iommu: apple-dart: Check for fwspec in the device probe path

We need to check for a fwspec in the probe path, to ensure that the
driver does not probe as a bus iommu driver. This, along with related
fixes to the IOMMU core code, fixes races and issues when multiple
IOMMUs assigned to the same device probe at different times.

Suggested-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Hector Martin <marcan@marcan.st>
iommu: apple-dart:

Author: marcan

drivers/iommu/apple-dart.c

@@ -776,7 +776,7 @@ static struct iommu_device *apple_dart_probe_device(struct device *dev)
 	struct apple_dart_stream_map *stream_map;
 	int i;
 
-	if (!cfg)
+	if (!dev_iommu_fwspec_get(dev) || !cfg)
 		return ERR_PTR(-ENODEV);
 
 	for_each_stream_map(i, cfg, stream_map)