arch/arm/mm/consistent.c - kernel/msm-4.19 - Gitiles

 /*
  *  linux/arch/arm/mm/consistent.c
  *
  *  Copyright (C) 2000-2004 Russell King
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 as
  * published by the Free Software Foundation.
  *
  *  DMA uncached mapping support.
  */
 #include <linux/module.h>
 #include <linux/mm.h>
 #include <linux/slab.h>
 #include <linux/errno.h>
 #include <linux/list.h>
 #include <linux/init.h>
 #include <linux/device.h>
 #include <linux/dma-mapping.h>

 #include <asm/memory.h>
 #include <asm/cacheflush.h>
 #include <asm/tlbflush.h>
 #include <asm/sizes.h>

 /* Sanity check size */
 #if (CONSISTENT_DMA_SIZE % SZ_2M)
 #error "CONSISTENT_DMA_SIZE must be multiple of 2MiB"
 #endif

 #define CONSISTENT_END	(0xffe00000)
 #define CONSISTENT_BASE	(CONSISTENT_END - CONSISTENT_DMA_SIZE)

 #define CONSISTENT_OFFSET(x)	(((unsigned long)(x) - CONSISTENT_BASE) >> PAGE_SHIFT)
 #define CONSISTENT_PTE_INDEX(x) (((unsigned long)(x) - CONSISTENT_BASE) >> PGDIR_SHIFT)
 #define NUM_CONSISTENT_PTES (CONSISTENT_DMA_SIZE >> PGDIR_SHIFT)


 /*
  * These are the page tables (2MB each) covering uncached, DMA consistent allocations
  */
 static pte_t *consistent_pte[NUM_CONSISTENT_PTES];
 static DEFINE_SPINLOCK(consistent_lock);

 /*
  * VM region handling support.
  *
  * This should become something generic, handling VM region allocations for
  * vmalloc and similar (ioremap, module space, etc).
  *
  * I envisage vmalloc()'s supporting vm_struct becoming:
  *
  *  struct vm_struct {
  *    struct vm_region	region;
  *    unsigned long	flags;
  *    struct page	**pages;
  *    unsigned int	nr_pages;
  *    unsigned long	phys_addr;
  *  };
  *
  * get_vm_area() would then call vm_region_alloc with an appropriate
  * struct vm_region head (eg):
  *
  *  struct vm_region vmalloc_head = {
  *	.vm_list	= LIST_HEAD_INIT(vmalloc_head.vm_list),
  *	.vm_start	= VMALLOC_START,
  *	.vm_end		= VMALLOC_END,
  *  };
  *
  * However, vmalloc_head.vm_start is variable (typically, it is dependent on
  * the amount of RAM found at boot time.)  I would imagine that get_vm_area()
  * would have to initialise this each time prior to calling vm_region_alloc().
  */
 struct vm_region {
 	struct list_head	vm_list;
 	unsigned long		vm_start;
 	unsigned long		vm_end;
 	struct page		*vm_pages;
 	int			vm_active;
 };

 static struct vm_region consistent_head = {
 	.vm_list	= LIST_HEAD_INIT(consistent_head.vm_list),
 	.vm_start	= CONSISTENT_BASE,
 	.vm_end		= CONSISTENT_END,
 };

 static struct vm_region *
 vm_region_alloc(struct vm_region *head, size_t size, gfp_t gfp)
 {
 	unsigned long addr = head->vm_start, end = head->vm_end - size;
 	unsigned long flags;
 	struct vm_region *c, *new;

 	new = kmalloc(sizeof(struct vm_region), gfp);
 	if (!new)
 		goto out;

 	spin_lock_irqsave(&consistent_lock, flags);

 	list_for_each_entry(c, &head->vm_list, vm_list) {
 		if ((addr + size) < addr)
 			goto nospc;
 		if ((addr + size) <= c->vm_start)
 			goto found;
 		addr = c->vm_end;
 		if (addr > end)
 			goto nospc;
 	}

