iommu: Ignore -ENODEV errors from add_device call-back

The -ENODEV error just means that the device is not
translated by an IOMMU. We shouldn't bail out of iommu
driver initialization when that happens, as this is a common
scenario on ARM.

Not returning -ENODEV in the drivers would be a bad idea, as
the IOMMU core would have no indication whether a device is
translated or not. This indication is not used at the
moment, but will probably be in the future.

Fixes: 19762d70 ("iommu: Propagate error in add_iommu_group")
Tested-by: NMarek Szyprowski <m.szyprowski@samsung.com>
Tested-by: NEric Auger <eric.auger@linaro.org>
Tested-by: NHeiko Stuebner <heiko@sntech.de>
Signed-off-by: NJoerg Roedel <jroedel@suse.de>

drivers/iommu/iommu.c

@@ -847,13 +847,24 @@ static int add_iommu_group(struct device *dev, void *data)
 {
 	struct iommu_callback_data *cb = data;
 	const struct iommu_ops *ops = cb->ops;
+	int ret;
 
 	if (!ops->add_device)
 		return 0;
 
 	WARN_ON(dev->iommu_group);
 
-	return ops->add_device(dev);
+	ret = ops->add_device(dev);
+
+	/*
+	 * We ignore -ENODEV errors for now, as they just mean that the
+	 * device is not translated by an IOMMU. We still care about
+	 * other errors and fail to initialize when they happen.
+	 */
+	if (ret == -ENODEV)
+		ret = 0;
+
+	return ret;
 }
 
 static int remove_iommu_group(struct device *dev, void *data)