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-contiguous.h>
   7 #include <linux/dma-map-ops.h>
   8 #include <linux/dma-noncoherent.h>
   9
  10 /*
  11  * Create scatter-list for the already allocated DMA buffer.
  12  */
  13 int dma_common_get_sgtable(struct device *dev, struct sg_table *sgt,
  14                  void *cpu_addr, dma_addr_t dma_addr, size_t size,
  15                  unsigned long attrs)
  16 {
  17         struct page *page = virt_to_page(cpu_addr);
  18         int ret;
  19
  20         ret = sg_alloc_table(sgt, 1, GFP_KERNEL);
  21         if (!ret)
  22                 sg_set_page(sgt->sgl, page, PAGE_ALIGN(size), 0);
  23         return ret;
  24 }
  25
  26 /*
  27  * Create userspace mapping for the DMA-coherent memory.
  28  */
  29 int dma_common_mmap(struct device *dev, struct vm_area_struct *vma,
  30                 void *cpu_addr, dma_addr_t dma_addr, size_t size,
  31                 unsigned long attrs)
  32 {
  33 #ifdef CONFIG_MMU
  34         unsigned long user_count = vma_pages(vma);
  35         unsigned long count = PAGE_ALIGN(size) >> PAGE_SHIFT;
  36         unsigned long off = vma->vm_pgoff;
  37         int ret = -ENXIO;
  38
  39         vma->vm_page_prot = dma_pgprot(dev, vma->vm_page_prot, attrs);
  40
  41         if (dma_mmap_from_dev_coherent(dev, vma, cpu_addr, size, &ret))
  42                 return ret;
  43
  44         if (off >= count || user_count > count - off)
  45                 return -ENXIO;
  46
  47         return remap_pfn_range(vma, vma->vm_start,
  48                         page_to_pfn(virt_to_page(cpu_addr)) + vma->vm_pgoff,
  49                         user_count << PAGE_SHIFT, vma->vm_page_prot);
  50 #else
  51         return -ENXIO;
  52 #endif /* CONFIG_MMU */
  53 }
  54
  55 struct page *dma_common_alloc_pages(struct device *dev, size_t size,
  56                 dma_addr_t *dma_handle, enum dma_data_direction dir, gfp_t gfp)
  57 {
  58         const struct dma_map_ops *ops = get_dma_ops(dev);
  59         struct page *page;
  60
  61         page = dma_alloc_contiguous(dev, size, gfp);
  62         if (!page)
  63                 page = alloc_pages_node(dev_to_node(dev), gfp, get_order(size));
  64         if (!page)
  65                 return NULL;
  66
  67         *dma_handle = ops->map_page(dev, page, 0, size, dir,
  68                                     DMA_ATTR_SKIP_CPU_SYNC);
  69         if (*dma_handle == DMA_MAPPING_ERROR) {
  70                 dma_free_contiguous(dev, page, size);
  71                 return NULL;
  72         }
  73
  74         memset(page_address(page), 0, size);
  75         return page;
  76 }
  77
  78 void dma_common_free_pages(struct device *dev, size_t size, struct page *page,
  79                 dma_addr_t dma_handle, enum dma_data_direction dir)
  80 {
  81         const struct dma_map_ops *ops = get_dma_ops(dev);
  82
  83         if (ops->unmap_page)
  84                 ops->unmap_page(dev, dma_handle, size, dir,
  85                                 DMA_ATTR_SKIP_CPU_SYNC);
  86         dma_free_contiguous(dev, page, size);
  87 }