/*
 * 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 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];
        wait_queue_head_t waitq;
        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;
};

#define POOL_TIMEOUT_JIFFIES    ((100 /* msec */ * HZ) / 1000)

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);

/**
 * 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);

        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;
        init_waitqueue_head(&retval->waitq);

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

/**
 * 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);
        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);

/**
 * 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)
{
        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);
 restart:
        list_for_each_entry(page, &pool->page_list, page_list) {
                if (page->offset < pool->allocation)
                        goto ready;
        }
        page = pool_alloc_page(pool, GFP_ATOMIC);
        if (!page) {
                if (mem_flags & __GFP_WAIT) {
                        DECLARE_WAITQUEUE(wait, current);

                        __set_current_state(TASK_UNINTERRUPTIBLE);
                        __add_wait_queue(&pool->waitq, &wait);
                        spin_unlock_irqrestore(&pool->lock, flags);

                        schedule_timeout(POOL_TIMEOUT_JIFFIES);

                        spin_lock_irqsave(&pool->lock, flags);
                        __remove_wait_queue(&pool->waitq, &wait);
                        goto restart;
                }
                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;
#ifdef  DMAPOOL_DEBUG
        memset(retval, POOL_POISON_ALLOCATED, pool->size);
#endif
 done:
        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;
}

/**
 * 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;

        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;
        if (waitqueue_active(&pool->waitq))
                wake_up_locked(&pool->waitq);
        /*
         * 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;
}

/**
 * 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_destroy(dev, dmam_pool_release, dmam_pool_match, pool));
        dma_pool_destroy(pool);
}
EXPORT_SYMBOL(dmam_pool_destroy);