/*
 *  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 and the remainder of memory is at the top an the DMA memory
 *  can be marked as ZONE_DMA. Anything beyond that such as discontigous
 *  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/device.h>
#include <linux/dma-mapping.h>
#include <linux/dmapool.h>
#include <linux/list.h>

#undef DEBUG

#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 dma_pool *pool;
        void            *safe;
        dma_addr_t      safe_dma_addr;
};

struct dmabounce_device_info {
        struct list_head node;

        struct device *dev;
        struct dma_pool *small_buffer_pool;
        struct dma_pool *large_buffer_pool;
        struct list_head safe_buffers;
        unsigned long small_buffer_size, large_buffer_size;
#ifdef STATS
        unsigned long sbp_allocs;
        unsigned long lbp_allocs;
        unsigned long total_allocs;
        unsigned long map_op_count;
        unsigned long bounce_count;
#endif
};

static LIST_HEAD(dmabounce_devs);

#ifdef STATS
static void print_alloc_stats(struct dmabounce_device_info *device_info)
{
        printk(KERN_INFO
                "%s: dmabounce: sbp: %lu, lbp: %lu, other: %lu, total: %lu\n",
                device_info->dev->bus_id,
                device_info->sbp_allocs, device_info->lbp_allocs,
                device_info->total_allocs - device_info->sbp_allocs -
                        device_info->lbp_allocs,
                device_info->total_allocs);
}
#endif

/* find the given device in the dmabounce device list */
static inline struct dmabounce_device_info *
find_dmabounce_dev(struct device *dev)
{
        struct list_head *entry;

        list_for_each(entry, &dmabounce_devs) {
                struct dmabounce_device_info *d =
                        list_entry(entry, struct dmabounce_device_info, node);

                if (d->dev == dev)
                        return d;
        }
        return NULL;
}


/* 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 dma_pool *pool;
        struct device *dev = device_info->dev;
        void *safe;
        dma_addr_t safe_dma_addr;

        dev_dbg(dev, "%s(ptr=%p, size=%d, dir=%d)\n",
                __func__, ptr, size, dir);

        DO_STATS ( device_info->total_allocs++ );

        buf = kmalloc(sizeof(struct safe_buffer), GFP_ATOMIC);
        if (buf == NULL) {
                dev_warn(dev, "%s: kmalloc failed\n", __func__);
                return NULL;
        }

        if (size <= device_info->small_buffer_size) {
                pool = device_info->small_buffer_pool;
                safe = dma_pool_alloc(pool, GFP_ATOMIC, &safe_dma_addr);

                DO_STATS ( device_info->sbp_allocs++ );
        } else if (size <= device_info->large_buffer_size) {
                pool = device_info->large_buffer_pool;
                safe = dma_pool_alloc(pool, GFP_ATOMIC, &safe_dma_addr);

                DO_STATS ( device_info->lbp_allocs++ );
        } else {
                pool = NULL;
                safe = dma_alloc_coherent(dev, size, &safe_dma_addr, GFP_ATOMIC);
        }

        if (safe == NULL) {
                dev_warn(device_info->dev,
                        "%s: could not alloc dma memory (size=%d)\n",
                       __func__, size);
                kfree(buf);
                return NULL;
        }

#ifdef STATS
        if (device_info->total_allocs % 1000 == 0)
                print_alloc_stats(device_info);
#endif

        buf->ptr = ptr;
        buf->size = size;
        buf->direction = dir;
        buf->pool = pool;
        buf->safe = safe;
        buf->safe_dma_addr = safe_dma_addr;

        list_add(&buf->node, &device_info->safe_buffers);

        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 list_head *entry;

        list_for_each(entry, &device_info->safe_buffers) {
                struct safe_buffer *b =
                        list_entry(entry, struct safe_buffer, node);

                if (b->safe_dma_addr == safe_dma_addr)
                        return b;
        }

        return NULL;
}

static inline void
free_safe_buffer(struct dmabounce_device_info *device_info, struct safe_buffer *buf)
{
        dev_dbg(device_info->dev, "%s(buf=%p)\n", __func__, buf);

        list_del(&buf->node);

        if (buf->pool)
                dma_pool_free(buf->pool, buf->safe, buf->safe_dma_addr);
        else
                dma_free_coherent(device_info->dev, buf->size, buf->safe,
                                    buf->safe_dma_addr);

        kfree(buf);
}

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

#ifdef STATS

static void print_map_stats(struct dmabounce_device_info *device_info)
{
        printk(KERN_INFO
                "%s: dmabounce: map_op_count=%lu, bounce_count=%lu\n",
                device_info->dev->bus_id,
                device_info->map_op_count, device_info->bounce_count);
}
#endif

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 = find_dmabounce_dev(dev);
        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 (phy=%p) mapped to %p (phy=%p)\n",
                        __func__, buf->ptr, (void *) virt_to_dma(dev, buf->ptr),
                        buf->safe, (void *) 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);
                }
                consistent_sync(buf->safe, size, dir);

                dma_addr = buf->safe_dma_addr;
        } else {
                consistent_sync(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 dmabounce_device_info *device_info = find_dmabounce_dev(dev);
        struct safe_buffer *buf = NULL;

