--- zzzz-none-000/linux-3.18.24/drivers/iommu/of_iommu.c	2015-10-31 20:39:51.000000000 +0000
+++ rtl96-5690pro-762/linux-3.18.24/drivers/iommu/of_iommu.c	2024-08-14 08:36:36.000000000 +0000
@@ -18,9 +18,14 @@
  */
 
 #include <linux/export.h>
+#include <linux/iommu.h>
 #include <linux/limits.h>
 #include <linux/of.h>
 #include <linux/of_iommu.h>
+#include <linux/slab.h>
+
+static const struct of_device_id __iommu_of_table_sentinel
+	__used __section(__iommu_of_table_end);
 
 /**
  * of_get_dma_window - Parse *dma-window property and returns 0 if found.
@@ -89,3 +94,93 @@
 	return 0;
 }
 EXPORT_SYMBOL_GPL(of_get_dma_window);
+
+struct of_iommu_node {
+	struct list_head list;
+	struct device_node *np;
+	struct iommu_ops *ops;
+};
+static LIST_HEAD(of_iommu_list);
+static DEFINE_SPINLOCK(of_iommu_lock);
+
+void of_iommu_set_ops(struct device_node *np, struct iommu_ops *ops)
+{
+	struct of_iommu_node *iommu = kzalloc(sizeof(*iommu), GFP_KERNEL);
+
+	if (WARN_ON(!iommu))
+		return;
+
+	INIT_LIST_HEAD(&iommu->list);
+	iommu->np = np;
+	iommu->ops = ops;
+	spin_lock(&of_iommu_lock);
+	list_add_tail(&iommu->list, &of_iommu_list);
+	spin_unlock(&of_iommu_lock);
+}
+
+struct iommu_ops *of_iommu_get_ops(struct device_node *np)
+{
+	struct of_iommu_node *node;
+	struct iommu_ops *ops = NULL;
+
+	spin_lock(&of_iommu_lock);
+	list_for_each_entry(node, &of_iommu_list, list)
+		if (node->np == np) {
+			ops = node->ops;
+			break;
+		}
+	spin_unlock(&of_iommu_lock);
+	return ops;
+}
+
+struct iommu_ops *of_iommu_configure(struct device *dev,
+				     struct device_node *master_np)
+{
+	struct of_phandle_args iommu_spec;
+	struct device_node *np;
+	struct iommu_ops *ops = NULL;
+	int idx = 0;
+
+	if (dev_is_pci(dev)) {
+		dev_err(dev, "IOMMU is currently not supported for PCI\n");
+		return NULL;
+	}
+
+	/*
+	 * We don't currently walk up the tree looking for a parent IOMMU.
+	 * See the `Notes:' section of
+	 * Documentation/devicetree/bindings/iommu/iommu.txt
+	 */
+	while (!of_parse_phandle_with_args(master_np, "iommus",
+					   "#iommu-cells", idx,
+					   &iommu_spec)) {
+		np = iommu_spec.np;
+		ops = of_iommu_get_ops(np);
+
+		if (!ops || !ops->of_xlate || ops->of_xlate(dev, &iommu_spec))
+			goto err_put_node;
+
+		of_node_put(np);
+		idx++;
+	}
+
+	return ops;
+
+err_put_node:
+	of_node_put(np);
+	return NULL;
+}
+
+void __init of_iommu_init(void)
+{
+	struct device_node *np;
+	const struct of_device_id *match, *matches = &__iommu_of_table;
+
+	for_each_matching_node_and_match(np, matches, &match) {
+		const of_iommu_init_fn init_fn = match->data;
+
+		if (init_fn(np))
+			pr_err("Failed to initialise IOMMU %s\n",
+				of_node_full_name(np));
+	}
+}