/*
   * Coherent per-device memory handling.
   * Borrowed from i386
   */
  #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;
  	phys_addr_t	pfn_base;
  	int		size;
  	int		flags;
  	unsigned long	*bitmap;
  };
  
  int dma_declare_coherent_memory(struct device *dev, dma_addr_t bus_addr,
  				dma_addr_t device_addr, size_t size, int flags)
  {
  	void __iomem *mem_base = NULL;
  	int pages = size >> PAGE_SHIFT;
  	int bitmap_size = BITS_TO_LONGS(pages) * sizeof(long);
  
  	if ((flags & (DMA_MEMORY_MAP | DMA_MEMORY_IO)) == 0)
  		goto out;
  	if (!size)
  		goto out;
  	if (dev->dma_mem)
  		goto out;
  
  	/* FIXME: this routine just ignores DMA_MEMORY_INCLUDES_CHILDREN */
  
  	mem_base = ioremap(bus_addr, size);
  	if (!mem_base)
  		goto out;
  
  	dev->dma_mem = kzalloc(sizeof(struct dma_coherent_mem), GFP_KERNEL);
  	if (!dev->dma_mem)
  		goto out;
  	dev->dma_mem->bitmap = kzalloc(bitmap_size, GFP_KERNEL);
  	if (!dev->dma_mem->bitmap)
  		goto free1_out;
  
  	dev->dma_mem->virt_base = mem_base;
  	dev->dma_mem->device_base = device_addr;
  	dev->dma_mem->pfn_base = PFN_DOWN(bus_addr);
  	dev->dma_mem->size = pages;
  	dev->dma_mem->flags = flags;
  
  	if (flags & DMA_MEMORY_MAP)
  		return DMA_MEMORY_MAP;
  
  	return DMA_MEMORY_IO;
  
   free1_out:
  	kfree(dev->dma_mem);
   out:
  	if (mem_base)
  		iounmap(mem_base);
  	return 0;
  }
  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;
  	dev->dma_mem = NULL;
  	iounmap(mem->virt_base);
  	kfree(mem->bitmap);
  	kfree(mem);
  }
  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;
  	int pos, err;
  
  	size += device_addr & ~PAGE_MASK;
  
  	if (!mem)
  		return ERR_PTR(-EINVAL);
  
  	pos = (device_addr - mem->device_base) >> PAGE_SHIFT;
  	err = bitmap_allocate_region(mem->bitmap, pos, get_order(size));
  	if (err != 0)
  		return ERR_PTR(err);
  	return mem->virt_base + (pos << PAGE_SHIFT);
  }
  EXPORT_SYMBOL(dma_mark_declared_memory_occupied);
  
  /**
   * dma_alloc_from_coherent() - try to allocate memory from the per-device coherent area
   *
   * @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_coherent(struct device *dev, ssize_t size,
  				       dma_addr_t *dma_handle, void **ret)
  {
  	struct dma_coherent_mem *mem;
  	int order = get_order(size);
  	int pageno;
  
  	if (!dev)
  		return 0;
  	mem = dev->dma_mem;
  	if (!mem)
  		return 0;
  
  	*ret = NULL;
  
  	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 per-device area.
  	 */
  	*dma_handle = mem->device_base + (pageno << PAGE_SHIFT);
  	*ret = mem->virt_base + (pageno << PAGE_SHIFT);
  	memset(*ret, 0, size);
  
  	return 1;
  
  err:
  	/*
  	 * 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;
  }
  EXPORT_SYMBOL(dma_alloc_from_coherent);
  
  /**
   * dma_release_from_coherent() - try to free the memory allocated from per-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
   * dma_release_coherent() should proceed with releasing memory from
   * generic pools.
   */
  int dma_release_from_coherent(struct device *dev, int order, void *vaddr)
  {
  	struct dma_coherent_mem *mem = dev ? dev->dma_mem : NULL;
  
  	if (mem && vaddr >= mem->virt_base && vaddr <
  		   (mem->virt_base + (mem->size << PAGE_SHIFT))) {
  		int page = (vaddr - mem->virt_base) >> PAGE_SHIFT;
  
  		bitmap_release_region(mem->bitmap, page, order);
  		return 1;
  	}
  	return 0;
  }
  EXPORT_SYMBOL(dma_release_from_coherent);
  
  /**
   * dma_mmap_from_coherent() - try to mmap the memory allocated from
   * per-device coherent memory pool to userspace
   * @dev:	device from which the memory was allocated
   * @vma:	vm_area for the userspace memory
   * @vaddr:	cpu address returned by dma_alloc_from_coherent
   * @size:	size of the memory buffer allocated by dma_alloc_from_coherent
   * @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 we correctly mapped the memory, or 0 if the caller should
   * proceed with mapping memory from generic pools.
   */
  int dma_mmap_from_coherent(struct device *dev, struct vm_area_struct *vma,
  			   void *vaddr, size_t size, int *ret)
  {
  	struct dma_coherent_mem *mem = dev ? dev->dma_mem : NULL;
  
  	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->vm_end - vma->vm_start) >> PAGE_SHIFT;
  		int count = size >> PAGE_SHIFT;
  
  		*ret = -ENXIO;
  		if (off < count && user_count <= count - off) {
  			unsigned 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;
  }
  EXPORT_SYMBOL(dma_mmap_from_coherent);