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/*

 * DMA Pool allocator

 *

 * Copyright 2001 David Brownell

 * Copyright 2007 Intel Corporation

 *   Author: Matthew Wilcox 

 *

 * 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 

#include 

#include 

#include 

#include 

struct dma_pool {       /* the pool */

    struct list_head page_list;

    struct mutex lock;

    size_t size;

    size_t allocation;

    size_t boundary;

    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);

/**

 * 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;

    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);

    allocation = (allocation+0x7FFF) & ~0x7FFF;

    if (!boundary) {

        boundary = allocation;

    } else if ((boundary < size) || (boundary & (boundary - 1))) {

        return NULL;

    }

    retval = kmalloc(sizeof(*retval), GFP_KERNEL);

    if (!retval)

        return retval;

    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);

    return retval;

}

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)

{

    struct dma_page *page;

    page = malloc(sizeof(*page));

    if (!page)

        return NULL;

    page->vaddr = (void*)KernelAlloc(pool->allocation);

    dbgprintf("%s 0x%0x ",__FUNCTION__, page->vaddr);

    if (page->vaddr)

    {

        page->dma = GetPgAddr(page->vaddr);

        dbgprintf("dma 0x%0x\n", page->dma);

        pool_initialise_page(pool, page);

        list_add(&page->page_list, &pool->page_list);

        page->in_use = 0;

        page->offset = 0;

    } else {

        free(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;

    KernelFree(page->vaddr);

    list_del(&page->page_list);

    free(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)

{

    mutex_lock(&pools_lock);

    list_del(&pool->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))

        {

            printk(KERN_ERR "dma_pool_destroy %p busy\n",

                   page->vaddr);

            /* leak the still-in-use consistent memory */

            list_del(&page->page_list);

            kfree(page);

        } else

            pool_free_page(pool, page);

    }

    kfree(pool);

}

/**

 * 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)

{

    u32_t   efl;

    struct  dma_page *page;

    size_t  offset;

    void   *retval;

    efl = safe_cli();

 restart:

    list_for_each_entry(page, &pool->page_list, page_list) {

        if (page->offset < pool->allocation)

            goto ready;

    }

    page = pool_alloc_page(pool);

    if (!page)

    {

        retval = NULL;

        goto done;

    }

 ready:

    page->in_use++;

    offset = page->offset;

    page->offset = *(int *)(page->vaddr + offset);

    retval = offset + page->vaddr;

    *handle = offset + page->dma;

 done:

    safe_sti(efl);

    return retval;

}

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

{

    struct dma_page *page;

    u32_t  efl;

    efl = safe_cli();

    list_for_each_entry(page, &pool->page_list, page_list) {

        if (dma < page->dma)

            continue;

        if (dma < (page->dma + pool->allocation))

            goto done;

    }

    page = NULL;

 done:

    safe_sti(efl);

    return page;

}

/**

 * 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_page *page;

    unsigned long flags;

    unsigned int offset;

    u32_t efl;

    page = pool_find_page(pool, dma);

    if (!page) {

        printk(KERN_ERR "dma_pool_free %p/%lx (bad dma)\n",

               vaddr, (unsigned long)dma);

        return;

    }

    offset = vaddr - page->vaddr;

    efl = safe_cli();

    {

        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.

     */

    }safe_sti(efl);

}