arch/arm/common/dmabounce.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  *  arch/arm/common/dmabounce.c
  *
  *  Special dma_{map/unmap/dma_sync}_* routines for systems that have
  *  limited DMA windows. These functions utilize bounce buffers to
  *  copy data to/from buffers located outside the DMA region. This
  *  only works for systems in which DMA memory is at the bottom of
  *  RAM, the remainder of memory is at the top and the DMA memory
  *  can be marked as ZONE_DMA. Anything beyond that such as discontiguous
  *  DMA windows will require custom implementations that reserve memory
  *  areas at early bootup.
  *
  *  Original version by Brad Parker (brad@heeltoe.com)
  *  Re-written by Christopher Hoover <ch@murgatroid.com>
  *  Made generic by Deepak Saxena <dsaxena@plexity.net>
  *
  *  Copyright (C) 2002 Hewlett Packard Company.
  *  Copyright (C) 2004 MontaVista Software, Inc.
  */

 #include <linux/module.h>
 #include <linux/init.h>
 #include <linux/slab.h>
 #include <linux/page-flags.h>
 #include <linux/device.h>
 #include <linux/dma-mapping.h>
 #include <linux/dmapool.h>
 #include <linux/list.h>
 #include <linux/scatterlist.h>

 #include <asm/cacheflush.h>
 #include <asm/dma-iommu.h>

 #undef STATS

 #ifdef STATS
 #define DO_STATS(X) do { X ; } while (0)
 #else
 #define DO_STATS(X) do { } while (0)
 #endif

 /* ************************************************** */

 struct safe_buffer {
 	struct list_head node;

 	/* original request */
 	void		*ptr;
 	size_t		size;
 	int		direction;

 	/* safe buffer info */
 	struct dmabounce_pool *pool;
 	void		*safe;
 	dma_addr_t	safe_dma_addr;
 };

 struct dmabounce_pool {
 	unsigned long	size;
 	struct dma_pool	*pool;
 #ifdef STATS
 	unsigned long	allocs;
 #endif
 };

 struct dmabounce_device_info {
 	struct device *dev;
 	struct list_head safe_buffers;
 #ifdef STATS
 	unsigned long total_allocs;
 	unsigned long map_op_count;
 	unsigned long bounce_count;
 	int attr_res;
 #endif
 	struct dmabounce_pool	small;
 	struct dmabounce_pool	large;

 	rwlock_t lock;

 	int (*needs_bounce)(struct device *, dma_addr_t, size_t);
 };

 #ifdef STATS
 static ssize_t dmabounce_show(struct device *dev, struct device_attribute *attr,
 			      char *buf)
 {
 	struct dmabounce_device_info *device_info = dev->archdata.dmabounce;
 	return sprintf(buf, "%lu %lu %lu %lu %lu %lu\n",
 		device_info->small.allocs,
 		device_info->large.allocs,
 		device_info->total_allocs - device_info->small.allocs -
 			device_info->large.allocs,
 		device_info->total_allocs,
 		device_info->map_op_count,
 		device_info->bounce_count);
 }

 static DEVICE_ATTR(dmabounce_stats, 0400, dmabounce_show, NULL);
 #endif


 /* allocate a 'safe' buffer and keep track of it */
 static inline struct safe_buffer *
 alloc_safe_buffer(struct dmabounce_device_info *device_info, void *ptr,
 		  size_t size, enum dma_data_direction dir)
 {
 	struct safe_buffer *buf;
 	struct dmabounce_pool *pool;
 	struct device *dev = device_info->dev;
 	unsigned long flags;

 	dev_dbg(dev, "%s(ptr=%p, size=%d, dir=%d)\n",
 		__func__, ptr, size, dir);

 	if (size <= device_info->small.size) {
 		pool = &device_info->small;
 	} else if (size <= device_info->large.size) {
 		pool = &device_info->large;
 	} else {
 		pool = NULL;
 	}

 	buf = kmalloc(sizeof(struct safe_buffer), GFP_ATOMIC);
 	if (buf == NULL) {
 		dev_warn(dev, "%s: kmalloc failed\n", __func__);
 		return NULL;
 	}

 	buf->ptr = ptr;
 	buf->size = size;
 	buf->direction = dir;
 	buf->pool = pool;

 	if (pool) {
 		buf->safe = dma_pool_alloc(pool->pool, GFP_ATOMIC,
 					   &buf->safe_dma_addr);
 	} else {
 		buf->safe = dma_alloc_coherent(dev, size, &buf->safe_dma_addr,
 					       GFP_ATOMIC);
 	}

 	if (buf->safe == NULL) {
 		dev_warn(dev,
 			 "%s: could not alloc dma memory (size=%d)\n",
 			 __func__, size);
 		kfree(buf);
 		return NULL;
 	}

