arch/arm/mm/ioremap.c

   1 /*
   2  *  linux/arch/arm/mm/ioremap.c
   3  *
   4  * Re-map IO memory to kernel address space so that we can access it.
   5  *
   6  * (C) Copyright 1995 1996 Linus Torvalds
   7  *
   8  * Hacked for ARM by Phil Blundell <philb@gnu.org>
   9  * Hacked to allow all architectures to build, and various cleanups
  10  * by Russell King
  11  *
  12  * This allows a driver to remap an arbitrary region of bus memory into
  13  * virtual space.  One should *only* use readl, writel, memcpy_toio and
  14  * so on with such remapped areas.
  15  *
  16  * Because the ARM only has a 32-bit address space we can't address the
  17  * whole of the (physical) PCI space at once.  PCI huge-mode addressing
  18  * allows us to circumvent this restriction by splitting PCI space into
  19  * two 2GB chunks and mapping only one at a time into processor memory.
  20  * We use MMU protection domains to trap any attempt to access the bank
  21  * that is not currently mapped.  (This isn't fully implemented yet.)
  22  */
  23 #include <linux/module.h>
  24 #include <linux/errno.h>
  25 #include <linux/mm.h>
  26 #include <linux/vmalloc.h>
  27
  28 #include <asm/cacheflush.h>
  29 #include <asm/io.h>
  30 #include <asm/tlbflush.h>
  31
  32 static inline void
  33 remap_area_pte(pte_t * pte, unsigned long address, unsigned long size,
  34                unsigned long phys_addr, pgprot_t pgprot)
  35 {
  36         unsigned long end;
  37
  38         address &= ~PMD_MASK;
  39         end = address + size;
  40         if (end > PMD_SIZE)
  41                 end = PMD_SIZE;
  42         BUG_ON(address >= end);
  43         do {
  44                 if (!pte_none(*pte))
  45                         goto bad;
  46
  47                 set_pte(pte, pfn_pte(phys_addr >> PAGE_SHIFT, pgprot));
  48                 address += PAGE_SIZE;
  49                 phys_addr += PAGE_SIZE;
  50                 pte++;
  51         } while (address && (address < end));
  52         return;
  53
  54  bad:
  55         printk("remap_area_pte: page already exists\n");
  56         BUG();
  57 }
  58
  59 static inline int
  60 remap_area_pmd(pmd_t * pmd, unsigned long address, unsigned long size,
  61                unsigned long phys_addr, unsigned long flags)
  62 {
  63         unsigned long end;
  64         pgprot_t pgprot;
  65
  66         address &= ~PGDIR_MASK;
  67         end = address + size;
  68
  69         if (end > PGDIR_SIZE)
  70                 end = PGDIR_SIZE;
  71
  72         phys_addr -= address;
  73         BUG_ON(address >= end);
  74
  75         pgprot = __pgprot(L_PTE_PRESENT | L_PTE_YOUNG | L_PTE_DIRTY | L_PTE_WRITE | flags);
  76         do {
  77                 pte_t * pte = pte_alloc_kernel(&init_mm, pmd, address);
  78                 if (!pte)
  79                         return -ENOMEM;
  80                 remap_area_pte(pte, address, end - address, address + phys_addr, pgprot);
  81                 address = (address + PMD_SIZE) & PMD_MASK;
  82                 pmd++;
  83         } while (address && (address < end));
  84         return 0;
  85 }
  86
  87 static int
  88 remap_area_pages(unsigned long start, unsigned long phys_addr,
  89                  unsigned long size, unsigned long flags)
  90 {
  91         unsigned long address = start;
  92         unsigned long end = start + size;
  93         int err = 0;
  94         pgd_t * dir;
  95
  96         phys_addr -= address;
  97         dir = pgd_offset(&init_mm, address);
  98         BUG_ON(address >= end);
  99         spin_lock(&init_mm.page_table_lock);
 100         do {
 101                 pmd_t *pmd = pmd_alloc(&init_mm, dir, address);
 102                 if (!pmd) {
 103                         err = -ENOMEM;
 104                         break;
 105                 }
 106                 if (remap_area_pmd(pmd, address, end - address,
 107                                          phys_addr + address, flags)) {
 108                         err = -ENOMEM;
 109                         break;
 110                 }
 111
 112                 address = (address + PGDIR_SIZE) & PGDIR_MASK;
 113                 dir++;
 114         } while (address && (address < end));
 115
 116         spin_unlock(&init_mm.page_table_lock);
 117         flush_cache_vmap(start, end);
 118         return err;
 119 }
 120
 121 /*
 122  * Remap an arbitrary physical address space into the kernel virtual
 123  * address space. Needed when the kernel wants to access high addresses
 124  * directly.
 125  *
 126  * NOTE! We need to allow non-page-aligned mappings too: we will obviously
 127  * have to convert them into an offset in a page-aligned mapping, but the
 128  * caller shouldn't need to know that small detail.
 129  *
 130  * 'flags' are the extra L_PTE_ flags that you want to specify for this
 131  * mapping.  See include/asm-arm/proc-armv/pgtable.h for more information.
 132  */
 133 void __iomem *
 134 __ioremap(unsigned long phys_addr, size_t size, unsigned long flags,
 135           unsigned long align)
 136 {
 137         void * addr;
 138         struct vm_struct * area;
 139         unsigned long offset, last_addr;
 140
 141         /* Don't allow wraparound or zero size */
 142         last_addr = phys_addr + size - 1;
 143         if (!size || last_addr < phys_addr)
 144                 return NULL;
 145
 146         /*
 147          * Mappings have to be page-aligned
 148          */
 149         offset = phys_addr & ~PAGE_MASK;
 150         phys_addr &= PAGE_MASK;
 151         size = PAGE_ALIGN(last_addr + 1) - phys_addr;
 152
 153         /*
 154          * Ok, go for it..
 155          */
 156         area = get_vm_area(size, VM_IOREMAP);
 157         if (!area)
 158                 return NULL;
 159         addr = area->addr;
 160         if (remap_area_pages((unsigned long) addr, phys_addr, size, flags)) {
 161                 vfree(addr);
 162                 return NULL;
 163         }
 164         return (void __iomem *) (offset + (char *)addr);
 165 }
 166 EXPORT_SYMBOL(__ioremap);
 167
 168 void __iounmap(void __iomem *addr)
 169 {
 170         vfree((void *) (PAGE_MASK & (unsigned long) addr));
 171 }
 172 EXPORT_SYMBOL(__iounmap);