Resolving ADAS imaging subsystem functional safety quagmire

Nowadays it has become common practice to use multi core SoCs in safety related Advanced Driver Assistance Systems (ADAS). The ISO 26262 functional safety standard provides requirements to avoid or reduce the risk caused by these systems. In safety related systems, a comprehensive test strategy is required to guarantee successful normal operation for the SoC throughout its life cycle. Software based self-tests have been proposed as an effective alternative to hardware based self-tests in order to eliminate area and save new hardware IP development costs. This paper proposes software based self-test scheme to ensure integrity of Imaging subsystems to prevent violation of the defined safety goals for several camera based ADAS applications. The proposal uses a hand crafted functional time triggered non-concurrent online test based solution, The proposed solution covers permanent and intermittent faults in imaging sub-systems by introducing a known golden reference image processing run every fault tolerant time interval. For a sample 1080p30 input capture, considering a fault tolerant time interval of 300ms for a typical ADAS application and considering that this hand-crafted test pattern is run after every 8 frames, the proposed solution enables the hardware self-test at an additional 12.5% clocking requirement for the imaging sub-system and an additional 12.5% DDR throughput requirement.