 #ifdef STATS
 	if (pool)
 		pool->allocs++;
 	device_info->total_allocs++;
 #endif

 	write_lock_irqsave(&device_info->lock, flags);
 	list_add(&buf->node, &device_info->safe_buffers);
 	write_unlock_irqrestore(&device_info->lock, flags);

 	return buf;
 }

 /* determine if a buffer is from our "safe" pool */
 static inline struct safe_buffer *
 find_safe_buffer(struct dmabounce_device_info *device_info, dma_addr_t safe_dma_addr)
 {
 	struct safe_buffer *b, *rb = NULL;
 	unsigned long flags;

 	read_lock_irqsave(&device_info->lock, flags);

 	list_for_each_entry(b, &device_info->safe_buffers, node)
 		if (b->safe_dma_addr <= safe_dma_addr &&
 		    b->safe_dma_addr + b->size > safe_dma_addr) {
 			rb = b;
 			break;
 		}

 	read_unlock_irqrestore(&device_info->lock, flags);
 	return rb;
 }

 static inline void
 free_safe_buffer(struct dmabounce_device_info *device_info, struct safe_buffer *buf)
 {
 	unsigned long flags;

 	dev_dbg(device_info->dev, "%s(buf=%p)\n", __func__, buf);

 	write_lock_irqsave(&device_info->lock, flags);

 	list_del(&buf->node);

 	write_unlock_irqrestore(&device_info->lock, flags);

 	if (buf->pool)
 		dma_pool_free(buf->pool->pool, buf->safe, buf->safe_dma_addr);
 	else
 		dma_free_coherent(device_info->dev, buf->size, buf->safe,
 				    buf->safe_dma_addr);

 	kfree(buf);
 }

 /* ************************************************** */

 static struct safe_buffer *find_safe_buffer_dev(struct device *dev,
 		dma_addr_t dma_addr, const char *where)
 {
 	if (!dev || !dev->archdata.dmabounce)
 		return NULL;
 	if (dma_mapping_error(dev, dma_addr)) {
 		dev_err(dev, "Trying to %s invalid mapping\n", where);
 		return NULL;
 	}
 	return find_safe_buffer(dev->archdata.dmabounce, dma_addr);
 }

 static int needs_bounce(struct device *dev, dma_addr_t dma_addr, size_t size)
 {
 	if (!dev || !dev->archdata.dmabounce)
 		return 0;

 	if (dev->dma_mask) {
 		unsigned long limit, mask = *dev->dma_mask;

 		limit = (mask + 1) & ~mask;
 		if (limit && size > limit) {
 			dev_err(dev, "DMA mapping too big (requested %#x "
 				"mask %#Lx)\n", size, *dev->dma_mask);
 			return -E2BIG;
 		}

 		/* Figure out if we need to bounce from the DMA mask. */
 		if ((dma_addr | (dma_addr + size - 1)) & ~mask)
 			return 1;
 	}

 	return !!dev->archdata.dmabounce->needs_bounce(dev, dma_addr, size);
 }

 static inline dma_addr_t map_single(struct device *dev, void *ptr, size_t size,
 				    enum dma_data_direction dir,
 				    unsigned long attrs)
 {
 	struct dmabounce_device_info *device_info = dev->archdata.dmabounce;
 	struct safe_buffer *buf;

 	if (device_info)
 		DO_STATS ( device_info->map_op_count++ );

 	buf = alloc_safe_buffer(device_info, ptr, size, dir);
 	if (buf == NULL) {
 		dev_err(dev, "%s: unable to map unsafe buffer %p!\n",
 		       __func__, ptr);
 		return DMA_MAPPING_ERROR;
 	}

 	dev_dbg(dev, "%s: unsafe buffer %p (dma=%#x) mapped to %p (dma=%#x)\n",
 		__func__, buf->ptr, virt_to_dma(dev, buf->ptr),
 		buf->safe, buf->safe_dma_addr);

 	if ((dir == DMA_TO_DEVICE || dir == DMA_BIDIRECTIONAL) &&
 	    !(attrs & DMA_ATTR_SKIP_CPU_SYNC)) {
 		dev_dbg(dev, "%s: copy unsafe %p to safe %p, size %d\n",
 			__func__, ptr, buf->safe, size);
 		memcpy(buf->safe, ptr, size);
 	}

 	return buf->safe_dma_addr;
 }

 static inline void unmap_single(struct device *dev, struct safe_buffer *buf,
 				size_t size, enum dma_data_direction dir,
 				unsigned long attrs)
 {
 	BUG_ON(buf->size != size);
 	BUG_ON(buf->direction != dir);

 	dev_dbg(dev, "%s: unsafe buffer %p (dma=%#x) mapped to %p (dma=%#x)\n",
 		__func__, buf->ptr, virt_to_dma(dev, buf->ptr),
 		buf->safe, buf->safe_dma_addr);

 	DO_STATS(dev->archdata.dmabounce->bounce_count++);

 	if ((dir == DMA_FROM_DEVICE || dir == DMA_BIDIRECTIONAL) &&
 	    !(attrs & DMA_ATTR_SKIP_CPU_SYNC)) {
 		void *ptr = buf->ptr;

 		dev_dbg(dev, "%s: copy back safe %p to unsafe %p size %d\n",
 			__func__, buf->safe, ptr, size);
 		memcpy(ptr, buf->safe, size);

