dmapool.c

Go to the documentation of this file.

/*
 * DMA Pool allocator
 *
 * Copyright 2001 David Brownell
 * Copyright 2007 Intel Corporation
 *   Author: Matthew Wilcox <[email protected]>
 *
 * 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 within the page.  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_pool {       /* the pool */
    struct list_head page_list;
    spinlock_t lock;
    size_t size;
    struct device *dev;
    size_t allocation;
    size_t 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;
    unsigned int in_use;
    unsigned int offset;
};

static DEFINE_MUTEX(pools_lock);

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

    next = buf;
    size = PAGE_SIZE;

    temp = scnprintf(next, size, "poolinfo - 0.1\n");
    size -= temp;
    next += temp;

    mutex_lock(&pools_lock);
    list_for_each_entry(pool, &dev->dma_pools, pools) {
        unsigned pages = 0;
        unsigned blocks = 0;

        spin_lock_irq(&pool->lock);
        list_for_each_entry(page, &pool->page_list, page_list) {
            pages++;
            blocks += page->in_use;
        }
        spin_unlock_irq(&pool->lock);

        /* per-pool info, no real statistics yet */
        temp = scnprintf(next, size, "%-16s %4u %4Zu %4Zu %2u\n",
                 pool->name, blocks,
                 pages * (pool->allocation / pool->size),
                 pool->size, pages);
        size -= temp;
        next += temp;
    }
    mutex_unlock(&pools_lock);

    return PAGE_SIZE - size;
}

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

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;

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

    if (size == 0) {
        return NULL;
    } else if (size < 4) {
        size = 4;
    }

    if ((size % align) != 0)
        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;
    }

    retval = kmalloc_node(sizeof(*retval), GFP_KERNEL, dev_to_node(dev));
    if (!retval)
        return retval;

    strlcpy(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;

    if (dev) {
        int ret;

        mutex_lock(&pools_lock);
        if (list_empty(&dev->dma_pools))
            ret = device_create_file(dev, &dev_attr_pools);
        else
            ret = 0;
        /* note:  not currently insisting "name" be unique */
        if (!ret)
            list_add(&retval->pools, &dev->dma_pools);
        else {
            kfree(retval);
            retval = NULL;
        }
        mutex_unlock(&pools_lock);
    } else
        INIT_LIST_HEAD(&retval->pools);

    return retval;
}
EXPORT_SYMBOL(dma_pool_create);

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

    do {
        unsigned int next = offset + pool->size;
        if (unlikely((next + pool->size) >= next_boundary)) {
            next = next_boundary;
            next_boundary += pool->boundary;
        }
        *(int *)(page->vaddr + offset) = next;
        offset = next;
    } while (offset < pool->allocation);
}

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) {
#ifdef  DMAPOOL_DEBUG
        memset(page->vaddr, POOL_POISON_FREED, pool->allocation);
#endif
        pool_initialise_page(pool, page);
        page->in_use = 0;
        page->offset = 0;
    } else {
        kfree(page);
        page = NULL;
    }
    return page;
}

static inline int is_page_busy(struct dma_page *page)
{
    return page->in_use != 0;
}

static void pool_free_page(struct dma_pool *pool, struct dma_page *page)
{
    dma_addr_t dma = page->dma;

#ifdef  DMAPOOL_DEBUG
    memset(page->vaddr, POOL_POISON_FREED, pool->allocation);
#endif
    dma_free_coherent(pool->dev, pool->allocation, page->vaddr, dma);
    list_del(&page->page_list);
    kfree(page);
}

void dma_pool_destroy(struct dma_pool *pool)
{
    mutex_lock(&pools_lock);
    list_del(&pool->pools);
    if (pool->dev && list_empty(&pool->dev->dma_pools))
        device_remove_file(pool->dev, &dev_attr_pools);
    mutex_unlock(&pools_lock);

