diff --git a/drivers/acpi/arm64/iort.c b/drivers/acpi/arm64/iort.c
index 95255ecfae7c..a84a5787bbd2 100644
--- a/drivers/acpi/arm64/iort.c
+++ b/drivers/acpi/arm64/iort.c
@@ -366,7 +366,6 @@ static struct acpi_iort_node *iort_node_get_id(struct acpi_iort_node *node,
 	return NULL;
 }
 
-#if (ACPI_CA_VERSION > 0x20170929)
 static int iort_get_id_mapping_index(struct acpi_iort_node *node)
 {
 	struct acpi_iort_smmu_v3 *smmu;
@@ -400,12 +399,6 @@ static int iort_get_id_mapping_index(struct acpi_iort_node *node)
 		return -EINVAL;
 	}
 }
-#else
-static inline int iort_get_id_mapping_index(struct acpi_iort_node *node)
-{
-	return -EINVAL;
-}
-#endif
 
 static struct acpi_iort_node *iort_node_map_id(struct acpi_iort_node *node,
 					       u32 id_in, u32 *id_out,