iommu: provide helper function to configure an IOMMU for an of master

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.

Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Joerg Roedel <jroedel@suse.de>
Acked-by: Marek Szyprowski <m.szyprowski@samsung.com>
Tested-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

3 files changed, 40 insertions, 1 deletions

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 89b903406968..73236d3cc955 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>
@@ -93,6 +94,38 @@ int of_get_dma_window(struct device_node *dn, const char *prefix, int index,
 }
 EXPORT_SYMBOL_GPL(of_get_dma_window);
 
+struct iommu_ops *of_iommu_configure(struct device *dev)
+{
+        struct of_phandle_args iommu_spec;
+        struct device_node *np;
+        struct iommu_ops *ops = NULL;
+        int idx = 0;
+
+        /*
+         * 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)) {
+                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;
diff --git a/include/linux/of_iommu.h b/include/linux/of_iommu.h
index 5762cdc8effe..d03abbb11c34 100644
--- a/include/linux/of_iommu.h
+++ b/include/linux/of_iommu.h
@@ -1,6 +1,7 @@
 #ifndef __OF_IOMMU_H
 #define __OF_IOMMU_H
 
+#include <linux/device.h>
 #include <linux/iommu.h>
 #include <linux/of.h>
 
@@ -11,6 +12,7 @@ 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_ops *of_iommu_configure(struct device *dev);
 
 #else
 
@@ -22,6 +24,10 @@ 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_ops *of_iommu_configure(struct device *dev)
+{
+        return NULL;
+}
 
 #endif  /* CONFIG_OF_IOMMU */