arch/arm64/mm/dma-mapping.c - arm/linux-arm64-legacy - Git at Google

 /*
  * SWIOTLB-based DMA API implementation
  *
  * Copyright (C) 2012 ARM Ltd.
  * Author: Catalin Marinas <catalin.marinas@arm.com>
  *
  * 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.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */

 #include <linux/gfp.h>
 #include <linux/export.h>
 #include <linux/slab.h>
 #include <linux/dma-mapping.h>
 #include <linux/dma-contiguous.h>
 #include <linux/of.h>
 #include <linux/platform_device.h>
 #include <linux/vmalloc.h>
 #include <linux/swiotlb.h>
 #include <linux/amba/bus.h>
 #include <linux/pci.h>

 #include <asm/cacheflush.h>

 struct dma_map_ops *dma_ops;
 EXPORT_SYMBOL(dma_ops);

 static pgprot_t __get_dma_pgprot(struct dma_attrs *attrs, pgprot_t prot,
 				 bool coherent)
 {
 	if (!coherent || dma_get_attr(DMA_ATTR_WRITE_COMBINE, attrs))
 		return pgprot_writecombine(prot);
 	return prot;
 }

 static void *__dma_alloc_coherent(struct device *dev, size_t size,
 				  dma_addr_t *dma_handle, gfp_t flags,
 				  struct dma_attrs *attrs)
 {
 	if (dev == NULL) {
 		WARN_ONCE(1, "Use an actual device structure for DMA allocation\n");
 		return NULL;
 	}

 	if (IS_ENABLED(CONFIG_ZONE_DMA) &&
 	    dev->coherent_dma_mask <= DMA_BIT_MASK(32))
 		flags |= GFP_DMA;
 	if (IS_ENABLED(CONFIG_DMA_CMA)) {
 		struct page *page;

 		size = PAGE_ALIGN(size);
 		page = dma_alloc_from_contiguous(dev, size >> PAGE_SHIFT,
 							get_order(size));
 		if (!page)
 			return NULL;

 		*dma_handle = phys_to_dma(dev, page_to_phys(page));
 		return page_address(page);
 	} else {
 		return swiotlb_alloc_coherent(dev, size, dma_handle, flags);
 	}
 }

 static void __dma_free_coherent(struct device *dev, size_t size,
 				void *vaddr, dma_addr_t dma_handle,
 				struct dma_attrs *attrs)
 {
 	if (dev == NULL) {
 		WARN_ONCE(1, "Use an actual device structure for DMA allocation\n");
 		return;
 	}

 	if (IS_ENABLED(CONFIG_DMA_CMA)) {
 		phys_addr_t paddr = dma_to_phys(dev, dma_handle);

 		dma_release_from_contiguous(dev,
 					phys_to_page(paddr),
 					size >> PAGE_SHIFT);
 	} else {
 		swiotlb_free_coherent(dev, size, vaddr, dma_handle);
 	}
 }

 static void *__dma_alloc_noncoherent(struct device *dev, size_t size,
 				     dma_addr_t *dma_handle, gfp_t flags,
 				     struct dma_attrs *attrs)
 {
 	struct page *page, **map;
 	void *ptr, *coherent_ptr;
 	int order, i;

 	size = PAGE_ALIGN(size);
 	order = get_order(size);

 	ptr = __dma_alloc_coherent(dev, size, dma_handle, flags, attrs);
 	if (!ptr)
 		goto no_mem;
 	map = kmalloc(sizeof(struct page *) << order, flags & ~GFP_DMA);
 	if (!map)
 		goto no_map;

 	/* remove any dirty cache lines on the kernel alias */
 	__dma_flush_range(ptr, ptr + size);

