linux-kernel - [PATCH v2 2/4] iommu: Implement of_iommu_get_resv

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Date:   Fri,  4 Sep 2020 14:59:58 +0200
From:   Thierry Reding <thierry.reding@...il.com>
To:     Joerg Roedel <joro@...tes.org>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        iommu@...ts.linux-foundation.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2 2/4] iommu: Implement of_iommu_get_resv_regions()

From: Thierry Reding <treding@...dia.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. These
regions will be used to create 1:1 mappings in the IOMMU domain that
the devices will be attached to.

Cc: Frank Rowand <frowand.list@...il.com>
Cc: devicetree@...r.kernel.org
Signed-off-by: Thierry Reding <treding@...dia.com>
---
Hi Rob,

you had previously reviewed this patch, but I haven't included that here
because there's a new property now that you might not be okay with.

Thierry

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

 drivers/iommu/of_iommu.c | 49 ++++++++++++++++++++++++++++++++++++++++
 include/linux/of_iommu.h |  8 +++++++
 2 files changed, 57 insertions(+)

diff --git a/drivers/iommu/of_iommu.c b/drivers/iommu/of_iommu.c
index e505b9130a1c..3341d27fbbba 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>
@@ -245,3 +246,51 @@ 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)
+{
+	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;
+
+		/*
+		 * Active memory regions are expected to be accessed by
+		 * hardware during boot and must therefore have an identity
+		 * mapping created prior to the driver taking control of the
+		 * hardware. This ensures that non-quiescent hardware doesn't
+		 * cause IOMMU faults during boot.
+		 */
+		if (!of_property_read_bool(it.node, "active"))
+			continue;
+
+		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;
+		}
+
+		region = iommu_alloc_resv_region(res.start, resource_size(&res),
+						 IOMMU_READ | IOMMU_WRITE,
+						 IOMMU_RESV_DIRECT_RELAXABLE);
+		if (!region)
+			continue;
+
+		list_add_tail(&region->list, list);
+	}
+}
+EXPORT_SYMBOL(of_iommu_get_resv_regions);
diff --git a/include/linux/of_iommu.h b/include/linux/of_iommu.h
index 16f4b3e87f20..8412437acaac 100644
--- a/include/linux/of_iommu.h
+++ b/include/linux/of_iommu.h
@@ -16,6 +16,9 @@ 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 int of_get_dma_window(struct device_node *dn, const char *prefix,
@@ -32,6 +35,11 @@ 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 */
-- 
2.28.0