lib/dma-virt.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  *      lib/dma-virt.c
   4  *
   5  * DMA operations that map to virtual 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
  12 static void *dma_virt_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 = (uintptr_t)ret;
  21         return ret;
  22 }
  23
  24 static void dma_virt_free(struct device *dev, size_t size,
  25                           void *cpu_addr, dma_addr_t dma_addr,
  26                           unsigned long attrs)
  27 {
  28         free_pages((unsigned long)cpu_addr, get_order(size));
  29 }
  30
  31 static dma_addr_t dma_virt_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         return (uintptr_t)(page_address(page) + offset);
  37 }
  38
  39 static int dma_virt_map_sg(struct device *dev, struct scatterlist *sgl,
  40                            int nents, enum dma_data_direction dir,
  41                            unsigned long attrs)
  42 {
  43         int i;
  44         struct scatterlist *sg;
  45
  46         for_each_sg(sgl, sg, nents, i) {
  47                 BUG_ON(!sg_page(sg));
  48                 sg_dma_address(sg) = (uintptr_t)sg_virt(sg);
  49                 sg_dma_len(sg) = sg->length;
  50         }
  51
  52         return nents;
  53 }
  54
  55 const struct dma_map_ops dma_virt_ops = {
  56         .alloc                  = dma_virt_alloc,
  57         .free                   = dma_virt_free,
  58         .map_page               = dma_virt_map_page,
  59         .map_sg                 = dma_virt_map_sg,
  60 };
  61 EXPORT_SYMBOL(dma_virt_ops);