1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Stub IOMMU driver which does nothing.
4 * The main purpose of it being present is to reuse generic IOMMU device tree
5 * bindings by Xen grant DMA-mapping layer.
6 *
7 * Copyright (C) 2022 EPAM Systems Inc.
8 */
9
10 #include <linux/iommu.h>
11 #include <linux/of.h>
12 #include <linux/platform_device.h>
13
14 struct grant_dma_iommu_device {
15 struct device *dev;
16 struct iommu_device iommu;
17 };
18
grant_dma_iommu_probe_device(struct device * dev)19 static struct iommu_device *grant_dma_iommu_probe_device(struct device *dev)
20 {
21 return ERR_PTR(-ENODEV);
22 }
23
24 /* Nothing is really needed here except a dummy probe_device callback */
25 static const struct iommu_ops grant_dma_iommu_ops = {
26 .probe_device = grant_dma_iommu_probe_device,
27 };
28
29 static const struct of_device_id grant_dma_iommu_of_match[] = {
30 { .compatible = "xen,grant-dma" },
31 { },
32 };
33
grant_dma_iommu_probe(struct platform_device * pdev)34 static int grant_dma_iommu_probe(struct platform_device *pdev)
35 {
36 struct grant_dma_iommu_device *mmu;
37 int ret;
38
39 mmu = devm_kzalloc(&pdev->dev, sizeof(*mmu), GFP_KERNEL);
40 if (!mmu)
41 return -ENOMEM;
42
43 mmu->dev = &pdev->dev;
44
45 ret = iommu_device_register(&mmu->iommu, &grant_dma_iommu_ops, &pdev->dev);
46 if (ret)
47 return ret;
48
49 platform_set_drvdata(pdev, mmu);
50
51 return 0;
52 }
53
grant_dma_iommu_remove(struct platform_device * pdev)54 static int grant_dma_iommu_remove(struct platform_device *pdev)
55 {
56 struct grant_dma_iommu_device *mmu = platform_get_drvdata(pdev);
57
58 platform_set_drvdata(pdev, NULL);
59 iommu_device_unregister(&mmu->iommu);
60
61 return 0;
62 }
63
64 static struct platform_driver grant_dma_iommu_driver = {
65 .driver = {
66 .name = "grant-dma-iommu",
67 .of_match_table = grant_dma_iommu_of_match,
68 },
69 .probe = grant_dma_iommu_probe,
70 .remove = grant_dma_iommu_remove,
71 };
72
grant_dma_iommu_init(void)73 static int __init grant_dma_iommu_init(void)
74 {
75 struct device_node *iommu_np;
76
77 iommu_np = of_find_matching_node(NULL, grant_dma_iommu_of_match);
78 if (!iommu_np)
79 return 0;
80
81 of_node_put(iommu_np);
82
83 return platform_driver_register(&grant_dma_iommu_driver);
84 }
85 subsys_initcall(grant_dma_iommu_init);
86