iommu: Keep dev->iommu state consistent

At the moment, if of_iommu_configure() allocates dev->iommu itself via
iommu_fwspec_init(), then suffers a DT parsing failure, it cleans up the
fwspec but leaves the empty dev_iommu hanging around. So far this is
benign (if a tiny bit wasteful), but we'd like to be able to reason
about dev->iommu having a consistent and unambiguous lifecycle. Thus
make sure that the of_iommu cleanup undoes precisely whatever it did.

Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/d219663a3f23001f23d520a883ac622d70b4e642.1740753261.git.robin.murphy@arm.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>

drivers/iommu/iommu-priv.h

@@ -17,6 +17,8 @@ static inline const struct iommu_ops *dev_iommu_ops(struct device *dev)
 	return dev->iommu->iommu_dev->ops;
 }
 
+void dev_iommu_free(struct device *dev);
+
 const struct iommu_ops *iommu_ops_from_fwnode(const struct fwnode_handle *fwnode);
 
 static inline const struct iommu_ops *iommu_fwspec_ops(struct iommu_fwspec *fwspec)

drivers/iommu/iommu.c

@@ -355,7 +355,7 @@ static struct dev_iommu *dev_iommu_get(struct device *dev)
 	return param;
 }
 
-static void dev_iommu_free(struct device *dev)
+void dev_iommu_free(struct device *dev)
 {
 	struct dev_iommu *param = dev->iommu;
 

drivers/iommu/of_iommu.c

@@ -116,6 +116,7 @@ static void of_pci_check_device_ats(struct device *dev, struct device_node *np)
 int of_iommu_configure(struct device *dev, struct device_node *master_np,
 		       const u32 *id)
 {
+	bool dev_iommu_present;
 	int err;
 
 	if (!master_np)
@@ -127,6 +128,7 @@ int of_iommu_configure(struct device *dev, struct device_node *master_np,
 		mutex_unlock(&iommu_probe_device_lock);
 		return 0;
 	}
+	dev_iommu_present = dev->iommu;
 
 	/*
 	 * We don't currently walk up the tree looking for a parent IOMMU.
@@ -147,8 +149,10 @@ int of_iommu_configure(struct device *dev, struct device_node *master_np,
 		err = of_iommu_configure_device(master_np, dev, id);
 	}
 
-	if (err)
+	if (err && dev_iommu_present)
 		iommu_fwspec_free(dev);
+	else if (err && dev->iommu)
+		dev_iommu_free(dev);
 	mutex_unlock(&iommu_probe_device_lock);
 
 	if (!err && dev->bus)