kernel/dma/coherent.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /*
  * Coherent per-device memory handling.
  * Borrowed from i386
  */
 #include <linux/io.h>
 #include <linux/slab.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/dma-mapping.h>

 struct dma_coherent_mem {
 	void		*virt_base;
 	dma_addr_t	device_base;
 	unsigned long	pfn_base;
 	int		size;
 	int		flags;
 	unsigned long	*bitmap;
 	spinlock_t	spinlock;
 	bool		use_dev_dma_pfn_offset;
 };

 static struct dma_coherent_mem *dma_coherent_default_memory __ro_after_init;

 static inline struct dma_coherent_mem *dev_get_coherent_memory(struct device *dev)
 {
 	if (dev && dev->dma_mem)
 		return dev->dma_mem;
 	return NULL;
 }

 static inline dma_addr_t dma_get_device_base(struct device *dev,
 					     struct dma_coherent_mem * mem)
 {
 	if (mem->use_dev_dma_pfn_offset)
 		return (mem->pfn_base - dev->dma_pfn_offset) << PAGE_SHIFT;
 	else
 		return mem->device_base;
 }

 static int dma_init_coherent_memory(
 	phys_addr_t phys_addr, dma_addr_t device_addr, size_t size, int flags,
 	struct dma_coherent_mem **mem)
 {
 	struct dma_coherent_mem *dma_mem = NULL;
 	void __iomem *mem_base = NULL;
 	int pages = size >> PAGE_SHIFT;
 	int bitmap_size = BITS_TO_LONGS(pages) * sizeof(long);
 	int ret;

 	if (!size) {
 		ret = -EINVAL;
 		goto out;
 	}

 	mem_base = memremap(phys_addr, size, MEMREMAP_WC);
 	if (!mem_base) {
 		ret = -EINVAL;
 		goto out;
 	}
 	dma_mem = kzalloc(sizeof(struct dma_coherent_mem), GFP_KERNEL);
 	if (!dma_mem) {
 		ret = -ENOMEM;
 		goto out;
 	}
 	dma_mem->bitmap = kzalloc(bitmap_size, GFP_KERNEL);
 	if (!dma_mem->bitmap) {
 		ret = -ENOMEM;
 		goto out;
 	}

 	dma_mem->virt_base = mem_base;
 	dma_mem->device_base = device_addr;
 	dma_mem->pfn_base = PFN_DOWN(phys_addr);
 	dma_mem->size = pages;
 	dma_mem->flags = flags;
 	spin_lock_init(&dma_mem->spinlock);

 	*mem = dma_mem;
 	return 0;

 out:
 	kfree(dma_mem);
 	if (mem_base)
 		memunmap(mem_base);
 	return ret;
 }

 static void dma_release_coherent_memory(struct dma_coherent_mem *mem)
 {
 	if (!mem)
 		return;

 	memunmap(mem->virt_base);
 	kfree(mem->bitmap);
 	kfree(mem);
 }

 static int dma_assign_coherent_memory(struct device *dev,
 				      struct dma_coherent_mem *mem)
 {
 	if (!dev)
 		return -ENODEV;

 	if (dev->dma_mem)
 		return -EBUSY;

 	dev->dma_mem = mem;
 	return 0;
 }

 int dma_declare_coherent_memory(struct device *dev, phys_addr_t phys_addr,
 				dma_addr_t device_addr, size_t size, int flags)
 {
 	struct dma_coherent_mem *mem;
 	int ret;

 	ret = dma_init_coherent_memory(phys_addr, device_addr, size, flags, &mem);
 	if (ret)
 		return ret;

 	ret = dma_assign_coherent_memory(dev, mem);
 	if (ret)
 		dma_release_coherent_memory(mem);
 	return ret;
 }
 EXPORT_SYMBOL(dma_declare_coherent_memory);

 void dma_release_declared_memory(struct device *dev)
 {
 	struct dma_coherent_mem *mem = dev->dma_mem;

 	if (!mem)
 		return;
 	dma_release_coherent_memory(mem);
 	dev->dma_mem = NULL;
 }
 EXPORT_SYMBOL(dma_release_declared_memory);

