arch/arm/common/dmabounce.c - kernel/msm - Gitiles

 /*
  *  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.
  *
  *  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.
  */

 #include <linux/module.h>
 #include <linux/init.h>
 #include <linux/slab.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>

 #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;
 };

 #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) {
 			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 inline dma_addr_t
 map_single(struct device *dev, void *ptr, size_t size,
 		enum dma_data_direction dir)
 {
 	struct dmabounce_device_info *device_info = dev->archdata.dmabounce;
 	dma_addr_t dma_addr;
 	int needs_bounce = 0;

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

 	dma_addr = virt_to_dma(dev, ptr);

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

 		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 ~0;
 		}

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

 	if (device_info && (needs_bounce || dma_needs_bounce(dev, dma_addr, size))) {
 		struct safe_buffer *buf;

 		buf = alloc_safe_buffer(device_info, ptr, size, dir);
 		if (buf == 0) {
 			dev_err(dev, "%s: unable to map unsafe buffer %p!\n",
 			       __func__, ptr);
 			return 0;
 		}

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

 		dma_addr = buf->safe_dma_addr;
 	} else {
 		/*
 		 * We don't need to sync the DMA buffer since
 		 * it was allocated via the coherent allocators.
 		 */
 		dma_cache_maint(ptr, size, dir);
 	}

 	return dma_addr;
 }

 static inline void
 unmap_single(struct device *dev, dma_addr_t dma_addr, size_t size,
 		enum dma_data_direction dir)
 {
 	struct dmabounce_device_info *device_info = dev->archdata.dmabounce;
 	struct safe_buffer *buf = NULL;

 	/*
 	 * Trying to unmap an invalid mapping
 	 */
 	if (dma_mapping_error(dev, dma_addr)) {
 		dev_err(dev, "Trying to unmap invalid mapping\n");
 		return;
 	}

 	if (device_info)
 		buf = find_safe_buffer(device_info, dma_addr);

 	if (buf) {
 		BUG_ON(buf->size != size);

 		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 ( device_info->bounce_count++ );

 		if (dir == DMA_FROM_DEVICE || dir == DMA_BIDIRECTIONAL) {
 			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);

 			/*
 			 * DMA buffers must have the same cache properties
 			 * as if they were really used for DMA - which means
 			 * data must be written back to RAM.  Note that
 			 * we don't use dmac_flush_range() here for the
 			 * bidirectional case because we know the cache
 			 * lines will be coherent with the data written.
 			 */
 			dmac_clean_range(ptr, ptr + size);
 			outer_clean_range(__pa(ptr), __pa(ptr) + size);
 		}
 		free_safe_buffer(device_info, buf);
 	}
 }

 static int sync_single(struct device *dev, dma_addr_t dma_addr, size_t size,
 			enum dma_data_direction dir)
 {
 	struct dmabounce_device_info *device_info = dev->archdata.dmabounce;
 	struct safe_buffer *buf = NULL;

 	if (device_info)
 		buf = find_safe_buffer(device_info, dma_addr);

 	if (buf) {
 		/*
 		 * Both of these checks from original code need to be
 		 * commented out b/c some drivers rely on the following:
 		 *
 		 * 1) Drivers may map a large chunk of memory into DMA space
 		 *    but only sync a small portion of it. Good example is
 		 *    allocating a large buffer, mapping it, and then
 		 *    breaking it up into small descriptors. No point
 		 *    in syncing the whole buffer if you only have to
 		 *    touch one descriptor.
 		 *
 		 * 2) Buffers that are mapped as DMA_BIDIRECTIONAL are
 		 *    usually only synced in one dir at a time.
 		 *
 		 * See drivers/net/eepro100.c for examples of both cases.
 		 *
 		 * -ds
 		 *
 		 * 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 ( device_info->bounce_count++ );

 		switch (dir) {
 		case DMA_FROM_DEVICE:
 			dev_dbg(dev,
 				"%s: copy back safe %p to unsafe %p size %d\n",
 				__func__, buf->safe, buf->ptr, size);
 			memcpy(buf->ptr, buf->safe, size);
 			break;
 		case DMA_TO_DEVICE:
 			dev_dbg(dev,
 				"%s: copy out unsafe %p to safe %p, size %d\n",
 				__func__,buf->ptr, buf->safe, size);
 			memcpy(buf->safe, buf->ptr, size);
 			break;
 		case DMA_BIDIRECTIONAL:
 			BUG();	/* is this allowed?  what does it mean? */
 		default:
 			BUG();
 		}
 		/*
 		 * No need to sync the safe buffer - it was allocated
 		 * via the coherent allocators.
 		 */
 		return 0;
 	} else {
 		return 1;
 	}
 }

