dmabounce.c

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/*
 *  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 ([email protected])
 *  Re-written by Christopher Hoover <[email protected]>
 *  Made generic by Deepak Saxena <[email protected]>
 *
 *  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;

    int (*needs_bounce)(struct device *, dma_addr_t, size_t);
};

#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 &&
            b->safe_dma_addr + b->size > 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)) {
        dev_err(dev, "Trying to %s invalid mapping\n", where);
        return NULL;
    }
    return find_safe_buffer(dev->archdata.dmabounce, dma_addr);
}

static int needs_bounce(struct device *dev, dma_addr_t dma_addr, size_t size)
{
    if (!dev || !dev->archdata.dmabounce)
        return 0;

    if (dev->dma_mask) {
        unsigned long limit, mask = *dev->dma_mask;

        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 -E2BIG;
        }

        /* Figure out if we need to bounce from the DMA mask. */
        if ((dma_addr | (dma_addr + size - 1)) & ~mask)
            return 1;
    }

    return !!dev->archdata.dmabounce->needs_bounce(dev, dma_addr, size);
}

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;
    struct safe_buffer *buf;

    if (device_info)
        DO_STATS ( device_info->map_op_count++ );

    buf = alloc_safe_buffer(device_info, ptr, size, dir);
    if (buf == NULL) {
        dev_err(dev, "%s: unable to map unsafe buffer %p!\n",
               __func__, ptr);
        return DMA_ERROR_CODE;
    }

    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);
    }

    return buf->safe_dma_addr;
}

static inline void unmap_single(struct device *dev, struct safe_buffer *buf,
        size_t size, enum dma_data_direction dir)
{
    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);

        /*
         * Since we may have written to a page cache page,
         * we need to ensure that the data will be coherent
         * with user mappings.
         */
        __cpuc_flush_dcache_area(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)
 */
static dma_addr_t dmabounce_map_page(struct device *dev, struct page *page,
        unsigned long offset, size_t size, enum dma_data_direction dir,
        struct dma_attrs *attrs)
{
    dma_addr_t dma_addr;
    int ret;

    dev_dbg(dev, "%s(page=%p,off=%#lx,size=%zx,dir=%x)\n",
        __func__, page, offset, size, dir);

    dma_addr = pfn_to_dma(dev, page_to_pfn(page)) + offset;

    ret = needs_bounce(dev, dma_addr, size);
    if (ret < 0)
        return DMA_ERROR_CODE;

    if (ret == 0) {
        arm_dma_ops.sync_single_for_device(dev, dma_addr, size, dir);
        return dma_addr;
    }

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

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

/*
 * 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)
 */
static void dmabounce_unmap_page(struct device *dev, dma_addr_t dma_addr, size_t size,
        enum dma_data_direction dir, struct dma_attrs *attrs)
{
    struct safe_buffer *buf;

    dev_dbg(dev, "%s(dma=%#x,size=%d,dir=%x)\n",
        __func__, dma_addr, size, dir);

    buf = find_safe_buffer_dev(dev, dma_addr, __func__);
    if (!buf) {
        arm_dma_ops.sync_single_for_cpu(dev, dma_addr, size, dir);
        return;
    }

    unmap_single(dev, buf, size, dir);
}

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

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

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

    off = addr - buf->safe_dma_addr;

    BUG_ON(buf->direction != dir);

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

static void dmabounce_sync_for_cpu(struct device *dev,
        dma_addr_t handle, size_t size, enum dma_data_direction dir)
{
    if (!__dmabounce_sync_for_cpu(dev, handle, size, dir))
        return;

    arm_dma_ops.sync_single_for_cpu(dev, handle, size, dir);
}

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

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

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

    off = addr - buf->safe_dma_addr;

    BUG_ON(buf->direction != dir);

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

static void dmabounce_sync_for_device(struct device *dev,
        dma_addr_t handle, size_t size, enum dma_data_direction dir)
{
    if (!__dmabounce_sync_for_device(dev, handle, size, dir))
        return;

    arm_dma_ops.sync_single_for_device(dev, handle, size, dir);
}

static int dmabounce_set_mask(struct device *dev, u64 dma_mask)
{
    if (dev->archdata.dmabounce)
        return 0;

    return arm_dma_ops.set_dma_mask(dev, dma_mask);
}

static struct dma_map_ops dmabounce_ops = {
    .alloc          = arm_dma_alloc,
    .free           = arm_dma_free,
    .mmap           = arm_dma_mmap,
    .get_sgtable        = arm_dma_get_sgtable,
    .map_page       = dmabounce_map_page,
    .unmap_page     = dmabounce_unmap_page,
    .sync_single_for_cpu    = dmabounce_sync_for_cpu,
    .sync_single_for_device = dmabounce_sync_for_device,
    .map_sg         = arm_dma_map_sg,
    .unmap_sg       = arm_dma_unmap_sg,
    .sync_sg_for_cpu    = arm_dma_sync_sg_for_cpu,
    .sync_sg_for_device = arm_dma_sync_sg_for_device,
    .set_dma_mask       = dmabounce_set_mask,
};

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,
        int (*needs_bounce_fn)(struct device *, dma_addr_t, size_t))
{
    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);
    device_info->needs_bounce = needs_bounce_fn;

#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;
    set_dma_ops(dev, &dmabounce_ops);

    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;
    set_dma_ops(dev, 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 <[email protected]>, Deepak Saxena <[email protected]>");
MODULE_DESCRIPTION("Special dma_{map/unmap/dma_sync}_* routines for systems with limited DMA windows");
MODULE_LICENSE("GPL");