 		/*
 		 * Since we may have written to a page cache page,
 		 * we need to ensure that the data will be coherent
 		 * with user mappings.
 		 */
 		__cpuc_flush_dcache_area(ptr, size);
 	}
 	free_safe_buffer(dev->archdata.dmabounce, buf);
 }

 /* ************************************************** */

 /*
  * see if a buffer address is in an 'unsafe' range.  if it is
  * allocate a 'safe' buffer and copy the unsafe buffer into it.
  * substitute the safe buffer for the unsafe one.
  * (basically move the buffer from an unsafe area to a safe one)
  */
 static dma_addr_t dmabounce_map_page(struct device *dev, struct page *page,
 		unsigned long offset, size_t size, enum dma_data_direction dir,
 		unsigned long attrs)
 {
 	dma_addr_t dma_addr;
 	int ret;

 	dev_dbg(dev, "%s(page=%p,off=%#lx,size=%zx,dir=%x)\n",
 		__func__, page, offset, size, dir);

 	dma_addr = pfn_to_dma(dev, page_to_pfn(page)) + offset;

 	ret = needs_bounce(dev, dma_addr, size);
 	if (ret < 0)
 		return DMA_MAPPING_ERROR;

 	if (ret == 0) {
 		arm_dma_ops.sync_single_for_device(dev, dma_addr, size, dir);
 		return dma_addr;
 	}

 	if (PageHighMem(page)) {
 		dev_err(dev, "DMA buffer bouncing of HIGHMEM pages is not supported\n");
 		return DMA_MAPPING_ERROR;
 	}

 	return map_single(dev, page_address(page) + offset, size, dir, attrs);
 }

 /*
  * see if a mapped address was really a "safe" buffer and if so, copy
  * the data from the safe buffer back to the unsafe buffer and free up
  * the safe buffer.  (basically return things back to the way they
  * should be)
  */
 static void dmabounce_unmap_page(struct device *dev, dma_addr_t dma_addr, size_t size,
 		enum dma_data_direction dir, unsigned long attrs)
 {
 	struct safe_buffer *buf;

 	dev_dbg(dev, "%s(dma=%#x,size=%d,dir=%x)\n",
 		__func__, dma_addr, size, dir);

 	buf = find_safe_buffer_dev(dev, dma_addr, __func__);
 	if (!buf) {
 		arm_dma_ops.sync_single_for_cpu(dev, dma_addr, size, dir);
 		return;
 	}

 	unmap_single(dev, buf, size, dir, attrs);
 }

 static int __dmabounce_sync_for_cpu(struct device *dev, dma_addr_t addr,
 		size_t sz, enum dma_data_direction dir)
 {
 	struct safe_buffer *buf;
 	unsigned long off;

 	dev_dbg(dev, "%s(dma=%#x,sz=%zx,dir=%x)\n",
 		__func__, addr, sz, dir);

 	buf = find_safe_buffer_dev(dev, addr, __func__);
 	if (!buf)
 		return 1;

 	off = addr - buf->safe_dma_addr;

 	BUG_ON(buf->direction != dir);

 	dev_dbg(dev, "%s: unsafe buffer %p (dma=%#x off=%#lx) mapped to %p (dma=%#x)\n",
 		__func__, buf->ptr, virt_to_dma(dev, buf->ptr), off,
 		buf->safe, buf->safe_dma_addr);

 	DO_STATS(dev->archdata.dmabounce->bounce_count++);

 	if (dir == DMA_FROM_DEVICE || dir == DMA_BIDIRECTIONAL) {
 		dev_dbg(dev, "%s: copy back safe %p to unsafe %p size %d\n",
 			__func__, buf->safe + off, buf->ptr + off, sz);
 		memcpy(buf->ptr + off, buf->safe + off, sz);
 	}
 	return 0;
 }

 static void dmabounce_sync_for_cpu(struct device *dev,
 		dma_addr_t handle, size_t size, enum dma_data_direction dir)
 {
 	if (!__dmabounce_sync_for_cpu(dev, handle, size, dir))
 		return;

 	arm_dma_ops.sync_single_for_cpu(dev, handle, size, dir);
 }

 static int __dmabounce_sync_for_device(struct device *dev, dma_addr_t addr,
 		size_t sz, enum dma_data_direction dir)
 {
 	struct safe_buffer *buf;
 	unsigned long off;

 	dev_dbg(dev, "%s(dma=%#x,sz=%zx,dir=%x)\n",
 		__func__, addr, sz, dir);

 	buf = find_safe_buffer_dev(dev, addr, __func__);
 	if (!buf)
 		return 1;

 	off = addr - buf->safe_dma_addr;

 	BUG_ON(buf->direction != dir);

 	dev_dbg(dev, "%s: unsafe buffer %p (dma=%#x off=%#lx) mapped to %p (dma=%#x)\n",
 		__func__, buf->ptr, virt_to_dma(dev, buf->ptr), off,
 		buf->safe, buf->safe_dma_addr);