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

 /*
  * 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)
  */
 dma_addr_t
 dma_map_single(struct device *dev, void *ptr, size_t size,
 		enum dma_data_direction dir)
 {
 	dma_addr_t dma_addr;

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

 	BUG_ON(dir == DMA_NONE);

 	dma_addr = map_single(dev, ptr, size, dir);

 	return dma_addr;
 }

 /*
  * 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)
  */

 void
 dma_unmap_single(struct device *dev, dma_addr_t dma_addr, size_t size,
 			enum dma_data_direction dir)
 {
 	dev_dbg(dev, "%s(ptr=%p,size=%d,dir=%x)\n",
 		__func__, (void *) dma_addr, size, dir);

 	BUG_ON(dir == DMA_NONE);

 	unmap_single(dev, dma_addr, size, dir);
 }

 int
 dma_map_sg(struct device *dev, struct scatterlist *sg, int nents,
 		enum dma_data_direction dir)
 {
 	int i;

 	dev_dbg(dev, "%s(sg=%p,nents=%d,dir=%x)\n",
 		__func__, sg, nents, dir);

 	BUG_ON(dir == DMA_NONE);

 	for (i = 0; i < nents; i++, sg++) {
 		struct page *page = sg_page(sg);
 		unsigned int offset = sg->offset;
 		unsigned int length = sg->length;
 		void *ptr = page_address(page) + offset;

 		sg->dma_address =
 			map_single(dev, ptr, length, dir);
 	}

 	return nents;
 }

 void
 dma_unmap_sg(struct device *dev, struct scatterlist *sg, int nents,
 		enum dma_data_direction dir)
 {
 	int i;

 	dev_dbg(dev, "%s(sg=%p,nents=%d,dir=%x)\n",
 		__func__, sg, nents, dir);

 	BUG_ON(dir == DMA_NONE);

 	for (i = 0; i < nents; i++, sg++) {
 		dma_addr_t dma_addr = sg->dma_address;
 		unsigned int length = sg->length;

 		unmap_single(dev, dma_addr, length, dir);
 	}
 }

 void dma_sync_single_range_for_cpu(struct device *dev, dma_addr_t dma_addr,
 				   unsigned long offset, size_t size,
 				   enum dma_data_direction dir)
 {
 	dev_dbg(dev, "%s(dma=%#x,off=%#lx,size=%zx,dir=%x)\n",
 		__func__, dma_addr, offset, size, dir);

 	if (sync_single(dev, dma_addr, offset + size, dir))
 		dma_cache_maint(dma_to_virt(dev, dma_addr) + offset, size, dir);
 }
 EXPORT_SYMBOL(dma_sync_single_range_for_cpu);

 void dma_sync_single_range_for_device(struct device *dev, dma_addr_t dma_addr,
 				      unsigned long offset, size_t size,
 				      enum dma_data_direction dir)
 {
 	dev_dbg(dev, "%s(dma=%#x,off=%#lx,size=%zx,dir=%x)\n",
 		__func__, dma_addr, offset, size, dir);

 	if (sync_single(dev, dma_addr, offset + size, dir))
 		dma_cache_maint(dma_to_virt(dev, dma_addr) + offset, size, dir);
 }
 EXPORT_SYMBOL(dma_sync_single_range_for_device);

 void
 dma_sync_sg_for_cpu(struct device *dev, struct scatterlist *sg, int nents,
 			enum dma_data_direction dir)
 {
 	int i;

 	dev_dbg(dev, "%s(sg=%p,nents=%d,dir=%x)\n",
 		__func__, sg, nents, dir);

 	BUG_ON(dir == DMA_NONE);

 	for (i = 0; i < nents; i++, sg++) {
 		dma_addr_t dma_addr = sg->dma_address;
 		unsigned int length = sg->length;

 		sync_single(dev, dma_addr, length, dir);
 	}
 }

 void
 dma_sync_sg_for_device(struct device *dev, struct scatterlist *sg, int nents,
 			enum dma_data_direction dir)
 {
 	int i;

 	dev_dbg(dev, "%s(sg=%p,nents=%d,dir=%x)\n",
 		__func__, sg, nents, dir);

 	BUG_ON(dir == DMA_NONE);

 	for (i = 0; i < nents; i++, sg++) {
 		dma_addr_t dma_addr = sg->dma_address;
 		unsigned int length = sg->length;

 		sync_single(dev, dma_addr, length, dir);
 	}
 }

 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)
 {
 	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);

 #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;