 	/* create a coherent mapping */
 	page = virt_to_page(ptr);
 	for (i = 0; i < (size >> PAGE_SHIFT); i++)
 		map[i] = page + i;
 	coherent_ptr = vmap(map, size >> PAGE_SHIFT, VM_MAP,
 			    __get_dma_pgprot(attrs, __pgprot(PROT_NORMAL_NC), false));
 	kfree(map);
 	if (!coherent_ptr)
 		goto no_map;

 	return coherent_ptr;

 no_map:
 	__dma_free_coherent(dev, size, ptr, *dma_handle, attrs);
 no_mem:
 	*dma_handle = ~0;
 	return NULL;
 }

 static void __dma_free_noncoherent(struct device *dev, size_t size,
 				   void *vaddr, dma_addr_t dma_handle,
 				   struct dma_attrs *attrs)
 {
 	void *swiotlb_addr = phys_to_virt(dma_to_phys(dev, dma_handle));

 	vunmap(vaddr);
 	__dma_free_coherent(dev, size, swiotlb_addr, dma_handle, attrs);
 }

 static dma_addr_t __swiotlb_map_page(struct device *dev, struct page *page,
 				     unsigned long offset, size_t size,
 				     enum dma_data_direction dir,
 				     struct dma_attrs *attrs)
 {
 	dma_addr_t dev_addr;

 	dev_addr = swiotlb_map_page(dev, page, offset, size, dir, attrs);
 	__dma_map_area(phys_to_virt(dma_to_phys(dev, dev_addr)), size, dir);

 	return dev_addr;
 }


 static void __swiotlb_unmap_page(struct device *dev, dma_addr_t dev_addr,
 				 size_t size, enum dma_data_direction dir,
 				 struct dma_attrs *attrs)
 {
 	__dma_unmap_area(phys_to_virt(dma_to_phys(dev, dev_addr)), size, dir);
 	swiotlb_unmap_page(dev, dev_addr, size, dir, attrs);
 }

 static int __swiotlb_map_sg_attrs(struct device *dev, struct scatterlist *sgl,
 				  int nelems, enum dma_data_direction dir,
 				  struct dma_attrs *attrs)
 {
 	struct scatterlist *sg;
 	int i, ret;

 	ret = swiotlb_map_sg_attrs(dev, sgl, nelems, dir, attrs);
 	for_each_sg(sgl, sg, ret, i)
 		__dma_map_area(phys_to_virt(dma_to_phys(dev, sg->dma_address)),
 			       sg->length, dir);

 	return ret;
 }

 static void __swiotlb_unmap_sg_attrs(struct device *dev,
 				     struct scatterlist *sgl, int nelems,
 				     enum dma_data_direction dir,
 				     struct dma_attrs *attrs)
 {
 	struct scatterlist *sg;
 	int i;

 	for_each_sg(sgl, sg, nelems, i)
 		__dma_unmap_area(phys_to_virt(dma_to_phys(dev, sg->dma_address)),
 				 sg->length, dir);
 	swiotlb_unmap_sg_attrs(dev, sgl, nelems, dir, attrs);
 }

 static void __swiotlb_sync_single_for_cpu(struct device *dev,
 					  dma_addr_t dev_addr, size_t size,
 					  enum dma_data_direction dir)
 {
 	__dma_unmap_area(phys_to_virt(dma_to_phys(dev, dev_addr)), size, dir);
 	swiotlb_sync_single_for_cpu(dev, dev_addr, size, dir);
 }

 static void __swiotlb_sync_single_for_device(struct device *dev,
 					     dma_addr_t dev_addr, size_t size,
 					     enum dma_data_direction dir)
 {
 	swiotlb_sync_single_for_device(dev, dev_addr, size, dir);
 	__dma_map_area(phys_to_virt(dma_to_phys(dev, dev_addr)), size, dir);
 }

 static void __swiotlb_sync_sg_for_cpu(struct device *dev,
 				      struct scatterlist *sgl, int nelems,
 				      enum dma_data_direction dir)
 {
 	struct scatterlist *sg;
 	int i;

 	for_each_sg(sgl, sg, nelems, i)
 		__dma_unmap_area(phys_to_virt(dma_to_phys(dev, sg->dma_address)),
 				 sg->length, dir);
 	swiotlb_sync_sg_for_cpu(dev, sgl, nelems, dir);
 }

 static void __swiotlb_sync_sg_for_device(struct device *dev,
 					 struct scatterlist *sgl, int nelems,
 					 enum dma_data_direction dir)
 {
 	struct scatterlist *sg;
 	int i;

 	swiotlb_sync_sg_for_device(dev, sgl, nelems, dir);
 	for_each_sg(sgl, sg, nelems, i)
 		__dma_map_area(phys_to_virt(dma_to_phys(dev, sg->dma_address)),
 			       sg->length, dir);
 }

