dma-nommu.c

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/*
 * DMA mapping support for platforms lacking IOMMUs.
 *
 * Copyright (C) 2009  Paul Mundt
 *
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 */
#include <linux/dma-mapping.h>
#include <linux/io.h>

static dma_addr_t nommu_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 addr = page_to_phys(page) + offset;

    WARN_ON(size == 0);
    dma_cache_sync(dev, page_address(page) + offset, size, dir);

    return addr;
}

static int nommu_map_sg(struct device *dev, struct scatterlist *sg,
            int nents, enum dma_data_direction dir,
            struct dma_attrs *attrs)
{
    struct scatterlist *s;
    int i;

    WARN_ON(nents == 0 || sg[0].length == 0);

    for_each_sg(sg, s, nents, i) {
        BUG_ON(!sg_page(s));

        dma_cache_sync(dev, sg_virt(s), s->length, dir);

        s->dma_address = sg_phys(s);
        s->dma_length = s->length;
    }

    return nents;
}

#ifdef CONFIG_DMA_NONCOHERENT
static void nommu_sync_single(struct device *dev, dma_addr_t addr,
                  size_t size, enum dma_data_direction dir)
{
    dma_cache_sync(dev, phys_to_virt(addr), size, dir);
}

static void nommu_sync_sg(struct device *dev, struct scatterlist *sg,
              int nelems, enum dma_data_direction dir)
{
    struct scatterlist *s;
    int i;

    for_each_sg(sg, s, nelems, i)
        dma_cache_sync(dev, sg_virt(s), s->length, dir);
}
#endif

struct dma_map_ops nommu_dma_ops = {
    .alloc          = dma_generic_alloc_coherent,
    .free           = dma_generic_free_coherent,
    .map_page       = nommu_map_page,
    .map_sg         = nommu_map_sg,
#ifdef CONFIG_DMA_NONCOHERENT
    .sync_single_for_device = nommu_sync_single,
    .sync_sg_for_device = nommu_sync_sg,
#endif
    .is_phys        = 1,
};

void __init no_iommu_init(void)
{
    if (dma_ops)
        return;
    dma_ops = &nommu_dma_ops;
}