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 static struct page *dma_common_vaddr_to_page(void *cpu_addr)
   9 {
  10         if (is_vmalloc_addr(cpu_addr))
  11                 return vmalloc_to_page(cpu_addr);
  12         return virt_to_page(cpu_addr);
  13 }
  14
  15 /*
  16  * Create scatter-list for the already allocated DMA buffer.
  17  */
  18 int dma_common_get_sgtable(struct device *dev, struct sg_table *sgt,
  19                  void *cpu_addr, dma_addr_t dma_addr, size_t size,
  20                  unsigned long attrs)
  21 {
  22         struct page *page = dma_common_vaddr_to_page(cpu_addr);
  23         int ret;
  24
  25         ret = sg_alloc_table(sgt, 1, GFP_KERNEL);
  26         if (!ret)
  27                 sg_set_page(sgt->sgl, page, PAGE_ALIGN(size), 0);
  28         return ret;
  29 }
  30
  31 /*
  32  * Create userspace mapping for the DMA-coherent memory.
  33  */
  34 int dma_common_mmap(struct device *dev, struct vm_area_struct *vma,
  35                 void *cpu_addr, dma_addr_t dma_addr, size_t size,
  36                 unsigned long attrs)
  37 {
  38 #ifdef CONFIG_MMU
  39         unsigned long user_count = vma_pages(vma);
  40         unsigned long count = PAGE_ALIGN(size) >> PAGE_SHIFT;
  41         unsigned long off = vma->vm_pgoff;
  42         struct page *page = dma_common_vaddr_to_page(cpu_addr);
  43         int ret = -ENXIO;
  44
  45         vma->vm_page_prot = dma_pgprot(dev, vma->vm_page_prot, attrs);
  46
  47         if (dma_mmap_from_dev_coherent(dev, vma, cpu_addr, size, &ret))
  48                 return ret;
  49
  50         if (off >= count || user_count > count - off)
  51                 return -ENXIO;
  52
  53         return remap_pfn_range(vma, vma->vm_start,
  54                         page_to_pfn(page) + vma->vm_pgoff,
  55                         user_count << PAGE_SHIFT, vma->vm_page_prot);
  56 #else
  57         return -ENXIO;
  58 #endif /* CONFIG_MMU */
  59 }
  60
  61 struct page *dma_common_alloc_pages(struct device *dev, size_t size,
  62                 dma_addr_t *dma_handle, enum dma_data_direction dir, gfp_t gfp)
  63 {
  64         const struct dma_map_ops *ops = get_dma_ops(dev);
  65         struct page *page;
  66
  67         page = dma_alloc_contiguous(dev, size, gfp);
  68         if (!page)
  69                 page = alloc_pages_node(dev_to_node(dev), gfp, get_order(size));
  70         if (!page)
  71                 return NULL;
  72
  73         *dma_handle = ops->map_page(dev, page, 0, size, dir,
  74                                     DMA_ATTR_SKIP_CPU_SYNC);
  75         if (*dma_handle == DMA_MAPPING_ERROR) {
  76                 dma_free_contiguous(dev, page, size);
  77                 return NULL;
  78         }
  79
  80         memset(page_address(page), 0, size);
  81         return page;
  82 }
  83
  84 void dma_common_free_pages(struct device *dev, size_t size, struct page *page,
  85                 dma_addr_t dma_handle, enum dma_data_direction dir)
  86 {
  87         const struct dma_map_ops *ops = get_dma_ops(dev);
  88
  89         if (ops->unmap_page)
  90                 ops->unmap_page(dev, dma_handle, size, dir,
  91                                 DMA_ATTR_SKIP_CPU_SYNC);
  92         dma_free_contiguous(dev, page, size);
  93 }