arm: dma-mapping: Set DMA IOMMU ops in arm_iommu_attach_device()

Commit 4bb25789ed28228a ("arm: dma-mapping: plumb our iommu mapping ops
into arch_setup_dma_ops") moved the setting of the DMA operations from
arm_iommu_attach_device() to arch_setup_dma_ops() where the DMA
operations to be used are selected based on whether the device is
connected to an IOMMU. However, the IOMMU detection scheme requires the
IOMMU driver to be ported to the new IOMMU of_xlate API. As no driver
has been ported yet, this effectively breaks all IOMMU ARM users that
depend on the IOMMU being handled transparently by the DMA mapping API.

Fix this by restoring the setting of DMA IOMMU ops in
arm_iommu_attach_device() and splitting the rest of the function into a
new internal __arm_iommu_attach_device() function, called by
arch_setup_dma_ops().

Signed-off-by: Laurent Pinchart <[e-mail]>
Acked-by: Will Deacon <[e-mail]>
Tested-by: Heiko Stuebner <[e-mail]>
Signed-off-by: Olof Johansson <[e-mail]>

arch/arm/mm/dma-mapping.c

···
 }
 EXPORT_SYMBOL_GPL(arm_iommu_release_mapping);
 
-/**
- * arm_iommu_attach_device
- * @dev: valid struct device pointer
- * @mapping: io address space mapping structure (returned from
- *	arm_iommu_create_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)
+static int __arm_iommu_attach_device(struct device *dev,
+				     struct dma_iommu_mapping *mapping)
 {
 	int err;
 
···
 	pr_debug("Attached IOMMU controller to %s device.\n", dev_name(dev));
 	return 0;
 }
-EXPORT_SYMBOL_GPL(arm_iommu_attach_device);
 
 /**
- * arm_iommu_detach_device
+ * arm_iommu_attach_device
  * @dev: valid struct device pointer
+ * @mapping: io address space mapping structure (returned from
+ *	arm_iommu_create_mapping)
  *
- * Detaches the provided device from a previously attached map.
+ * 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.
  */
-void arm_iommu_detach_device(struct device *dev)
+int arm_iommu_attach_device(struct device *dev,
+			    struct dma_iommu_mapping *mapping)
+{
+	int err;
+
+	err = __arm_iommu_attach_device(dev, mapping);
+	if (err)
+		return err;
+
+	set_dma_ops(dev, &iommu_ops);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(arm_iommu_attach_device);
+
+static void __arm_iommu_detach_device(struct device *dev)
 {
 	struct dma_iommu_mapping *mapping;
 
···
 	dev->archdata.mapping = NULL;
 
 	pr_debug("Detached IOMMU controller from %s device.\n", dev_name(dev));
+}
+
+/**
+ * arm_iommu_detach_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)
+{
+	__arm_iommu_detach_device(dev);
+	set_dma_ops(dev, NULL);
 }
 EXPORT_SYMBOL_GPL(arm_iommu_detach_device);
 
···
 		return false;
 	}
 
-	if (arm_iommu_attach_device(dev, mapping)) {
+	if (__arm_iommu_attach_device(dev, mapping)) {
 		pr_warn("Failed to attached device %s to IOMMU_mapping\n",
 				dev_name(dev));
 		arm_iommu_release_mapping(mapping);
···
 {
 	struct dma_iommu_mapping *mapping = dev->archdata.mapping;
 
-	arm_iommu_detach_device(dev);
+	__arm_iommu_detach_device(dev);
 	arm_iommu_release_mapping(mapping);
 }