dmapool.c

/*
 * DMA Pool allocator
 *
 * Copyright 2001 David Brownell
 * Copyright 2007 Intel Corporation
 *   Author: Matthew Wilcox <willy@linux.intel.com>
 *
 * This software may be redistributed and/or modified under the terms of
 * the GNU General Public License ("GPL") version 2 as published by the
 * Free Software Foundation.
 *
 * This allocator returns small blocks of a given size which are DMA-able by
 * the given device.  It uses the dma_alloc_coherent page allocator to get
 * new pages, then splits them up into blocks of the required size.
 * Many older drivers still have their own code to do this.
 *
 * The current design of this allocator is fairly simple.  The pool is
 * represented by the 'struct dma_pool' which keeps a doubly-linked list of
 * allocated pages.  Each page in the page_list is split into blocks of at
 * least 'size' bytes.  Free blocks are tracked in an unsorted singly-linked
 * list of free blocks across all pages.  Used blocks aren't tracked, but we
 * keep a count of how many are currently allocated from each page.
 */

#include <linux/device.h>
#include <linux/dma-mapping.h>
#include <linux/dmapool.h>
#include <linux/kernel.h>
#include <linux/list.h>
#include <linux/export.h>
#include <linux/mutex.h>
#include <linux/poison.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/stat.h>
#include <linux/spinlock.h>
#include <linux/string.h>
#include <linux/types.h>
#include <linux/wait.h>

#if defined(CONFIG_DEBUG_SLAB) || defined(CONFIG_SLUB_DEBUG_ON)
#define DMAPOOL_DEBUG 1
#endif

struct dma_block {
	struct dma_block *next_block;
	dma_addr_t dma;
};

struct dma_pool {		/* the pool */
	struct list_head page_list;
	spinlock_t lock;
	struct dma_block *next_block;
	size_t nr_blocks;
	size_t nr_active;
	size_t nr_pages;
	struct device *dev;
	unsigned int size;
	unsigned int allocation;
	unsigned int boundary;
	char name[32];
	struct list_head pools;
};

struct dma_page {		/* cacheable header for 'allocation' bytes */
	struct list_head page_list;
	void *vaddr;
	dma_addr_t dma;
};

static DEFINE_MUTEX(pools_lock);
static DEFINE_MUTEX(pools_reg_lock);

static ssize_t
show_pools(struct device *dev, struct device_attribute *attr, char *buf)
{
	struct dma_pool *pool;
	unsigned size;

	size = sysfs_emit(buf, "poolinfo - 0.1\n");

	mutex_lock(&pools_lock);
	list_for_each_entry(pool, &dev->dma_pools, pools) {
		/* per-pool info, no real statistics yet */
		size += sysfs_emit_at(buf, size, "%-16s %4zu %4zu %4u %2zu\n",
				      pool->name, pool->nr_active,
				      pool->nr_blocks, pool->size,
				      pool->nr_pages);
	}
	mutex_unlock(&pools_lock);

	return size;
}

static DEVICE_ATTR(pools, S_IRUGO, show_pools, NULL);

#ifdef DMAPOOL_DEBUG
static void pool_check_block(struct dma_pool *pool, struct dma_block *block,
			     gfp_t mem_flags)
{
	u8 *data = (void *)block;
	int i;

	for (i = sizeof(struct dma_block); i < pool->size; i++) {
		if (data[i] == POOL_POISON_FREED)
			continue;
		dev_err(pool->dev, "%s %s, %p (corrupted)\n", __func__,
			pool->name, block);

