/*
   *  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/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>
  
  #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
  ",
  		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)
  ",
  		__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
  ", __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)
  ",
  			 __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)
  ", __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
  ", 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)
  ", 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)
  {
  	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!
  ",
  		       __func__, ptr);
  		return DMA_ERROR_CODE;
  	}
  
  	dev_dbg(dev, "%s: unsafe buffer %p (dma=%#x) mapped to %p (dma=%#x)
  ",
  		__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
  ",
  			__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)
  {
  	BUG_ON(buf->size != size);
  	BUG_ON(buf->direction != dir);
  
  	dev_dbg(dev, "%s: unsafe buffer %p (dma=%#x) mapped to %p (dma=%#x)
  ",
  		__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) {
  		void *ptr = buf->ptr;
  
  		dev_dbg(dev, "%s: copy back safe %p to unsafe %p size %d
  ",
  			__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,
  		struct dma_attrs *attrs)
  {
  	dma_addr_t dma_addr;
  	int ret;
  
  	dev_dbg(dev, "%s(page=%p,off=%#lx,size=%zx,dir=%x)
  ",
  		__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_ERROR_CODE;
  
  	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
  ");
  		return DMA_ERROR_CODE;
  	}
  
  	return map_single(dev, page_address(page) + offset, size, dir);
  }
  
  /*
   * 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, struct dma_attrs *attrs)
  {
  	struct safe_buffer *buf;
  
  	dev_dbg(dev, "%s(dma=%#x,size=%d,dir=%x)
  ",
  		__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);
  }
  
  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)
  ",
  		__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)
  ",
  		__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
  ",
  			__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)
  ",
  		__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)
  ",
  		__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
  ",
  			__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_set_mask(struct device *dev, u64 dma_mask)
  {
  	if (dev->archdata.dmabounce)
  		return 0;
  
  	return arm_dma_ops.set_dma_mask(dev, dma_mask);
  }
  
  static 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,
  	.set_dma_mask		= dmabounce_set_mask,
  };
  
  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
  ");
  		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
  ",
  			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
  ",
  				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
  ");
  
  	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!
  ");
  		return;
  	}
  
  	if (!list_empty(&device_info->safe_buffers)) {
  		dev_err(dev,
  			"Removing from dmabounce with pending buffers!
  ");
  		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
  ");
  }
  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");