1 // SPDX-License-Identifier: GPL-2.0
2 /* Fallback functions when the main IOMMU code is not compiled in. This
3 code is roughly equivalent to i386. */
4 #include <linux/dma-direct.h>
5 #include <linux/scatterlist.h>
6 #include <linux/string.h>
11 #include <asm/processor.h>
12 #include <asm/iommu.h>
15 #define NOMMU_MAPPING_ERROR 0
18 check_addr(char *name, struct device *hwdev, dma_addr_t bus, size_t size)
20 if (hwdev && !dma_capable(hwdev, bus, size)) {
21 if (*hwdev->dma_mask >= DMA_BIT_MASK(32))
23 "nommu_%s: overflow %Lx+%zu of device mask %Lx\n",
24 name, (long long)bus, size,
25 (long long)*hwdev->dma_mask);
31 static dma_addr_t nommu_map_page(struct device *dev, struct page *page,
32 unsigned long offset, size_t size,
33 enum dma_data_direction dir,
36 dma_addr_t bus = phys_to_dma(dev, page_to_phys(page)) + offset;
38 if (!check_addr("map_single", dev, bus, size))
39 return NOMMU_MAPPING_ERROR;
43 /* Map a set of buffers described by scatterlist in streaming
44 * mode for DMA. This is the scatter-gather version of the
45 * above pci_map_single interface. Here the scatter gather list
46 * elements are each tagged with the appropriate dma address
47 * and length. They are obtained via sg_dma_{address,length}(SG).
49 * NOTE: An implementation may be able to use a smaller number of
50 * DMA address/length pairs than there are SG table elements.
51 * (for example via virtual mapping capabilities)
52 * The routine returns the number of addr/length pairs actually
53 * used, at most nents.
55 * Device ownership issues as mentioned above for pci_map_single are
58 static int nommu_map_sg(struct device *hwdev, struct scatterlist *sg,
59 int nents, enum dma_data_direction dir,
62 struct scatterlist *s;
65 WARN_ON(nents == 0 || sg[0].length == 0);
67 for_each_sg(sg, s, nents, i) {
69 s->dma_address = sg_phys(s);
70 if (!check_addr("map_sg", hwdev, s->dma_address, s->length))
72 s->dma_length = s->length;
77 static int nommu_mapping_error(struct device *dev, dma_addr_t dma_addr)
79 return dma_addr == NOMMU_MAPPING_ERROR;
82 const struct dma_map_ops nommu_dma_ops = {
83 .alloc = dma_generic_alloc_coherent,
84 .free = dma_generic_free_coherent,
85 .map_sg = nommu_map_sg,
86 .map_page = nommu_map_page,
88 .mapping_error = nommu_mapping_error,
89 .dma_supported = x86_dma_supported,