  found:
 	/*
 	 * Insert this entry _before_ the one we found.
 	 */
 	list_add_tail(&new->vm_list, &c->vm_list);
 	new->vm_start = addr;
 	new->vm_end = addr + size;
 	new->vm_active = 1;

 	spin_unlock_irqrestore(&consistent_lock, flags);
 	return new;

  nospc:
 	spin_unlock_irqrestore(&consistent_lock, flags);
 	kfree(new);
  out:
 	return NULL;
 }

 static struct vm_region *vm_region_find(struct vm_region *head, unsigned long addr)
 {
 	struct vm_region *c;

 	list_for_each_entry(c, &head->vm_list, vm_list) {
 		if (c->vm_active && c->vm_start == addr)
 			goto out;
 	}
 	c = NULL;
  out:
 	return c;
 }

 #ifdef CONFIG_HUGETLB_PAGE
 #error ARM Coherent DMA allocator does not (yet) support huge TLB
 #endif

 static void *
 __dma_alloc(struct device *dev, size_t size, dma_addr_t *handle, gfp_t gfp,
 	    pgprot_t prot)
 {
 	struct page *page;
 	struct vm_region *c;
 	unsigned long order;
 	u64 mask = ISA_DMA_THRESHOLD, limit;

 	if (!consistent_pte[0]) {
 		printk(KERN_ERR "%s: not initialised\n", __func__);
 		dump_stack();
 		return NULL;
 	}

 	if (dev) {
 		mask = dev->coherent_dma_mask;

 		/*
 		 * Sanity check the DMA mask - it must be non-zero, and
 		 * must be able to be satisfied by a DMA allocation.
 		 */
 		if (mask == 0) {
 			dev_warn(dev, "coherent DMA mask is unset\n");
 			goto no_page;
 		}

 		if ((~mask) & ISA_DMA_THRESHOLD) {
 			dev_warn(dev, "coherent DMA mask %#llx is smaller "
 				 "than system GFP_DMA mask %#llx\n",
 				 mask, (unsigned long long)ISA_DMA_THRESHOLD);
 			goto no_page;
 		}
 	}

 	/*
 	 * Sanity check the allocation size.
 	 */
 	size = PAGE_ALIGN(size);
 	limit = (mask + 1) & ~mask;
 	if ((limit && size >= limit) ||
 	    size >= (CONSISTENT_END - CONSISTENT_BASE)) {
 		printk(KERN_WARNING "coherent allocation too big "
 		       "(requested %#x mask %#llx)\n", size, mask);
 		goto no_page;
 	}

 	order = get_order(size);

 	if (mask != 0xffffffff)
 		gfp |= GFP_DMA;

 	page = alloc_pages(gfp, order);
 	if (!page)
 		goto no_page;

 	/*
 	 * Invalidate any data that might be lurking in the
 	 * kernel direct-mapped region for device DMA.
 	 */
 	{
 		unsigned long kaddr = (unsigned long)page_address(page);
 		memset(page_address(page), 0, size);
 		dmac_flush_range(kaddr, kaddr + size);
 	}

 	/*
 	 * Allocate a virtual address in the consistent mapping region.
 	 */
 	c = vm_region_alloc(&consistent_head, size,
 			    gfp & ~(__GFP_DMA | __GFP_HIGHMEM));
 	if (c) {
 		pte_t *pte;
 		struct page *end = page + (1 << order);
 		int idx = CONSISTENT_PTE_INDEX(c->vm_start);
 		u32 off = CONSISTENT_OFFSET(c->vm_start) & (PTRS_PER_PTE-1);

 		pte = consistent_pte[idx] + off;
 		c->vm_pages = page;

 		split_page(page, order);

 		/*
 		 * Set the "dma handle"
 		 */
 		*handle = page_to_dma(dev, page);

 		do {
 			BUG_ON(!pte_none(*pte));