 	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;
 }

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

 	dev->archdata.dmabounce = 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(dma_map_single);
 EXPORT_SYMBOL(dma_unmap_single);
 EXPORT_SYMBOL(dma_map_sg);
 EXPORT_SYMBOL(dma_unmap_sg);
 EXPORT_SYMBOL(dma_sync_sg_for_cpu);
 EXPORT_SYMBOL(dma_sync_sg_for_device);
 EXPORT_SYMBOL(dmabounce_register_dev);
 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");
	/*
	* 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.
	*
	* 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.
	*/

	#include <linux/module.h>
	#include <linux/init.h>
	#include <linux/slab.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>

	#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;
	};

	#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) {
	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 inline dma_addr_t
	map_single(struct device dev, void ptr, size_t size,
	enum dma_data_direction dir)
	{
	struct dmabounce_device_info *device_info = dev->archdata.dmabounce;
	dma_addr_t dma_addr;
	int needs_bounce = 0;

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

	dma_addr = virt_to_dma(dev, ptr);

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

	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 ~0;
	}

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

	if (device_info && (needs_bounce \|\| dma_needs_bounce(dev, dma_addr, size))) {
	struct safe_buffer *buf;

	buf = alloc_safe_buffer(device_info, ptr, size, dir);
	if (buf == 0) {
	dev_err(dev, "%s: unable to map unsafe buffer %p!\n",
	__func__, ptr);
	return 0;
	}

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

	dma_addr = buf->safe_dma_addr;
	} else {
	/*
	* We don't need to sync the DMA buffer since
	* it was allocated via the coherent allocators.
	*/
	dma_cache_maint(ptr, size, dir);
	}

	return dma_addr;
	}

	static inline void
	unmap_single(struct device *dev, dma_addr_t dma_addr, size_t size,
	enum dma_data_direction dir)
	{
	struct dmabounce_device_info *device_info = dev->archdata.dmabounce;
	struct safe_buffer *buf = NULL;

	/*
	* Trying to unmap an invalid mapping
	*/
	if (dma_mapping_error(dev, dma_addr)) {
	dev_err(dev, "Trying to unmap invalid mapping\n");
	return;
	}

	if (device_info)
	buf = find_safe_buffer(device_info, dma_addr);

	if (buf) {
	BUG_ON(buf->size != size);

	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 ( device_info->bounce_count++ );

	if (dir == DMA_FROM_DEVICE \|\| dir == DMA_BIDIRECTIONAL) {
	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);

	/*
	* DMA buffers must have the same cache properties
	* as if they were really used for DMA - which means
	* data must be written back to RAM. Note that
	* we don't use dmac_flush_range() here for the
	* bidirectional case because we know the cache
	* lines will be coherent with the data written.
	*/
	dmac_clean_range(ptr, ptr + size);
	outer_clean_range(__pa(ptr), __pa(ptr) + size);
	}
	free_safe_buffer(device_info, buf);
	}
	}

	static int sync_single(struct device *dev, dma_addr_t dma_addr, size_t size,
	enum dma_data_direction dir)
	{
	struct dmabounce_device_info *device_info = dev->archdata.dmabounce;
	struct safe_buffer *buf = NULL;

	if (device_info)
	buf = find_safe_buffer(device_info, dma_addr);

	if (buf) {
	/*
	* Both of these checks from original code need to be
	* commented out b/c some drivers rely on the following:
	*
	* 1) Drivers may map a large chunk of memory into DMA space
	* but only sync a small portion of it. Good example is
	* allocating a large buffer, mapping it, and then
	* breaking it up into small descriptors. No point
	* in syncing the whole buffer if you only have to
	* touch one descriptor.
	*
	* 2) Buffers that are mapped as DMA_BIDIRECTIONAL are
	* usually only synced in one dir at a time.
	*
	* See drivers/net/eepro100.c for examples of both cases.
	*
	* -ds
	*
	* 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 ( device_info->bounce_count++ );

	switch (dir) {
	case DMA_FROM_DEVICE:
	dev_dbg(dev,
	"%s: copy back safe %p to unsafe %p size %d\n",
	__func__, buf->safe, buf->ptr, size);
	memcpy(buf->ptr, buf->safe, size);
	break;
	case DMA_TO_DEVICE:
	dev_dbg(dev,
	"%s: copy out unsafe %p to safe %p, size %d\n",
	__func__,buf->ptr, buf->safe, size);
	memcpy(buf->safe, buf->ptr, size);
	break;
	case DMA_BIDIRECTIONAL:
	BUG(); /* is this allowed? what does it mean? */
	default:
	BUG();
	}
	/*
	* No need to sync the safe buffer - it was allocated
	* via the coherent allocators.
	*/
	return 0;
	} else {
	return 1;
	}
	}

