There are six TBUs supported by the SMMU TCU. These are listed in Table: System Masters with their system masters.
The SMMU uses a 15-bit stream ID to perform address translations. This information is part of a transaction and indicates which master originated the request. Bits [9:0] of the stream ID are the master ID defined in Table: Master IDs List. Bits [14:10] are the TBU number the master transaction passes through. For example, for the GEM0 PS master, its master ID is 10'h074 and its TBU number is 5'h02. Concatenating these fields gives GEM0 a stream ID of 15'h0874.