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ioremap.c

/*
 *  linux/arch/arm/mm/ioremap.c
 *
 * Re-map IO memory to kernel address space so that we can access it.
 *
 * (C) Copyright 1995 1996 Linus Torvalds
 *
 * Hacked for ARM by Phil Blundell <philb@gnu.org>
 * Hacked to allow all architectures to build, and various cleanups
 * by Russell King
 *
 * This allows a driver to remap an arbitrary region of bus memory into
 * virtual space.  One should *only* use readl, writel, memcpy_toio and
 * so on with such remapped areas.
 *
 * Because the ARM only has a 32-bit address space we can't address the
 * whole of the (physical) PCI space at once.  PCI huge-mode addressing
 * allows us to circumvent this restriction by splitting PCI space into
 * two 2GB chunks and mapping only one at a time into processor memory.
 * We use MMU protection domains to trap any attempt to access the bank
 * that is not currently mapped.  (This isn't fully implemented yet.)
 */
#include <linux/module.h>
#include <linux/errno.h>
#include <linux/mm.h>
#include <linux/vmalloc.h>

#include <asm/cacheflush.h>
#include <asm/io.h>
#include <asm/mmu_context.h>
#include <asm/pgalloc.h>
#include <asm/tlbflush.h>
#include <asm/sizes.h>

#include <asm/mach/map.h>
#include "mm.h"

/*
 * Used by ioremap() and iounmap() code to mark (super)section-mapped
 * I/O regions in vm_struct->flags field.
 */
#define VM_ARM_SECTION_MAPPING      0x80000000

static int remap_area_pte(pmd_t *pmd, unsigned long addr, unsigned long end,
                    unsigned long phys_addr, const struct mem_type *type)
{
      pgprot_t prot = __pgprot(type->prot_pte);
      pte_t *pte;

      pte = pte_alloc_kernel(pmd, addr);
      if (!pte)
            return -ENOMEM;

      do {
            if (!pte_none(*pte))
                  goto bad;

            set_pte_ext(pte, pfn_pte(phys_addr >> PAGE_SHIFT, prot),
                      type->prot_pte_ext);
            phys_addr += PAGE_SIZE;
      } while (pte++, addr += PAGE_SIZE, addr != end);
      return 0;

 bad:
      printk(KERN_CRIT "remap_area_pte: page already exists\n");
      BUG();
}

static inline int remap_area_pmd(pgd_t *pgd, unsigned long addr,
                         unsigned long end, unsigned long phys_addr,
                         const struct mem_type *type)
{
      unsigned long next;
      pmd_t *pmd;
      int ret = 0;

      pmd = pmd_alloc(&init_mm, pgd, addr);
      if (!pmd)
            return -ENOMEM;

      do {
            next = pmd_addr_end(addr, end);
            ret = remap_area_pte(pmd, addr, next, phys_addr, type);
            if (ret)
                  return ret;
            phys_addr += next - addr;
      } while (pmd++, addr = next, addr != end);
      return ret;
}

static int remap_area_pages(unsigned long start, unsigned long pfn,
                      size_t size, const struct mem_type *type)
{
      unsigned long addr = start;
      unsigned long next, end = start + size;
      unsigned long phys_addr = __pfn_to_phys(pfn);
      pgd_t *pgd;
      int err = 0;

      BUG_ON(addr >= end);
      pgd = pgd_offset_k(addr);
      do {
            next = pgd_addr_end(addr, end);
            err = remap_area_pmd(pgd, addr, next, phys_addr, type);
            if (err)
                  break;
            phys_addr += next - addr;
      } while (pgd++, addr = next, addr != end);

      return err;
}


void __check_kvm_seq(struct mm_struct *mm)
{
      unsigned int seq;

      do {
            seq = init_mm.context.kvm_seq;
            memcpy(pgd_offset(mm, VMALLOC_START),
                   pgd_offset_k(VMALLOC_START),
                   sizeof(pgd_t) * (pgd_index(VMALLOC_END) -
                              pgd_index(VMALLOC_START)));
            mm->context.kvm_seq = seq;
      } while (seq != init_mm.context.kvm_seq);
}

#ifndef CONFIG_SMP
/*
 * Section support is unsafe on SMP - If you iounmap and ioremap a region,
 * the other CPUs will not see this change until their next context switch.
 * Meanwhile, (eg) if an interrupt comes in on one of those other CPUs
 * which requires the new ioremap'd region to be referenced, the CPU will
 * reference the _old_ region.
 *
 * Note that get_vm_area() allocates a guard 4K page, so we need to mask
 * the size back to 1MB aligned or we will overflow in the loop below.
 */
static void unmap_area_sections(unsigned long virt, unsigned long size)
{
      unsigned long addr = virt, end = virt + (size & ~SZ_1M);
      pgd_t *pgd;

      flush_cache_vunmap(addr, end);
      pgd = pgd_offset_k(addr);
      do {
            pmd_t pmd, *pmdp = pmd_offset(pgd, addr);

            pmd = *pmdp;
            if (!pmd_none(pmd)) {
                  /*
                   * Clear the PMD from the page table, and
                   * increment the kvm sequence so others
                   * notice this change.
                   *
                   * Note: this is still racy on SMP machines.
                   */
                  pmd_clear(pmdp);
                  init_mm.context.kvm_seq++;

                  /*
                   * Free the page table, if there was one.
                   */
                  if ((pmd_val(pmd) & PMD_TYPE_MASK) == PMD_TYPE_TABLE)
                        pte_free_kernel(&init_mm, pmd_page_vaddr(pmd));
            }

            addr += PGDIR_SIZE;
            pgd++;
      } while (addr < end);

