[RFC PATCH v3 7/7] arm: dma-mapping: plumb our iommu mapping ops into arch_setup_dma_ops

[Will Deacon]

This patch plumbs the existing ARM IOMMU DMA infrastructure (which isn't
actually called outside of a few drivers) into arch_setup_dma_ops, so
that we can use IOMMUs for DMA transfers in a more generic fashion.

Since this significantly complicates the arch_setup_dma_ops function,
it is moved out of line into dma-mapping.c. If CONFIG_ARM_DMA_USE_IOMMU
is not set, the iommu paramater is ignored and the normal ops are used
instead.

Signed-off-by: Will Deacon <will.deacon at arm.com>
---
 arch/arm/include/asm/dma-mapping.h |  9 ++---
 arch/arm/mm/dma-mapping.c          | 68 +++++++++++++++++++++++++++++++++-----
 2 files changed, 62 insertions(+), 15 deletions(-)

diff --git a/arch/arm/include/asm/dma-mapping.h b/arch/arm/include/asm/dma-mapping.h
index a8bb0c494bb3..e1cd4445c100 100644
--- a/arch/arm/include/asm/dma-mapping.h
+++ b/arch/arm/include/asm/dma-mapping.h
@@ -121,14 +121,9 @@ static inline unsigned long dma_max_pfn(struct device *dev)
 }
 #define dma_max_pfn(dev) dma_max_pfn(dev)
 
-static inline void arch_setup_dma_ops(struct device *dev, u64 dma_base,
-				      u64 size, struct iommu_dma_mapping *iommu,
-				      bool coherent)
-{
-	if (coherent)
-		set_dma_ops(dev, &arm_coherent_dma_ops);
-}
 #define arch_setup_dma_ops arch_setup_dma_ops
+extern void arch_setup_dma_ops(struct device *dev, u64 dma_base, u64 size,
+			       struct iommu_dma_mapping *iommu, bool coherent);
 
 static inline dma_addr_t phys_to_dma(struct device *dev, phys_addr_t paddr)
 {
diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index 7a996aaa061e..bcd5f836f27e 100644
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c
@@ -2041,10 +2041,9 @@ EXPORT_SYMBOL_GPL(arm_iommu_release_mapping);
  * @mapping: io address space mapping structure (returned from
  *	arm_iommu_create_mapping)
  *
- * Attaches specified io address space mapping to the provided device,
- * this replaces the dma operations (dma_map_ops pointer) with the
- * IOMMU aware version. More than one client might be attached to
- * the same io address space mapping.
+ * Attaches specified io address space mapping to the provided device.
+ * More than one client might be attached to the same io address space
+ * mapping.
  */
 int arm_iommu_attach_device(struct device *dev,
 			    struct dma_iommu_mapping *mapping)
@@ -2057,7 +2056,6 @@ int arm_iommu_attach_device(struct device *dev,
 
 	kref_get(&mapping->kref);
 	dev->archdata.mapping = mapping;
-	set_dma_ops(dev, &iommu_ops);
 
 	pr_debug("Attached IOMMU controller to %s device.\n", dev_name(dev));
 	return 0;
@@ -2069,7 +2067,6 @@ EXPORT_SYMBOL_GPL(arm_iommu_attach_device);
  * @dev: valid struct device pointer
  *
  * Detaches the provided device from a previously attached map.
- * This voids the dma operations (dma_map_ops pointer)
  */
 void arm_iommu_detach_device(struct device *dev)
 {
@@ -2084,10 +2081,65 @@ void arm_iommu_detach_device(struct device *dev)
 	iommu_detach_device(mapping->domain, dev);
 	kref_put(&mapping->kref, release_iommu_mapping);
 	dev->archdata.mapping = NULL;
-	set_dma_ops(dev, NULL);
 
 	pr_debug("Detached IOMMU controller from %s device.\n", dev_name(dev));
 }
 EXPORT_SYMBOL_GPL(arm_iommu_detach_device);
 
-#endif
+static bool arm_setup_iommu_dma_ops(struct device *dev, u64 dma_base, u64 size)
+{
+	struct dma_iommu_mapping *mapping;
+
+	mapping = arm_iommu_create_mapping(dev->bus, dma_base, size);
+	if (IS_ERR(mapping)) {
+		pr_warn("Failed to create %llu-byte IOMMU mapping for device %s\n",
+				size, dev_name(dev));
+		return false;
+	}
+
+	if (arm_iommu_attach_device(dev, mapping)) {
+		pr_warn("Failed to attach device %s to IOMMU mapping\n",
+				dev_name(dev));
+		arm_iommu_release_mapping(mapping);
+		return false;
+	}
+
+	return true;
+}
+
+static struct dma_map_ops *arm_get_iommu_dma_map_ops(bool coherent)
+{
+	return coherent ? &iommu_coherent_ops : &iommu_ops;
+}
+
+#else
+
+static bool arm_setup_iommu_dma_ops(struct device *dev, u64 dma_base, u64 size)
+{
+	return false;
+}
+
+#define arm_get_iommu_dma_map_ops arm_get_dma_map_ops
+
+#endif /* CONFIG_ARM_DMA_USE_IOMMU */
+
+static struct dma_map_ops *arm_get_dma_map_ops(bool coherent)
+{
+	return coherent ? &arm_coherent_dma_ops : &arm_dma_ops;
+}
+
+void arch_setup_dma_ops(struct device *dev, u64 dma_base, u64 size,
+			struct iommu_dma_mapping *iommu, bool coherent)
+{
+	struct dma_map_ops *dma_ops;
+
+	if (iommu && arm_setup_iommu_dma_ops(dev, dma_base, size)) {
+		dev->dma_pfn_offset = 0;
+		dma_ops = arm_get_iommu_dma_map_ops(coherent);
+	} else {
+		dma_ops = arm_get_dma_map_ops(coherent);
+	}
+
+	set_dma_ops(dev, dma_ops);
+}
+EXPORT_SYMBOL_GPL(arch_setup_dma_ops);
-- 
2.1.0