System and method for scalable trace unit timestamping
An integrated circuit includes a trace subsystem that provides timestamps for events occurring in a trace source that does not natively support time stamping trace data. A timestamp inserter is coupled to such a trace source. The timestamp inserter generates a modified trace data stream by arranging a reference or references with the trace information from the trace source on a trace bus. A trace destination receives the modified trace data stream including the reference(s). In some embodiments, a timestamp inserter receives a timestamp request and stores a reference in a buffer. Upon later receipt of trace information associated with the request, the timestamp inserter inserts the reference, a current reference and the received trace information into the trace data stream.
1. A system for providing timestamps from trace sources that do not natively support time stamping trace data, the system comprising:
a trace source arranged to communicate trace information using a trace protocol that does not support a timestamp;
a timestamp inserter coupled to the trace source via a trace bus and responsive to a timestamp request associated with a trace data generated by the trace source, the timestamp inserter configured to:
forward a first current reference to a trace destination in response to receipt of the timestamp request;
monitor the trace bus for arrival of the trace data;
upon arrival of the trace data, modify the trace data to include the first current reference and a second current reference; and
forward the modified trace data to the trace destination;
wherein the trace source and the timestamp inserter are arranged on an integrated circuit; and
wherein the modified trace data is useful for correcting timing error resulting from the trace data residing in the trace destination.
2. The system of claim 1 , wherein the trace source is a hardware core trace unit.
3. The system of claim 2 , wherein the trace information is interleaved with additional trace information from at least one additional source of trace information.
4. The system of claim 3 , wherein the trace protocol used by the trace source is different from a second trace protocol used by the at least one additional source of trace information.
5. The system of claim 1 , wherein the trace source communicates the timestamp request.
6. The system of claim 5 , wherein the trace source waits for an acknowledgement signal before communicating the trace information to the timestamp inserter.
7. The system of claim 6 , wherein the trace source communicates an identifier with the trace information.
8. The system of claim 1 , wherein the trace destination is a first-in first-out buffer.
9. The system of claim 1 , wherein the first current reference and the second current reference are counts generated from a system clock signal.
10. The system of claim 1 , wherein the trace destination is a trace sink.
11. The system of claim 10 , wherein the trace sink is selected from the group consisting of a trace protocol interface unit (TPIU), a universal serial bus (USB), a double-data rate (DDR) bus, a peripheral component interconnect express (PCIe) interface and a memory element.
12. The system of claim 1 , wherein the timestamp inserter is arranged with timestamp request logic responsive to one or more of events that occur in the trace source and an interaction between a hardware core trace element and a processing core, the timestamp request logic arranged to insert an identifier in a timestamp request.
13. The system of claim 12 , wherein timestamp insertion logic inserts a first current value responsive to the reference and the timestamp request into a first-in first-out buffer.
14. The system of claim 13 , wherein the timestamp insertion logic inserts a second current value responsive to the reference when the trace information marked with the identifier arrives at the timestamp insertion logic.