SPRUJ28E November 2021 – September 2024 AM68 , AM68A , TDA4AL-Q1 , TDA4VE-Q1 , TDA4VL-Q1
To support quality of service, QoS, the north bridge allows for configuring multiple VBUSM source interfaces. This not only allows defining particular sources to be realtime to achieve better qos, but also to load balance and effectively utilize any extra bandwidth provided by the VBUSM.C interface. There are registers (NB_THREADMAP) allowing programming of which source interfaces map to which of the two VBUSM.C threads, normal or realtime traffic. All traffic on the source will always map to the defined thread.
Any sources mapped to the realtime thread will be arbitrated first, before any sources mapped to the normal thread, to provide the QoS. If there are multiple sources mapped to the same thread then they are arbitrated based on priority and if they are the same priority then by round robin.
To route return traffic from the VBUSM.C back to the correct VBUSM source, the orderid is used. As such, each source mapped to each thread must use a different orderid value in the SoC. This would mean that if there are 8 sources total, with 4 mapped to each thread, then each group of 4 should not share the same orderid for any traffic routed to it in the SoC to keep their pathid values unique. The bridge is configured to identify which VBUSM source uses which orderid value(s).