 void *dma_mark_declared_memory_occupied(struct device *dev,
 					dma_addr_t device_addr, size_t size)
 {
 	struct dma_coherent_mem *mem = dev->dma_mem;
 	unsigned long flags;
 	int pos, err;

 	size += device_addr & ~PAGE_MASK;

 	if (!mem)
 		return ERR_PTR(-EINVAL);

 	spin_lock_irqsave(&mem->spinlock, flags);
 	pos = PFN_DOWN(device_addr - dma_get_device_base(dev, mem));
 	err = bitmap_allocate_region(mem->bitmap, pos, get_order(size));
 	spin_unlock_irqrestore(&mem->spinlock, flags);

 	if (err != 0)
 		return ERR_PTR(err);
 	return mem->virt_base + (pos << PAGE_SHIFT);
 }
 EXPORT_SYMBOL(dma_mark_declared_memory_occupied);

 static void *__dma_alloc_from_coherent(struct dma_coherent_mem *mem,
 		ssize_t size, dma_addr_t *dma_handle)
 {
 	int order = get_order(size);
 	unsigned long flags;
 	int pageno;
 	void *ret;

 	spin_lock_irqsave(&mem->spinlock, flags);

 	if (unlikely(size > (mem->size << PAGE_SHIFT)))
 		goto err;

 	pageno = bitmap_find_free_region(mem->bitmap, mem->size, order);
 	if (unlikely(pageno < 0))
 		goto err;

 	/*
 	 * Memory was found in the coherent area.
 	 */
 	*dma_handle = mem->device_base + (pageno << PAGE_SHIFT);
 	ret = mem->virt_base + (pageno << PAGE_SHIFT);
 	spin_unlock_irqrestore(&mem->spinlock, flags);
 	memset(ret, 0, size);
 	return ret;
 err:
 	spin_unlock_irqrestore(&mem->spinlock, flags);
 	return NULL;
 }

 /**
  * dma_alloc_from_dev_coherent() - allocate memory from device coherent pool
  * @dev:	device from which we allocate memory
  * @size:	size of requested memory area
  * @dma_handle:	This will be filled with the correct dma handle
  * @ret:	This pointer will be filled with the virtual address
  *		to allocated area.
  *
  * This function should be only called from per-arch dma_alloc_coherent()
  * to support allocation from per-device coherent memory pools.
  *
  * Returns 0 if dma_alloc_coherent should continue with allocating from
  * generic memory areas, or !0 if dma_alloc_coherent should return @ret.
  */
 int dma_alloc_from_dev_coherent(struct device *dev, ssize_t size,
 		dma_addr_t *dma_handle, void **ret)
 {
 	struct dma_coherent_mem *mem = dev_get_coherent_memory(dev);

 	if (!mem)
 		return 0;

 	*ret = __dma_alloc_from_coherent(mem, size, dma_handle);
 	if (*ret)
 		return 1;

 	/*
 	 * In the case where the allocation can not be satisfied from the
 	 * per-device area, try to fall back to generic memory if the
 	 * constraints allow it.
 	 */
 	return mem->flags & DMA_MEMORY_EXCLUSIVE;
 }

 void *dma_alloc_from_global_coherent(ssize_t size, dma_addr_t *dma_handle)
 {
 	if (!dma_coherent_default_memory)
 		return NULL;

 	return __dma_alloc_from_coherent(dma_coherent_default_memory, size,
 			dma_handle);
 }

 static int __dma_release_from_coherent(struct dma_coherent_mem *mem,
 				       int order, void *vaddr)
 {
 	if (mem && vaddr >= mem->virt_base && vaddr <
 		   (mem->virt_base + (mem->size << PAGE_SHIFT))) {
 		int page = (vaddr - mem->virt_base) >> PAGE_SHIFT;
 		unsigned long flags;

 		spin_lock_irqsave(&mem->spinlock, flags);
 		bitmap_release_region(mem->bitmap, page, order);
 		spin_unlock_irqrestore(&mem->spinlock, flags);
 		return 1;
 	}
 	return 0;
 }