 			/*
 			 * x86 does not mark the pages reserved...
 			 */
 			SetPageReserved(page);
 			set_pte(pte, mk_pte(page, prot));
 			page++;
 			pte++;
 			off++;
 			if (off >= PTRS_PER_PTE) {
 				off = 0;
 				pte = consistent_pte[++idx];
 			}
 		} while (size -= PAGE_SIZE);

 		/*
 		 * Free the otherwise unused pages.
 		 */
 		while (page < end) {
 			__free_page(page);
 			page++;
 		}

 		return (void *)c->vm_start;
 	}

 	if (page)
 		__free_pages(page, order);
  no_page:
 	*handle = ~0;
 	return NULL;
 }

 /*
  * Allocate DMA-coherent memory space and return both the kernel remapped
  * virtual and bus address for that space.
  */
 void *
 dma_alloc_coherent(struct device *dev, size_t size, dma_addr_t *handle, gfp_t gfp)
 {
 	if (arch_is_coherent()) {
 		void *virt;

 		virt = kmalloc(size, gfp);
 		if (!virt)
 			return NULL;
 		*handle =  virt_to_dma(dev, virt);

 		return virt;
 	}

 	return __dma_alloc(dev, size, handle, gfp,
 			   pgprot_noncached(pgprot_kernel));
 }
 EXPORT_SYMBOL(dma_alloc_coherent);

 /*
  * Allocate a writecombining region, in much the same way as
  * dma_alloc_coherent above.
  */
 void *
 dma_alloc_writecombine(struct device *dev, size_t size, dma_addr_t *handle, gfp_t gfp)
 {
 	return __dma_alloc(dev, size, handle, gfp,
 			   pgprot_writecombine(pgprot_kernel));
 }
 EXPORT_SYMBOL(dma_alloc_writecombine);

 static int dma_mmap(struct device *dev, struct vm_area_struct *vma,
 		    void *cpu_addr, dma_addr_t dma_addr, size_t size)
 {
 	unsigned long flags, user_size, kern_size;
 	struct vm_region *c;
 	int ret = -ENXIO;

 	user_size = (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;

 	spin_lock_irqsave(&consistent_lock, flags);
 	c = vm_region_find(&consistent_head, (unsigned long)cpu_addr);
 	spin_unlock_irqrestore(&consistent_lock, flags);

 	if (c) {
 		unsigned long off = vma->vm_pgoff;

 		kern_size = (c->vm_end - c->vm_start) >> PAGE_SHIFT;

 		if (off < kern_size &&
 		    user_size <= (kern_size - off)) {
 			vma->vm_flags |= VM_RESERVED;
 			ret = remap_pfn_range(vma, vma->vm_start,
 					      page_to_pfn(c->vm_pages) + off,
 					      user_size << PAGE_SHIFT,
 					      vma->vm_page_prot);
 		}
 	}

 	return ret;
 }

 int dma_mmap_coherent(struct device *dev, struct vm_area_struct *vma,
 		      void *cpu_addr, dma_addr_t dma_addr, size_t size)
 {
 	vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
 	return dma_mmap(dev, vma, cpu_addr, dma_addr, size);
 }
 EXPORT_SYMBOL(dma_mmap_coherent);

 int dma_mmap_writecombine(struct device *dev, struct vm_area_struct *vma,
 			  void *cpu_addr, dma_addr_t dma_addr, size_t size)
 {
 	vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot);
 	return dma_mmap(dev, vma, cpu_addr, dma_addr, size);
 }
 EXPORT_SYMBOL(dma_mmap_writecombine);

 /*
  * free a page as defined by the above mapping.
  * Must not be called with IRQs disabled.
  */
 void dma_free_coherent(struct device *dev, size_t size, void *cpu_addr, dma_addr_t handle)
 {
 	struct vm_region *c;
 	unsigned long flags, addr;
 	pte_t *ptep;
 	int idx;
 	u32 off;

