[PATCH v9 2/5] iommu: Implement of_iommu_get_resv_regions()

[Thierry Reding <thierry.reding@gmail.com>]

From: Thierry Reding <treding@nvidia.com>

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.

Cc: Frank Rowand <frowand.list@gmail.com>
Cc: devicetree@vger.kernel.org
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Thierry Reding <treding@nvidia.com>
---
Changes in v9:
- address review comments by Robin Murphy:
  - warn about non-direct mappings since they are not supported yet
  - cleanup code to require less indentation
  - narrow scope of variables

Changes in v8:
- cleanup set-but-unused variables

Changes in v6:
- remove reference to now unused dt-bindings/reserved-memory.h include

Changes in v5:
- update for new "iommu-addresses" device tree bindings

Changes in v4:
- fix build failure on !CONFIG_OF_ADDRESS

Changes in v3:
- change "active" property to identity mapping flag that is part of the
  memory region specifier (as defined by #memory-region-cells) to allow
  per-reference flags to be used

Changes in v2:
- use "active" property to determine whether direct mappings are needed

 drivers/iommu/of_iommu.c | 104 +++++++++++++++++++++++++++++++++++++++
 include/linux/of_iommu.h |   8 +++
 2 files changed, 112 insertions(+)

diff --git a/drivers/iommu/of_iommu.c b/drivers/iommu/of_iommu.c
index 5696314ae69e..0bf2b08bca0a 100644
--- a/drivers/iommu/of_iommu.c
+++ b/drivers/iommu/of_iommu.c
@@ -11,6 +11,7 @@
 #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>
@@ -172,3 +173,106 @@ const struct iommu_ops *of_iommu_configure(struct device *dev,
 
 	return ops;
 }
+
+static inline bool check_direct_mapping(struct device *dev, struct resource *phys,
+					phys_addr_t start, phys_addr_t end)
+{
+	if (start != phys->start || end != phys->end) {
+		dev_warn(dev, "treating non-direct mapping [%pr] -> [%pap-%pap] as reservation\n",
+			 &phys, &start, &end);
+		return false;
+	}
+
+	return true;
+}
+
+/**
+ * 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) {
+		const __be32 *maps, *end;
+		struct resource res;
+		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)
+			continue;
+
+		end = maps + size / sizeof(__be32);
+
+		while (maps < end) {
+			struct device_node *np;
+			u32 phandle;
+			int na, ns;
+
+			phandle = be32_to_cpup(maps++);
+			np = of_find_node_by_phandle(phandle);
+			na = of_n_addr_cells(np);
+			ns = of_n_size_cells(np);
+
+			if (np == dev->of_node) {
+				int prot = IOMMU_READ | IOMMU_WRITE;
+				struct iommu_resv_region *region;
+				enum iommu_resv_type type;
+				phys_addr_t start;
+				size_t length;
+
+				start = of_translate_dma_address(np, maps);
+				length = of_read_number(maps + na, ns);
+
+				/*
+				 * IOMMU regions without an associated physical region cannot be
+				 * mapped and are simply reservations.
+				 */
+				if (res.end > res.start) {
+					phys_addr_t end = start + length - 1;
+
+					if (check_direct_mapping(dev, &res, start, end))
+						type = IOMMU_RESV_DIRECT_RELAXABLE;
+					else
+						type = IOMMU_RESV_RESERVED;
+				} 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;
+		}
+	}
+#endif
+}
+EXPORT_SYMBOL(of_iommu_get_resv_regions);
diff --git a/include/linux/of_iommu.h b/include/linux/of_iommu.h
index 55c1eb300a86..9a5e6b410dd2 100644
--- a/include/linux/of_iommu.h
+++ b/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 */
-- 
2.37.3