      /*
       * Ensure that the active_mm is up to date - we want to
       * catch any use-after-iounmap cases.
       */
      if (current->active_mm->context.kvm_seq != init_mm.context.kvm_seq)
            __check_kvm_seq(current->active_mm);

      flush_tlb_kernel_range(virt, end);
}

static int
remap_area_sections(unsigned long virt, unsigned long pfn,
                size_t size, const struct mem_type *type)
{
      unsigned long addr = virt, end = virt + size;
      pgd_t *pgd;

      /*
       * Remove and free any PTE-based mapping, and
       * sync the current kernel mapping.
       */
      unmap_area_sections(virt, size);

      pgd = pgd_offset_k(addr);
      do {
            pmd_t *pmd = pmd_offset(pgd, addr);

            pmd[0] = __pmd(__pfn_to_phys(pfn) | type->prot_sect);
            pfn += SZ_1M >> PAGE_SHIFT;
            pmd[1] = __pmd(__pfn_to_phys(pfn) | type->prot_sect);
            pfn += SZ_1M >> PAGE_SHIFT;
            flush_pmd_entry(pmd);

            addr += PGDIR_SIZE;
            pgd++;
      } while (addr < end);

      return 0;
}

static int
remap_area_supersections(unsigned long virt, unsigned long pfn,
                   size_t size, const struct mem_type *type)
{
      unsigned long addr = virt, end = virt + size;
      pgd_t *pgd;

      /*
       * Remove and free any PTE-based mapping, and
       * sync the current kernel mapping.
       */
      unmap_area_sections(virt, size);

      pgd = pgd_offset_k(virt);
      do {
            unsigned long super_pmd_val, i;

            super_pmd_val = __pfn_to_phys(pfn) | type->prot_sect |
                        PMD_SECT_SUPER;
            super_pmd_val |= ((pfn >> (32 - PAGE_SHIFT)) & 0xf) << 20;

            for (i = 0; i < 8; i++) {
                  pmd_t *pmd = pmd_offset(pgd, addr);

                  pmd[0] = __pmd(super_pmd_val);
                  pmd[1] = __pmd(super_pmd_val);
                  flush_pmd_entry(pmd);

                  addr += PGDIR_SIZE;
                  pgd++;
            }

            pfn += SUPERSECTION_SIZE >> PAGE_SHIFT;
      } while (addr < end);

      return 0;
}
#endif


/*
 * 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.
 *
 * 'flags' are the extra L_PTE_ flags that you want to specify for this
 * mapping.  See <asm/pgtable.h> for more information.
 */
void __iomem *
__arm_ioremap_pfn(unsigned long pfn, unsigned long offset, size_t size,
              unsigned int mtype)
{
      const struct mem_type *type;
      int err;
      unsigned long addr;
      struct vm_struct * area;

      /*
       * High mappings must be supersection aligned
       */
      if (pfn >= 0x100000 && (__pfn_to_phys(pfn) & ~SUPERSECTION_MASK))
            return NULL;

      type = get_mem_type(mtype);
      if (!type)
            return NULL;

      /*
       * Page align the mapping size, taking account of any offset.
       */
      size = PAGE_ALIGN(offset + size);

      area = get_vm_area(size, VM_IOREMAP);
      if (!area)
            return NULL;
      addr = (unsigned long)area->addr;

#ifndef CONFIG_SMP
      if (DOMAIN_IO == 0 &&
          (((cpu_architecture() >= CPU_ARCH_ARMv6) && (get_cr() & CR_XP)) ||
             cpu_is_xsc3()) && pfn >= 0x100000 &&
             !((__pfn_to_phys(pfn) | size | addr) & ~SUPERSECTION_MASK)) {
            area->flags |= VM_ARM_SECTION_MAPPING;
            err = remap_area_supersections(addr, pfn, size, type);
      } else if (!((__pfn_to_phys(pfn) | size | addr) & ~PMD_MASK)) {
            area->flags |= VM_ARM_SECTION_MAPPING;
            err = remap_area_sections(addr, pfn, size, type);
      } else
#endif
            err = remap_area_pages(addr, pfn, size, type);

      if (err) {
            vunmap((void *)addr);
            return NULL;
      }

      flush_cache_vmap(addr, addr + size);
      return (void __iomem *) (offset + addr);
}
EXPORT_SYMBOL(__arm_ioremap_pfn);

void __iomem *
__arm_ioremap(unsigned long phys_addr, size_t size, unsigned int mtype)
{
      unsigned long last_addr;
      unsigned long offset = phys_addr & ~PAGE_MASK;
      unsigned long pfn = __phys_to_pfn(phys_addr);

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

      return __arm_ioremap_pfn(pfn, offset, size, mtype);
}
EXPORT_SYMBOL(__arm_ioremap);

void __iounmap(volatile void __iomem *addr)
{
#ifndef CONFIG_SMP
      struct vm_struct **p, *tmp;
#endif
      unsigned int section_mapping = 0;

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

#ifndef CONFIG_SMP
      /*
       * If this is a section based mapping we need to handle it
       * specially as the VM subsystem does not know how to handle
       * such a beast. We need the lock here b/c we need to clear
       * all the mappings before the area can be reclaimed
       * by someone else.
       */
      write_lock(&vmlist_lock);
      for (p = &vmlist ; (tmp = *p) ; p = &tmp->next) {
            if((tmp->flags & VM_IOREMAP) && (tmp->addr == addr)) {
                  if (tmp->flags & VM_ARM_SECTION_MAPPING) {
                        *p = tmp->next;
                        unmap_area_sections((unsigned long)tmp->addr,
                                        tmp->size);
                        kfree(tmp);
                        section_mapping = 1;
                  }
                  break;
            }
      }
      write_unlock(&vmlist_lock);
#endif

      if (!section_mapping)
            vunmap((void __force *)addr);
}
EXPORT_SYMBOL(__iounmap);

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