pci-nommu.c

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/* Fallback functions when the main IOMMU code is not compiled in. This
   code is roughly equivalent to i386. */
#include <linux/dma-mapping.h>
#include <linux/scatterlist.h>
#include <linux/string.h>
#include <linux/init.h>
#include <linux/gfp.h>
#include <linux/pci.h>
#include <linux/mm.h>

#include <asm/processor.h>
#include <asm/iommu.h>
#include <asm/dma.h>

static int
check_addr(char *name, struct device *hwdev, dma_addr_t bus, size_t size)
{
    if (hwdev && !dma_capable(hwdev, bus, size)) {
        if (*hwdev->dma_mask >= DMA_BIT_MASK(32))
            printk(KERN_ERR
                "nommu_%s: overflow %Lx+%zu of device mask %Lx\n",
                name, (long long)bus, size,
                (long long)*hwdev->dma_mask);
        return 0;
    }
    return 1;
}

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 bus = page_to_phys(page) + offset;
    WARN_ON(size == 0);
    if (!check_addr("map_single", dev, bus, size))
        return DMA_ERROR_CODE;
    flush_write_buffers();
    return bus;
}

/* Map a set of buffers described by scatterlist in streaming
 * mode for DMA.  This is the scatter-gather version of the
 * above pci_map_single interface.  Here the scatter gather list
 * elements are each tagged with the appropriate dma address
 * and length.  They are obtained via sg_dma_{address,length}(SG).
 *
 * NOTE: An implementation may be able to use a smaller number of
 *       DMA address/length pairs than there are SG table elements.
 *       (for example via virtual mapping capabilities)
 *       The routine returns the number of addr/length pairs actually
 *       used, at most nents.
 *
 * Device ownership issues as mentioned above for pci_map_single are
 * the same here.
 */
static int nommu_map_sg(struct device *hwdev, 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));
        s->dma_address = sg_phys(s);
        if (!check_addr("map_sg", hwdev, s->dma_address, s->length))
            return 0;
        s->dma_length = s->length;
    }
    flush_write_buffers();
    return nents;
}

static void nommu_sync_single_for_device(struct device *dev,
            dma_addr_t addr, size_t size,
            enum dma_data_direction dir)
{
    flush_write_buffers();
}


static void nommu_sync_sg_for_device(struct device *dev,
            struct scatterlist *sg, int nelems,
            enum dma_data_direction dir)
{
    flush_write_buffers();
}

struct dma_map_ops nommu_dma_ops = {
    .alloc          = dma_generic_alloc_coherent,
    .free           = dma_generic_free_coherent,
    .map_sg         = nommu_map_sg,
    .map_page       = nommu_map_page,
    .sync_single_for_device = nommu_sync_single_for_device,
    .sync_sg_for_device = nommu_sync_sg_for_device,
    .is_phys        = 1,
};