 	DO_STATS(dev->archdata.dmabounce->bounce_count++);

 	if (dir == DMA_TO_DEVICE || dir == DMA_BIDIRECTIONAL) {
 		dev_dbg(dev, "%s: copy out unsafe %p to safe %p, size %d\n",
 			__func__,buf->ptr + off, buf->safe + off, sz);
 		memcpy(buf->safe + off, buf->ptr + off, sz);
 	}
 	return 0;
 }

 static void dmabounce_sync_for_device(struct device *dev,
 		dma_addr_t handle, size_t size, enum dma_data_direction dir)
 {
 	if (!__dmabounce_sync_for_device(dev, handle, size, dir))
 		return;

 	arm_dma_ops.sync_single_for_device(dev, handle, size, dir);
 }

 static int dmabounce_dma_supported(struct device *dev, u64 dma_mask)
 {
 	if (dev->archdata.dmabounce)
 		return 0;

 	return arm_dma_ops.dma_supported(dev, dma_mask);
 }

 static const struct dma_map_ops dmabounce_ops = {
 	.alloc			= arm_dma_alloc,
 	.free			= arm_dma_free,
 	.mmap			= arm_dma_mmap,
 	.get_sgtable		= arm_dma_get_sgtable,
 	.map_page		= dmabounce_map_page,
 	.unmap_page		= dmabounce_unmap_page,
 	.sync_single_for_cpu	= dmabounce_sync_for_cpu,
 	.sync_single_for_device	= dmabounce_sync_for_device,
 	.map_sg			= arm_dma_map_sg,
 	.unmap_sg		= arm_dma_unmap_sg,
 	.sync_sg_for_cpu	= arm_dma_sync_sg_for_cpu,
 	.sync_sg_for_device	= arm_dma_sync_sg_for_device,
 	.dma_supported		= dmabounce_dma_supported,
 };

 static int dmabounce_init_pool(struct dmabounce_pool *pool, struct device *dev,
 		const char *name, unsigned long size)
 {
 	pool->size = size;
 	DO_STATS(pool->allocs = 0);
 	pool->pool = dma_pool_create(name, dev, size,
 				     0 /* byte alignment */,
 				     0 /* no page-crossing issues */);

 	return pool->pool ? 0 : -ENOMEM;
 }

 int dmabounce_register_dev(struct device *dev, unsigned long small_buffer_size,
 		unsigned long large_buffer_size,
 		int (*needs_bounce_fn)(struct device *, dma_addr_t, size_t))
 {
 	struct dmabounce_device_info *device_info;
 	int ret;

 	device_info = kmalloc(sizeof(struct dmabounce_device_info), GFP_ATOMIC);
 	if (!device_info) {
 		dev_err(dev,
 			"Could not allocated dmabounce_device_info\n");
 		return -ENOMEM;
 	}

 	ret = dmabounce_init_pool(&device_info->small, dev,
 				  "small_dmabounce_pool", small_buffer_size);
 	if (ret) {
 		dev_err(dev,
 			"dmabounce: could not allocate DMA pool for %ld byte objects\n",
 			small_buffer_size);
 		goto err_free;
 	}

 	if (large_buffer_size) {
 		ret = dmabounce_init_pool(&device_info->large, dev,
 					  "large_dmabounce_pool",
 					  large_buffer_size);
 		if (ret) {
 			dev_err(dev,
 				"dmabounce: could not allocate DMA pool for %ld byte objects\n",
 				large_buffer_size);
 			goto err_destroy;
 		}
 	}

 	device_info->dev = dev;
 	INIT_LIST_HEAD(&device_info->safe_buffers);
 	rwlock_init(&device_info->lock);
 	device_info->needs_bounce = needs_bounce_fn;

 #ifdef STATS
 	device_info->total_allocs = 0;
 	device_info->map_op_count = 0;
 	device_info->bounce_count = 0;
 	device_info->attr_res = device_create_file(dev, &dev_attr_dmabounce_stats);
 #endif

 	dev->archdata.dmabounce = device_info;
 	set_dma_ops(dev, &dmabounce_ops);

 	dev_info(dev, "dmabounce: registered device\n");

 	return 0;

  err_destroy:
 	dma_pool_destroy(device_info->small.pool);
  err_free:
 	kfree(device_info);
 	return ret;
 }
 EXPORT_SYMBOL(dmabounce_register_dev);

 void dmabounce_unregister_dev(struct device *dev)
 {
 	struct dmabounce_device_info *device_info = dev->archdata.dmabounce;

 	dev->archdata.dmabounce = NULL;
 	set_dma_ops(dev, NULL);

 	if (!device_info) {
 		dev_warn(dev,
 			 "Never registered with dmabounce but attempting"
 			 "to unregister!\n");
 		return;
 	}

 	if (!list_empty(&device_info->safe_buffers)) {
 		dev_err(dev,
 			"Removing from dmabounce with pending buffers!\n");
 		BUG();
 	}

 	if (device_info->small.pool)
 		dma_pool_destroy(device_info->small.pool);
 	if (device_info->large.pool)
 		dma_pool_destroy(device_info->large.pool);

