arch/x86/kernel/pci-nommu.c

   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-mapping.h>
   5 #include <linux/scatterlist.h>
   6 #include <linux/string.h>
   7 #include <linux/gfp.h>
   8 #include <linux/pci.h>
   9 #include <linux/mm.h>
  10
  11 #include <asm/processor.h>
  12 #include <asm/iommu.h>
  13 #include <asm/dma.h>
  14
  15 #define NOMMU_MAPPING_ERROR             0
  16
  17 static int
  18 check_addr(char *name, struct device *hwdev, dma_addr_t bus, size_t size)
  19 {
  20         if (hwdev && !dma_capable(hwdev, bus, size)) {
  21                 if (*hwdev->dma_mask >= DMA_BIT_MASK(32))
  22                         printk(KERN_ERR
  23                             "nommu_%s: overflow %Lx+%zu of device mask %Lx\n",
  24                                 name, (long long)bus, size,
  25                                 (long long)*hwdev->dma_mask);
  26                 return 0;
  27         }
  28         return 1;
  29 }
  30
  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,
  34                                  unsigned long attrs)
  35 {
  36         dma_addr_t bus = phys_to_dma(dev, page_to_phys(page)) + offset;
  37         WARN_ON(size == 0);
  38         if (!check_addr("map_single", dev, bus, size))
  39                 return NOMMU_MAPPING_ERROR;
  40         flush_write_buffers();
  41         return bus;
  42 }
  43
  44 /* Map a set of buffers described by scatterlist in streaming
  45  * mode for DMA.  This is the scatter-gather version of the
  46  * above pci_map_single interface.  Here the scatter gather list
  47  * elements are each tagged with the appropriate dma address
  48  * and length.  They are obtained via sg_dma_{address,length}(SG).
  49  *
  50  * NOTE: An implementation may be able to use a smaller number of
  51  *       DMA address/length pairs than there are SG table elements.
  52  *       (for example via virtual mapping capabilities)
  53  *       The routine returns the number of addr/length pairs actually
  54  *       used, at most nents.
  55  *
  56  * Device ownership issues as mentioned above for pci_map_single are
  57  * the same here.
  58  */
  59 static int nommu_map_sg(struct device *hwdev, struct scatterlist *sg,
  60                         int nents, enum dma_data_direction dir,
  61                         unsigned long attrs)
  62 {
  63         struct scatterlist *s;
  64         int i;
  65
  66         WARN_ON(nents == 0 || sg[0].length == 0);
  67
  68         for_each_sg(sg, s, nents, i) {
  69                 BUG_ON(!sg_page(s));
  70                 s->dma_address = sg_phys(s);
  71                 if (!check_addr("map_sg", hwdev, s->dma_address, s->length))
  72                         return 0;
  73                 s->dma_length = s->length;
  74         }
  75         flush_write_buffers();
  76         return nents;
  77 }
  78
  79 static void nommu_sync_single_for_device(struct device *dev,
  80                         dma_addr_t addr, size_t size,
  81                         enum dma_data_direction dir)
  82 {
  83         flush_write_buffers();
  84 }
  85
  86
  87 static void nommu_sync_sg_for_device(struct device *dev,
  88                         struct scatterlist *sg, int nelems,
  89                         enum dma_data_direction dir)
  90 {
  91         flush_write_buffers();
  92 }
  93
  94 static int nommu_mapping_error(struct device *dev, dma_addr_t dma_addr)
  95 {
  96         return dma_addr == NOMMU_MAPPING_ERROR;
  97 }
  98
  99 const struct dma_map_ops nommu_dma_ops = {
 100         .alloc                  = dma_generic_alloc_coherent,
 101         .free                   = dma_generic_free_coherent,
 102         .map_sg                 = nommu_map_sg,
 103         .map_page               = nommu_map_page,
 104         .sync_single_for_device = nommu_sync_single_for_device,
 105         .sync_sg_for_device     = nommu_sync_sg_for_device,
 106         .is_phys                = 1,
 107         .mapping_error          = nommu_mapping_error,
 108         .dma_supported          = x86_dma_supported,
 109 };