A Decentralized Scheduler for On-line Self-test Routines in Multi-core Automotive System-on-Chips

Modern System-on-Chips (SoCs) deployed for safety-critical applications typically embed one or more processing cores along with a variable number of peripherals. The compliance of such designs with functional safety standards is achieved by a combination of different techniques based on hardware redundancy and in-field test mechanisms. Among these, Software Test Libraries (STLs) are rapidly becoming adopted for testing the CPU and peripherals modules. The STL is usually composed of two sets of self-test procedures: boot-time and run-time tests. The former set is typically executed during the boot or power-on phase of the SoC since it requires full access to the available hardware (e.g., these programs need to manipulate the Interrupt Vector Table and to access the system RAM). The latter set instead, is designed to coexist with the user application and can be executed without requiring special constraints. When the STL is intended for testing the different cores within a multi-core SoC, the concurrent execution of the boot-time self-tests becomes an issue since this could lead to a longer power-up phase and excessive utilization of system resources. The main intent of this work is to present the architecture of a decentralized software scheduler, conceived for the concurrent execution of the STL on the available cores. The proposed solution considers the typical constraints of an STL in a multi-core scenario when deployed in field, namely minimum system resources usage (i.e., code and data memory). The effectiveness of the proposed scheduler was experimentally evaluated on an industrial STL developed for a multi-core SoC manufactured by STMicroelectronics.