Introduction

In the automotive industry, ensuring functional safety compliance is crucial, especially when integrating third-party intellectual property (IP) such as ARM soft IP into safety-critical applications. A safety case for ARM soft IP demonstrates how the IP meets ISO 26262 requirements and supports the overall system’s safety goals.

Understanding ARM Soft IP in Automotive Safety

ARM soft IP refers to synthesizable processor cores and other functional blocks that can be integrated into automotive SoCs (System-on-Chip). These IP blocks are essential for implementing safety-critical functionalities in ADAS (Advanced Driver Assistance Systems), autonomous driving, and powertrain applications. Since ARM soft IP is typically delivered as RTL (Register Transfer Level) code, it requires additional safety analysis and verification to ensure it complies with ISO 26262 requirements.

Key Components of a Safety Case

A safety case is a structured argument that provides evidence that a system is acceptably safe for its intended use. For ARM soft IP, the safety case should cover the following aspects:

1. Definition of Safety Goals and ASIL Requirements

• Identify the safety goals at the system level where ARM soft IP is integrated.
• Determine the Automotive Safety Integrity Level (ASIL) requirements based on system safety analysis.
• Ensure that ARM soft IP supports ASIL decomposition where applicable.

2. Safety Analysis of ARM Soft IP

• Failure Modes and Effects Analysis (FMEA): Identify potential failure modes at the IP level and their impact on the system.
• Fault Tree Analysis (FTA): Analyze dependencies between IP failures and system-level failures.
• Hardware Metrics Analysis: Ensure the IP meets PMHF (Probabilistic Metric for Hardware Failure) and SPFM (Single Point Fault Metric) as required by ISO 26262 Part 5.

3. Development Process Compliance

• Verify that the ARM soft IP is developed following a safety-complaint process.
• Ensure traceability of requirements, design, implementation, and verification.
• Assess whether ARM’s development lifecycle aligns with ISO 26262 Part 8 requirements.

4. Verification and Validation

• Perform static and dynamic analysis using tools like LDRA or similar to ensure compliance with safety coding guidelines.
• Conduct hardware-in-the-loop (HIL) testing and fault injection to validate IP behavior under failure conditions.
• Validate the effectiveness of safety mechanisms (e.g., ECC, watchdogs, and lockstep architectures).

5. Assumptions of Use (AoU) and Safety Mechanisms

• Define assumptions regarding how the ARM soft IP will be used within the system.
• Identify necessary external safety mechanisms to be implemented at the system level.
• Ensure that diagnostic coverage is adequate for the required ASIL level.

6. Safety Work Products and Documentation

• Prepare work products such as the Safety Plan, Safety Manual, and FMEDA report.
• Ensure ARM provides a Safety Element out of Context (SEooC) argument if the IP is developed independently of a specific system.
• Maintain traceability between ARM IP safety claims and system-level safety requirements.

Challenges in Developing a Safety Case for ARM Soft IP

• Lack of Direct Control: Since ARM provides soft IP as RTL, the integrator must perform additional verification and validation to ensure safety.
• ASIL Decomposition Complexity: Some functionalities may require ASIL decomposition, necessitating careful partitioning and verification.
• Tool Qualification: Ensuring that tools used for synthesis, verification, and validation are ISO 26262-compliant.
• Meeting Hardware Metrics: Achieving PMHF and SPFM compliance can be challenging, requiring additional safety mechanisms at the SoC level.

Conclusion

Developing a safety case for ARM soft IP is a critical step in ensuring its safe integration into automotive applications. By following a structured safety argument, performing thorough analysis, and maintaining compliance with ISO 26262, automotive developers can ensure that ARM soft IP contributes to overall vehicle safety. As the industry moves towards more complex ADAS and autonomous driving applications, robust safety cases will be essential for certifying and deploying ARM-based automotive SoCs.