xref: /linux/kernel/dma/ops_helpers.c (revision 2da68a77)
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 }
94