lib/dma-noop.c

   1 /*
   2  *      lib/dma-noop.c
   3  *
   4  * DMA operations that map to physical addresses without flushing memory.
   5  */
   6 #include <linux/export.h>
   7 #include <linux/mm.h>
   8 #include <linux/dma-mapping.h>
   9 #include <linux/scatterlist.h>
  10 #include <linux/pfn.h>
  11
  12 static void *dma_noop_alloc(struct device *dev, size_t size,
  13                             dma_addr_t *dma_handle, gfp_t gfp,
  14                             unsigned long attrs)
  15 {
  16         void *ret;
  17
  18         ret = (void *)__get_free_pages(gfp, get_order(size));
  19         if (ret)
  20                 *dma_handle = virt_to_phys(ret) - PFN_PHYS(dev->dma_pfn_offset);
  21
  22         return ret;
  23 }
  24
  25 static void dma_noop_free(struct device *dev, size_t size,
  26                           void *cpu_addr, dma_addr_t dma_addr,
  27                           unsigned long attrs)
  28 {
  29         free_pages((unsigned long)cpu_addr, get_order(size));
  30 }
  31
  32 static dma_addr_t dma_noop_map_page(struct device *dev, struct page *page,
  33                                       unsigned long offset, size_t size,
  34                                       enum dma_data_direction dir,
  35                                       unsigned long attrs)
  36 {
  37         return page_to_phys(page) + offset - PFN_PHYS(dev->dma_pfn_offset);
  38 }
  39
  40 static int dma_noop_map_sg(struct device *dev, struct scatterlist *sgl, int nents,
  41                              enum dma_data_direction dir,
  42                              unsigned long attrs)
  43 {
  44         int i;
  45         struct scatterlist *sg;
  46
  47         for_each_sg(sgl, sg, nents, i) {
  48                 dma_addr_t offset = PFN_PHYS(dev->dma_pfn_offset);
  49                 void *va;
  50
  51                 BUG_ON(!sg_page(sg));
  52                 va = sg_virt(sg);
  53                 sg_dma_address(sg) = (dma_addr_t)virt_to_phys(va) - offset;
  54                 sg_dma_len(sg) = sg->length;
  55         }
  56
  57         return nents;
  58 }
  59
  60 const struct dma_map_ops dma_noop_ops = {
  61         .alloc                  = dma_noop_alloc,
  62         .free                   = dma_noop_free,
  63         .map_page               = dma_noop_map_page,
  64         .map_sg                 = dma_noop_map_sg,
  65 };
  66
  67 EXPORT_SYMBOL(dma_noop_ops);