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1ca55d50e5
In order to reuse generic IOMMU device tree bindings by Xen grant DMA-mapping layer we need to add this stub driver from a fw_devlink perspective (grant-dma-ops cannot be converted into the proper IOMMU driver). Otherwise, just reusing IOMMU bindings (without having a corresponding driver) leads to the deferred probe timeout afterwards, because the IOMMU device never becomes available. This stub driver does nothing except registering empty iommu_ops, the upper layer "of_iommu" will treat this as NO_IOMMU condition and won't return -EPROBE_DEFER. As this driver is quite different from the most hardware IOMMU implementations and only needed in Xen guests, place it in drivers/xen directory. The subsequent commit will make use of it. Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com> Reviewed-by: Stefano Stabellini <sstabellini@kernel.org> Link: https://lore.kernel.org/r/1654197833-25362-7-git-send-email-olekstysh@gmail.com Signed-off-by: Juergen Gross <jgross@suse.com>
78 lines
1.7 KiB
C
78 lines
1.7 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Stub IOMMU driver which does nothing.
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* The main purpose of it being present is to reuse generic IOMMU device tree
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* bindings by Xen grant DMA-mapping layer.
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*
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* Copyright (C) 2022 EPAM Systems Inc.
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*/
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#include <linux/iommu.h>
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#include <linux/of.h>
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#include <linux/platform_device.h>
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struct grant_dma_iommu_device {
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struct device *dev;
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struct iommu_device iommu;
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};
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/* Nothing is really needed here */
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static const struct iommu_ops grant_dma_iommu_ops;
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static const struct of_device_id grant_dma_iommu_of_match[] = {
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{ .compatible = "xen,grant-dma" },
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{ },
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};
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static int grant_dma_iommu_probe(struct platform_device *pdev)
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{
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struct grant_dma_iommu_device *mmu;
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int ret;
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mmu = devm_kzalloc(&pdev->dev, sizeof(*mmu), GFP_KERNEL);
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if (!mmu)
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return -ENOMEM;
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mmu->dev = &pdev->dev;
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ret = iommu_device_register(&mmu->iommu, &grant_dma_iommu_ops, &pdev->dev);
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if (ret)
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return ret;
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platform_set_drvdata(pdev, mmu);
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return 0;
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}
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static int grant_dma_iommu_remove(struct platform_device *pdev)
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{
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struct grant_dma_iommu_device *mmu = platform_get_drvdata(pdev);
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platform_set_drvdata(pdev, NULL);
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iommu_device_unregister(&mmu->iommu);
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return 0;
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}
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static struct platform_driver grant_dma_iommu_driver = {
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.driver = {
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.name = "grant-dma-iommu",
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.of_match_table = grant_dma_iommu_of_match,
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},
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.probe = grant_dma_iommu_probe,
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.remove = grant_dma_iommu_remove,
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};
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static int __init grant_dma_iommu_init(void)
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{
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struct device_node *iommu_np;
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iommu_np = of_find_matching_node(NULL, grant_dma_iommu_of_match);
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if (!iommu_np)
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return 0;
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of_node_put(iommu_np);
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return platform_driver_register(&grant_dma_iommu_driver);
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}
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subsys_initcall(grant_dma_iommu_init);
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