/*
 *  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 (brad@heeltoe.com)
 *  Re-written by Christopher Hoover <ch@murgatroid.com>
 *  Made generic by Deepak Saxena <dsaxena@plexity.net>
 *
 *  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/page-flags.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 struct safe_buffer *find_safe_buffer_dev(struct device *dev,
                dma_addr_t dma_addr, const char *where)
{
        if (!dev || !dev->archdata.dmabounce)
                return NULL;
        if (dma_mapping_error(dev, dma_addr)) {
                if (dev)
                        dev_err(dev, "Trying to %s invalid mapping\n", where);
                else
                        pr_err("unknown device: Trying to %s invalid mapping\n", where);
                return NULL;
        }
        return find_safe_buffer(dev->archdata.dmabounce, dma_addr);
}

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 (dma=%#x) mapped to %p (dma=%#x)\n",
                        __func__, buf->ptr, virt_to_dma(dev, buf->ptr),
                        buf->safe, 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 safe_buffer *buf = find_safe_buffer_dev(dev, dma_addr, "unmap");

        if (buf) {
                BUG_ON(buf->size != size);
                BUG_ON(buf->direction != dir);

                dev_dbg(dev,
                        "%s: unsafe buffer %p (dma=%#x) mapped to %p (dma=%#x)\n",
                        __func__, buf->ptr, virt_to_dma(dev, buf->ptr),
                        buf->safe, buf->safe_dma_addr);

                DO_STATS(dev->archdata.dmabounce->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(dev->archdata.dmabounce, buf);
        }
}

/* ************************************************** */

/*
 * see if a buffer address is in an 'unsafe' range.  if it is
 * allocate a 'safe' buffer and copy the unsafe buffer into it.
 * substitute the safe buffer for the unsafe one.
 * (basically move the buffer from an unsafe area to a safe one)
 */
dma_addr_t dma_map_single(struct device *dev, void *ptr, size_t size,
                enum dma_data_direction dir)
{
        dev_dbg(dev, "%s(ptr=%p,size=%d,dir=%x)\n",
                __func__, ptr, size, dir);

        BUG_ON(!valid_dma_direction(dir));

        return map_single(dev, ptr, size, dir);
}
EXPORT_SYMBOL(dma_map_single);

dma_addr_t dma_map_page(struct device *dev, struct page *page,
                unsigned long offset, size_t size, enum dma_data_direction dir)
{
        dev_dbg(dev, "%s(page=%p,off=%#lx,size=%zx,dir=%x)\n",
                __func__, page, offset, size, dir);

        BUG_ON(!valid_dma_direction(dir));

        if (PageHighMem(page)) {
                dev_err(dev, "DMA buffer bouncing of HIGHMEM pages "
                             "is not supported\n");
                return ~0;
        }

        return map_single(dev, page_address(page) + offset, size, dir);
}
EXPORT_SYMBOL(dma_map_page);

/*
 * see if a mapped address was really a "safe" buffer and if so, copy
 * the data from the safe buffer back to the unsafe buffer and free up
 * the safe buffer.  (basically return things back to the way they
 * should be)
 */

void dma_unmap_single(struct device *dev, dma_addr_t dma_addr, size_t size,
                enum dma_data_direction dir)
{
        dev_dbg(dev, "%s(ptr=%p,size=%d,dir=%x)\n",
                __func__, (void *) dma_addr, size, dir);

        unmap_single(dev, dma_addr, size, dir);
}
EXPORT_SYMBOL(dma_unmap_single);

int dmabounce_sync_for_cpu(struct device *dev, dma_addr_t addr,
                unsigned long off, size_t sz, enum dma_data_direction dir)
{
        struct safe_buffer *buf;

        dev_dbg(dev, "%s(dma=%#x,off=%#lx,sz=%zx,dir=%x)\n",
                __func__, addr, off, sz, dir);

        buf = find_safe_buffer_dev(dev, addr, __func__);
        if (!buf)
                return 1;

        BUG_ON(buf->direction != dir);

        dev_dbg(dev, "%s: unsafe buffer %p (dma=%#x) mapped to %p (dma=%#x)\n",
                __func__, buf->ptr, virt_to_dma(dev, buf->ptr),
                buf->safe, buf->safe_dma_addr);

        DO_STATS(dev->archdata.dmabounce->bounce_count++);

        if (dir == DMA_FROM_DEVICE || dir == DMA_BIDIRECTIONAL) {
                dev_dbg(dev, "%s: copy back safe %p to unsafe %p size %d\n",
                        __func__, buf->safe + off, buf->ptr + off, sz);
                memcpy(buf->ptr + off, buf->safe + off, sz);
        }
        return 0;
}
EXPORT_SYMBOL(dmabounce_sync_for_cpu);

int dmabounce_sync_for_device(struct device *dev, dma_addr_t addr,
                unsigned long off, size_t sz, enum dma_data_direction dir)
{
        struct safe_buffer *buf;

        dev_dbg(dev, "%s(dma=%#x,off=%#lx,sz=%zx,dir=%x)\n",
                __func__, addr, off, sz, dir);

        buf = find_safe_buffer_dev(dev, addr, __func__);
        if (!buf)
                return 1;

