arch/x86/kernel/pci-nommu.c

   1 /* Fallback functions when the main IOMMU code is not compiled in. This
   2    code is roughly equivalent to i386. */
   3 #include <linux/dma-mapping.h>
   4 #include <linux/scatterlist.h>
   5 #include <linux/string.h>
   6 #include <linux/init.h>
   7 #include <linux/pci.h>
   8 #include <linux/mm.h>
   9
  10 #include <asm/processor.h>
  11 #include <asm/iommu.h>
  12 #include <asm/dma.h>
  13
  14 static int
  15 check_addr(char *name, struct device *hwdev, dma_addr_t bus, size_t size)
  16 {
  17         if (hwdev && !is_buffer_dma_capable(*hwdev->dma_mask, bus, size)) {
  18                 if (*hwdev->dma_mask >= DMA_32BIT_MASK)
  19                         printk(KERN_ERR
  20                             "nommu_%s: overflow %Lx+%zu of device mask %Lx\n",
  21                                 name, (long long)bus, size,
  22                                 (long long)*hwdev->dma_mask);
  23                 return 0;
  24         }
  25         return 1;
  26 }
  27
  28 static dma_addr_t nommu_map_page(struct device *dev, struct page *page,
  29                                  unsigned long offset, size_t size,
  30                                  enum dma_data_direction dir,
  31                                  struct dma_attrs *attrs)
  32 {
  33         dma_addr_t bus = page_to_phys(page) + offset;
  34         WARN_ON(size == 0);
  35         if (!check_addr("map_single", dev, bus, size))
  36                 return bad_dma_address;
  37         flush_write_buffers();
  38         return bus;
  39 }
  40
  41 /* Map a set of buffers described by scatterlist in streaming
  42  * mode for DMA.  This is the scatter-gather version of the
  43  * above pci_map_single interface.  Here the scatter gather list
  44  * elements are each tagged with the appropriate dma address
  45  * and length.  They are obtained via sg_dma_{address,length}(SG).
  46  *
  47  * NOTE: An implementation may be able to use a smaller number of
  48  *       DMA address/length pairs than there are SG table elements.
  49  *       (for example via virtual mapping capabilities)
  50  *       The routine returns the number of addr/length pairs actually
  51  *       used, at most nents.
  52  *
  53  * Device ownership issues as mentioned above for pci_map_single are
  54  * the same here.
  55  */
  56 static int nommu_map_sg(struct device *hwdev, struct scatterlist *sg,
  57                         int nents, enum dma_data_direction dir,
  58                         struct dma_attrs *attrs)
  59 {
  60         struct scatterlist *s;
  61         int i;
  62
  63         WARN_ON(nents == 0 || sg[0].length == 0);
  64
  65         for_each_sg(sg, s, nents, i) {
  66                 BUG_ON(!sg_page(s));
  67                 s->dma_address = sg_phys(s);
  68                 if (!check_addr("map_sg", hwdev, s->dma_address, s->length))
  69                         return 0;
  70                 s->dma_length = s->length;
  71         }
  72         flush_write_buffers();
  73         return nents;
  74 }
  75
  76 static void nommu_free_coherent(struct device *dev, size_t size, void *vaddr,
  77                                 dma_addr_t dma_addr)
  78 {
  79         free_pages((unsigned long)vaddr, get_order(size));
  80 }
  81
  82 struct dma_map_ops nommu_dma_ops = {
  83         .alloc_coherent = dma_generic_alloc_coherent,
  84         .free_coherent  = nommu_free_coherent,
  85         .map_sg         = nommu_map_sg,
  86         .map_page       = nommu_map_page,
  87         .is_phys        = 1,
  88 };
  89
  90 void __init no_iommu_init(void)
  91 {
  92         if (dma_ops)
  93                 return;
  94
  95         force_iommu = 0; /* no HW IOMMU */
  96         dma_ops = &nommu_dma_ops;
  97 }