arch/arm/mm/ioremap.c - kernel/msm - Gitiles

 /*
  *  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>

 /*
  * 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, pgprot_t prot)
 {
 	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), 0);
 		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,
 				 pgprot_t prot)
 {
 	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, prot);
 		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,
 			    unsigned long size, unsigned long flags)
 {
 	unsigned long addr = start;
 	unsigned long next, end = start + size;
 	unsigned long phys_addr = __pfn_to_phys(pfn);
 	pgprot_t prot = __pgprot(L_PTE_PRESENT | L_PTE_YOUNG |
 				 L_PTE_DIRTY | L_PTE_WRITE | flags);
 	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, prot);
 		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(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,
 		    unsigned long size, unsigned long flags)
 {
 	unsigned long prot, 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);

 	prot = PMD_TYPE_SECT | PMD_SECT_AP_WRITE | PMD_DOMAIN(DOMAIN_IO) |
 	       (flags & (L_PTE_CACHEABLE | L_PTE_BUFFERABLE));

 	/*
 	 * ARMv6 and above need XN set to prevent speculative prefetches
 	 * hitting IO.
 	 */
 	if (cpu_architecture() >= CPU_ARCH_ARMv6)
 		prot |= PMD_SECT_XN;

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

 		pmd[0] = __pmd(__pfn_to_phys(pfn) | prot);
 		pfn += SZ_1M >> PAGE_SHIFT;
 		pmd[1] = __pmd(__pfn_to_phys(pfn) | prot);
 		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,
 			 unsigned long size, unsigned long flags)
 {
 	unsigned long prot, 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);

 	prot = PMD_TYPE_SECT | PMD_SECT_SUPER | PMD_SECT_AP_WRITE |
 			PMD_DOMAIN(DOMAIN_IO) |
 			(flags & (L_PTE_CACHEABLE | L_PTE_BUFFERABLE));

 	/*
 	 * ARMv6 and above need XN set to prevent speculative prefetches
 	 * hitting IO.
 	 */
 	if (cpu_architecture() >= CPU_ARCH_ARMv6)
 		prot |= PMD_SECT_XN;

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

 		super_pmd_val = __pfn_to_phys(pfn) | prot;
 		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 include/asm-arm/proc-armv/pgtable.h for more information.
  */
 void __iomem *
 __ioremap_pfn(unsigned long pfn, unsigned long offset, size_t size,
 	      unsigned long flags)
 {
 	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;

 	size = PAGE_ALIGN(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_to_phys(pfn) | size | addr) & ~SUPERSECTION_MASK)) {
 		area->flags |= VM_ARM_SECTION_MAPPING;
 		err = remap_area_supersections(addr, pfn, size, flags);
 	} else if (!((__pfn_to_phys(pfn) | size | addr) & ~PMD_MASK)) {
 		area->flags |= VM_ARM_SECTION_MAPPING;
 		err = remap_area_sections(addr, pfn, size, flags);
 	} else
 #endif
 		err = remap_area_pages(addr, pfn, size, flags);

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

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

 void __iomem *
 __ioremap(unsigned long phys_addr, size_t size, unsigned long flags)
 {
 	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;

 	/*
  	 * Page align the mapping size
 	 */
 	size = PAGE_ALIGN(last_addr + 1) - phys_addr;

  	return __ioremap_pfn(pfn, offset, size, flags);
 }
 EXPORT_SYMBOL(__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 subysystem 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);
	/*
	* 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>

	/*
	* 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, pgprot_t prot)
	{
	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), 0);
	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,
	pgprot_t prot)
	{
	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, prot);
	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,
	unsigned long size, unsigned long flags)
	{
	unsigned long addr = start;
	unsigned long next, end = start + size;
	unsigned long phys_addr = __pfn_to_phys(pfn);
	pgprot_t prot = __pgprot(L_PTE_PRESENT \| L_PTE_YOUNG \|
	L_PTE_DIRTY \| L_PTE_WRITE \| flags);
	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, prot);
	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(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,
	unsigned long size, unsigned long flags)
	{
	unsigned long prot, 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);

	prot = PMD_TYPE_SECT \| PMD_SECT_AP_WRITE \| PMD_DOMAIN(DOMAIN_IO) \|
	(flags & (L_PTE_CACHEABLE \| L_PTE_BUFFERABLE));

	/*
	* ARMv6 and above need XN set to prevent speculative prefetches
	* hitting IO.
	*/
	if (cpu_architecture() >= CPU_ARCH_ARMv6)
	prot \|= PMD_SECT_XN;

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

	pmd[0] = __pmd(__pfn_to_phys(pfn) \| prot);
	pfn += SZ_1M >> PAGE_SHIFT;
	pmd[1] = __pmd(__pfn_to_phys(pfn) \| prot);
	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,
	unsigned long size, unsigned long flags)
	{
	unsigned long prot, 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);

	prot = PMD_TYPE_SECT \| PMD_SECT_SUPER \| PMD_SECT_AP_WRITE \|
	PMD_DOMAIN(DOMAIN_IO) \|
	(flags & (L_PTE_CACHEABLE \| L_PTE_BUFFERABLE));

	/*
	* ARMv6 and above need XN set to prevent speculative prefetches
	* hitting IO.
	*/
	if (cpu_architecture() >= CPU_ARCH_ARMv6)
	prot \|= PMD_SECT_XN;

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

	super_pmd_val = __pfn_to_phys(pfn) \| prot;
	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 include/asm-arm/proc-armv/pgtable.h for more information.
	*/
	void __iomem *
	__ioremap_pfn(unsigned long pfn, unsigned long offset, size_t size,
	unsigned long flags)
	{
	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;

	size = PAGE_ALIGN(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_to_phys(pfn) \| size \| addr) & ~SUPERSECTION_MASK)) {
	area->flags \|= VM_ARM_SECTION_MAPPING;
	err = remap_area_supersections(addr, pfn, size, flags);
	} else if (!((__pfn_to_phys(pfn) \| size \| addr) & ~PMD_MASK)) {
	area->flags \|= VM_ARM_SECTION_MAPPING;
	err = remap_area_sections(addr, pfn, size, flags);
	} else
	#endif
	err = remap_area_pages(addr, pfn, size, flags);

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

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

	void __iomem *
	__ioremap(unsigned long phys_addr, size_t size, unsigned long flags)
	{
	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;

	/*
	* Page align the mapping size
	*/
	size = PAGE_ALIGN(last_addr + 1) - phys_addr;

	return __ioremap_pfn(pfn, offset, size, flags);
	}
	EXPORT_SYMBOL(__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 subysystem 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);