 /* vma->vm_page_prot must be set appropriately before calling this function */
 static int __dma_common_mmap(struct device *dev, struct vm_area_struct *vma,
 			     void *cpu_addr, dma_addr_t dma_addr, size_t size)
 {
 	int ret = -ENXIO;
 	unsigned long nr_vma_pages = (vma->vm_end - vma->vm_start) >>
 					PAGE_SHIFT;
 	unsigned long nr_pages = PAGE_ALIGN(size) >> PAGE_SHIFT;
 	unsigned long pfn = dma_to_phys(dev, dma_addr) >> PAGE_SHIFT;
 	unsigned long off = vma->vm_pgoff;

 	if (dma_mmap_from_coherent(dev, vma, cpu_addr, size, &ret))
 		return ret;

 	if (off < nr_pages && nr_vma_pages <= (nr_pages - off)) {
 		ret = remap_pfn_range(vma, vma->vm_start,
 				      pfn + off,
 				      vma->vm_end - vma->vm_start,
 				      vma->vm_page_prot);
 	}

 	return ret;
 }

 static int __swiotlb_mmap_noncoherent(struct device *dev,
 		struct vm_area_struct *vma,
 		void *cpu_addr, dma_addr_t dma_addr, size_t size,
 		struct dma_attrs *attrs)
 {
 	vma->vm_page_prot = __get_dma_pgprot(attrs, vma->vm_page_prot, false);
 	return __dma_common_mmap(dev, vma, cpu_addr, dma_addr, size);
 }

 static int __swiotlb_mmap_coherent(struct device *dev,
 		struct vm_area_struct *vma,
 		void *cpu_addr, dma_addr_t dma_addr, size_t size,
 		struct dma_attrs *attrs)
 {
 	/* Just use whatever page_prot attributes were specified */
 	return __dma_common_mmap(dev, vma, cpu_addr, dma_addr, size);
 }

 struct dma_map_ops noncoherent_swiotlb_dma_ops = {
 	.alloc = __dma_alloc_noncoherent,
 	.free = __dma_free_noncoherent,
 	.mmap = __swiotlb_mmap_noncoherent,
 	.map_page = __swiotlb_map_page,
 	.unmap_page = __swiotlb_unmap_page,
 	.map_sg = __swiotlb_map_sg_attrs,
 	.unmap_sg = __swiotlb_unmap_sg_attrs,
 	.sync_single_for_cpu = __swiotlb_sync_single_for_cpu,
 	.sync_single_for_device = __swiotlb_sync_single_for_device,
 	.sync_sg_for_cpu = __swiotlb_sync_sg_for_cpu,
 	.sync_sg_for_device = __swiotlb_sync_sg_for_device,
 	.dma_supported = swiotlb_dma_supported,
 	.mapping_error = swiotlb_dma_mapping_error,
 };
 EXPORT_SYMBOL(noncoherent_swiotlb_dma_ops);

 struct dma_map_ops coherent_swiotlb_dma_ops = {
 	.alloc = __dma_alloc_coherent,
 	.free = __dma_free_coherent,
 	.mmap = __swiotlb_mmap_coherent,
 	.map_page = swiotlb_map_page,
 	.unmap_page = swiotlb_unmap_page,
 	.map_sg = swiotlb_map_sg_attrs,
 	.unmap_sg = swiotlb_unmap_sg_attrs,
 	.sync_single_for_cpu = swiotlb_sync_single_for_cpu,
 	.sync_single_for_device = swiotlb_sync_single_for_device,
 	.sync_sg_for_cpu = swiotlb_sync_sg_for_cpu,
 	.sync_sg_for_device = swiotlb_sync_sg_for_device,
 	.dma_supported = swiotlb_dma_supported,
 	.mapping_error = swiotlb_dma_mapping_error,
 };
 EXPORT_SYMBOL(coherent_swiotlb_dma_ops);

