kernel/dma/ops_helpers.c

0001 // SPDX-License-Identifier: GPL-2.0
0002 /*
0003  * Helpers for DMA ops implementations.  These generally rely on the fact that
0004  * the allocated memory contains normal pages in the direct kernel mapping.
0005  */
0006 #include <linux/dma-map-ops.h>
0007
0008 static struct page *dma_common_vaddr_to_page(void *cpu_addr)
0009 {
0010     if (is_vmalloc_addr(cpu_addr))
0011         return vmalloc_to_page(cpu_addr);
0012     return virt_to_page(cpu_addr);
0013 }
0014
0015 /*
0016  * Create scatter-list for the already allocated DMA buffer.
0017  */
0018 int dma_common_get_sgtable(struct device *dev, struct sg_table *sgt,
0019          void *cpu_addr, dma_addr_t dma_addr, size_t size,
0020          unsigned long attrs)
0021 {
0022     struct page *page = dma_common_vaddr_to_page(cpu_addr);
0023     int ret;
0024
0025     ret = sg_alloc_table(sgt, 1, GFP_KERNEL);
0026     if (!ret)
0027         sg_set_page(sgt->sgl, page, PAGE_ALIGN(size), 0);
0028     return ret;
0029 }
0030
0031 /*
0032  * Create userspace mapping for the DMA-coherent memory.
0033  */
0034 int dma_common_mmap(struct device *dev, struct vm_area_struct *vma,
0035         void *cpu_addr, dma_addr_t dma_addr, size_t size,
0036         unsigned long attrs)
0037 {
0038 #ifdef CONFIG_MMU
0039     unsigned long user_count = vma_pages(vma);
0040     unsigned long count = PAGE_ALIGN(size) >> PAGE_SHIFT;
0041     unsigned long off = vma->vm_pgoff;
0042     struct page *page = dma_common_vaddr_to_page(cpu_addr);
0043     int ret = -ENXIO;
0044
0045     vma->vm_page_prot = dma_pgprot(dev, vma->vm_page_prot, attrs);
0046
0047     if (dma_mmap_from_dev_coherent(dev, vma, cpu_addr, size, &ret))
0048         return ret;
0049
0050     if (off >= count || user_count > count - off)
0051         return -ENXIO;
0052
0053     return remap_pfn_range(vma, vma->vm_start,
0054             page_to_pfn(page) + vma->vm_pgoff,
0055             user_count << PAGE_SHIFT, vma->vm_page_prot);
0056 #else
0057     return -ENXIO;
0058 #endif /* CONFIG_MMU */
0059 }
0060
0061 struct page *dma_common_alloc_pages(struct device *dev, size_t size,
0062         dma_addr_t *dma_handle, enum dma_data_direction dir, gfp_t gfp)
0063 {
0064     const struct dma_map_ops *ops = get_dma_ops(dev);
0065     struct page *page;
0066
0067     page = dma_alloc_contiguous(dev, size, gfp);
0068     if (!page)
0069         page = alloc_pages_node(dev_to_node(dev), gfp, get_order(size));
0070     if (!page)
0071         return NULL;
0072
0073     *dma_handle = ops->map_page(dev, page, 0, size, dir,
0074                     DMA_ATTR_SKIP_CPU_SYNC);
0075     if (*dma_handle == DMA_MAPPING_ERROR) {
0076         dma_free_contiguous(dev, page, size);
0077         return NULL;
0078     }
0079
0080     memset(page_address(page), 0, size);
0081     return page;
0082 }
0083
0084 void dma_common_free_pages(struct device *dev, size_t size, struct page *page,
0085         dma_addr_t dma_handle, enum dma_data_direction dir)
0086 {
0087     const struct dma_map_ops *ops = get_dma_ops(dev);
0088
0089     if (ops->unmap_page)
0090         ops->unmap_page(dev, dma_handle, size, dir,
0091                 DMA_ATTR_SKIP_CPU_SYNC);
0092     dma_free_contiguous(dev, page, size);
0093 }