 #ifdef STATS
 	if (device_info->attr_res == 0)
 		device_remove_file(dev, &dev_attr_dmabounce_stats);
 #endif

 	kfree(device_info);

 	dev_info(dev, "dmabounce: device unregistered\n");
 }
 EXPORT_SYMBOL(dmabounce_unregister_dev);

 MODULE_AUTHOR("Christopher Hoover <ch@hpl.hp.com>, Deepak Saxena <dsaxena@plexity.net>");
 MODULE_DESCRIPTION("Special dma_{map/unmap/dma_sync}_* routines for systems with limited DMA windows");
 MODULE_LICENSE("GPL");
	// SPDX-License-Identifier: GPL-2.0-only
	/*
	* arch/arm/common/dmabounce.c
	*
	* Special dma_{map/unmap/dma_sync}_* routines for systems that have
	* limited DMA windows. These functions utilize bounce buffers to
	* copy data to/from buffers located outside the DMA region. This
	* only works for systems in which DMA memory is at the bottom of
	* RAM, the remainder of memory is at the top and the DMA memory
	* can be marked as ZONE_DMA. Anything beyond that such as discontiguous
	* DMA windows will require custom implementations that reserve memory
	* areas at early bootup.
	*
	* Original version by Brad Parker (brad@heeltoe.com)
	* Re-written by Christopher Hoover <ch@murgatroid.com>
	* Made generic by Deepak Saxena <dsaxena@plexity.net>
	*
	* Copyright (C) 2002 Hewlett Packard Company.
	* Copyright (C) 2004 MontaVista Software, Inc.
	*/

	#include <linux/module.h>
	#include <linux/init.h>
	#include <linux/slab.h>
	#include <linux/page-flags.h>
	#include <linux/device.h>
	#include <linux/dma-mapping.h>
	#include <linux/dmapool.h>
	#include <linux/list.h>
	#include <linux/scatterlist.h>

	#include <asm/cacheflush.h>
	#include <asm/dma-iommu.h>

	#undef STATS

	#ifdef STATS
	#define DO_STATS(X) do { X ; } while (0)
	#else
	#define DO_STATS(X) do { } while (0)
	#endif

	/* ************************************************** */

	struct safe_buffer {
	struct list_head node;

	/* original request */
	void *ptr;
	size_t size;
	int direction;

	/* safe buffer info */
	struct dmabounce_pool *pool;
	void *safe;
	dma_addr_t safe_dma_addr;
	};

	struct dmabounce_pool {
	unsigned long size;
	struct dma_pool *pool;
	#ifdef STATS
	unsigned long allocs;
	#endif
	};

	struct dmabounce_device_info {
	struct device *dev;
	struct list_head safe_buffers;
	#ifdef STATS
	unsigned long total_allocs;
	unsigned long map_op_count;
	unsigned long bounce_count;
	int attr_res;
	#endif
	struct dmabounce_pool small;
	struct dmabounce_pool large;

	rwlock_t lock;

	int (needs_bounce)(struct device , dma_addr_t, size_t);
	};

	#ifdef STATS
	static ssize_t dmabounce_show(struct device dev, struct device_attribute attr,
	char *buf)
	{
	struct dmabounce_device_info *device_info = dev->archdata.dmabounce;
	return sprintf(buf, "%lu %lu %lu %lu %lu %lu\n",
	device_info->small.allocs,
	device_info->large.allocs,
	device_info->total_allocs - device_info->small.allocs -
	device_info->large.allocs,
	device_info->total_allocs,
	device_info->map_op_count,
	device_info->bounce_count);
	}

	static DEVICE_ATTR(dmabounce_stats, 0400, dmabounce_show, NULL);
	#endif


	/* allocate a 'safe' buffer and keep track of it */
	static inline struct safe_buffer *
	alloc_safe_buffer(struct dmabounce_device_info device_info, void ptr,
	size_t size, enum dma_data_direction dir)
	{
	struct safe_buffer *buf;
	struct dmabounce_pool *pool;
	struct device *dev = device_info->dev;
	unsigned long flags;

	dev_dbg(dev, "%s(ptr=%p, size=%d, dir=%d)\n",
	__func__, ptr, size, dir);

	if (size <= device_info->small.size) {
	pool = &device_info->small;
	} else if (size <= device_info->large.size) {
	pool = &device_info->large;
	} else {
	pool = NULL;
	}

	buf = kmalloc(sizeof(struct safe_buffer), GFP_ATOMIC);
	if (buf == NULL) {
	dev_warn(dev, "%s: kmalloc failed\n", __func__);
	return NULL;
	}

	buf->ptr = ptr;
	buf->size = size;
	buf->direction = dir;
	buf->pool = pool;

	if (pool) {
	buf->safe = dma_pool_alloc(pool->pool, GFP_ATOMIC,
	&buf->safe_dma_addr);
	} else {
	buf->safe = dma_alloc_coherent(dev, size, &buf->safe_dma_addr,
	GFP_ATOMIC);
	}

	if (buf->safe == NULL) {
	dev_warn(dev,
	"%s: could not alloc dma memory (size=%d)\n",
	__func__, size);
	kfree(buf);
	return NULL;
	}

