LFSR Stall Injection for GPU Interface Error Checking
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Solution Overview
Problem
Determining the nature and root cause of performance problems in complex systems like GPUs is difficult, time-consuming, and error-prone, and existing methods for testing interface stall states are inefficient, especially post-silicon.
Innovation Solution
Implementing a system to inject stalls into communication interfaces using a Linear Feedback Shift Register (LFSR) in a pseudo-random manner and count these stalls to identify errors in the interface or receiver device, enabling observability in both pre-silicon and post-silicon testing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional interface error checking methods are used, then error detection capability is limited, but system complexity and debugging time increase
Solution Approach 1:
The patent applies preliminary action by injecting predetermined stall patterns into the communication interface before actual data transmission. The LFSR generates known stall sequences that are injected into the interface, allowing errors to be detected proactively rather than reactively during normal operation. This enables pre-characterization of interface reliability under controlled stall conditions.
Solution Approach 2:
The patent introduces an intermediary component - the LFSR-based stall injection mechanism - that mediates between the test controller and the communication interface. This intermediary generates and injects controlled stall patterns, acting as a bridge that enables systematic error detection without requiring direct manipulation of the interface under test, thereby simplifying the testing architecture.
2Measurement precision
If comprehensive interface testing is performed, then error detection accuracy improves, but testing time and resource consumption increase
Solution Approach 1:
The patent employs periodic action through the LFSR, which continuously generates pseudo-random stall patterns at regular intervals. This periodic injection of test patterns enables systematic coverage of various stall scenarios without requiring manual intervention for each test case, thereby improving detection accuracy while maintaining efficient test execution through automated, rhythmic testing cycles.
Solution Approach 2:
The patent uses copying by generating multiple instances of stall patterns through the LFSR's pseudo-random sequence generation. Instead of manually creating and applying each test pattern, the LFSR copies and varies the basic stall pattern structure, producing a diverse set of test scenarios from a single pattern template. This approach comprehensively tests interface robustness while minimizing the time required to prepare and apply multiple test cases.
3Adaptability or versatility
If external circuitry is added for stall injection, then testing capability improves, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent achieves universality by designing the LFSR-based stall injection mechanism to be integrated within the existing GPU architecture, allowing the same hardware block to serve multiple functions: normal graphics processing, stall pattern generation, and error detection. This multi-functional approach eliminates the need for separate external testing circuitry, maintaining manufacturing simplicity while providing comprehensive testing capability.
Solution Approach 2:
The patent implements self-service by enabling the GPU's own internal resources to perform testing functions. The LFSR and stall injection logic are built into the device, allowing it to self-test and self-diagnose interface errors without requiring external testing equipment. This self-service capability maintains ease of manufacture while providing adaptability for various testing scenarios through software-controlled activation.
Data Source
AI summary
A system that includes determining whether an interface between sender and receiver devices is defective. For an interface between a sender device and a receiver device: a configured number of stalls can be injected in a communication from the sender device to the receiver device. Based on the counted number of stalls being less than an injected number of stalls or exceeding the injected number of stalls by more than a threshold level, the interface can be identified as defective with respect to stall state counting. Based on the counted number of stalls being the same as the injected number of stalls or exceeding the injected number of stalls by not more than the threshold level, the interface can be identified as non-defective with respect to stall state counting.