Reporter:PCLee

With a significant increase in the design complexity of cores and associated communication among them, post-silicon validation has become a demanding task in System on Chips (SoCs) design. To ensure that final products are fault-free and ready for market, the post-silicon validation goal is to catch bugs and pinpoint the root causes of errors that could escape from pre-silicon verification tools. Post-silicon validation involves running a hardware prototype in an environment that is similar to its final platform with its expected workload. As new SoCs tend to have many cores, the interactions among these cores are becoming so complex that post-silicon debug techniques should address not only validation of the functional aspects of a design but such techniques have to “bulletproof” the communication and synchronization among cores inside an SoC.

In this paper, we propose an AXI based environment for post- silicon validation. The proposed environment involves Local Debugging Unit (LDU) and Shared Debugging Unit (SDU). LDU monitors trace of transactions issued by the hardware prototype and detect undesired conditions on bus. SDU combines debug traces from different LDUs. We embed the proposed SDU inside an AXI configurable interconnect. Major benefits of using our proposed debug platform over traditional techniques for silicon validation are as follows: 1) it detects and bypasses real time severe faulty conditions such as deadlocks resulting from design errors or electrical faults 2) there is no need for internal trace memory because SDU can communicate to the external memory through slave ports 3) it enables online monitoring of the trace buffer.

Design for Debug method[1] Achieve the required real-time observability[13][19] Embedded Logic Analyzer(ELA)[19] Assertion checker in wireless system[6] Synthesis of assertion [7] NOC debug system[9] A distributed performance analysis mechanism in AXI- based system[20] Assertion checker inside the bus[15] MBAC[15] THIS PAPER

Problem: Design errors and the electrical errors are two major source of failure in first-silicon. Conventional debug methods and tools tend to focus more on the computational part of a system. e. g. the processor and its interaction with main memory. Proposed method LDU: They are distributed among AXI Master Interfaces that connect master devices to the bus. They trace the transaction signals and detect the undesired condition. SDU: LDUs are connected to the central SDU and transmit their debug traces to that module. And then schedule it to external memory. It is implemented inside AXI interconnection.

Design error and electrical error may lead to following error. DEADLOCK  len: number of transfer  If slave expected more data transfer but master is waiting ack from slave.  If slave expected less data transfer but master still transfer.

RACE CONDITION  It usually happens when multiple master are writing to the same place.  The result is different depend on the order. LIVELOCK  a system performs continuously the same sequence of operations without any changes in the status of that system. DATA DPENDENCY  It occurs because data dependency.

Master request 1. Master issue a tansfer 2. If the corresponding TR has already set. 3. If set, add new line in transaction table(valid, transaction ID, number of request, expected transaction ID). If it doesn’t set, set 1 and add new line. Slave response: Compare the expected ID at transaction table to detect if it violates the order. Assertion checker has 83 statement. They use MBAC for converting them to hardware.

SDU combines trace information from LDUs and schedules them to the trace memory. SDU traces failure patterns that might lead to erroneous conditions on bus.

The platform include 2 16-bit SAYEH processors. They intentionally inserted design error in the processors, memory controller, AXI interface. The errors are tuned to represent the corner case.  Memory controller: memory scheduler  Processor: inject fault into forwarding unit, cache controller and interrupt controller.

Deadlock never happen in this platform. 94% errors of controller has detected by LDU. 87% errors of interface has detected by LDU.

This paper proposed AXI-based post-silicon validation platform. This platform detect and bypass severe faulty condition resulting from design error and electrical error. It can access trace memory in an online manner.

Because we will verify the AXI checker and tracer later. So this paper can help as to ensure if we can capture the errors they described. Some details doesn’t explain in this paper. I will find these and study them.

Efficient Automata- Based Assertion- Checker Synthesis of SEREs for Hardware Emulation Efficient Automata-Based Assertion-Checker Synthesis of PSL properties Assertion Checkers – Enablers of Quality Design Assertion-based Formal Compliance Verification of Interface Protocols Formal method This paper Pre-siliconPost-silicon