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ioremap_32.c

/*
 * arch/i386/mm/ioremap.c
 *
 * Re-map IO memory to kernel address space so that we can access it.
 * This is needed for high PCI addresses that aren't mapped in the
 * 640k-1MB IO memory area on PC's
 *
 * (C) Copyright 1995 1996 Linus Torvalds
 */

#include <linux/vmalloc.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/io.h>
#include <asm/fixmap.h>
#include <asm/cacheflush.h>
#include <asm/tlbflush.h>
#include <asm/pgtable.h>

#define ISA_START_ADDRESS     0xa0000
#define ISA_END_ADDRESS       0x100000

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

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

      /*
       * Don't remap the low PCI/ISA area, it's always mapped..
       */
      if (phys_addr >= ISA_START_ADDRESS && last_addr < ISA_END_ADDRESS)
            return (void __iomem *) phys_to_virt(phys_addr);

      /*
       * Don't allow anybody to remap normal RAM that we're using..
       */
      if (phys_addr <= virt_to_phys(high_memory - 1)) {
            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;
      }

      prot = __pgprot(_PAGE_PRESENT | _PAGE_RW | _PAGE_DIRTY
                  | _PAGE_ACCESSED | flags);

      /*
       * 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 | (flags << 20));
      if (!area)
            return NULL;
      area->phys_addr = phys_addr;
      addr = (void __iomem *) area->addr;
      if (ioremap_page_range((unsigned long) addr,
                  (unsigned long) addr + size, phys_addr, prot)) {
            vunmap((void __force *) addr);
            return NULL;
      }
      return (void __iomem *) (offset + (char __iomem *)addr);
}
EXPORT_SYMBOL(__ioremap);

/**
 * ioremap_nocache     -   map bus memory into CPU space
 * @offset:    bus address of the memory
 * @size:      size of the resource to map
 *
 * ioremap_nocache performs a platform specific sequence of operations to
 * make bus memory CPU accessible via the readb/readw/readl/writeb/
 * writew/writel functions and the other mmio helpers. The returned
 * address is not guaranteed to be usable directly as a virtual
 * address. 
 *
 * This version of ioremap ensures that the memory is marked uncachable
 * on the CPU as well as honouring existing caching rules from things like
 * the PCI bus. Note that there are other caches and buffers on many 
 * busses. In particular driver authors should read up on PCI writes
 *
 * It's useful if some control registers are in such an area and
 * write combining or read caching is not desirable:
 * 
 * Must be freed with iounmap.
 */

void __iomem *ioremap_nocache (unsigned long phys_addr, unsigned long size)
{
      unsigned long last_addr;
      void __iomem *p = __ioremap(phys_addr, size, _PAGE_PCD);
      if (!p) 
            return p; 

      /* Guaranteed to be > phys_addr, as per __ioremap() */
      last_addr = phys_addr + size - 1;

      if (last_addr < virt_to_phys(high_memory) - 1) {
            struct page *ppage = virt_to_page(__va(phys_addr));         
            unsigned long npages;

            phys_addr &= PAGE_MASK;

            /* This might overflow and become zero.. */
            last_addr = PAGE_ALIGN(last_addr);

            /* .. but that's ok, because modulo-2**n arithmetic will make
            * the page-aligned "last - first" come out right.
            */
            npages = (last_addr - phys_addr) >> PAGE_SHIFT;

            if (change_page_attr(ppage, npages, PAGE_KERNEL_NOCACHE) < 0) { 
                  iounmap(p); 
                  p = NULL;
            }
            global_flush_tlb();
      }

      return p;                           
}
EXPORT_SYMBOL(ioremap_nocache);

/**
 * iounmap - Free a IO remapping
 * @addr: virtual address from ioremap_*
 *
 * Caller must ensure there is only one unmapping for the same pointer.
 */
void iounmap(volatile void __iomem *addr)
{
      struct vm_struct *p, *o;

      if ((void __force *)addr <= high_memory)
            return;

      /*
       * __ioremap special-cases the PCI/ISA range by not instantiating a
       * vm_area and by simply returning an address into the kernel mapping
       * of ISA space.   So handle that here.
       */
      if (addr >= phys_to_virt(ISA_START_ADDRESS) &&
                  addr < phys_to_virt(ISA_END_ADDRESS))
            return;

      addr = (volatile void __iomem *)(PAGE_MASK & (unsigned long __force)addr);

      /* Use the vm area unlocked, assuming the caller
         ensures there isn't another iounmap for the same address
         in parallel. Reuse of the virtual address is prevented by
         leaving it in the global lists until we're done with it.
         cpa takes care of the direct mappings. */
      read_lock(&vmlist_lock);
      for (p = vmlist; p; p = p->next) {
            if (p->addr == addr)
                  break;
      }
      read_unlock(&vmlist_lock);

      if (!p) {
            printk("iounmap: bad address %p\n", addr);
            dump_stack();
            return;
      }

      /* Reset the direct mapping. Can block */
      if ((p->flags >> 20) && p->phys_addr < virt_to_phys(high_memory) - 1) {
            change_page_attr(virt_to_page(__va(p->phys_addr)),
                         get_vm_area_size(p) >> PAGE_SHIFT,
                         PAGE_KERNEL);
            global_flush_tlb();
      } 

      /* Finally remove it */
      o = remove_vm_area((void *)addr);
      BUG_ON(p != o || o == NULL);
      kfree(p); 
}
EXPORT_SYMBOL(iounmap);

void __init *bt_ioremap(unsigned long phys_addr, unsigned long size)
{
      unsigned long offset, last_addr;
      unsigned int nrpages;
      enum fixed_addresses idx;

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

      /*
       * Don't remap the low PCI/ISA area, it's always mapped..
       */
      if (phys_addr >= ISA_START_ADDRESS && last_addr < ISA_END_ADDRESS)
            return phys_to_virt(phys_addr);

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

      /*
       * Mappings have to fit in the FIX_BTMAP area.
       */
      nrpages = size >> PAGE_SHIFT;
      if (nrpages > NR_FIX_BTMAPS)
            return NULL;

      /*
       * Ok, go for it..
       */
      idx = FIX_BTMAP_BEGIN;
      while (nrpages > 0) {
            set_fixmap(idx, phys_addr);
            phys_addr += PAGE_SIZE;
            --idx;
            --nrpages;
      }
      return (void*) (offset + fix_to_virt(FIX_BTMAP_BEGIN));
}

void __init bt_iounmap(void *addr, unsigned long size)
{
      unsigned long virt_addr;
      unsigned long offset;
      unsigned int nrpages;
      enum fixed_addresses idx;

      virt_addr = (unsigned long)addr;
      if (virt_addr < fix_to_virt(FIX_BTMAP_BEGIN))
            return;
      offset = virt_addr & ~PAGE_MASK;
      nrpages = PAGE_ALIGN(offset + size - 1) >> PAGE_SHIFT;

      idx = FIX_BTMAP_BEGIN;
      while (nrpages > 0) {
            clear_fixmap(idx);
            --idx;
            --nrpages;
      }
}

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