	#ifdef STATS
	if (pool)
	pool->allocs++;
	device_info->total_allocs++;
	#endif

	write_lock_irqsave(&device_info->lock, flags);
	list_add(&buf->node, &device_info->safe_buffers);
	write_unlock_irqrestore(&device_info->lock, flags);

	return buf;
	}

	/* determine if a buffer is from our "safe" pool */
	static inline struct safe_buffer *
	find_safe_buffer(struct dmabounce_device_info *device_info, dma_addr_t safe_dma_addr)
	{
	struct safe_buffer b, rb = NULL;
	unsigned long flags;

	read_lock_irqsave(&device_info->lock, flags);

	list_for_each_entry(b, &device_info->safe_buffers, node)
	if (b->safe_dma_addr <= safe_dma_addr &&
	b->safe_dma_addr + b->size > safe_dma_addr) {
	rb = b;
	break;
	}

	read_unlock_irqrestore(&device_info->lock, flags);
	return rb;
	}

	static inline void
	free_safe_buffer(struct dmabounce_device_info device_info, struct safe_buffer buf)
	{
	unsigned long flags;

	dev_dbg(device_info->dev, "%s(buf=%p)\n", __func__, buf);

	write_lock_irqsave(&device_info->lock, flags);

	list_del(&buf->node);

	write_unlock_irqrestore(&device_info->lock, flags);

	if (buf->pool)
	dma_pool_free(buf->pool->pool, buf->safe, buf->safe_dma_addr);
	else
	dma_free_coherent(device_info->dev, buf->size, buf->safe,
	buf->safe_dma_addr);

	kfree(buf);
	}

	/* ************************************************** */

	static struct safe_buffer find_safe_buffer_dev(struct device dev,
	dma_addr_t dma_addr, const char *where)
	{
	if (!dev \|\| !dev->archdata.dmabounce)
	return NULL;
	if (dma_mapping_error(dev, dma_addr)) {
	dev_err(dev, "Trying to %s invalid mapping\n", where);
	return NULL;
	}
	return find_safe_buffer(dev->archdata.dmabounce, dma_addr);
	}

	static int needs_bounce(struct device *dev, dma_addr_t dma_addr, size_t size)
	{
	if (!dev \|\| !dev->archdata.dmabounce)
	return 0;

	if (dev->dma_mask) {
	unsigned long limit, mask = *dev->dma_mask;

	limit = (mask + 1) & ~mask;
	if (limit && size > limit) {
	dev_err(dev, "DMA mapping too big (requested %#x "
	"mask %#Lx)\n", size, *dev->dma_mask);
	return -E2BIG;
	}

	/* Figure out if we need to bounce from the DMA mask. */
	if ((dma_addr \| (dma_addr + size - 1)) & ~mask)
	return 1;
	}

	return !!dev->archdata.dmabounce->needs_bounce(dev, dma_addr, size);
	}

	static inline dma_addr_t map_single(struct device dev, void ptr, size_t size,
	enum dma_data_direction dir,
	unsigned long attrs)
	{
	struct dmabounce_device_info *device_info = dev->archdata.dmabounce;
	struct safe_buffer *buf;

	if (device_info)
	DO_STATS ( device_info->map_op_count++ );

	buf = alloc_safe_buffer(device_info, ptr, size, dir);
	if (buf == NULL) {
	dev_err(dev, "%s: unable to map unsafe buffer %p!\n",
	__func__, ptr);
	return DMA_MAPPING_ERROR;
	}

	dev_dbg(dev, "%s: unsafe buffer %p (dma=%#x) mapped to %p (dma=%#x)\n",
	__func__, buf->ptr, virt_to_dma(dev, buf->ptr),
	buf->safe, buf->safe_dma_addr);

	if ((dir == DMA_TO_DEVICE \|\| dir == DMA_BIDIRECTIONAL) &&
	!(attrs & DMA_ATTR_SKIP_CPU_SYNC)) {
	dev_dbg(dev, "%s: copy unsafe %p to safe %p, size %d\n",
	__func__, ptr, buf->safe, size);
	memcpy(buf->safe, ptr, size);
	}

	return buf->safe_dma_addr;
	}

	static inline void unmap_single(struct device dev, struct safe_buffer buf,
	size_t size, enum dma_data_direction dir,
	unsigned long attrs)
	{
	BUG_ON(buf->size != size);
	BUG_ON(buf->direction != dir);

	dev_dbg(dev, "%s: unsafe buffer %p (dma=%#x) mapped to %p (dma=%#x)\n",
	__func__, buf->ptr, virt_to_dma(dev, buf->ptr),
	buf->safe, buf->safe_dma_addr);

	DO_STATS(dev->archdata.dmabounce->bounce_count++);

	if ((dir == DMA_FROM_DEVICE \|\| dir == DMA_BIDIRECTIONAL) &&
	!(attrs & DMA_ATTR_SKIP_CPU_SYNC)) {
	void *ptr = buf->ptr;

	dev_dbg(dev, "%s: copy back safe %p to unsafe %p size %d\n",
	__func__, buf->safe, ptr, size);
	memcpy(ptr, buf->safe, size);