        BUG_ON(buf->direction != dir);

        dev_dbg(dev, "%s: unsafe buffer %p (dma=%#x) mapped to %p (dma=%#x)\n",
                __func__, buf->ptr, virt_to_dma(dev, buf->ptr),
                buf->safe, buf->safe_dma_addr);

        DO_STATS(dev->archdata.dmabounce->bounce_count++);

        if (dir == DMA_TO_DEVICE || dir == DMA_BIDIRECTIONAL) {
                dev_dbg(dev, "%s: copy out unsafe %p to safe %p, size %d\n",
                        __func__,buf->ptr + off, buf->safe + off, sz);
                memcpy(buf->safe + off, buf->ptr + off, sz);
        }
        return 0;
}
EXPORT_SYMBOL(dmabounce_sync_for_device);

static int dmabounce_init_pool(struct dmabounce_pool *pool, struct device *dev,
                const char *name, unsigned long size)
{
        pool->size = size;
        DO_STATS(pool->allocs = 0);
        pool->pool = dma_pool_create(name, dev, size,
                                     0 /* byte alignment */,
                                     0 /* no page-crossing issues */);

        return pool->pool ? 0 : -ENOMEM;
}

int dmabounce_register_dev(struct device *dev, unsigned long small_buffer_size,
                unsigned long large_buffer_size)
{
        struct dmabounce_device_info *device_info;
        int ret;

        device_info = kmalloc(sizeof(struct dmabounce_device_info), GFP_ATOMIC);
        if (!device_info) {
                dev_err(dev,
                        "Could not allocated dmabounce_device_info\n");
                return -ENOMEM;
        }

        ret = dmabounce_init_pool(&device_info->small, dev,
                                  "small_dmabounce_pool", small_buffer_size);
        if (ret) {
                dev_err(dev,
                        "dmabounce: could not allocate DMA pool for %ld byte objects\n",
                        small_buffer_size);
                goto err_free;
        }

        if (large_buffer_size) {
                ret = dmabounce_init_pool(&device_info->large, dev,
                                          "large_dmabounce_pool",
                                          large_buffer_size);
                if (ret) {
                        dev_err(dev,
                                "dmabounce: could not allocate DMA pool for %ld byte objects\n",
                                large_buffer_size);
                        goto err_destroy;
                }
        }

        device_info->dev = dev;
        INIT_LIST_HEAD(&device_info->safe_buffers);
        rwlock_init(&device_info->lock);

#ifdef STATS
        device_info->total_allocs = 0;
        device_info->map_op_count = 0;
        device_info->bounce_count = 0;
        device_info->attr_res = device_create_file(dev, &dev_attr_dmabounce_stats);
#endif

        dev->archdata.dmabounce = device_info;

        dev_info(dev, "dmabounce: registered device\n");

        return 0;

 err_destroy:
        dma_pool_destroy(device_info->small.pool);
 err_free:
        kfree(device_info);
        return ret;
}
EXPORT_SYMBOL(dmabounce_register_dev);

void dmabounce_unregister_dev(struct device *dev)
{
        struct dmabounce_device_info *device_info = dev->archdata.dmabounce;

        dev->archdata.dmabounce = NULL;

        if (!device_info) {
                dev_warn(dev,
                         "Never registered with dmabounce but attempting"
                         "to unregister!\n");
                return;
        }

        if (!list_empty(&device_info->safe_buffers)) {
                dev_err(dev,
                        "Removing from dmabounce with pending buffers!\n");
                BUG();
        }

        if (device_info->small.pool)
                dma_pool_destroy(device_info->small.pool);
        if (device_info->large.pool)
                dma_pool_destroy(device_info->large.pool);

#ifdef STATS
        if (device_info->attr_res == 0)
                device_remove_file(dev, &dev_attr_dmabounce_stats);
#endif

        kfree(device_info);

        dev_info(dev, "dmabounce: device unregistered\n");
}
EXPORT_SYMBOL(dmabounce_unregister_dev);

MODULE_AUTHOR("Christopher Hoover <ch@hpl.hp.com>, Deepak Saxena <dsaxena@plexity.net>");
MODULE_DESCRIPTION("Special dma_{map/unmap/dma_sync}_* routines for systems with limited DMA windows");
MODULE_LICENSE("GPL");