kernel/dma/ops_helpers.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Helpers for DMA ops implementations.  These generally rely on the fact that
   4  * the allocated memory contains normal pages in the direct kernel mapping.
   5  */
   6 #include <linux/dma-map-ops.h>
   7
   8 /*
   9  * Create scatter-list for the already allocated DMA buffer.
  10  */
  11 int dma_common_get_sgtable(struct device *dev, struct sg_table *sgt,
  12                  void *cpu_addr, dma_addr_t dma_addr, size_t size,
  13                  unsigned long attrs)
  14 {
  15         struct page *page = virt_to_page(cpu_addr);
  16         int ret;
  17
  18         ret = sg_alloc_table(sgt, 1, GFP_KERNEL);
  19         if (!ret)
  20                 sg_set_page(sgt->sgl, page, PAGE_ALIGN(size), 0);
  21         return ret;
  22 }
  23
  24 /*
  25  * Create userspace mapping for the DMA-coherent memory.
  26  */
  27 int dma_common_mmap(struct device *dev, struct vm_area_struct *vma,
  28                 void *cpu_addr, dma_addr_t dma_addr, size_t size,
  29                 unsigned long attrs)
  30 {
  31 #ifdef CONFIG_MMU
  32         unsigned long user_count = vma_pages(vma);
  33         unsigned long count = PAGE_ALIGN(size) >> PAGE_SHIFT;
  34         unsigned long off = vma->vm_pgoff;
  35         int ret = -ENXIO;
  36
  37         vma->vm_page_prot = dma_pgprot(dev, vma->vm_page_prot, attrs);
  38
  39         if (dma_mmap_from_dev_coherent(dev, vma, cpu_addr, size, &ret))
  40                 return ret;
  41
  42         if (off >= count || user_count > count - off)
  43                 return -ENXIO;
  44
  45         return remap_pfn_range(vma, vma->vm_start,
  46                         page_to_pfn(virt_to_page(cpu_addr)) + vma->vm_pgoff,
  47                         user_count << PAGE_SHIFT, vma->vm_page_prot);
  48 #else
  49         return -ENXIO;
  50 #endif /* CONFIG_MMU */
  51 }
  52
  53 struct page *dma_common_alloc_pages(struct device *dev, size_t size,
  54                 dma_addr_t *dma_handle, enum dma_data_direction dir, gfp_t gfp)
  55 {
  56         const struct dma_map_ops *ops = get_dma_ops(dev);
  57         struct page *page;
  58
  59         page = dma_alloc_contiguous(dev, size, gfp);
  60         if (!page)
  61                 page = alloc_pages_node(dev_to_node(dev), gfp, get_order(size));
  62         if (!page)
  63                 return NULL;
  64
  65         *dma_handle = ops->map_page(dev, page, 0, size, dir,
  66                                     DMA_ATTR_SKIP_CPU_SYNC);
  67         if (*dma_handle == DMA_MAPPING_ERROR) {
  68                 dma_free_contiguous(dev, page, size);
  69                 return NULL;
  70         }
  71
  72         memset(page_address(page), 0, size);
  73         return page;
  74 }
  75
  76 void dma_common_free_pages(struct device *dev, size_t size, struct page *page,
  77                 dma_addr_t dma_handle, enum dma_data_direction dir)
  78 {
  79         const struct dma_map_ops *ops = get_dma_ops(dev);
  80
  81         if (ops->unmap_page)
  82                 ops->unmap_page(dev, dma_handle, size, dir,
  83                                 DMA_ATTR_SKIP_CPU_SYNC);
  84         dma_free_contiguous(dev, page, size);
  85 }