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

	/*
	* 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)
	*/
	dma_addr_t
	dma_map_single(struct device dev, void ptr, size_t size,
	enum dma_data_direction dir)
	{
	dma_addr_t dma_addr;

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

	BUG_ON(dir == DMA_NONE);

	dma_addr = map_single(dev, ptr, size, dir);

	return dma_addr;
	}

	/*
	* 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)
	*/

	void
	dma_unmap_single(struct device *dev, dma_addr_t dma_addr, size_t size,
	enum dma_data_direction dir)
	{
	dev_dbg(dev, "%s(ptr=%p,size=%d,dir=%x)\n",
	__func__, (void *) dma_addr, size, dir);

	BUG_ON(dir == DMA_NONE);

	unmap_single(dev, dma_addr, size, dir);
	}

	int
	dma_map_sg(struct device dev, struct scatterlist sg, int nents,
	enum dma_data_direction dir)
	{
	int i;

	dev_dbg(dev, "%s(sg=%p,nents=%d,dir=%x)\n",
	__func__, sg, nents, dir);

	BUG_ON(dir == DMA_NONE);

	for (i = 0; i < nents; i++, sg++) {
	struct page *page = sg_page(sg);
	unsigned int offset = sg->offset;
	unsigned int length = sg->length;
	void *ptr = page_address(page) + offset;

	sg->dma_address =
	map_single(dev, ptr, length, dir);
	}

	return nents;
	}

	void
	dma_unmap_sg(struct device dev, struct scatterlist sg, int nents,
	enum dma_data_direction dir)
	{
	int i;

	dev_dbg(dev, "%s(sg=%p,nents=%d,dir=%x)\n",
	__func__, sg, nents, dir);

	BUG_ON(dir == DMA_NONE);

	for (i = 0; i < nents; i++, sg++) {
	dma_addr_t dma_addr = sg->dma_address;
	unsigned int length = sg->length;

	unmap_single(dev, dma_addr, length, dir);
	}
	}

	void dma_sync_single_range_for_cpu(struct device *dev, dma_addr_t dma_addr,
	unsigned long offset, size_t size,
	enum dma_data_direction dir)
	{
	dev_dbg(dev, "%s(dma=%#x,off=%#lx,size=%zx,dir=%x)\n",
	__func__, dma_addr, offset, size, dir);

	if (sync_single(dev, dma_addr, offset + size, dir))
	dma_cache_maint(dma_to_virt(dev, dma_addr) + offset, size, dir);
	}
	EXPORT_SYMBOL(dma_sync_single_range_for_cpu);

	void dma_sync_single_range_for_device(struct device *dev, dma_addr_t dma_addr,
	unsigned long offset, size_t size,
	enum dma_data_direction dir)
	{
	dev_dbg(dev, "%s(dma=%#x,off=%#lx,size=%zx,dir=%x)\n",
	__func__, dma_addr, offset, size, dir);

	if (sync_single(dev, dma_addr, offset + size, dir))
	dma_cache_maint(dma_to_virt(dev, dma_addr) + offset, size, dir);
	}
	EXPORT_SYMBOL(dma_sync_single_range_for_device);

	void
	dma_sync_sg_for_cpu(struct device dev, struct scatterlist sg, int nents,
	enum dma_data_direction dir)
	{
	int i;

	dev_dbg(dev, "%s(sg=%p,nents=%d,dir=%x)\n",
	__func__, sg, nents, dir);

	BUG_ON(dir == DMA_NONE);

	for (i = 0; i < nents; i++, sg++) {
	dma_addr_t dma_addr = sg->dma_address;
	unsigned int length = sg->length;

	sync_single(dev, dma_addr, length, dir);
	}
	}

	void
	dma_sync_sg_for_device(struct device dev, struct scatterlist sg, int nents,
	enum dma_data_direction dir)
	{
	int i;

	dev_dbg(dev, "%s(sg=%p,nents=%d,dir=%x)\n",
	__func__, sg, nents, dir);

	BUG_ON(dir == DMA_NONE);

	for (i = 0; i < nents; i++, sg++) {
	dma_addr_t dma_addr = sg->dma_address;
	unsigned int length = sg->length;

	sync_single(dev, dma_addr, length, dir);
	}
	}

	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)
	{
	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);

	#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;

	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;
	}

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

	dev->archdata.dmabounce = 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(dma_map_single);
	EXPORT_SYMBOL(dma_unmap_single);
	EXPORT_SYMBOL(dma_map_sg);
	EXPORT_SYMBOL(dma_unmap_sg);
	EXPORT_SYMBOL(dma_sync_sg_for_cpu);
	EXPORT_SYMBOL(dma_sync_sg_for_device);
	EXPORT_SYMBOL(dmabounce_register_dev);
	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");