 /**
  * dma_release_from_dev_coherent() - free memory to device coherent memory pool
  * @dev:	device from which the memory was allocated
  * @order:	the order of pages allocated
  * @vaddr:	virtual address of allocated pages
  *
  * This checks whether the memory was allocated from the per-device
  * coherent memory pool and if so, releases that memory.
  *
  * Returns 1 if we correctly released the memory, or 0 if the caller should
  * proceed with releasing memory from generic pools.
  */
 int dma_release_from_dev_coherent(struct device *dev, int order, void *vaddr)
 {
 	struct dma_coherent_mem *mem = dev_get_coherent_memory(dev);

 	return __dma_release_from_coherent(mem, order, vaddr);
 }

 int dma_release_from_global_coherent(int order, void *vaddr)
 {
 	if (!dma_coherent_default_memory)
 		return 0;

 	return __dma_release_from_coherent(dma_coherent_default_memory, order,
 			vaddr);
 }

 static int __dma_mmap_from_coherent(struct dma_coherent_mem *mem,
 		struct vm_area_struct *vma, void *vaddr, size_t size, int *ret)
 {
 	if (mem && vaddr >= mem->virt_base && vaddr + size <=
 		   (mem->virt_base + (mem->size << PAGE_SHIFT))) {
 		unsigned long off = vma->vm_pgoff;
 		int start = (vaddr - mem->virt_base) >> PAGE_SHIFT;
 		int user_count = vma_pages(vma);
 		int count = PAGE_ALIGN(size) >> PAGE_SHIFT;

 		*ret = -ENXIO;
 		if (off < count && user_count <= count - off) {
 			unsigned long pfn = mem->pfn_base + start + off;
 			*ret = remap_pfn_range(vma, vma->vm_start, pfn,
 					       user_count << PAGE_SHIFT,
 					       vma->vm_page_prot);
 		}
 		return 1;
 	}
 	return 0;
 }

 /**
  * dma_mmap_from_dev_coherent() - mmap memory from the device coherent pool
  * @dev:	device from which the memory was allocated
  * @vma:	vm_area for the userspace memory
  * @vaddr:	cpu address returned by dma_alloc_from_dev_coherent
  * @size:	size of the memory buffer allocated
  * @ret:	result from remap_pfn_range()
  *
  * This checks whether the memory was allocated from the per-device
  * coherent memory pool and if so, maps that memory to the provided vma.
  *
  * Returns 1 if @vaddr belongs to the device coherent pool and the caller
  * should return @ret, or 0 if they should proceed with mapping memory from
  * generic areas.
  */
 int dma_mmap_from_dev_coherent(struct device *dev, struct vm_area_struct *vma,
 			   void *vaddr, size_t size, int *ret)
 {
 	struct dma_coherent_mem *mem = dev_get_coherent_memory(dev);

 	return __dma_mmap_from_coherent(mem, vma, vaddr, size, ret);
 }
 EXPORT_SYMBOL(dma_mmap_from_dev_coherent);

 int dma_mmap_from_global_coherent(struct vm_area_struct *vma, void *vaddr,
 				   size_t size, int *ret)
 {
 	if (!dma_coherent_default_memory)
 		return 0;

 	return __dma_mmap_from_coherent(dma_coherent_default_memory, vma,
 					vaddr, size, ret);
 }

 /*
  * Support for reserved memory regions defined in device tree
  */
 #ifdef CONFIG_OF_RESERVED_MEM
 #include <linux/of.h>
 #include <linux/of_fdt.h>
 #include <linux/of_reserved_mem.h>

 static struct reserved_mem *dma_reserved_default_memory __initdata;

 static int rmem_dma_device_init(struct reserved_mem *rmem, struct device *dev)
 {
 	struct dma_coherent_mem *mem = rmem->priv;
 	int ret;

 	if (!mem) {
 		ret = dma_init_coherent_memory(rmem->base, rmem->base,
 					       rmem->size,
 					       DMA_MEMORY_EXCLUSIVE, &mem);
 		if (ret) {
 			pr_err("Reserved memory: failed to init DMA memory pool at %pa, size %ld MiB\n",
 				&rmem->base, (unsigned long)rmem->size / SZ_1M);
 			return ret;
 		}
 	}
 	mem->use_dev_dma_pfn_offset = true;
 	rmem->priv = mem;
 	dma_assign_coherent_memory(dev, mem);
 	return 0;
 }