 	WARN_ON(irqs_disabled());

 	if (arch_is_coherent()) {
 		kfree(cpu_addr);
 		return;
 	}

 	size = PAGE_ALIGN(size);

 	spin_lock_irqsave(&consistent_lock, flags);
 	c = vm_region_find(&consistent_head, (unsigned long)cpu_addr);
 	if (!c)
 		goto no_area;

 	c->vm_active = 0;
 	spin_unlock_irqrestore(&consistent_lock, flags);

 	if ((c->vm_end - c->vm_start) != size) {
 		printk(KERN_ERR "%s: freeing wrong coherent size (%ld != %d)\n",
 		       __func__, c->vm_end - c->vm_start, size);
 		dump_stack();
 		size = c->vm_end - c->vm_start;
 	}

 	idx = CONSISTENT_PTE_INDEX(c->vm_start);
 	off = CONSISTENT_OFFSET(c->vm_start) & (PTRS_PER_PTE-1);
 	ptep = consistent_pte[idx] + off;
 	addr = c->vm_start;
 	do {
 		pte_t pte = ptep_get_and_clear(&init_mm, addr, ptep);
 		unsigned long pfn;

 		ptep++;
 		addr += PAGE_SIZE;
 		off++;
 		if (off >= PTRS_PER_PTE) {
 			off = 0;
 			ptep = consistent_pte[++idx];
 		}

 		if (!pte_none(pte) && pte_present(pte)) {
 			pfn = pte_pfn(pte);

 			if (pfn_valid(pfn)) {
 				struct page *page = pfn_to_page(pfn);

 				/*
 				 * x86 does not mark the pages reserved...
 				 */
 				ClearPageReserved(page);

 				__free_page(page);
 				continue;
 			}
 		}

 		printk(KERN_CRIT "%s: bad page in kernel page table\n",
 		       __func__);
 	} while (size -= PAGE_SIZE);

 	flush_tlb_kernel_range(c->vm_start, c->vm_end);

 	spin_lock_irqsave(&consistent_lock, flags);
 	list_del(&c->vm_list);
 	spin_unlock_irqrestore(&consistent_lock, flags);

 	kfree(c);
 	return;

  no_area:
 	spin_unlock_irqrestore(&consistent_lock, flags);
 	printk(KERN_ERR "%s: trying to free invalid coherent area: %p\n",
 	       __func__, cpu_addr);
 	dump_stack();
 }
 EXPORT_SYMBOL(dma_free_coherent);

 /*
  * Initialise the consistent memory allocation.
  */
 static int __init consistent_init(void)
 {
 	pgd_t *pgd;
 	pmd_t *pmd;
 	pte_t *pte;
 	int ret = 0, i = 0;
 	u32 base = CONSISTENT_BASE;

 	do {
 		pgd = pgd_offset(&init_mm, base);
 		pmd = pmd_alloc(&init_mm, pgd, base);
 		if (!pmd) {
 			printk(KERN_ERR "%s: no pmd tables\n", __func__);
 			ret = -ENOMEM;
 			break;
 		}
 		WARN_ON(!pmd_none(*pmd));

 		pte = pte_alloc_kernel(pmd, base);
 		if (!pte) {
 			printk(KERN_ERR "%s: no pte tables\n", __func__);
 			ret = -ENOMEM;
 			break;
 		}

 		consistent_pte[i++] = pte;
 		base += (1 << PGDIR_SHIFT);
 	} while (base < CONSISTENT_END);

 	return ret;
 }

 core_initcall(consistent_init);

