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
14struct grant_dma_iommu_device {
15	struct device *dev;
16	struct iommu_device iommu;
17};
18
19/* Nothing is really needed here */
20static const struct iommu_ops grant_dma_iommu_ops;
21
22static const struct of_device_id grant_dma_iommu_of_match[] = {
23	{ .compatible = "xen,grant-dma" },
24	{ },
25};
26
27static int grant_dma_iommu_probe(struct platform_device *pdev)
28{
29	struct grant_dma_iommu_device *mmu;
30	int ret;
31
32	mmu = devm_kzalloc(&pdev->dev, sizeof(*mmu), GFP_KERNEL);
33	if (!mmu)
34		return -ENOMEM;
35
36	mmu->dev = &pdev->dev;
37
38	ret = iommu_device_register(&mmu->iommu, &grant_dma_iommu_ops, &pdev->dev);
39	if (ret)
40		return ret;
41
42	platform_set_drvdata(pdev, mmu);
43
44	return 0;
45}
46
47static int grant_dma_iommu_remove(struct platform_device *pdev)
48{
49	struct grant_dma_iommu_device *mmu = platform_get_drvdata(pdev);
50
51	platform_set_drvdata(pdev, NULL);
52	iommu_device_unregister(&mmu->iommu);
53
54	return 0;
55}
56
57static struct platform_driver grant_dma_iommu_driver = {
58	.driver = {
59		.name = "grant-dma-iommu",
60		.of_match_table = grant_dma_iommu_of_match,
61	},
62	.probe = grant_dma_iommu_probe,
63	.remove = grant_dma_iommu_remove,
64};
65
66static int __init grant_dma_iommu_init(void)
67{
68	struct device_node *iommu_np;
69
70	iommu_np = of_find_matching_node(NULL, grant_dma_iommu_of_match);
71	if (!iommu_np)
72		return 0;
73
74	of_node_put(iommu_np);
75
76	return platform_driver_register(&grant_dma_iommu_driver);
77}
78subsys_initcall(grant_dma_iommu_init);