dmabounce.c

优龙2410linux2.6.8内核源代码

/*
 *  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 and the remainder of memory is at the top an the DMA memory
 *  can be marked as ZONE_DMA. Anything beyond that such as discontigous
 *  DMA windows will require custom implementations that reserve memory
 *  areas at early bootup.
 *
 *  Original version by Brad Parker ([e-mail])
 *  Re-written by Christopher Hoover <[e-mail]>
 *  Made generic by Deepak Saxena <[e-mail]>
 *
 *  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>

#undef DEBUG

#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 dma_pool *pool;
	void		*safe;
	dma_addr_t	safe_dma_addr;
};

struct dmabounce_device_info {
	struct list_head node;

	struct device *dev;
	struct dma_pool *small_buffer_pool;
	struct dma_pool *large_buffer_pool;
	struct list_head safe_buffers;
	unsigned long small_buffer_size, large_buffer_size;
#ifdef STATS
	unsigned long sbp_allocs;
	unsigned long lbp_allocs;
	unsigned long total_allocs;
	unsigned long map_op_count;
	unsigned long bounce_count;
#endif
};

static LIST_HEAD(dmabounce_devs);

#ifdef STATS
static void print_alloc_stats(struct dmabounce_device_info *device_info)
{
	printk(KERN_INFO
		"%s: dmabounce: sbp: %lu, lbp: %lu, other: %lu, total: %lu\n",
		device_info->dev->bus_id,
		device_info->sbp_allocs, device_info->lbp_allocs,
		device_info->total_allocs - device_info->sbp_allocs -
			device_info->lbp_allocs,
		device_info->total_allocs);
}
#endif

/* find the given device in the dmabounce device list */
static inline struct dmabounce_device_info *
find_dmabounce_dev(struct device *dev)
{
	struct list_head *entry;

	list_for_each(entry, &dmabounce_devs) {
		struct dmabounce_device_info *d =
			list_entry(entry, struct dmabounce_device_info, node);

		if (d->dev == dev)
			return d;
	}
	return NULL;
}


/* 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 dma_pool *pool;
	struct device *dev = device_info->dev;
	void *safe;
	dma_addr_t safe_dma_addr;

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

	DO_STATS ( device_info->total_allocs++ );

	buf = kmalloc(sizeof(struct safe_buffer), GFP_ATOMIC);
	if (buf == 0) {
		dev_warn(dev, "%s: kmalloc failed\n", __func__);
		return 0;
	}

	if (size <= device_info->small_buffer_size) {
		pool = device_info->small_buffer_pool;
		safe = dma_pool_alloc(pool, GFP_ATOMIC, &safe_dma_addr);

		DO_STATS ( device_info->sbp_allocs++ );
	} else if (size <= device_info->large_buffer_size) {
		pool = device_info->large_buffer_pool;
		safe = dma_pool_alloc(pool, GFP_ATOMIC, &safe_dma_addr);

		DO_STATS ( device_info->lbp_allocs++ );
	} else {
		pool = 0;
		safe = dma_alloc_coherent(dev, size, &safe_dma_addr, GFP_ATOMIC);
	}

	if (safe == 0) {
		dev_warn(device_info->dev,
			"%s: could not alloc dma memory (size=%d)\n",
		       __func__, size);
		kfree(buf);
		return 0;
	}

#ifdef STATS
	if (device_info->total_allocs % 1000 == 0)
		print_alloc_stats(device_info);
#endif

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

	list_add(&buf->node, &device_info->safe_buffers);

	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 list_head *entry;

	list_for_each(entry, &device_info->safe_buffers) {
		struct safe_buffer *b =
			list_entry(entry, struct safe_buffer, node);

		if (b->safe_dma_addr == safe_dma_addr)
			return b;
	}

	return NULL;
}

static inline void
free_safe_buffer(struct dmabounce_device_info *device_info, struct safe_buffer *buf)
{
	dev_dbg(device_info->dev, "%s(buf=%p)\n", __func__, buf);

	list_del(&buf->node);

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

	kfree(buf);
}

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

#ifdef STATS

static void print_map_stats(struct dmabounce_device_info *device_info)
{
	printk(KERN_INFO
		"%s: dmabounce: map_op_count=%lu, bounce_count=%lu\n",
		device_info->dev->bus_id,
		device_info->map_op_count, device_info->bounce_count);
}
#endif

static inline dma_addr_t
map_single(struct device *dev, void *ptr, size_t size,
		enum dma_data_direction dir)
{
	dma_addr_t dma_addr;
	struct dmabounce_device_info *device_info = find_dmabounce_dev(dev);

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

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

		limit = (*dev->dma_mask + 1) & ~(*dev->dma_mask);
		if (limit && (size > limit)) {
			dev_err(dev, "DMA mapping too big "
				"(requested %#x mask %#Lx)\n",
				size, *dev->dma_mask);
			return ~0;
		}
	}

	dma_addr = virt_to_dma(dev, ptr);

	if (device_info && 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 (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);

		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);
		}
		consistent_sync(buf->safe, size, dir);

		dma_addr = buf->safe_dma_addr;
	} else {
		consistent_sync(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 = find_dmabounce_dev(dev);
	struct safe_buffer *buf = NULL;

	/*
	 * Trying to unmap an invalid mapping
	 */
	if (dma_addr == ~0) {
		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 (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++ );

		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, buf->ptr, size);
			memcpy(buf->ptr, buf->safe, size);
		}
		free_safe_buffer(device_info, buf);
	}
}

static inline void
sync_single(struct device *dev, dma_addr_t dma_addr, size_t size,
		enum dma_data_direction dir)
{
	struct dmabounce_device_info *device_info = find_dmabounce_dev(dev);
	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);