 /*
  * Make an area consistent for devices.
  * Note: Drivers should NOT use this function directly, as it will break
  * platforms with CONFIG_DMABOUNCE.
  * Use the driver DMA support - see dma-mapping.h (dma_sync_*)
  */
 void consistent_sync(void *vaddr, size_t size, int direction)
 {
 	unsigned long start = (unsigned long)vaddr;
 	unsigned long end   = start + size;

 	switch (direction) {
 	case DMA_FROM_DEVICE:		/* invalidate only */
 		dmac_inv_range(start, end);
 		break;
 	case DMA_TO_DEVICE:		/* writeback only */
 		dmac_clean_range(start, end);
 		break;
 	case DMA_BIDIRECTIONAL:		/* writeback and invalidate */
 		dmac_flush_range(start, end);
 		break;
 	default:
 		BUG();
 	}
 }
 EXPORT_SYMBOL(consistent_sync);
	/*
	* linux/arch/arm/mm/consistent.c
	*
	* Copyright (C) 2000-2004 Russell King
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License version 2 as
	* published by the Free Software Foundation.
	*
	* DMA uncached mapping support.
	*/
	#include <linux/module.h>
	#include <linux/mm.h>
	#include <linux/slab.h>
	#include <linux/errno.h>
	#include <linux/list.h>
	#include <linux/init.h>
	#include <linux/device.h>
	#include <linux/dma-mapping.h>

	#include <asm/memory.h>
	#include <asm/cacheflush.h>
	#include <asm/tlbflush.h>
	#include <asm/sizes.h>

	/* Sanity check size */
	#if (CONSISTENT_DMA_SIZE % SZ_2M)
	#error "CONSISTENT_DMA_SIZE must be multiple of 2MiB"
	#endif

	#define CONSISTENT_END (0xffe00000)
	#define CONSISTENT_BASE (CONSISTENT_END - CONSISTENT_DMA_SIZE)

	#define CONSISTENT_OFFSET(x) (((unsigned long)(x) - CONSISTENT_BASE) >> PAGE_SHIFT)
	#define CONSISTENT_PTE_INDEX(x) (((unsigned long)(x) - CONSISTENT_BASE) >> PGDIR_SHIFT)
	#define NUM_CONSISTENT_PTES (CONSISTENT_DMA_SIZE >> PGDIR_SHIFT)


	/*
	* These are the page tables (2MB each) covering uncached, DMA consistent allocations
	*/
	static pte_t *consistent_pte[NUM_CONSISTENT_PTES];
	static DEFINE_SPINLOCK(consistent_lock);

	/*
	* VM region handling support.
	*
	* This should become something generic, handling VM region allocations for
	* vmalloc and similar (ioremap, module space, etc).
	*
	* I envisage vmalloc()'s supporting vm_struct becoming:
	*
	* struct vm_struct {
	* struct vm_region region;
	* unsigned long flags;
	* struct page **pages;
	* unsigned int nr_pages;
	* unsigned long phys_addr;
	* };
	*
	* get_vm_area() would then call vm_region_alloc with an appropriate
	* struct vm_region head (eg):
	*
	* struct vm_region vmalloc_head = {
	* .vm_list = LIST_HEAD_INIT(vmalloc_head.vm_list),
	* .vm_start = VMALLOC_START,
	* .vm_end = VMALLOC_END,
	* };
	*
	* However, vmalloc_head.vm_start is variable (typically, it is dependent on
	* the amount of RAM found at boot time.) I would imagine that get_vm_area()
	* would have to initialise this each time prior to calling vm_region_alloc().
	*/
	struct vm_region {
	struct list_head vm_list;
	unsigned long vm_start;
	unsigned long vm_end;
	struct page *vm_pages;
	int vm_active;
	};

	static struct vm_region consistent_head = {
	.vm_list = LIST_HEAD_INIT(consistent_head.vm_list),
	.vm_start = CONSISTENT_BASE,
	.vm_end = CONSISTENT_END,
	};

	static struct vm_region *
	vm_region_alloc(struct vm_region *head, size_t size, gfp_t gfp)
	{
	unsigned long addr = head->vm_start, end = head->vm_end - size;
	unsigned long flags;
	struct vm_region c, new;

	new = kmalloc(sizeof(struct vm_region), gfp);
	if (!new)
	goto out;

