dmabounce.c

linux 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, 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 ([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>
#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 (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);
		}
		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(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 (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) {
			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 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 = dev->archdata.dmabounce;
	struct safe_buffer *buf = NULL;