iommu: apple-dart: Disallow identity domains for locked DARTs

The register controlling bypass support is read-only for locked DARTs.
In addition trnaslation can not be disabled so blocking domain has to be
implemented with an empty translation table.

Signed-off-by: Janne Grunau <j@jannau.net>

Author: jannau

drivers/iommu/apple-dart.c

@@ -865,6 +865,9 @@ static int apple_dart_attach_dev_identity(struct iommu_domain *domain,
 	if (!cfg->supports_bypass)
 		return -EINVAL;
 
+	if (cfg->locked)
+		return -EINVAL;
+
 	for_each_stream_map(i, cfg, stream_map)
 		WARN_ON(pm_runtime_get_sync(stream_map->dart->dev) < 0);
 
@@ -892,6 +895,9 @@ static int apple_dart_attach_dev_blocked(struct iommu_domain *domain,
 	struct apple_dart_stream_map *stream_map;
 	int i;
 
+	if (cfg->locked)
+		return -EINVAL;
+
 	for_each_stream_map(i, cfg, stream_map)
 		WARN_ON(pm_runtime_get_sync(stream_map->dart->dev) < 0);