        /*
         * Trying to unmap an invalid mapping
         */
        if (dma_addr == ~0) {
                dev_err(dev, "Trying to unmap invalid mapping\n");
                return;
        }

        if (device_info)
                buf = find_safe_buffer(device_info, dma_addr);

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

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


                DO_STATS ( device_info->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, buf->ptr, size);
                        memcpy(buf->ptr, buf->safe, size);
                }
                free_safe_buffer(device_info, buf);
        }
}

static inline void
sync_single(struct device *dev, dma_addr_t dma_addr, size_t size,
                enum dma_data_direction dir)
{
        struct dmabounce_device_info *device_info = find_dmabounce_dev(dev);
        struct safe_buffer *buf = NULL;

        if (device_info)
                buf = find_safe_buffer(device_info, dma_addr);

        if (buf) {
                /*
                 * Both of these checks from original code need to be
                 * commented out b/c some drivers rely on the following:
                 *
                 * 1) Drivers may map a large chunk of memory into DMA space
                 *    but only sync a small portion of it. Good example is
                 *    allocating a large buffer, mapping it, and then
                 *    breaking it up into small descriptors. No point
                 *    in syncing the whole buffer if you only have to
                 *    touch one descriptor.
                 *
                 * 2) Buffers that are mapped as DMA_BIDIRECTIONAL are
                 *    usually only synced in one dir at a time.
                 *
                 * See drivers/net/eepro100.c for examples of both cases.
                 *
                 * -ds
                 *
                 * BUG_ON(buf->size != size);
                 * BUG_ON(buf->direction != dir);
                 */

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

                DO_STATS ( device_info->bounce_count++ );

                switch (dir) {
                case DMA_FROM_DEVICE:
                        dev_dbg(dev,
                                "%s: copy back safe %p to unsafe %p size %d\n",
                                __func__, buf->safe, buf->ptr, size);
                        memcpy(buf->ptr, buf->safe, size);
                        break;
                case DMA_TO_DEVICE:
                        dev_dbg(dev,
                                "%s: copy out unsafe %p to safe %p, size %d\n",
                                __func__,buf->ptr, buf->safe, size);
                        memcpy(buf->safe, buf->ptr, size);
                        break;
                case DMA_BIDIRECTIONAL:
                        BUG();  /* is this allowed?  what does it mean? */
                default:
                        BUG();
                }
                consistent_sync(buf->safe, size, dir);
        } else {
                consistent_sync(dma_to_virt(dev, dma_addr), size, dir);
        }
}

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

/*
 * 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)
{
        unsigned long flags;
        dma_addr_t dma_addr;

        dev_dbg(dev, "%s(ptr=%p,size=%d,dir=%x)\n",
                __func__, ptr, size, dir);

        BUG_ON(dir == DMA_NONE);

        local_irq_save(flags);

        dma_addr = map_single(dev, ptr, size, dir);

        local_irq_restore(flags);

        return dma_addr;
}

/*
 * 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)
{
        unsigned long flags;

        dev_dbg(dev, "%s(ptr=%p,size=%d,dir=%x)\n",
                __func__, (void *) dma_addr, size, dir);

        BUG_ON(dir == DMA_NONE);

        local_irq_save(flags);

        unmap_single(dev, dma_addr, size, dir);

        local_irq_restore(flags);
}

int
dma_map_sg(struct device *dev, struct scatterlist *sg, int nents,
                enum dma_data_direction dir)
{
        unsigned long flags;
        int i;

        dev_dbg(dev, "%s(sg=%p,nents=%d,dir=%x)\n",
                __func__, sg, nents, dir);

        BUG_ON(dir == DMA_NONE);

        local_irq_save(flags);

        for (i = 0; i < nents; i++, sg++) {
                struct page *page = sg->page;
                unsigned int offset = sg->offset;
                unsigned int length = sg->length;
                void *ptr = page_address(page) + offset;

                sg->dma_address =
                        map_single(dev, ptr, length, dir);
        }

        local_irq_restore(flags);

        return nents;
}

void
dma_unmap_sg(struct device *dev, struct scatterlist *sg, int nents,
                enum dma_data_direction dir)
{
        unsigned long flags;
        int i;

        dev_dbg(dev, "%s(sg=%p,nents=%d,dir=%x)\n",
                __func__, sg, nents, dir);

