iommu: Implement of_iommu_get_resv_regions()

This is an implementation that IOMMU drivers can use to obtain reserved
memory regions from a device tree node. It uses the reserved-memory DT
bindings to find the regions associated with a given device. If these
regions are marked accordingly, identity mappings will be created for
them in the IOMMU domain that the devices will be attached to.

Signed-off-by: Thierry Reding <treding@nvidia.com>

drivers/iommu/of_iommu.c

@@ -11,12 +11,15 @@
 #include <linux/module.h>
 #include <linux/msi.h>
 #include <linux/of.h>
+#include <linux/of_address.h>
 #include <linux/of_iommu.h>
 #include <linux/of_pci.h>
 #include <linux/pci.h>
 #include <linux/slab.h>
 #include <linux/fsl/mc.h>
 
+#include <dt-bindings/reserved-memory.h>
+
 #define NO_IOMMU	1
 
 static int of_iommu_xlate(struct device *dev,
@@ -172,3 +175,90 @@ const struct iommu_ops *of_iommu_configure(struct device *dev,
 
 	return ops;
 }
+
+/**
+ * of_iommu_get_resv_regions - reserved region driver helper for device tree
+ * @dev: device for which to get reserved regions
+ * @list: reserved region list
+ *
+ * IOMMU drivers can use this to implement their .get_resv_regions() callback
+ * for memory regions attached to a device tree node. See the reserved-memory
+ * device tree bindings on how to use these:
+ *
+ *   Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt
+ */
+void of_iommu_get_resv_regions(struct device *dev, struct list_head *list)
+{
+#if IS_ENABLED(CONFIG_OF_ADDRESS)
+	struct of_phandle_iterator it;
+	int err;
+
+	of_for_each_phandle(&it, err, dev->of_node, "memory-region", NULL, 0) {
+		struct iommu_resv_region *region;
+		struct resource res;
+		const __be32 *maps;
+		int size;
+
+		memset(&res, 0, sizeof(res));
+
+		/*
+		 * The "reg" property is optional and can be omitted by reserved-memory regions
+		 * that represent reservations in the IOVA space, which are regions that should
+		 * not be mapped.
+		 */
+		if (of_find_property(it.node, "reg", NULL)) {
+			err = of_address_to_resource(it.node, 0, &res);
+			if (err < 0) {
+				dev_err(dev, "failed to parse memory region %pOF: %d\n",
+					it.node, err);
+				continue;
+			}
+		}
+
+		maps = of_get_property(it.node, "iommu-addresses", &size);
+		if (maps) {
+			const __be32 *end = maps + size / sizeof(__be32);
+			struct device_node *np;
+			unsigned int index = 0;
+			u32 phandle;
+			int na, ns;
+
+			while (maps < end) {
+				phys_addr_t start, end;
+				size_t length;
+
+				phandle = be32_to_cpup(maps++);
+				np = of_find_node_by_phandle(phandle);
+				na = of_n_addr_cells(np);
+				ns = of_n_size_cells(np);
+
+				start = of_translate_dma_address(np, maps);
+				length = of_read_number(maps + na, ns);
+				end = start + length - 1;
+
+				if (np == dev->of_node) {
+					int prot = IOMMU_READ | IOMMU_WRITE;
+					enum iommu_resv_type type;
+
+					/*
+					 * IOMMU regions without an associated physical region
+					 * cannot be mapped and are simply reservations.
+					 */
+					if (res.end > res.start)
+						type = IOMMU_RESV_DIRECT_RELAXABLE;
+					else
+						type = IOMMU_RESV_RESERVED;
+
+					region = iommu_alloc_resv_region(start, length, prot, type);
+					if (region)
+						list_add_tail(&region->list, list);
+				}
+
+				maps += na + ns;
+				index++;
+			}
+		}
+	}
+#endif
+}
+EXPORT_SYMBOL(of_iommu_get_resv_regions);

include/linux/of_iommu.h

@@ -12,6 +12,9 @@ extern const struct iommu_ops *of_iommu_configure(struct device *dev,
 					struct device_node *master_np,
 					const u32 *id);
 
+extern void of_iommu_get_resv_regions(struct device *dev,
+				      struct list_head *list);
+
 #else
 
 static inline const struct iommu_ops *of_iommu_configure(struct device *dev,
@@ -21,6 +24,11 @@ static inline const struct iommu_ops *of_iommu_configure(struct device *dev,
 	return NULL;
 }
 
+static inline void of_iommu_get_resv_regions(struct device *dev,
+					     struct list_head *list)
+{
+}
+
 #endif	/* CONFIG_OF_IOMMU */
 
 #endif /* __OF_IOMMU_H */