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/mm.h>
   4 #include <linux/init.h>
   5 #include <linux/pci.h>
   6 #include <linux/string.h>
   7 #include <linux/dma-mapping.h>
   8 #include <linux/scatterlist.h>
   9
  10 #include <asm/iommu.h>
  11 #include <asm/processor.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
  29 nommu_map_single(struct device *hwdev, phys_addr_t paddr, size_t size,
  30                int direction)
  31 {
  32         dma_addr_t bus = paddr;
  33         WARN_ON(size == 0);
  34         if (!check_addr("map_single", hwdev, bus, size))
  35                                 return bad_dma_address;
  36         flush_write_buffers();
  37         return bus;
  38 }
  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, int direction)
  58 {
  59         struct scatterlist *s;
  60         int i;
  61
  62         WARN_ON(nents == 0 || sg[0].length == 0);
  63
  64         for_each_sg(sg, s, nents, i) {
  65                 BUG_ON(!sg_page(s));
  66                 s->dma_address = sg_phys(s);
  67                 if (!check_addr("map_sg", hwdev, s->dma_address, s->length))
  68                         return 0;
  69                 s->dma_length = s->length;
  70         }
  71         flush_write_buffers();
  72         return nents;
  73 }
  74
  75 static void *
  76 nommu_alloc_coherent(struct device *hwdev, size_t size,
  77                      dma_addr_t *dma_addr, gfp_t gfp)
  78 {
  79         unsigned long dma_mask;
  80         int node;
  81         struct page *page;
  82         dma_addr_t addr;
  83
  84         dma_mask = dma_alloc_coherent_mask(hwdev, gfp);
  85
  86         gfp |= __GFP_ZERO;
  87
  88         node = dev_to_node(hwdev);
  89 again:
  90         page = alloc_pages_node(node, gfp, get_order(size));
  91         if (!page)
  92                 return NULL;
  93
  94         addr = page_to_phys(page);
  95         if (!is_buffer_dma_capable(dma_mask, addr, size) && !(gfp & GFP_DMA)) {
  96                 free_pages((unsigned long)page_address(page), get_order(size));
  97                 gfp |= GFP_DMA;
  98                 goto again;
  99         }
 100
 101         if (check_addr("alloc_coherent", hwdev, addr, size)) {
 102                 *dma_addr = addr;
 103                 flush_write_buffers();
 104                 return page_address(page);
 105         }
 106
 107         free_pages((unsigned long)page_address(page), get_order(size));
 108
 109         return NULL;
 110 }
 111
 112 static void nommu_free_coherent(struct device *dev, size_t size, void *vaddr,
 113                                 dma_addr_t dma_addr)
 114 {
 115         free_pages((unsigned long)vaddr, get_order(size));
 116 }
 117
 118 struct dma_mapping_ops nommu_dma_ops = {
 119         .alloc_coherent = nommu_alloc_coherent,
 120         .free_coherent = nommu_free_coherent,
 121         .map_single = nommu_map_single,
 122         .map_sg = nommu_map_sg,
 123         .is_phys = 1,
 124 };
 125
 126 void __init no_iommu_init(void)
 127 {
 128         if (dma_ops)
 129                 return;
 130
 131         force_iommu = 0; /* no HW IOMMU */
 132         dma_ops = &nommu_dma_ops;
 133 }