lib/dma-noop.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  *      lib/dma-noop.c
   4  *
   5  * DMA operations that map to physical addresses without flushing memory.
   6  */
   7 #include <linux/export.h>
   8 #include <linux/mm.h>
   9 #include <linux/dma-mapping.h>
  10 #include <linux/scatterlist.h>
  11 #include <linux/pfn.h>
  12
  13 static void *dma_noop_alloc(struct device *dev, size_t size,
  14                             dma_addr_t *dma_handle, gfp_t gfp,
  15                             unsigned long attrs)
  16 {
  17         void *ret;
  18
  19         ret = (void *)__get_free_pages(gfp, get_order(size));
  20         if (ret)
  21                 *dma_handle = virt_to_phys(ret) - PFN_PHYS(dev->dma_pfn_offset);
  22
  23         return ret;
  24 }
  25
  26 static void dma_noop_free(struct device *dev, size_t size,
  27                           void *cpu_addr, dma_addr_t dma_addr,
  28                           unsigned long attrs)
  29 {
  30         free_pages((unsigned long)cpu_addr, get_order(size));
  31 }
  32
  33 static dma_addr_t dma_noop_map_page(struct device *dev, struct page *page,
  34                                       unsigned long offset, size_t size,
  35                                       enum dma_data_direction dir,
  36                                       unsigned long attrs)
  37 {
  38         return page_to_phys(page) + offset - PFN_PHYS(dev->dma_pfn_offset);
  39 }
  40
  41 static int dma_noop_map_sg(struct device *dev, struct scatterlist *sgl, int nents,
  42                              enum dma_data_direction dir,
  43                              unsigned long attrs)
  44 {
  45         int i;
  46         struct scatterlist *sg;
  47
  48         for_each_sg(sgl, sg, nents, i) {
  49                 dma_addr_t offset = PFN_PHYS(dev->dma_pfn_offset);
  50                 void *va;
  51
  52                 BUG_ON(!sg_page(sg));
  53                 va = sg_virt(sg);
  54                 sg_dma_address(sg) = (dma_addr_t)virt_to_phys(va) - offset;
  55                 sg_dma_len(sg) = sg->length;
  56         }
  57
  58         return nents;
  59 }
  60
  61 const struct dma_map_ops dma_noop_ops = {
  62         .alloc                  = dma_noop_alloc,
  63         .free                   = dma_noop_free,
  64         .map_page               = dma_noop_map_page,
  65         .map_sg                 = dma_noop_map_sg,
  66 };
  67
  68 EXPORT_SYMBOL(dma_noop_ops);