	spin_lock_irqsave(&consistent_lock, flags);

	list_for_each_entry(c, &head->vm_list, vm_list) {
	if ((addr + size) < addr)
	goto nospc;
	if ((addr + size) <= c->vm_start)
	goto found;
	addr = c->vm_end;
	if (addr > end)
	goto nospc;
	}

	found:
	/*
	* Insert this entry _before_ the one we found.
	*/
	list_add_tail(&new->vm_list, &c->vm_list);
	new->vm_start = addr;
	new->vm_end = addr + size;
	new->vm_active = 1;

	spin_unlock_irqrestore(&consistent_lock, flags);
	return new;

	nospc:
	spin_unlock_irqrestore(&consistent_lock, flags);
	kfree(new);
	out:
	return NULL;
	}

	static struct vm_region vm_region_find(struct vm_region head, unsigned long addr)
	{
	struct vm_region *c;

	list_for_each_entry(c, &head->vm_list, vm_list) {
	if (c->vm_active && c->vm_start == addr)
	goto out;
	}
	c = NULL;
	out:
	return c;
	}

	#ifdef CONFIG_HUGETLB_PAGE
	#error ARM Coherent DMA allocator does not (yet) support huge TLB
	#endif

	static void *
	__dma_alloc(struct device dev, size_t size, dma_addr_t handle, gfp_t gfp,
	pgprot_t prot)
	{
	struct page *page;
	struct vm_region *c;
	unsigned long order;
	u64 mask = ISA_DMA_THRESHOLD, limit;

	if (!consistent_pte[0]) {
	printk(KERN_ERR "%s: not initialised\n", __func__);
	dump_stack();
	return NULL;
	}

	if (dev) {
	mask = dev->coherent_dma_mask;

	/*
	* Sanity check the DMA mask - it must be non-zero, and
	* must be able to be satisfied by a DMA allocation.
	*/
	if (mask == 0) {
	dev_warn(dev, "coherent DMA mask is unset\n");
	goto no_page;
	}

	if ((~mask) & ISA_DMA_THRESHOLD) {
	dev_warn(dev, "coherent DMA mask %#llx is smaller "
	"than system GFP_DMA mask %#llx\n",
	mask, (unsigned long long)ISA_DMA_THRESHOLD);
	goto no_page;
	}
	}

	/*
	* Sanity check the allocation size.
	*/
	size = PAGE_ALIGN(size);
	limit = (mask + 1) & ~mask;
	if ((limit && size >= limit) \|\|
	size >= (CONSISTENT_END - CONSISTENT_BASE)) {
	printk(KERN_WARNING "coherent allocation too big "
	"(requested %#x mask %#llx)\n", size, mask);
	goto no_page;
	}

	order = get_order(size);

	if (mask != 0xffffffff)
	gfp \|= GFP_DMA;

	page = alloc_pages(gfp, order);
	if (!page)
	goto no_page;

	/*
	* Invalidate any data that might be lurking in the
	* kernel direct-mapped region for device DMA.
	*/
	{
	unsigned long kaddr = (unsigned long)page_address(page);
	memset(page_address(page), 0, size);
	dmac_flush_range(kaddr, kaddr + size);
	}

	/*
	* Allocate a virtual address in the consistent mapping region.
	*/
	c = vm_region_alloc(&consistent_head, size,
	gfp & ~(__GFP_DMA \| __GFP_HIGHMEM));
	if (c) {
	pte_t *pte;
	struct page *end = page + (1 << order);
	int idx = CONSISTENT_PTE_INDEX(c->vm_start);
	u32 off = CONSISTENT_OFFSET(c->vm_start) & (PTRS_PER_PTE-1);

	pte = consistent_pte[idx] + off;
	c->vm_pages = page;

	split_page(page, order);

	/*
	* Set the "dma handle"
	*/
	*handle = page_to_dma(dev, page);

	do {
	BUG_ON(!pte_none(*pte));