		/*
		 * Dump the first 4 bytes even if they are not
		 * POOL_POISON_FREED
		 */
		print_hex_dump(KERN_ERR, "", DUMP_PREFIX_OFFSET, 16, 1,
				data, pool->size, 1);
		break;
	}

	if (!want_init_on_alloc(mem_flags))
		memset(block, POOL_POISON_ALLOCATED, pool->size);
}

static struct dma_page *pool_find_page(struct dma_pool *pool, dma_addr_t dma)
{
	struct dma_page *page;

	list_for_each_entry(page, &pool->page_list, page_list) {
		if (dma < page->dma)
			continue;
		if ((dma - page->dma) < pool->allocation)
			return page;
	}
	return NULL;
}

static bool pool_block_err(struct dma_pool *pool, void *vaddr, dma_addr_t dma)
{
	struct dma_block *block = pool->next_block;
	struct dma_page *page;

	page = pool_find_page(pool, dma);
	if (!page) {
		dev_err(pool->dev, "%s %s, %p/%pad (bad dma)\n",
			__func__, pool->name, vaddr, &dma);
		return true;
	}

	while (block) {
		if (block != vaddr) {
			block = block->next_block;
			continue;
		}
		dev_err(pool->dev, "%s %s, dma %pad already free\n",
			__func__, pool->name, &dma);
		return true;
	}

	memset(vaddr, POOL_POISON_FREED, pool->size);
	return false;
}

static void pool_init_page(struct dma_pool *pool, struct dma_page *page)
{
	memset(page->vaddr, POOL_POISON_FREED, pool->allocation);
}
#else
static void pool_check_block(struct dma_pool *pool, struct dma_block *block,
			     gfp_t mem_flags)
{
}

static bool pool_block_err(struct dma_pool *pool, void *vaddr, dma_addr_t dma)
{
	if (want_init_on_free())
		memset(vaddr, 0, pool->size);
	return false;
}

static void pool_init_page(struct dma_pool *pool, struct dma_page *page)
{
}
#endif

static struct dma_block *pool_block_pop(struct dma_pool *pool)
{
	struct dma_block *block = pool->next_block;

	if (block) {
		pool->next_block = block->next_block;
		pool->nr_active++;
	}
	return block;
}

static void pool_block_push(struct dma_pool *pool, struct dma_block *block,
			    dma_addr_t dma)
{
	block->dma = dma;
	block->next_block = pool->next_block;
	pool->next_block = block;
}


/**
 * dma_pool_create - Creates a pool of consistent memory blocks, for dma.
 * @name: name of pool, for diagnostics
 * @dev: device that will be doing the DMA
 * @size: size of the blocks in this pool.
 * @align: alignment requirement for blocks; must be a power of two
 * @boundary: returned blocks won't cross this power of two boundary
 * Context: !in_interrupt()
 *
 * Returns a dma allocation pool with the requested characteristics, or
 * null if one can't be created.  Given one of these pools, dma_pool_alloc()
 * may be used to allocate memory.  Such memory will all have "consistent"
 * DMA mappings, accessible by the device and its driver without using
 * cache flushing primitives.  The actual size of blocks allocated may be
 * larger than requested because of alignment.
 *
 * If @boundary is nonzero, objects returned from dma_pool_alloc() won't
 * cross that size boundary.  This is useful for devices which have
 * addressing restrictions on individual DMA transfers, such as not crossing
 * boundaries of 4KBytes.
 */
struct dma_pool *dma_pool_create(const char *name, struct device *dev,
				 size_t size, size_t align, size_t boundary)
{
	struct dma_pool *retval;
	size_t allocation;
	bool empty;

	if (!dev)
		return NULL;

	if (align == 0)
		align = 1;
	else if (align & (align - 1))
		return NULL;

	if (size == 0 || size > INT_MAX)
		return NULL;
	if (size < sizeof(struct dma_block))
		size = sizeof(struct dma_block);

	size = ALIGN(size, align);
	allocation = max_t(size_t, size, PAGE_SIZE);

	if (!boundary)
		boundary = allocation;
	else if ((boundary < size) || (boundary & (boundary - 1)))
		return NULL;

	boundary = min(boundary, allocation);

	retval = kzalloc(sizeof(*retval), GFP_KERNEL);
	if (!retval)
		return retval;

	strscpy(retval->name, name, sizeof(retval->name));

	retval->dev = dev;

