dmabounce.c

linux 内核源代码

	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 (phy=%p) mapped to %p (phy=%p)\n",
			__func__, buf->ptr, (void *) virt_to_dma(dev, buf->ptr),
			buf->safe, (void *) 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.
		 */
	} else {
		dma_cache_maint(dma_to_virt(dev, dma_addr), size, dir);
	}
}

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

/*
 * 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_for_cpu(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);

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

void
dma_sync_single_for_device(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);

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

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) {
		printk(KERN_ERR
			"Could not allocated dmabounce_device_info for %s",
			dev->bus_id);
		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;

	printk(KERN_INFO "dmabounce: registered device %s on %s bus\n",
		dev->bus_id, dev->bus->name);

	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) {
		printk(KERN_WARNING
			"%s: Never registered with dmabounce but attempting" \
			"to unregister!\n", dev->bus_id);
		return;
	}

	if (!list_empty(&device_info->safe_buffers)) {
		printk(KERN_ERR
			"%s: Removing from dmabounce with pending buffers!\n",
			dev->bus_id);
		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);

	printk(KERN_INFO "dmabounce: device %s on %s bus unregistered\n",
		dev->bus_id, dev->bus->name);
}


EXPORT_SYMBOL(dma_map_single);
EXPORT_SYMBOL(dma_unmap_single);
EXPORT_SYMBOL(dma_map_sg);
EXPORT_SYMBOL(dma_unmap_sg);
EXPORT_SYMBOL(dma_sync_single_for_cpu);
EXPORT_SYMBOL(dma_sync_single_for_device);
EXPORT_SYMBOL(dma_sync_sg);
EXPORT_SYMBOL(dmabounce_register_dev);
EXPORT_SYMBOL(dmabounce_unregister_dev);

MODULE_AUTHOR("Christopher Hoover <[e-mail]>, Deepak Saxena <[e-mail]>");
MODULE_DESCRIPTION("Special dma_{map/unmap/dma_sync}_* routines for systems with limited DMA windows");
MODULE_LICENSE("GPL");