	/*
	* x86 does not mark the pages reserved...
	*/
	SetPageReserved(page);
	set_pte(pte, mk_pte(page, prot));
	page++;
	pte++;
	off++;
	if (off >= PTRS_PER_PTE) {
	off = 0;
	pte = consistent_pte[++idx];
	}
	} while (size -= PAGE_SIZE);

	/*
	* Free the otherwise unused pages.
	*/
	while (page < end) {
	__free_page(page);
	page++;
	}

	return (void *)c->vm_start;
	}

	if (page)
	__free_pages(page, order);
	no_page:
	*handle = ~0;
	return NULL;
	}

	/*
	* Allocate DMA-coherent memory space and return both the kernel remapped
	* virtual and bus address for that space.
	*/
	void *
	dma_alloc_coherent(struct device dev, size_t size, dma_addr_t handle, gfp_t gfp)
	{
	if (arch_is_coherent()) {
	void *virt;

	virt = kmalloc(size, gfp);
	if (!virt)
	return NULL;
	*handle = virt_to_dma(dev, virt);

	return virt;
	}

	return __dma_alloc(dev, size, handle, gfp,
	pgprot_noncached(pgprot_kernel));
	}
	EXPORT_SYMBOL(dma_alloc_coherent);

	/*
	* Allocate a writecombining region, in much the same way as
	* dma_alloc_coherent above.
	*/
	void *
	dma_alloc_writecombine(struct device dev, size_t size, dma_addr_t handle, gfp_t gfp)
	{
	return __dma_alloc(dev, size, handle, gfp,
	pgprot_writecombine(pgprot_kernel));
	}
	EXPORT_SYMBOL(dma_alloc_writecombine);

	static int dma_mmap(struct device dev, struct vm_area_struct vma,
	void *cpu_addr, dma_addr_t dma_addr, size_t size)
	{
	unsigned long flags, user_size, kern_size;
	struct vm_region *c;
	int ret = -ENXIO;

	user_size = (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;

	spin_lock_irqsave(&consistent_lock, flags);
	c = vm_region_find(&consistent_head, (unsigned long)cpu_addr);
	spin_unlock_irqrestore(&consistent_lock, flags);

	if (c) {
	unsigned long off = vma->vm_pgoff;

	kern_size = (c->vm_end - c->vm_start) >> PAGE_SHIFT;

	if (off < kern_size &&
	user_size <= (kern_size - off)) {
	vma->vm_flags \|= VM_RESERVED;
	ret = remap_pfn_range(vma, vma->vm_start,
	page_to_pfn(c->vm_pages) + off,
	user_size << PAGE_SHIFT,
	vma->vm_page_prot);
	}
	}

	return ret;
	}

	int dma_mmap_coherent(struct device dev, struct vm_area_struct vma,
	void *cpu_addr, dma_addr_t dma_addr, size_t size)
	{
	vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
	return dma_mmap(dev, vma, cpu_addr, dma_addr, size);
	}
	EXPORT_SYMBOL(dma_mmap_coherent);

	int dma_mmap_writecombine(struct device dev, struct vm_area_struct vma,
	void *cpu_addr, dma_addr_t dma_addr, size_t size)
	{
	vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot);
	return dma_mmap(dev, vma, cpu_addr, dma_addr, size);
	}
	EXPORT_SYMBOL(dma_mmap_writecombine);

	/*
	* free a page as defined by the above mapping.
	* Must not be called with IRQs disabled.
	*/
	void dma_free_coherent(struct device dev, size_t size, void cpu_addr, dma_addr_t handle)
	{
	struct vm_region *c;
	unsigned long flags, addr;
	pte_t *ptep;
	int idx;
	u32 off;