 static int dma_bus_notifier(struct notifier_block *nb,
 			    unsigned long event, void *_dev)
 {
 	struct device *dev = _dev, *pdev = _dev;

 	if (event != BUS_NOTIFY_ADD_DEVICE)
 		return NOTIFY_DONE;

     do {
         if (of_property_read_bool(pdev->of_node, "dma-coherent"))
             set_dma_ops(dev, &coherent_swiotlb_dma_ops);
         // if we've found the first parent from devtree and it's not coherent
         // we're done
         if (pdev->of_node)
             break;
         pdev = pdev->parent;
     } while (pdev);

 	return NOTIFY_OK;
 }


 static struct notifier_block platform_bus_nb = {
 	.notifier_call = dma_bus_notifier,
 };

 static struct notifier_block amba_bus_nb = {
 	.notifier_call = dma_bus_notifier,
 };

 static struct notifier_block pci_bus_nb = {
 	.notifier_call = dma_bus_notifier,
 };

 extern int swiotlb_late_init_with_default_size(size_t default_size);

 static int __init swiotlb_late_init(void)
 {
 	size_t swiotlb_size = min(SZ_64M, MAX_ORDER_NR_PAGES << PAGE_SHIFT);

 	/*
 	 * These must be registered before of_platform_populate().
 	 */
 	bus_register_notifier(&platform_bus_type, &platform_bus_nb);
 	bus_register_notifier(&amba_bustype, &amba_bus_nb);
 	bus_register_notifier(&pci_bus_type, &pci_bus_nb);

 	dma_ops = &noncoherent_swiotlb_dma_ops;

 	return swiotlb_late_init_with_default_size(swiotlb_size);
 }
 arch_initcall(swiotlb_late_init);

 #define PREALLOC_DMA_DEBUG_ENTRIES	4096

 static int __init dma_debug_do_init(void)
 {
 	dma_debug_init(PREALLOC_DMA_DEBUG_ENTRIES);
 	return 0;
 }
 fs_initcall(dma_debug_do_init);
	/*
	* SWIOTLB-based DMA API implementation
	*
	* Copyright (C) 2012 ARM Ltd.
	* Author: Catalin Marinas <catalin.marinas@arm.com>
	*
	* 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.
	*
	* This program is distributed in the hope that it will be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	* GNU General Public License for more details.
	*
	* You should have received a copy of the GNU General Public License
	* along with this program. If not, see <http://www.gnu.org/licenses/>.
	*/

	#include <linux/gfp.h>
	#include <linux/export.h>
	#include <linux/slab.h>
	#include <linux/dma-mapping.h>
	#include <linux/dma-contiguous.h>
	#include <linux/of.h>
	#include <linux/platform_device.h>
	#include <linux/vmalloc.h>
	#include <linux/swiotlb.h>
	#include <linux/amba/bus.h>
	#include <linux/pci.h>

	#include <asm/cacheflush.h>

	struct dma_map_ops *dma_ops;
	EXPORT_SYMBOL(dma_ops);

	static pgprot_t __get_dma_pgprot(struct dma_attrs *attrs, pgprot_t prot,
	bool coherent)
	{
	if (!coherent \|\| dma_get_attr(DMA_ATTR_WRITE_COMBINE, attrs))
	return pgprot_writecombine(prot);
	return prot;
	}

	static void __dma_alloc_coherent(struct device dev, size_t size,
	dma_addr_t *dma_handle, gfp_t flags,
	struct dma_attrs *attrs)
	{
	if (dev == NULL) {
	WARN_ONCE(1, "Use an actual device structure for DMA allocation\n");
	return NULL;
	}

	if (IS_ENABLED(CONFIG_ZONE_DMA) &&
	dev->coherent_dma_mask <= DMA_BIT_MASK(32))
	flags \|= GFP_DMA;
	if (IS_ENABLED(CONFIG_DMA_CMA)) {
	struct page *page;

	size = PAGE_ALIGN(size);
	page = dma_alloc_from_contiguous(dev, size >> PAGE_SHIFT,
	get_order(size));
	if (!page)
	return NULL;