        BUG_ON(dir == DMA_NONE);

        local_irq_save(flags);

        for (i = 0; i < nents; i++, sg++) {
                dma_addr_t dma_addr = sg->dma_address;
                unsigned int length = sg->length;

                unmap_single(dev, dma_addr, length, dir);
        }

        local_irq_restore(flags);
}

void
dma_sync_single_for_cpu(struct device *dev, dma_addr_t dma_addr, size_t size,
                                enum dma_data_direction dir)
{
        unsigned long flags;

        dev_dbg(dev, "%s(ptr=%p,size=%d,dir=%x)\n",
                __func__, (void *) dma_addr, size, dir);

        local_irq_save(flags);

        sync_single(dev, dma_addr, size, dir);

        local_irq_restore(flags);
}

void
dma_sync_single_for_device(struct device *dev, dma_addr_t dma_addr, size_t size,
                                enum dma_data_direction dir)
{
        unsigned long flags;

        dev_dbg(dev, "%s(ptr=%p,size=%d,dir=%x)\n",
                __func__, (void *) dma_addr, size, dir);

        local_irq_save(flags);

        sync_single(dev, dma_addr, size, dir);

        local_irq_restore(flags);
}

void
dma_sync_sg_for_cpu(struct device *dev, struct scatterlist *sg, int nents,
                        enum dma_data_direction dir)
{
        unsigned long flags;
        int i;

        dev_dbg(dev, "%s(sg=%p,nents=%d,dir=%x)\n",
                __func__, sg, nents, dir);

        BUG_ON(dir == DMA_NONE);

        local_irq_save(flags);

        for (i = 0; i < nents; i++, sg++) {
                dma_addr_t dma_addr = sg->dma_address;
                unsigned int length = sg->length;

                sync_single(dev, dma_addr, length, dir);
        }

        local_irq_restore(flags);
}

void
dma_sync_sg_for_device(struct device *dev, struct scatterlist *sg, int nents,
                        enum dma_data_direction dir)
{
        unsigned long flags;
        int i;

        dev_dbg(dev, "%s(sg=%p,nents=%d,dir=%x)\n",
                __func__, sg, nents, dir);

        BUG_ON(dir == DMA_NONE);

        local_irq_save(flags);

        for (i = 0; i < nents; i++, sg++) {
                dma_addr_t dma_addr = sg->dma_address;
                unsigned int length = sg->length;

                sync_single(dev, dma_addr, length, dir);
        }

        local_irq_restore(flags);
}

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

        device_info = kmalloc(sizeof(struct dmabounce_device_info), GFP_ATOMIC);
        if (!device_info) {
                printk(KERN_ERR
                        "Could not allocated dmabounce_device_info for %s",
                        dev->bus_id);
                return -ENOMEM;
        }

        device_info->small_buffer_pool =
                dma_pool_create("small_dmabounce_pool",
                                dev,
                                small_buffer_size,
                                0 /* byte alignment */,
                                0 /* no page-crossing issues */);
        if (!device_info->small_buffer_pool) {
                printk(KERN_ERR
                        "dmabounce: could not allocate small DMA pool for %s\n",
                        dev->bus_id);
                kfree(device_info);
                return -ENOMEM;
        }

        if (large_buffer_size) {
                device_info->large_buffer_pool =
                        dma_pool_create("large_dmabounce_pool",
                                        dev,
                                        large_buffer_size,
                                        0 /* byte alignment */,
                                        0 /* no page-crossing issues */);
                if (!device_info->large_buffer_pool) {
                printk(KERN_ERR
                        "dmabounce: could not allocate large DMA pool for %s\n",
                        dev->bus_id);
                        dma_pool_destroy(device_info->small_buffer_pool);

                        return -ENOMEM;
                }
        }

        device_info->dev = dev;
        device_info->small_buffer_size = small_buffer_size;
        device_info->large_buffer_size = large_buffer_size;
        INIT_LIST_HEAD(&device_info->safe_buffers);

#ifdef STATS
        device_info->sbp_allocs = 0;
        device_info->lbp_allocs = 0;
        device_info->total_allocs = 0;
        device_info->map_op_count = 0;
        device_info->bounce_count = 0;
#endif

        list_add(&device_info->node, &dmabounce_devs);

        printk(KERN_INFO "dmabounce: registered device %s on %s bus\n",
                dev->bus_id, dev->bus->name);

        return 0;
}

void
dmabounce_unregister_dev(struct device *dev)
{
        struct dmabounce_device_info *device_info = find_dmabounce_dev(dev);

        if (!device_info) {
                printk(KERN_WARNING
                        "%s: Never registered with dmabounce but attempting" \
                        "to unregister!\n", dev->bus_id);
                return;
        }

        if (!list_empty(&device_info->safe_buffers)) {
                printk(KERN_ERR
                        "%s: Removing from dmabounce with pending buffers!\n",
                        dev->bus_id);
                BUG();
        }

        if (device_info->small_buffer_pool)
                dma_pool_destroy(device_info->small_buffer_pool);
        if (device_info->large_buffer_pool)
                dma_pool_destroy(device_info->large_buffer_pool);

#ifdef STATS
        print_alloc_stats(device_info);
        print_map_stats(device_info);
#endif

        list_del(&device_info->node);

        kfree(device_info);

        printk(KERN_INFO "dmabounce: device %s on %s bus unregistered\n",
                dev->bus_id, dev->bus->name);
}


EXPORT_SYMBOL(dma_map_single);
EXPORT_SYMBOL(dma_unmap_single);
EXPORT_SYMBOL(dma_map_sg);
EXPORT_SYMBOL(dma_unmap_sg);
EXPORT_SYMBOL(dma_sync_single);
EXPORT_SYMBOL(dma_sync_sg);
EXPORT_SYMBOL(dmabounce_register_dev);
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");