	/*
	* Since we may have written to a page cache page,
	* we need to ensure that the data will be coherent
	* with user mappings.
	*/
	__cpuc_flush_dcache_area(ptr, size);
	}
	free_safe_buffer(dev->archdata.dmabounce, buf);
	}

	/* ************************************************** */

	/*
	* see if a buffer address is in an 'unsafe' range. if it is
	* allocate a 'safe' buffer and copy the unsafe buffer into it.
	* substitute the safe buffer for the unsafe one.
	* (basically move the buffer from an unsafe area to a safe one)
	*/
	static dma_addr_t dmabounce_map_page(struct device dev, struct page page,
	unsigned long offset, size_t size, enum dma_data_direction dir,
	unsigned long attrs)
	{
	dma_addr_t dma_addr;
	int ret;

	dev_dbg(dev, "%s(page=%p,off=%#lx,size=%zx,dir=%x)\n",
	__func__, page, offset, size, dir);

	dma_addr = pfn_to_dma(dev, page_to_pfn(page)) + offset;

	ret = needs_bounce(dev, dma_addr, size);
	if (ret < 0)
	return DMA_MAPPING_ERROR;

	if (ret == 0) {
	arm_dma_ops.sync_single_for_device(dev, dma_addr, size, dir);
	return dma_addr;
	}

	if (PageHighMem(page)) {
	dev_err(dev, "DMA buffer bouncing of HIGHMEM pages is not supported\n");
	return DMA_MAPPING_ERROR;
	}

	return map_single(dev, page_address(page) + offset, size, dir, attrs);
	}

	/*
	* see if a mapped address was really a "safe" buffer and if so, copy
	* the data from the safe buffer back to the unsafe buffer and free up
	* the safe buffer. (basically return things back to the way they
	* should be)
	*/
	static void dmabounce_unmap_page(struct device *dev, dma_addr_t dma_addr, size_t size,
	enum dma_data_direction dir, unsigned long attrs)
	{
	struct safe_buffer *buf;

	dev_dbg(dev, "%s(dma=%#x,size=%d,dir=%x)\n",
	__func__, dma_addr, size, dir);

	buf = find_safe_buffer_dev(dev, dma_addr, __func__);
	if (!buf) {
	arm_dma_ops.sync_single_for_cpu(dev, dma_addr, size, dir);
	return;
	}

	unmap_single(dev, buf, size, dir, attrs);
	}

	static int __dmabounce_sync_for_cpu(struct device *dev, dma_addr_t addr,
	size_t sz, enum dma_data_direction dir)
	{
	struct safe_buffer *buf;
	unsigned long off;

	dev_dbg(dev, "%s(dma=%#x,sz=%zx,dir=%x)\n",
	__func__, addr, sz, dir);

	buf = find_safe_buffer_dev(dev, addr, __func__);
	if (!buf)
	return 1;

	off = addr - buf->safe_dma_addr;

	BUG_ON(buf->direction != dir);

	dev_dbg(dev, "%s: unsafe buffer %p (dma=%#x off=%#lx) mapped to %p (dma=%#x)\n",
	__func__, buf->ptr, virt_to_dma(dev, buf->ptr), off,
	buf->safe, buf->safe_dma_addr);

	DO_STATS(dev->archdata.dmabounce->bounce_count++);

	if (dir == DMA_FROM_DEVICE \|\| dir == DMA_BIDIRECTIONAL) {
	dev_dbg(dev, "%s: copy back safe %p to unsafe %p size %d\n",
	__func__, buf->safe + off, buf->ptr + off, sz);
	memcpy(buf->ptr + off, buf->safe + off, sz);
	}
	return 0;
	}

	static void dmabounce_sync_for_cpu(struct device *dev,
	dma_addr_t handle, size_t size, enum dma_data_direction dir)
	{
	if (!__dmabounce_sync_for_cpu(dev, handle, size, dir))
	return;

	arm_dma_ops.sync_single_for_cpu(dev, handle, size, dir);
	}

	static int __dmabounce_sync_for_device(struct device *dev, dma_addr_t addr,
	size_t sz, enum dma_data_direction dir)
	{
	struct safe_buffer *buf;
	unsigned long off;

	dev_dbg(dev, "%s(dma=%#x,sz=%zx,dir=%x)\n",
	__func__, addr, sz, dir);

	buf = find_safe_buffer_dev(dev, addr, __func__);
	if (!buf)
	return 1;

	off = addr - buf->safe_dma_addr;

	BUG_ON(buf->direction != dir);

	dev_dbg(dev, "%s: unsafe buffer %p (dma=%#x off=%#lx) mapped to %p (dma=%#x)\n",
	__func__, buf->ptr, virt_to_dma(dev, buf->ptr), off,
	buf->safe, buf->safe_dma_addr);

