[RFC PATCH v2 4/7] iommu: provide helper function to configure an IOMMU for an of master

[Will Deacon]

The generic IOMMU device-tree bindings can be used to add arbitrary OF
masters to an IOMMU with a compliant binding.

This patch introduces of_iommu_configure, which does exactly that.

Signed-off-by: Will Deacon <will.deacon at arm.com>
---
 drivers/iommu/Kconfig       |  2 +-
 drivers/iommu/of_iommu.c    | 52 +++++++++++++++++++++++++++++++++++++++++++++
 include/linux/dma-mapping.h |  7 ++++++
 include/linux/of_iommu.h    |  8 +++++++
 4 files changed, 68 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
index dd5112265cc9..6d13f962f156 100644
--- a/drivers/iommu/Kconfig
+++ b/drivers/iommu/Kconfig
@@ -15,7 +15,7 @@ if IOMMU_SUPPORT
 
 config OF_IOMMU
        def_bool y
-       depends on OF
+       depends on OF && IOMMU_API
 
 config FSL_PAMU
 	bool "Freescale IOMMU support"
diff --git a/drivers/iommu/of_iommu.c b/drivers/iommu/of_iommu.c
index f9209666157c..1188c929ffa7 100644
--- a/drivers/iommu/of_iommu.c
+++ b/drivers/iommu/of_iommu.c
@@ -18,6 +18,7 @@
  */
 
 #include <linux/export.h>
+#include <linux/iommu.h>
 #include <linux/limits.h>
 #include <linux/of.h>
 #include <linux/of_iommu.h>
@@ -90,6 +91,57 @@ int of_get_dma_window(struct device_node *dn, const char *prefix, int index,
 }
 EXPORT_SYMBOL_GPL(of_get_dma_window);
 
+struct iommu_dma_mapping *of_iommu_configure(struct device *dev)
+{
+	struct of_phandle_args iommu_spec;
+	struct iommu_dma_mapping *mapping;
+	struct bus_type *bus = dev->bus;
+	const struct iommu_ops *ops = bus->iommu_ops;
+	struct iommu_data *iommu = NULL;
+	int idx = 0;
+
+	if (!iommu_present(bus) || !ops->of_xlate)
+		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(dev->of_node, "iommus",
+					   "#iommu-cells", idx,
+					   &iommu_spec)) {
+		struct device_node *np = iommu_spec.np;
+		struct iommu_data *data = of_iommu_get_data(np);
+
+		if (!iommu) {
+			if (!ops->of_xlate(dev, &iommu_spec))
+				iommu = data;
+		} else if (iommu != data) {
+			pr_warn("Rejecting device %s with multiple IOMMU instances\n",
+				dev_name(dev));
+			iommu = NULL;
+		}
+
+		of_node_put(np);
+
+		if (!iommu)
+			break;
+
+		idx++;
+	}
+
+	if (!iommu)
+		return NULL;
+
+	mapping = devm_kzalloc(dev, sizeof(*mapping), GFP_KERNEL);
+	if (!mapping)
+		return NULL;
+
+	mapping->iommu = iommu;
+	return mapping;
+}
+
 void __init of_iommu_init(void)
 {
 	struct device_node *np;
diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index 0f7f7b68b0db..16bf92f71c3e 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -62,6 +62,13 @@ struct dma_map_ops {
 	int is_phys;
 };
 
+struct iommu_data;
+
+struct iommu_dma_mapping {
+	struct iommu_data *iommu;
+	struct list_head node;
+};
+
 #define DMA_BIT_MASK(n)	(((n) == 64) ? ~0ULL : ((1ULL<<(n))-1))
 
 #define DMA_MASK_NONE	0x0ULL
diff --git a/include/linux/of_iommu.h b/include/linux/of_iommu.h
index a39e2d78f735..f2d3b1e780d7 100644
--- a/include/linux/of_iommu.h
+++ b/include/linux/of_iommu.h
@@ -1,9 +1,12 @@
 #ifndef __OF_IOMMU_H
 #define __OF_IOMMU_H
 
+#include <linux/device.h>
 #include <linux/iommu.h>
 #include <linux/of.h>
 
+struct iommu_dma_mapping;
+
 #ifdef CONFIG_OF_IOMMU
 
 extern int of_get_dma_window(struct device_node *dn, const char *prefix,
@@ -11,6 +14,7 @@ extern int of_get_dma_window(struct device_node *dn, const char *prefix,
 			     size_t *size);
 
 extern void of_iommu_init(void);
+extern struct iommu_dma_mapping *of_iommu_configure(struct device *dev);
 
 #else
 
@@ -22,6 +26,10 @@ static inline int of_get_dma_window(struct device_node *dn, const char *prefix,
 }
 
 static inline void of_iommu_init(void) { }
+static inline struct iommu_dma_mapping *of_iommu_configure(struct device *dev)
+{
+	return NULL;
+}
 
 #endif	/* CONFIG_OF_IOMMU */
 
-- 
2.1.0