgd_offset(&init_mm, address);
  70         flush_cache_all();
  71         if (address >= end)
  72                 BUG();
  73         do {
  74                 pmd_t *pmd;
  75                 pmd = pmd_alloc_kernel(dir, address);
  76                 if (!pmd)
  77                         return -ENOMEM;
  78                 if (remap_area_pmd(pmd, address, end - address,
  79                                          phys_addr + address, flags))
  80                         return -ENOMEM;
  81                 set_pgdir(address, *dir);
  82                 address = (address + PGDIR_SIZE) & PGDIR_MASK;
  83                 dir++;
  84         } while (address && (address < end));
  85         flush_tlb_all();
  86         return 0;
  87 }
  88
  89 /*
  90  * Generic mapping function (not visible outside):
  91  */
  92
  93 /*
  94  * Remap an arbitrary physical address space into the kernel virtual
  95  * address space. Needed when the kernel wants to access high addresses
  96  * directly.
  97  *
  98  * NOTE! We need to allow non-page-aligned mappings too: we will obviously
  99  * have to convert them into an offset in a page-aligned mapping, but the
 100  * caller shouldn't need to know that small detail.
 101  */
 102 void * __ioremap(unsigned long phys_addr, unsigned long size, unsigned long flags)
 103 {
 104         void * addr;
 105         struct vm_struct * area;
 106         unsigned long offset, last_addr;
 107
 108         /* Don't allow wraparound or zero size */
 109         last_addr = phys_addr + size - 1;
 110         if (!size || last_addr < phys_addr)
 111                 return NULL;
 112
 113         /*
 114          * Don't remap the low PCI/ISA area, it's always mapped..
 115          */
 116         if (phys_addr >= 0xA0000 && last_addr < 0x100000)
 117                 return phys_to_virt(phys_addr);
 118
 119         /*
 120          * Don't allow anybody to remap normal RAM that we're using..
 121          */
 122         if (phys_addr < virt_to_phys(high_memory)) {
 123                 char *t_addr, *t_end;
 124                 int i;
 125
 126                 t_addr = __va(phys_addr);
 127                 t_end = t_addr + (size - 1);
 128
 129                 for(i = MAP_NR(t_addr); i < MAP_NR(t_end); i++) {
 130                         if(!PageReserved(mem_map + i))
 131                                 return NULL;
 132                 }
 133         }
 134
 135         /*
 136          * Mappings have to be page-aligned
 137          */
 138         offset = phys_addr & ~PAGE_MASK;
 139         phys_addr &= PAGE_MASK;
 140         size = PAGE_ALIGN(last_addr) - phys_addr;
 141
 142         /*
 143          * Ok, go for it..
 144          */
 145         area = get_vm_area(size, VM_IOREMAP);
 146         if (!area)
 147                 return NULL;
 148         addr = area->addr;
 149         if (remap_area_pages(VMALLOC_VMADDR(addr), phys_addr, size, flags)) {
 150                 vfree(addr);
 151                 return NULL;
 152         }
 153         return (void *) (offset + (char *)addr);
 154 }
 155
 156 void iounmap(void *addr)
 157 {
 158         if (addr > high_memory)
 159                 return vfree((void *) (PAGE_MASK & (unsigned long) addr));
 160 }