    while (!list_empty(&pool->page_list)) {
        struct dma_page *page;
        page = list_entry(pool->page_list.next,
                  struct dma_page, page_list);
        if (is_page_busy(page)) {
            if (pool->dev)
                dev_err(pool->dev,
                    "dma_pool_destroy %s, %p busy\n",
                    pool->name, page->vaddr);
            else
                printk(KERN_ERR
                       "dma_pool_destroy %s, %p busy\n",
                       pool->name, page->vaddr);
            /* leak the still-in-use consistent memory */
            list_del(&page->page_list);
            kfree(page);
        } else
            pool_free_page(pool, page);
    }

    kfree(pool);
}
EXPORT_SYMBOL(dma_pool_destroy);

void *dma_pool_alloc(struct dma_pool *pool, gfp_t mem_flags,
             dma_addr_t *handle)
{
    unsigned long flags;
    struct dma_page *page;
    size_t offset;
    void *retval;

    might_sleep_if(mem_flags & __GFP_WAIT);

    spin_lock_irqsave(&pool->lock, flags);
    list_for_each_entry(page, &pool->page_list, page_list) {
        if (page->offset < pool->allocation)
            goto ready;
    }

    /* pool_alloc_page() might sleep, so temporarily drop &pool->lock */
    spin_unlock_irqrestore(&pool->lock, flags);

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

    spin_lock_irqsave(&pool->lock, flags);

    list_add(&page->page_list, &pool->page_list);
 ready:
    page->in_use++;
    offset = page->offset;
    page->offset = *(int *)(page->vaddr + offset);
    retval = offset + page->vaddr;
    *handle = offset + page->dma;
#ifdef  DMAPOOL_DEBUG
    memset(retval, POOL_POISON_ALLOCATED, pool->size);
#endif
    spin_unlock_irqrestore(&pool->lock, flags);
    return retval;
}
EXPORT_SYMBOL(dma_pool_alloc);

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;
}

void dma_pool_free(struct dma_pool *pool, void *vaddr, dma_addr_t dma)
{
    struct dma_page *page;
    unsigned long flags;
    unsigned int offset;

    spin_lock_irqsave(&pool->lock, flags);
    page = pool_find_page(pool, dma);
    if (!page) {
        spin_unlock_irqrestore(&pool->lock, flags);
        if (pool->dev)
            dev_err(pool->dev,
                "dma_pool_free %s, %p/%lx (bad dma)\n",
                pool->name, vaddr, (unsigned long)dma);
        else
            printk(KERN_ERR "dma_pool_free %s, %p/%lx (bad dma)\n",
                   pool->name, vaddr, (unsigned long)dma);
        return;
    }

    offset = vaddr - page->vaddr;
#ifdef  DMAPOOL_DEBUG
    if ((dma - page->dma) != offset) {
        spin_unlock_irqrestore(&pool->lock, flags);
        if (pool->dev)
            dev_err(pool->dev,
                "dma_pool_free %s, %p (bad vaddr)/%Lx\n",
                pool->name, vaddr, (unsigned long long)dma);
        else
            printk(KERN_ERR
                   "dma_pool_free %s, %p (bad vaddr)/%Lx\n",
                   pool->name, vaddr, (unsigned long long)dma);
        return;
    }
    {
        unsigned int chain = page->offset;
        while (chain < pool->allocation) {
            if (chain != offset) {
                chain = *(int *)(page->vaddr + chain);
                continue;
            }
            spin_unlock_irqrestore(&pool->lock, flags);
            if (pool->dev)
                dev_err(pool->dev, "dma_pool_free %s, dma %Lx "
                    "already free\n", pool->name,
                    (unsigned long long)dma);
            else
                printk(KERN_ERR "dma_pool_free %s, dma %Lx "
                    "already free\n", pool->name,
                    (unsigned long long)dma);
            return;
        }
    }
    memset(vaddr, POOL_POISON_FREED, pool->size);
#endif

    page->in_use--;
    *(int *)vaddr = page->offset;
    page->offset = offset;
    /*
     * Resist a temptation to do
     *    if (!is_page_busy(page)) pool_free_page(pool, page);
     * Better have a few empty pages hang around.
     */
    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;
}

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);

void dmam_pool_destroy(struct dma_pool *pool)
{
    struct device *dev = pool->dev;

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