	INIT_LIST_HEAD(&retval->page_list);
	spin_lock_init(&retval->lock);
	retval->size = size;
	retval->boundary = boundary;
	retval->allocation = allocation;
	INIT_LIST_HEAD(&retval->pools);

	/*
	 * pools_lock ensures that the ->dma_pools list does not get corrupted.
	 * pools_reg_lock ensures that there is not a race between
	 * dma_pool_create() and dma_pool_destroy() or within dma_pool_create()
	 * when the first invocation of dma_pool_create() failed on
	 * device_create_file() and the second assumes that it has been done (I
	 * know it is a short window).
	 */
	mutex_lock(&pools_reg_lock);
	mutex_lock(&pools_lock);
	empty = list_empty(&dev->dma_pools);
	list_add(&retval->pools, &dev->dma_pools);
	mutex_unlock(&pools_lock);
	if (empty) {
		int err;

		err = device_create_file(dev, &dev_attr_pools);
		if (err) {
			mutex_lock(&pools_lock);
			list_del(&retval->pools);
			mutex_unlock(&pools_lock);
			mutex_unlock(&pools_reg_lock);
			kfree(retval);
			return NULL;
		}
	}
	mutex_unlock(&pools_reg_lock);
	return retval;
}
EXPORT_SYMBOL(dma_pool_create);

static void pool_initialise_page(struct dma_pool *pool, struct dma_page *page)
{
	unsigned int next_boundary = pool->boundary, offset = 0;
	struct dma_block *block, *first = NULL, *last = NULL;

	pool_init_page(pool, page);
	while (offset + pool->size <= pool->allocation) {
		if (offset + pool->size > next_boundary) {
			offset = next_boundary;
			next_boundary += pool->boundary;
			continue;
		}

		block = page->vaddr + offset;
		block->dma = page->dma + offset;
		block->next_block = NULL;

		if (last)
			last->next_block = block;
		else
			first = block;
		last = block;

		offset += pool->size;
		pool->nr_blocks++;
	}

	last->next_block = pool->next_block;
	pool->next_block = first;

	list_add(&page->page_list, &pool->page_list);
	pool->nr_pages++;
}

static struct dma_page *pool_alloc_page(struct dma_pool *pool, gfp_t mem_flags)
{
	struct dma_page *page;

	page = kmalloc(sizeof(*page), mem_flags);
	if (!page)
		return NULL;

	page->vaddr = dma_alloc_coherent(pool->dev, pool->allocation,
					 &page->dma, mem_flags);
	if (!page->vaddr) {
		kfree(page);
		return NULL;
	}

	return page;
}

/**
 * dma_pool_destroy - destroys a pool of dma memory blocks.
 * @pool: dma pool that will be destroyed
 * Context: !in_interrupt()
 *
 * Caller guarantees that no more memory from the pool is in use,
 * and that nothing will try to use the pool after this call.
 */
void dma_pool_destroy(struct dma_pool *pool)
{
	struct dma_page *page, *tmp;
	bool empty, busy = false;

	if (unlikely(!pool))
		return;

	mutex_lock(&pools_reg_lock);
	mutex_lock(&pools_lock);
	list_del(&pool->pools);
	empty = list_empty(&pool->dev->dma_pools);
	mutex_unlock(&pools_lock);
	if (empty)
		device_remove_file(pool->dev, &dev_attr_pools);
	mutex_unlock(&pools_reg_lock);

	if (pool->nr_active) {
		dev_err(pool->dev, "%s %s busy\n", __func__, pool->name);
		busy = true;
	}

	list_for_each_entry_safe(page, tmp, &pool->page_list, page_list) {
		if (!busy)
			dma_free_coherent(pool->dev, pool->allocation,
					  page->vaddr, page->dma);
		list_del(&page->page_list);
		kfree(page);
	}

	kfree(pool);
}
EXPORT_SYMBOL(dma_pool_destroy);

