dma.c

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/*
 * Copyright (C) 2009-2010 PetaLogix
 * 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 <linux/gfp.h>
#include <linux/dma-debug.h>
#include <linux/export.h>
#include <asm/bug.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 (likely(dev))
        return (unsigned long)dev->archdata.dma_data;

    return PCI_DRAM_OFFSET; /* FIXME Not sure if is correct */
}

#define NOT_COHERENT_CACHE

static void *dma_direct_alloc_coherent(struct device *dev, size_t size,
                       dma_addr_t *dma_handle, gfp_t flag,
                       struct dma_attrs *attrs)
{
#ifdef NOT_COHERENT_CACHE
    return consistent_alloc(flag, size, dma_handle);
#else
    void *ret;
    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_phys(ret) + get_dma_direct_offset(dev);

    return ret;
#endif
}

static void dma_direct_free_coherent(struct device *dev, size_t size,
                     void *vaddr, dma_addr_t dma_handle,
                     struct dma_attrs *attrs)
{
#ifdef NOT_COHERENT_CACHE
    consistent_free(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;

    /* FIXME this part of code is untested */
    for_each_sg(sgl, sg, nents, i) {
        sg->dma_address = sg_phys(sg) + get_dma_direct_offset(dev);
        __dma_sync(page_to_phys(sg_page(sg)) + sg->offset,
                            sg->length, direction);
    }

    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)
{
    return 1;
}

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 direction,
                         struct dma_attrs *attrs)
{
    __dma_sync(page_to_phys(page) + offset, size, direction);
    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)
{
/* There is not necessary to do cache cleanup
 *
 * phys_to_virt is here because in __dma_sync_page is __virt_to_phys and
 * dma_address is physical address
 */
    __dma_sync(dma_address, size, direction);
}

static inline void
dma_direct_sync_single_for_cpu(struct device *dev,
                   dma_addr_t dma_handle, size_t size,
                   enum dma_data_direction direction)
{
    /*
     * It's pointless to flush the cache as the memory segment
     * is given to the CPU
     */

    if (direction == DMA_FROM_DEVICE)
        __dma_sync(dma_handle, size, direction);
}

static inline void
dma_direct_sync_single_for_device(struct device *dev,
                  dma_addr_t dma_handle, size_t size,
                  enum dma_data_direction direction)
{
    /*
     * It's pointless to invalidate the cache if the device isn't
     * supposed to write to the relevant region
     */

    if (direction == DMA_TO_DEVICE)
        __dma_sync(dma_handle, size, direction);
}

static inline void
dma_direct_sync_sg_for_cpu(struct device *dev,
               struct scatterlist *sgl, int nents,
               enum dma_data_direction direction)
{
    struct scatterlist *sg;
    int i;

    /* FIXME this part of code is untested */
    if (direction == DMA_FROM_DEVICE)
        for_each_sg(sgl, sg, nents, i)
            __dma_sync(sg->dma_address, sg->length, direction);
}

static inline void
dma_direct_sync_sg_for_device(struct device *dev,
                  struct scatterlist *sgl, int nents,
                  enum dma_data_direction direction)
{
    struct scatterlist *sg;
    int i;

    /* FIXME this part of code is untested */
    if (direction == DMA_TO_DEVICE)
        for_each_sg(sgl, sg, nents, i)
            __dma_sync(sg->dma_address, sg->length, direction);
}

struct dma_map_ops dma_direct_ops = {
    .alloc      = dma_direct_alloc_coherent,
    .free       = 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,
    .sync_single_for_cpu        = dma_direct_sync_single_for_cpu,
    .sync_single_for_device     = dma_direct_sync_single_for_device,
    .sync_sg_for_cpu        = dma_direct_sync_sg_for_cpu,
    .sync_sg_for_device     = dma_direct_sync_sg_for_device,
};
EXPORT_SYMBOL(dma_direct_ops);

/* Number of entries preallocated for DMA-API debugging */
#define PREALLOC_DMA_DEBUG_ENTRIES (1 << 16)

static int __init dma_init(void)
{
       dma_debug_init(PREALLOC_DMA_DEBUG_ENTRIES);

       return 0;
}
fs_initcall(dma_init);