IHI_0070_C_a_System_Memory_Management_Unit_Arm_Architecture_Specification.pdf

arm smmu spec.

A System Memory Management Unit (SMMU) performs a task that is analogous to that of an MMU in a PE,
translating addresses for DMA requests from system I/O devices before the requests are passed into the system
interconnect. It is active for DMA only. Traffic in the other direction, from the system or PE to the device, is
managed by other means – for example, the PE MMUs.