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
19static 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 */
25static const struct iommu_ops grant_dma_iommu_ops = {
26	.probe_device = grant_dma_iommu_probe_device,
27};
28
29static const struct of_device_id grant_dma_iommu_of_match[] = {
30	{ .compatible = "xen,grant-dma" },
31	{ },
32};
33
34static 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
54static 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
64static 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
73static 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}
85subsys_initcall(grant_dma_iommu_init);
86