	*dma_handle = phys_to_dma(dev, page_to_phys(page));
	return page_address(page);
	} else {
	return swiotlb_alloc_coherent(dev, size, dma_handle, flags);
	}
	}

	static void __dma_free_coherent(struct device *dev, size_t size,
	void *vaddr, dma_addr_t dma_handle,
	struct dma_attrs *attrs)
	{
	if (dev == NULL) {
	WARN_ONCE(1, "Use an actual device structure for DMA allocation\n");
	return;
	}

	if (IS_ENABLED(CONFIG_DMA_CMA)) {
	phys_addr_t paddr = dma_to_phys(dev, dma_handle);

	dma_release_from_contiguous(dev,
	phys_to_page(paddr),
	size >> PAGE_SHIFT);
	} else {
	swiotlb_free_coherent(dev, size, vaddr, dma_handle);
	}
	}

	static void __dma_alloc_noncoherent(struct device dev, size_t size,
	dma_addr_t *dma_handle, gfp_t flags,
	struct dma_attrs *attrs)
	{
	struct page page, *map;
	void ptr, coherent_ptr;
	int order, i;

	size = PAGE_ALIGN(size);
	order = get_order(size);

	ptr = __dma_alloc_coherent(dev, size, dma_handle, flags, attrs);
	if (!ptr)
	goto no_mem;
	map = kmalloc(sizeof(struct page *) << order, flags & ~GFP_DMA);
	if (!map)
	goto no_map;

	/* remove any dirty cache lines on the kernel alias */
	__dma_flush_range(ptr, ptr + size);

	/* create a coherent mapping */
	page = virt_to_page(ptr);
	for (i = 0; i < (size >> PAGE_SHIFT); i++)
	map[i] = page + i;
	coherent_ptr = vmap(map, size >> PAGE_SHIFT, VM_MAP,
	__get_dma_pgprot(attrs, __pgprot(PROT_NORMAL_NC), false));
	kfree(map);
	if (!coherent_ptr)
	goto no_map;

	return coherent_ptr;

	no_map:
	__dma_free_coherent(dev, size, ptr, *dma_handle, attrs);
	no_mem:
	*dma_handle = ~0;
	return NULL;
	}

	static void __dma_free_noncoherent(struct device *dev, size_t size,
	void *vaddr, dma_addr_t dma_handle,
	struct dma_attrs *attrs)
	{
	void *swiotlb_addr = phys_to_virt(dma_to_phys(dev, dma_handle));

	vunmap(vaddr);
	__dma_free_coherent(dev, size, swiotlb_addr, dma_handle, attrs);
	}

	static dma_addr_t __swiotlb_map_page(struct device dev, struct page page,
	unsigned long offset, size_t size,
	enum dma_data_direction dir,
	struct dma_attrs *attrs)
	{
	dma_addr_t dev_addr;

	dev_addr = swiotlb_map_page(dev, page, offset, size, dir, attrs);
	__dma_map_area(phys_to_virt(dma_to_phys(dev, dev_addr)), size, dir);

	return dev_addr;
	}


	static void __swiotlb_unmap_page(struct device *dev, dma_addr_t dev_addr,
	size_t size, enum dma_data_direction dir,
	struct dma_attrs *attrs)
	{
	__dma_unmap_area(phys_to_virt(dma_to_phys(dev, dev_addr)), size, dir);
	swiotlb_unmap_page(dev, dev_addr, size, dir, attrs);
	}

	static int __swiotlb_map_sg_attrs(struct device dev, struct scatterlist sgl,
	int nelems, enum dma_data_direction dir,
	struct dma_attrs *attrs)
	{
	struct scatterlist *sg;
	int i, ret;

