SPRUIV7B May 2022 – September 2023 AM620-Q1 , AM623 , AM625 , AM625-Q1 , AM625SIP
A proxy provides a mechanism for software to access the RINGACC coherently when the processor does not support large bursts. The RINGACC requires a single burst for each operation so that it maintains atomicity and coherence by relying on the atomicity of the bursts on the bus interconnect fabric, since it only delivers a single burst to the RINGACC before the next. Since processors are usually limited in the size of a burst they can deliver natively, such as 32 to 128 bits, they cannot be used directly with the data access region of the RINGACC for larger element sizes. The proxy solves this gap by providing a temporary space for the software to form a larger burst of data before it is sent to the RINGACC. The proxy allows smaller processor accesses to the data and only forwards to the RINGACC when the entire data burst is complete, as directed by the software.
Each proxy hardware can support multiple threads of software (whether on the same or different processors) operating on bursts at the same time, and they do not interfere with each other, as long as each thread of software only operates on its thread in the proxy. Each proxy thread also supports access to any RINGACC queue via different offsets similar to how the RINGACC provides access to the queues via different offsets.
A special version of a proxy is the Secure Proxy that provides secured access to RINGACC queues for communication to the security initiator of the system. It provides basically the same function as a normal proxy. The data burst size is fixed for message sizes to the security initiator, so there is no support for all the element sizes of the RINGACC. The security initiator locks down the RINGACC queue to access and direction for each proxy thread so that the software cannot access anything they shouldn’t, so the software only sees a single queue (unlike the normal proxy), and any attempts to access another queue or access it in violation of how the security initiator defined and an error will be flagged. This allows for a much more controlled setup for passing messages to the security initiator.