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dma.c

/*
 * Copyright (C) 2006 Benjamin Herrenschmidt, IBM Corporation
 *
 * Provide default implementations of the DMA mapping callbacks for
 * directly mapped busses.
 */

#include <linux/device.h>
#include <linux/dma-mapping.h>
#include <asm/bug.h>
#include <asm/abs_addr.h>

/*
 * Generic direct DMA implementation
 *
 * This implementation supports a per-device offset that can be applied if
 * the address at which memory is visible to devices is not 0. Platform code
 * can set archdata.dma_data to an unsigned long holding the offset. By
 * default the offset is PCI_DRAM_OFFSET.
 */

static unsigned long get_dma_direct_offset(struct device *dev)
{
      if (dev)
            return (unsigned long)dev->archdata.dma_data;

      return PCI_DRAM_OFFSET;
}

void *dma_direct_alloc_coherent(struct device *dev, size_t size,
                        dma_addr_t *dma_handle, gfp_t flag)
{
      void *ret;
#ifdef CONFIG_NOT_COHERENT_CACHE
      ret = __dma_alloc_coherent(size, dma_handle, flag);
      if (ret == NULL)
            return NULL;
      *dma_handle += get_dma_direct_offset(dev);
      return ret;
#else
      struct page *page;
      int node = dev_to_node(dev);

      /* ignore region specifiers */
      flag  &= ~(__GFP_HIGHMEM);

      page = alloc_pages_node(node, flag, get_order(size));
      if (page == NULL)
            return NULL;
      ret = page_address(page);
      memset(ret, 0, size);
      *dma_handle = virt_to_abs(ret) + get_dma_direct_offset(dev);

      return ret;
#endif
}

void dma_direct_free_coherent(struct device *dev, size_t size,
                        void *vaddr, dma_addr_t dma_handle)
{
#ifdef CONFIG_NOT_COHERENT_CACHE
      __dma_free_coherent(size, vaddr);
#else
      free_pages((unsigned long)vaddr, get_order(size));
#endif
}

static int dma_direct_map_sg(struct device *dev, struct scatterlist *sgl,
                       int nents, enum dma_data_direction direction,
                       struct dma_attrs *attrs)
{
      struct scatterlist *sg;
      int i;

      for_each_sg(sgl, sg, nents, i) {
            sg->dma_address = sg_phys(sg) + get_dma_direct_offset(dev);
            sg->dma_length = sg->length;
      }

      return nents;
}

static void dma_direct_unmap_sg(struct device *dev, struct scatterlist *sg,
                        int nents, enum dma_data_direction direction,
                        struct dma_attrs *attrs)
{
}

static int dma_direct_dma_supported(struct device *dev, u64 mask)
{
#ifdef CONFIG_PPC64
      /* Could be improved to check for memory though it better be
       * done via some global so platforms can set the limit in case
       * they have limited DMA windows
       */
      return mask >= DMA_32BIT_MASK;
#else
      return 1;
#endif
}

static inline dma_addr_t dma_direct_map_page(struct device *dev,
                                   struct page *page,
                                   unsigned long offset,
                                   size_t size,
                                   enum dma_data_direction dir,
                                   struct dma_attrs *attrs)
{
      BUG_ON(dir == DMA_NONE);
      __dma_sync_page(page, offset, size, dir);
      return page_to_phys(page) + offset + get_dma_direct_offset(dev);
}

static inline void dma_direct_unmap_page(struct device *dev,
                               dma_addr_t dma_address,
                               size_t size,
                               enum dma_data_direction direction,
                               struct dma_attrs *attrs)
{
}

struct dma_mapping_ops dma_direct_ops = {
      .alloc_coherent   = dma_direct_alloc_coherent,
      .free_coherent    = dma_direct_free_coherent,
      .map_sg           = dma_direct_map_sg,
      .unmap_sg   = dma_direct_unmap_sg,
      .dma_supported    = dma_direct_dma_supported,
      .map_page   = dma_direct_map_page,
      .unmap_page = dma_direct_unmap_page,
};
EXPORT_SYMBOL(dma_direct_ops);

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