	ret = swiotlb_map_sg_attrs(dev, sgl, nelems, dir, attrs);
	for_each_sg(sgl, sg, ret, i)
	__dma_map_area(phys_to_virt(dma_to_phys(dev, sg->dma_address)),
	sg->length, dir);

	return ret;
	}

	static void __swiotlb_unmap_sg_attrs(struct device *dev,
	struct scatterlist *sgl, int nelems,
	enum dma_data_direction dir,
	struct dma_attrs *attrs)
	{
	struct scatterlist *sg;
	int i;

	for_each_sg(sgl, sg, nelems, i)
	__dma_unmap_area(phys_to_virt(dma_to_phys(dev, sg->dma_address)),
	sg->length, dir);
	swiotlb_unmap_sg_attrs(dev, sgl, nelems, dir, attrs);
	}

	static void __swiotlb_sync_single_for_cpu(struct device *dev,
	dma_addr_t dev_addr, size_t size,
	enum dma_data_direction dir)
	{
	__dma_unmap_area(phys_to_virt(dma_to_phys(dev, dev_addr)), size, dir);
	swiotlb_sync_single_for_cpu(dev, dev_addr, size, dir);
	}

	static void __swiotlb_sync_single_for_device(struct device *dev,
	dma_addr_t dev_addr, size_t size,
	enum dma_data_direction dir)
	{
	swiotlb_sync_single_for_device(dev, dev_addr, size, dir);
	__dma_map_area(phys_to_virt(dma_to_phys(dev, dev_addr)), size, dir);
	}

	static void __swiotlb_sync_sg_for_cpu(struct device *dev,
	struct scatterlist *sgl, int nelems,
	enum dma_data_direction dir)
	{
	struct scatterlist *sg;
	int i;

	for_each_sg(sgl, sg, nelems, i)
	__dma_unmap_area(phys_to_virt(dma_to_phys(dev, sg->dma_address)),
	sg->length, dir);
	swiotlb_sync_sg_for_cpu(dev, sgl, nelems, dir);
	}

	static void __swiotlb_sync_sg_for_device(struct device *dev,
	struct scatterlist *sgl, int nelems,
	enum dma_data_direction dir)
	{
	struct scatterlist *sg;
	int i;

	swiotlb_sync_sg_for_device(dev, sgl, nelems, dir);
	for_each_sg(sgl, sg, nelems, i)
	__dma_map_area(phys_to_virt(dma_to_phys(dev, sg->dma_address)),
	sg->length, dir);
	}

	/* vma->vm_page_prot must be set appropriately before calling this function */
	static int __dma_common_mmap(struct device dev, struct vm_area_struct vma,
	void *cpu_addr, dma_addr_t dma_addr, size_t size)
	{
	int ret = -ENXIO;
	unsigned long nr_vma_pages = (vma->vm_end - vma->vm_start) >>
	PAGE_SHIFT;
	unsigned long nr_pages = PAGE_ALIGN(size) >> PAGE_SHIFT;
	unsigned long pfn = dma_to_phys(dev, dma_addr) >> PAGE_SHIFT;
	unsigned long off = vma->vm_pgoff;

	if (dma_mmap_from_coherent(dev, vma, cpu_addr, size, &ret))
	return ret;

	if (off < nr_pages && nr_vma_pages <= (nr_pages - off)) {
	ret = remap_pfn_range(vma, vma->vm_start,
	pfn + off,
	vma->vm_end - vma->vm_start,
	vma->vm_page_prot);
	}

	return ret;
	}

	static int __swiotlb_mmap_noncoherent(struct device *dev,
	struct vm_area_struct *vma,
	void *cpu_addr, dma_addr_t dma_addr, size_t size,
	struct dma_attrs *attrs)
	{
	vma->vm_page_prot = __get_dma_pgprot(attrs, vma->vm_page_prot, false);
	return __dma_common_mmap(dev, vma, cpu_addr, dma_addr, size);
	}

	static int __swiotlb_mmap_coherent(struct device *dev,
	struct vm_area_struct *vma,
	void *cpu_addr, dma_addr_t dma_addr, size_t size,
	struct dma_attrs *attrs)
	{
	/* Just use whatever page_prot attributes were specified */
	return __dma_common_mmap(dev, vma, cpu_addr, dma_addr, size);
	}