	DO_STATS(dev->archdata.dmabounce->bounce_count++);

	if (dir == DMA_TO_DEVICE \|\| dir == DMA_BIDIRECTIONAL) {
	dev_dbg(dev, "%s: copy out unsafe %p to safe %p, size %d\n",
	__func__,buf->ptr + off, buf->safe + off, sz);
	memcpy(buf->safe + off, buf->ptr + off, sz);
	}
	return 0;
	}

	static void dmabounce_sync_for_device(struct device *dev,
	dma_addr_t handle, size_t size, enum dma_data_direction dir)
	{
	if (!__dmabounce_sync_for_device(dev, handle, size, dir))
	return;

	arm_dma_ops.sync_single_for_device(dev, handle, size, dir);
	}

	static int dmabounce_dma_supported(struct device *dev, u64 dma_mask)
	{
	if (dev->archdata.dmabounce)
	return 0;

	return arm_dma_ops.dma_supported(dev, dma_mask);
	}

	static const struct dma_map_ops dmabounce_ops = {
	.alloc = arm_dma_alloc,
	.free = arm_dma_free,
	.mmap = arm_dma_mmap,
	.get_sgtable = arm_dma_get_sgtable,
	.map_page = dmabounce_map_page,
	.unmap_page = dmabounce_unmap_page,
	.sync_single_for_cpu = dmabounce_sync_for_cpu,
	.sync_single_for_device = dmabounce_sync_for_device,
	.map_sg = arm_dma_map_sg,
	.unmap_sg = arm_dma_unmap_sg,
	.sync_sg_for_cpu = arm_dma_sync_sg_for_cpu,
	.sync_sg_for_device = arm_dma_sync_sg_for_device,
	.dma_supported = dmabounce_dma_supported,
	};

	static int dmabounce_init_pool(struct dmabounce_pool pool, struct device dev,
	const char *name, unsigned long size)
	{
	pool->size = size;
	DO_STATS(pool->allocs = 0);
	pool->pool = dma_pool_create(name, dev, size,
	0 /* byte alignment */,
	0 /* no page-crossing issues */);

	return pool->pool ? 0 : -ENOMEM;
	}

	int dmabounce_register_dev(struct device *dev, unsigned long small_buffer_size,
	unsigned long large_buffer_size,
	int (needs_bounce_fn)(struct device , dma_addr_t, size_t))
	{
	struct dmabounce_device_info *device_info;
	int ret;

	device_info = kmalloc(sizeof(struct dmabounce_device_info), GFP_ATOMIC);
	if (!device_info) {
	dev_err(dev,
	"Could not allocated dmabounce_device_info\n");
	return -ENOMEM;
	}

	ret = dmabounce_init_pool(&device_info->small, dev,
	"small_dmabounce_pool", small_buffer_size);
	if (ret) {
	dev_err(dev,
	"dmabounce: could not allocate DMA pool for %ld byte objects\n",
	small_buffer_size);
	goto err_free;
	}

	if (large_buffer_size) {
	ret = dmabounce_init_pool(&device_info->large, dev,
	"large_dmabounce_pool",
	large_buffer_size);
	if (ret) {
	dev_err(dev,
	"dmabounce: could not allocate DMA pool for %ld byte objects\n",
	large_buffer_size);
	goto err_destroy;
	}
	}

	device_info->dev = dev;
	INIT_LIST_HEAD(&device_info->safe_buffers);
	rwlock_init(&device_info->lock);
	device_info->needs_bounce = needs_bounce_fn;

	#ifdef STATS
	device_info->total_allocs = 0;
	device_info->map_op_count = 0;
	device_info->bounce_count = 0;
	device_info->attr_res = device_create_file(dev, &dev_attr_dmabounce_stats);
	#endif

	dev->archdata.dmabounce = device_info;
	set_dma_ops(dev, &dmabounce_ops);

	dev_info(dev, "dmabounce: registered device\n");

	return 0;

	err_destroy:
	dma_pool_destroy(device_info->small.pool);
	err_free:
	kfree(device_info);
	return ret;
	}
	EXPORT_SYMBOL(dmabounce_register_dev);

	void dmabounce_unregister_dev(struct device *dev)
	{
	struct dmabounce_device_info *device_info = dev->archdata.dmabounce;

	dev->archdata.dmabounce = NULL;
	set_dma_ops(dev, NULL);

	if (!device_info) {
	dev_warn(dev,
	"Never registered with dmabounce but attempting"
	"to unregister!\n");
	return;
	}

	if (!list_empty(&device_info->safe_buffers)) {
	dev_err(dev,
	"Removing from dmabounce with pending buffers!\n");
	BUG();
	}

	if (device_info->small.pool)
	dma_pool_destroy(device_info->small.pool);
	if (device_info->large.pool)
	dma_pool_destroy(device_info->large.pool);

	#ifdef STATS
	if (device_info->attr_res == 0)
	device_remove_file(dev, &dev_attr_dmabounce_stats);
	#endif

	kfree(device_info);

	dev_info(dev, "dmabounce: device unregistered\n");
	}
	EXPORT_SYMBOL(dmabounce_unregister_dev);

	MODULE_AUTHOR("Christopher Hoover <ch@hpl.hp.com>, Deepak Saxena <dsaxena@plexity.net>");
	MODULE_DESCRIPTION("Special dma_{map/unmap/dma_sync}_* routines for systems with limited DMA windows");
	MODULE_LICENSE("GPL");