 static void rmem_dma_device_release(struct reserved_mem *rmem,
 				    struct device *dev)
 {
 	if (dev)
 		dev->dma_mem = NULL;
 }

 static const struct reserved_mem_ops rmem_dma_ops = {
 	.device_init	= rmem_dma_device_init,
 	.device_release	= rmem_dma_device_release,
 };

 static int __init rmem_dma_setup(struct reserved_mem *rmem)
 {
 	unsigned long node = rmem->fdt_node;

 	if (of_get_flat_dt_prop(node, "reusable", NULL))
 		return -EINVAL;

 #ifdef CONFIG_ARM
 	if (!of_get_flat_dt_prop(node, "no-map", NULL)) {
 		pr_err("Reserved memory: regions without no-map are not yet supported\n");
 		return -EINVAL;
 	}

 	if (of_get_flat_dt_prop(node, "linux,dma-default", NULL)) {
 		WARN(dma_reserved_default_memory,
 		     "Reserved memory: region for default DMA coherent area is redefined\n");
 		dma_reserved_default_memory = rmem;
 	}
 #endif

 	rmem->ops = &rmem_dma_ops;
 	pr_info("Reserved memory: created DMA memory pool at %pa, size %ld MiB\n",
 		&rmem->base, (unsigned long)rmem->size / SZ_1M);
 	return 0;
 }

 static int __init dma_init_reserved_memory(void)
 {
 	const struct reserved_mem_ops *ops;
 	int ret;

 	if (!dma_reserved_default_memory)
 		return -ENOMEM;

 	ops = dma_reserved_default_memory->ops;

 	/*
 	 * We rely on rmem_dma_device_init() does not propagate error of
 	 * dma_assign_coherent_memory() for "NULL" device.
 	 */
 	ret = ops->device_init(dma_reserved_default_memory, NULL);

 	if (!ret) {
 		dma_coherent_default_memory = dma_reserved_default_memory->priv;
 		pr_info("DMA: default coherent area is set\n");
 	}

 	return ret;
 }

 core_initcall(dma_init_reserved_memory);

 RESERVEDMEM_OF_DECLARE(dma, "shared-dma-pool", rmem_dma_setup);
 #endif
	// SPDX-License-Identifier: GPL-2.0
	/*
	* Coherent per-device memory handling.
	* Borrowed from i386
	*/
	#include <linux/io.h>
	#include <linux/slab.h>
	#include <linux/kernel.h>
	#include <linux/module.h>
	#include <linux/dma-mapping.h>

	struct dma_coherent_mem {
	void *virt_base;
	dma_addr_t device_base;
	unsigned long pfn_base;
	int size;
	int flags;
	unsigned long *bitmap;
	spinlock_t spinlock;
	bool use_dev_dma_pfn_offset;
	};

	static struct dma_coherent_mem *dma_coherent_default_memory __ro_after_init;

	static inline struct dma_coherent_mem dev_get_coherent_memory(struct device dev)
	{
	if (dev && dev->dma_mem)
	return dev->dma_mem;
	return NULL;
	}

	static inline dma_addr_t dma_get_device_base(struct device *dev,
	struct dma_coherent_mem * mem)
	{
	if (mem->use_dev_dma_pfn_offset)
	return (mem->pfn_base - dev->dma_pfn_offset) << PAGE_SHIFT;
	else
	return mem->device_base;
	}

	static int dma_init_coherent_memory(
	phys_addr_t phys_addr, dma_addr_t device_addr, size_t size, int flags,
	struct dma_coherent_mem **mem)
	{
	struct dma_coherent_mem *dma_mem = NULL;
	void __iomem *mem_base = NULL;
	int pages = size >> PAGE_SHIFT;
	int bitmap_size = BITS_TO_LONGS(pages) * sizeof(long);
	int ret;