	struct dma_map_ops noncoherent_swiotlb_dma_ops = {
	.alloc = __dma_alloc_noncoherent,
	.free = __dma_free_noncoherent,
	.mmap = __swiotlb_mmap_noncoherent,
	.map_page = __swiotlb_map_page,
	.unmap_page = __swiotlb_unmap_page,
	.map_sg = __swiotlb_map_sg_attrs,
	.unmap_sg = __swiotlb_unmap_sg_attrs,
	.sync_single_for_cpu = __swiotlb_sync_single_for_cpu,
	.sync_single_for_device = __swiotlb_sync_single_for_device,
	.sync_sg_for_cpu = __swiotlb_sync_sg_for_cpu,
	.sync_sg_for_device = __swiotlb_sync_sg_for_device,
	.dma_supported = swiotlb_dma_supported,
	.mapping_error = swiotlb_dma_mapping_error,
	};
	EXPORT_SYMBOL(noncoherent_swiotlb_dma_ops);

	struct dma_map_ops coherent_swiotlb_dma_ops = {
	.alloc = __dma_alloc_coherent,
	.free = __dma_free_coherent,
	.mmap = __swiotlb_mmap_coherent,
	.map_page = swiotlb_map_page,
	.unmap_page = swiotlb_unmap_page,
	.map_sg = swiotlb_map_sg_attrs,
	.unmap_sg = swiotlb_unmap_sg_attrs,
	.sync_single_for_cpu = swiotlb_sync_single_for_cpu,
	.sync_single_for_device = swiotlb_sync_single_for_device,
	.sync_sg_for_cpu = swiotlb_sync_sg_for_cpu,
	.sync_sg_for_device = swiotlb_sync_sg_for_device,
	.dma_supported = swiotlb_dma_supported,
	.mapping_error = swiotlb_dma_mapping_error,
	};
	EXPORT_SYMBOL(coherent_swiotlb_dma_ops);

	static int dma_bus_notifier(struct notifier_block *nb,
	unsigned long event, void *_dev)
	{
	struct device dev = _dev, pdev = _dev;

	if (event != BUS_NOTIFY_ADD_DEVICE)
	return NOTIFY_DONE;

	do {
	if (of_property_read_bool(pdev->of_node, "dma-coherent"))
	set_dma_ops(dev, &coherent_swiotlb_dma_ops);
	// if we've found the first parent from devtree and it's not coherent
	// we're done
	if (pdev->of_node)
	break;
	pdev = pdev->parent;
	} while (pdev);

	return NOTIFY_OK;
	}


	static struct notifier_block platform_bus_nb = {
	.notifier_call = dma_bus_notifier,
	};

	static struct notifier_block amba_bus_nb = {
	.notifier_call = dma_bus_notifier,
	};

	static struct notifier_block pci_bus_nb = {
	.notifier_call = dma_bus_notifier,
	};

	extern int swiotlb_late_init_with_default_size(size_t default_size);

	static int __init swiotlb_late_init(void)
	{
	size_t swiotlb_size = min(SZ_64M, MAX_ORDER_NR_PAGES << PAGE_SHIFT);

	/*
	* These must be registered before of_platform_populate().
	*/
	bus_register_notifier(&platform_bus_type, &platform_bus_nb);
	bus_register_notifier(&amba_bustype, &amba_bus_nb);
	bus_register_notifier(&pci_bus_type, &pci_bus_nb);

	dma_ops = &noncoherent_swiotlb_dma_ops;

	return swiotlb_late_init_with_default_size(swiotlb_size);
	}
	arch_initcall(swiotlb_late_init);

	#define PREALLOC_DMA_DEBUG_ENTRIES 4096

	static int __init dma_debug_do_init(void)
	{
	dma_debug_init(PREALLOC_DMA_DEBUG_ENTRIES);
	return 0;
	}
	fs_initcall(dma_debug_do_init);