	WARN_ON(irqs_disabled());

	if (arch_is_coherent()) {
	kfree(cpu_addr);
	return;
	}

	size = PAGE_ALIGN(size);

	spin_lock_irqsave(&consistent_lock, flags);
	c = vm_region_find(&consistent_head, (unsigned long)cpu_addr);
	if (!c)
	goto no_area;

	c->vm_active = 0;
	spin_unlock_irqrestore(&consistent_lock, flags);

	if ((c->vm_end - c->vm_start) != size) {
	printk(KERN_ERR "%s: freeing wrong coherent size (%ld != %d)\n",
	__func__, c->vm_end - c->vm_start, size);
	dump_stack();
	size = c->vm_end - c->vm_start;
	}

	idx = CONSISTENT_PTE_INDEX(c->vm_start);
	off = CONSISTENT_OFFSET(c->vm_start) & (PTRS_PER_PTE-1);
	ptep = consistent_pte[idx] + off;
	addr = c->vm_start;
	do {
	pte_t pte = ptep_get_and_clear(&init_mm, addr, ptep);
	unsigned long pfn;

	ptep++;
	addr += PAGE_SIZE;
	off++;
	if (off >= PTRS_PER_PTE) {
	off = 0;
	ptep = consistent_pte[++idx];
	}

	if (!pte_none(pte) && pte_present(pte)) {
	pfn = pte_pfn(pte);

	if (pfn_valid(pfn)) {
	struct page *page = pfn_to_page(pfn);

	/*
	* x86 does not mark the pages reserved...
	*/
	ClearPageReserved(page);

	__free_page(page);
	continue;
	}
	}

	printk(KERN_CRIT "%s: bad page in kernel page table\n",
	__func__);
	} while (size -= PAGE_SIZE);

	flush_tlb_kernel_range(c->vm_start, c->vm_end);

	spin_lock_irqsave(&consistent_lock, flags);
	list_del(&c->vm_list);
	spin_unlock_irqrestore(&consistent_lock, flags);

	kfree(c);
	return;

	no_area:
	spin_unlock_irqrestore(&consistent_lock, flags);
	printk(KERN_ERR "%s: trying to free invalid coherent area: %p\n",
	__func__, cpu_addr);
	dump_stack();
	}
	EXPORT_SYMBOL(dma_free_coherent);

	/*
	* Initialise the consistent memory allocation.
	*/
	static int __init consistent_init(void)
	{
	pgd_t *pgd;
	pmd_t *pmd;
	pte_t *pte;
	int ret = 0, i = 0;
	u32 base = CONSISTENT_BASE;

	do {
	pgd = pgd_offset(&init_mm, base);
	pmd = pmd_alloc(&init_mm, pgd, base);
	if (!pmd) {
	printk(KERN_ERR "%s: no pmd tables\n", __func__);
	ret = -ENOMEM;
	break;
	}
	WARN_ON(!pmd_none(*pmd));

	pte = pte_alloc_kernel(pmd, base);
	if (!pte) {
	printk(KERN_ERR "%s: no pte tables\n", __func__);
	ret = -ENOMEM;
	break;
	}

	consistent_pte[i++] = pte;
	base += (1 << PGDIR_SHIFT);
	} while (base < CONSISTENT_END);

	return ret;
	}

	core_initcall(consistent_init);

	/*
	* Make an area consistent for devices.
	* Note: Drivers should NOT use this function directly, as it will break
	* platforms with CONFIG_DMABOUNCE.
	* Use the driver DMA support - see dma-mapping.h (dma_sync_*)
	*/
	void consistent_sync(void *vaddr, size_t size, int direction)
	{
	unsigned long start = (unsigned long)vaddr;
	unsigned long end = start + size;

	switch (direction) {
	case DMA_FROM_DEVICE: /* invalidate only */
	dmac_inv_range(start, end);
	break;
	case DMA_TO_DEVICE: /* writeback only */
	dmac_clean_range(start, end);
	break;
	case DMA_BIDIRECTIONAL: /* writeback and invalidate */
	dmac_flush_range(start, end);
	break;
	default:
	BUG();
	}
	}
	EXPORT_SYMBOL(consistent_sync);