	if (!size) {
	ret = -EINVAL;
	goto out;
	}

	mem_base = memremap(phys_addr, size, MEMREMAP_WC);
	if (!mem_base) {
	ret = -EINVAL;
	goto out;
	}
	dma_mem = kzalloc(sizeof(struct dma_coherent_mem), GFP_KERNEL);
	if (!dma_mem) {
	ret = -ENOMEM;
	goto out;
	}
	dma_mem->bitmap = kzalloc(bitmap_size, GFP_KERNEL);
	if (!dma_mem->bitmap) {
	ret = -ENOMEM;
	goto out;
	}

	dma_mem->virt_base = mem_base;
	dma_mem->device_base = device_addr;
	dma_mem->pfn_base = PFN_DOWN(phys_addr);
	dma_mem->size = pages;
	dma_mem->flags = flags;
	spin_lock_init(&dma_mem->spinlock);

	*mem = dma_mem;
	return 0;

	out:
	kfree(dma_mem);
	if (mem_base)
	memunmap(mem_base);
	return ret;
	}

	static void dma_release_coherent_memory(struct dma_coherent_mem *mem)
	{
	if (!mem)
	return;

	memunmap(mem->virt_base);
	kfree(mem->bitmap);
	kfree(mem);
	}

	static int dma_assign_coherent_memory(struct device *dev,
	struct dma_coherent_mem *mem)
	{
	if (!dev)
	return -ENODEV;

	if (dev->dma_mem)
	return -EBUSY;

	dev->dma_mem = mem;
	return 0;
	}

	int dma_declare_coherent_memory(struct device *dev, phys_addr_t phys_addr,
	dma_addr_t device_addr, size_t size, int flags)
	{
	struct dma_coherent_mem *mem;
	int ret;

	ret = dma_init_coherent_memory(phys_addr, device_addr, size, flags, &mem);
	if (ret)
	return ret;

	ret = dma_assign_coherent_memory(dev, mem);
	if (ret)
	dma_release_coherent_memory(mem);
	return ret;
	}
	EXPORT_SYMBOL(dma_declare_coherent_memory);

	void dma_release_declared_memory(struct device *dev)
	{
	struct dma_coherent_mem *mem = dev->dma_mem;

	if (!mem)
	return;
	dma_release_coherent_memory(mem);
	dev->dma_mem = NULL;
	}
	EXPORT_SYMBOL(dma_release_declared_memory);

	void dma_mark_declared_memory_occupied(struct device dev,
	dma_addr_t device_addr, size_t size)
	{
	struct dma_coherent_mem *mem = dev->dma_mem;
	unsigned long flags;
	int pos, err;

	size += device_addr & ~PAGE_MASK;

	if (!mem)
	return ERR_PTR(-EINVAL);

	spin_lock_irqsave(&mem->spinlock, flags);
	pos = PFN_DOWN(device_addr - dma_get_device_base(dev, mem));
	err = bitmap_allocate_region(mem->bitmap, pos, get_order(size));
	spin_unlock_irqrestore(&mem->spinlock, flags);

	if (err != 0)
	return ERR_PTR(err);
	return mem->virt_base + (pos << PAGE_SHIFT);
	}
	EXPORT_SYMBOL(dma_mark_declared_memory_occupied);

	static void __dma_alloc_from_coherent(struct dma_coherent_mem mem,
	ssize_t size, dma_addr_t *dma_handle)
	{
	int order = get_order(size);
	unsigned long flags;
	int pageno;
	void *ret;

	spin_lock_irqsave(&mem->spinlock, flags);

	if (unlikely(size > (mem->size << PAGE_SHIFT)))
	goto err;

	pageno = bitmap_find_free_region(mem->bitmap, mem->size, order);
	if (unlikely(pageno < 0))
	goto err;

	/*
	* Memory was found in the coherent area.
	*/
	*dma_handle = mem->device_base + (pageno << PAGE_SHIFT);
	ret = mem->virt_base + (pageno << PAGE_SHIFT);
	spin_unlock_irqrestore(&mem->spinlock, flags);
	memset(ret, 0, size);
	return ret;
	err:
	spin_unlock_irqrestore(&mem->spinlock, flags);
	return NULL;
	}