/**
 * dma_pool_alloc - get a block of consistent memory
 * @pool: dma pool that will produce the block
 * @mem_flags: GFP_* bitmask
 * @handle: pointer to dma address of block
 *
 * This returns the kernel virtual address of a currently unused block,
 * and reports its dma address through the handle.
 * If such a memory block can't be allocated, %NULL is returned.
 */
void *dma_pool_alloc(struct dma_pool *pool, gfp_t mem_flags,
		     dma_addr_t *handle)
{
	struct dma_block *block;
	struct dma_page *page;
	unsigned long flags;

	might_sleep_if(gfpflags_allow_blocking(mem_flags));

	spin_lock_irqsave(&pool->lock, flags);
	block = pool_block_pop(pool);
	if (!block) {
		/*
		 * pool_alloc_page() might sleep, so temporarily drop
		 * &pool->lock
		 */
		spin_unlock_irqrestore(&pool->lock, flags);

		page = pool_alloc_page(pool, mem_flags & (~__GFP_ZERO));
		if (!page)
			return NULL;

		spin_lock_irqsave(&pool->lock, flags);
		pool_initialise_page(pool, page);
		block = pool_block_pop(pool);
	}
	spin_unlock_irqrestore(&pool->lock, flags);

	*handle = block->dma;
	pool_check_block(pool, block, mem_flags);
	if (want_init_on_alloc(mem_flags))
		memset(block, 0, pool->size);

	return block;
}
EXPORT_SYMBOL(dma_pool_alloc);

/**
 * dma_pool_free - put block back into dma pool
 * @pool: the dma pool holding the block
 * @vaddr: virtual address of block
 * @dma: dma address of block
 *
 * Caller promises neither device nor driver will again touch this block
 * unless it is first re-allocated.
 */
void dma_pool_free(struct dma_pool *pool, void *vaddr, dma_addr_t dma)
{
	struct dma_block *block = vaddr;
	unsigned long flags;

	spin_lock_irqsave(&pool->lock, flags);
	if (!pool_block_err(pool, vaddr, dma)) {
		pool_block_push(pool, block, dma);
		pool->nr_active--;
	}
	spin_unlock_irqrestore(&pool->lock, flags);
}
EXPORT_SYMBOL(dma_pool_free);

/*
 * Managed DMA pool
 */
static void dmam_pool_release(struct device *dev, void *res)
{
	struct dma_pool *pool = *(struct dma_pool **)res;

	dma_pool_destroy(pool);
}

static int dmam_pool_match(struct device *dev, void *res, void *match_data)
{
	return *(struct dma_pool **)res == match_data;
}

/**
 * dmam_pool_create - Managed dma_pool_create()
 * @name: name of pool, for diagnostics
 * @dev: device that will be doing the DMA
 * @size: size of the blocks in this pool.
 * @align: alignment requirement for blocks; must be a power of two
 * @allocation: returned blocks won't cross this boundary (or zero)
 *
 * Managed dma_pool_create().  DMA pool created with this function is
 * automatically destroyed on driver detach.
 */
struct dma_pool *dmam_pool_create(const char *name, struct device *dev,
				  size_t size, size_t align, size_t allocation)
{
	struct dma_pool **ptr, *pool;

	ptr = devres_alloc(dmam_pool_release, sizeof(*ptr), GFP_KERNEL);
	if (!ptr)
		return NULL;

	pool = *ptr = dma_pool_create(name, dev, size, align, allocation);
	if (pool)
		devres_add(dev, ptr);
	else
		devres_free(ptr);

	return pool;
}
EXPORT_SYMBOL(dmam_pool_create);

/**
 * dmam_pool_destroy - Managed dma_pool_destroy()
 * @pool: dma pool that will be destroyed
 *
 * Managed dma_pool_destroy().
 */
void dmam_pool_destroy(struct dma_pool *pool)
{
	struct device *dev = pool->dev;

	WARN_ON(devres_release(dev, dmam_pool_release, dmam_pool_match, pool));
}
EXPORT_SYMBOL(dmam_pool_destroy);