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dmabounce.c

/*
 *  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/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 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 dmabounce_device_info *device_info = dev->archdata.dmabounce;
      struct safe_buffer *buf = NULL;

      /*
       * Trying to unmap an invalid mapping
       */
      if (dma_mapping_error(dev, dma_addr)) {
            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 (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 ( device_info->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(device_info, buf);
      }
}

static int sync_single(struct device *dev, dma_addr_t dma_addr, size_t size,
                  enum dma_data_direction dir)
{
      struct dmabounce_device_info *device_info = dev->archdata.dmabounce;
      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 (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 ( 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();
            }
            /*
             * No need to sync the safe buffer - it was allocated
             * via the coherent allocators.
             */
            return 0;
      } else {
            return 1;
      }
}

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

/*
 * 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)
{
      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);

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

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

      BUG_ON(dir == DMA_NONE);

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

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

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

      BUG_ON(dir == DMA_NONE);

      for (i = 0; i < nents; i++, sg++) {
            struct page *page = sg_page(sg);
            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);
      }

      return nents;
}

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

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

      BUG_ON(dir == DMA_NONE);

      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);
      }
}

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

      if (sync_single(dev, dma_addr, offset + size, dir))
            dma_cache_maint(dma_to_virt(dev, dma_addr) + offset, size, dir);
}
EXPORT_SYMBOL(dma_sync_single_range_for_cpu);

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

      if (sync_single(dev, dma_addr, offset + size, dir))
            dma_cache_maint(dma_to_virt(dev, dma_addr) + offset, size, dir);
}
EXPORT_SYMBOL(dma_sync_single_range_for_device);

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

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

      BUG_ON(dir == DMA_NONE);

      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);
      }
}

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

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

      BUG_ON(dir == DMA_NONE);

      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);
      }
}

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;
}

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(dma_map_single);
EXPORT_SYMBOL(dma_unmap_single);
EXPORT_SYMBOL(dma_map_sg);
EXPORT_SYMBOL(dma_unmap_sg);
EXPORT_SYMBOL(dma_sync_sg_for_cpu);
EXPORT_SYMBOL(dma_sync_sg_for_device);
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");

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