	/**
	* dma_alloc_from_dev_coherent() - allocate memory from device coherent pool
	* @dev: device from which we allocate memory
	* @size: size of requested memory area
	* @dma_handle: This will be filled with the correct dma handle
	* @ret: This pointer will be filled with the virtual address
	* to allocated area.
	*
	* This function should be only called from per-arch dma_alloc_coherent()
	* to support allocation from per-device coherent memory pools.
	*
	* Returns 0 if dma_alloc_coherent should continue with allocating from
	* generic memory areas, or !0 if dma_alloc_coherent should return @ret.
	*/
	int dma_alloc_from_dev_coherent(struct device *dev, ssize_t size,
	dma_addr_t dma_handle, void *ret)
	{
	struct dma_coherent_mem *mem = dev_get_coherent_memory(dev);

	if (!mem)
	return 0;

	*ret = __dma_alloc_from_coherent(mem, size, dma_handle);
	if (*ret)
	return 1;

	/*
	* In the case where the allocation can not be satisfied from the
	* per-device area, try to fall back to generic memory if the
	* constraints allow it.
	*/
	return mem->flags & DMA_MEMORY_EXCLUSIVE;
	}

	void dma_alloc_from_global_coherent(ssize_t size, dma_addr_t dma_handle)
	{
	if (!dma_coherent_default_memory)
	return NULL;

	return __dma_alloc_from_coherent(dma_coherent_default_memory, size,
	dma_handle);
	}

	static int __dma_release_from_coherent(struct dma_coherent_mem *mem,
	int order, void *vaddr)
	{
	if (mem && vaddr >= mem->virt_base && vaddr <
	(mem->virt_base + (mem->size << PAGE_SHIFT))) {
	int page = (vaddr - mem->virt_base) >> PAGE_SHIFT;
	unsigned long flags;

	spin_lock_irqsave(&mem->spinlock, flags);
	bitmap_release_region(mem->bitmap, page, order);
	spin_unlock_irqrestore(&mem->spinlock, flags);
	return 1;
	}
	return 0;
	}

	/**
	* dma_release_from_dev_coherent() - free memory to device coherent memory pool
	* @dev: device from which the memory was allocated
	* @order: the order of pages allocated
	* @vaddr: virtual address of allocated pages
	*
	* This checks whether the memory was allocated from the per-device
	* coherent memory pool and if so, releases that memory.
	*
	* Returns 1 if we correctly released the memory, or 0 if the caller should
	* proceed with releasing memory from generic pools.
	*/
	int dma_release_from_dev_coherent(struct device dev, int order, void vaddr)
	{
	struct dma_coherent_mem *mem = dev_get_coherent_memory(dev);

	return __dma_release_from_coherent(mem, order, vaddr);
	}

	int dma_release_from_global_coherent(int order, void *vaddr)
	{
	if (!dma_coherent_default_memory)
	return 0;

	return __dma_release_from_coherent(dma_coherent_default_memory, order,
	vaddr);
	}

	static int __dma_mmap_from_coherent(struct dma_coherent_mem *mem,
	struct vm_area_struct vma, void vaddr, size_t size, int *ret)
	{
	if (mem && vaddr >= mem->virt_base && vaddr + size <=
	(mem->virt_base + (mem->size << PAGE_SHIFT))) {
	unsigned long off = vma->vm_pgoff;
	int start = (vaddr - mem->virt_base) >> PAGE_SHIFT;
	int user_count = vma_pages(vma);
	int count = PAGE_ALIGN(size) >> PAGE_SHIFT;

	*ret = -ENXIO;
	if (off < count && user_count <= count - off) {
	unsigned long pfn = mem->pfn_base + start + off;
	*ret = remap_pfn_range(vma, vma->vm_start, pfn,
	user_count << PAGE_SHIFT,
	vma->vm_page_prot);
	}
	return 1;
	}
	return 0;
	}

