The Arm Coresight Trace Funnel (CSTF) is an optional Arm Coresight component which can be used to funnel multiple trace data sources to one trace stream. Typical setups are where the ETM and ITM of a core are funneled together or when multi-core devices are used and the trace sources are spread across the different cores. The funneled data is then passed on to a TPIU.
SiFive Nexus Trace
The trace funnel in the SiFive Nexus Trace specification has the same function as it does for Arm tracing. It funnels multiple data sources together. Usually used on multi core devices where trace data can be generated from multiple cores. The funneled data is the passed on to the trace sink which can be SRAM or trace pins.