	/**
	* dma_mmap_from_dev_coherent() - mmap memory from the device coherent pool
	* @dev: device from which the memory was allocated
	* @vma: vm_area for the userspace memory
	* @vaddr: cpu address returned by dma_alloc_from_dev_coherent
	* @size: size of the memory buffer allocated
	* @ret: result from remap_pfn_range()
	*
	* This checks whether the memory was allocated from the per-device
	* coherent memory pool and if so, maps that memory to the provided vma.
	*
	* Returns 1 if @vaddr belongs to the device coherent pool and the caller
	* should return @ret, or 0 if they should proceed with mapping memory from
	* generic areas.
	*/
	int dma_mmap_from_dev_coherent(struct device dev, struct vm_area_struct vma,
	void vaddr, size_t size, int ret)
	{
	struct dma_coherent_mem *mem = dev_get_coherent_memory(dev);

	return __dma_mmap_from_coherent(mem, vma, vaddr, size, ret);
	}
	EXPORT_SYMBOL(dma_mmap_from_dev_coherent);

	int dma_mmap_from_global_coherent(struct vm_area_struct vma, void vaddr,
	size_t size, int *ret)
	{
	if (!dma_coherent_default_memory)
	return 0;

	return __dma_mmap_from_coherent(dma_coherent_default_memory, vma,
	vaddr, size, ret);
	}

	/*
	* Support for reserved memory regions defined in device tree
	*/
	#ifdef CONFIG_OF_RESERVED_MEM
	#include <linux/of.h>
	#include <linux/of_fdt.h>
	#include <linux/of_reserved_mem.h>

	static struct reserved_mem *dma_reserved_default_memory __initdata;

	static int rmem_dma_device_init(struct reserved_mem rmem, struct device dev)
	{
	struct dma_coherent_mem *mem = rmem->priv;
	int ret;

	if (!mem) {
	ret = dma_init_coherent_memory(rmem->base, rmem->base,
	rmem->size,
	DMA_MEMORY_EXCLUSIVE, &mem);
	if (ret) {
	pr_err("Reserved memory: failed to init DMA memory pool at %pa, size %ld MiB\n",
	&rmem->base, (unsigned long)rmem->size / SZ_1M);
	return ret;
	}
	}
	mem->use_dev_dma_pfn_offset = true;
	rmem->priv = mem;
	dma_assign_coherent_memory(dev, mem);
	return 0;
	}

	static void rmem_dma_device_release(struct reserved_mem *rmem,
	struct device *dev)
	{
	if (dev)
	dev->dma_mem = NULL;
	}

	static const struct reserved_mem_ops rmem_dma_ops = {
	.device_init = rmem_dma_device_init,
	.device_release = rmem_dma_device_release,
	};

	static int __init rmem_dma_setup(struct reserved_mem *rmem)
	{
	unsigned long node = rmem->fdt_node;

	if (of_get_flat_dt_prop(node, "reusable", NULL))
	return -EINVAL;

	#ifdef CONFIG_ARM
	if (!of_get_flat_dt_prop(node, "no-map", NULL)) {
	pr_err("Reserved memory: regions without no-map are not yet supported\n");
	return -EINVAL;
	}

	if (of_get_flat_dt_prop(node, "linux,dma-default", NULL)) {
	WARN(dma_reserved_default_memory,
	"Reserved memory: region for default DMA coherent area is redefined\n");
	dma_reserved_default_memory = rmem;
	}
	#endif

	rmem->ops = &rmem_dma_ops;
	pr_info("Reserved memory: created DMA memory pool at %pa, size %ld MiB\n",
	&rmem->base, (unsigned long)rmem->size / SZ_1M);
	return 0;
	}

	static int __init dma_init_reserved_memory(void)
	{
	const struct reserved_mem_ops *ops;
	int ret;

	if (!dma_reserved_default_memory)
	return -ENOMEM;

	ops = dma_reserved_default_memory->ops;

	/*
	* We rely on rmem_dma_device_init() does not propagate error of
	* dma_assign_coherent_memory() for "NULL" device.
	*/
	ret = ops->device_init(dma_reserved_default_memory, NULL);

	if (!ret) {
	dma_coherent_default_memory = dma_reserved_default_memory->priv;
	pr_info("DMA: default coherent area is set\n");
	}

	return ret;
	}

	core_initcall(dma_init_reserved_memory);

	RESERVEDMEM_OF_DECLARE(dma, "shared-dma-pool", rmem_dma_setup);
	#endif