From FPGA to ASIC: A RISC-V processor experience

This work document a correct design flow using these tools in the Lagarto RISC- V Processor and the RTL design considerations that must be taken into account, to move from a design for FPGA to design for ASIC

Constraint-Based Automatic SBST Generation for RISC-V Processor Families

Software-Based Self-Tests (SBST) allow at-speed, native online-testing of processors by running software programs on the processor core, requiring no Design for Testability (DfT) infrastructure. The creation of such SBST programs often requires time-consuming manual labour that is expensive and requires in-depth knowledge of the processor’s architecture to target hard-to-test faults. In contrast, encoding the SBST generation task as a Bounded Model Checking (BMC) problem allows using sophisticated, state-of-the-art BMC solvers to automatically generate an SBST. Constraints for the BMC problem are encoded in a circuit called Validity Checker Module (VCM) and applied during SBST generation.In this paper, we focus on presenting a VCM architecture and a constraint set that allows building SBSTs that make minimal assumptions about the firmware, targeting hard-to-test faults in the ALU and register file of multiple scalar, in-order RISC-V processor families. The VCM architecture consists of a processor-specific mapping layer and a generic constraint set connected via a well-defined interface. The generic constraint set enforces the desired SBST behaviour, including controlling the processor’s pipeline state, memory accesses, and with that executed instructions, register state, and fault propagations. Using a generic constraint set allows for rapid SBST generation targeting new RISC-V processor families while keeping the generic constraints untouched. Lastly, we evaluate this approach on two RISC-V processor families, namely the DarkRISCV and a proprietary, industrial core showing the portability and strength of the approach, allowing for rapidly targeting new processors

Multi-core devices for safety-critical systems: a survey

Multi-core devices are envisioned to support the development of next-generation safety-critical systems, enabling the on-chip integration of functions of different criticality. This integration provides multiple system-level potential benefits such as cost, size, power, and weight reduction. However, safety certification becomes a challenge and several fundamental safety technical requirements must be addressed, such as temporal and spatial independence, reliability, and diagnostic coverage. This survey provides a categorization and overview at different device abstraction levels (nanoscale, component, and device) of selected key research contributions that support the compliance with these fundamental safety requirements.This work has been partially supported by the Spanish Ministry of Economy and Competitiveness under grant TIN2015-65316-P, Basque Government under grant KK-2019-00035 and the HiPEAC Network of Excellence. The Spanish Ministry of Economy and Competitiveness has also partially supported Jaume Abella under Ramon y Cajal postdoctoral fellowship (RYC-2013-14717).Peer ReviewedPostprint (author's final draft

Vector extensions in COTS processors to increase guaranteed performance in real-time systems

The need for increased application performance in high-integrity systems like those in avionics is on the rise as software continues to implement more complex functionalities. The prevalent computing solution for future high-integrity embedded products are multi-processors systems-on-chip (MPSoC) processors. MPSoCs include CPU multicores that enable improving performance via thread-level parallelism. MPSoCs also include generic accelerators (GPUs) and application-specific accelerators. However, the data processing approach (DPA) required to exploit each of these underlying parallel hardware blocks carries several open challenges to enable the safe deployment in high-integrity domains. The main challenges include the qualification of its associated runtime system and the difficulties in analyzing programs deploying the DPA with out-of-the-box timing analysis and code coverage tools. In this work, we perform a thorough analysis of vector extensions (VExt) in current COTS processors for high-integrity systems. We show that VExt prevent many of the challenges arising with parallel programming models and GPUs. Unlike other DPAs, VExt require no runtime support, prevent by design race conditions that might arise with parallel programming models, and have minimum impact on the software ecosystem enabling the use of existing code coverage and timing analysis tools. We develop vectorized versions of neural network kernels and show that the NVIDIA Xavier VExt provide a reasonable increase in guaranteed application performance of up to 2.7x. Our analysis contends that VExt are the DPA approach with arguably the fastest path for adoption in high-integrity systems.This work has received funding from the the European Research Council (ERC) grant agreement No. 772773 (SuPerCom) and the Spanish Ministry of Science and Innovation (AEI/10.13039/501100011033) under grants PID2019-107255GB-C21 and IJC2020-045931-I.Peer ReviewedPostprint (author's final draft

Designing Neural Networks for Real-Time Systems

Artificial Neural Networks (ANNs) are increasingly being used within safety-critical Cyber-Physical Systems (CPSs). They are often co-located with traditional embedded software, and may perform advisory or control-based roles. It is important to validate both the timing and functional correctness of these systems. However, most approaches in the literature consider guaranteeing only the functionality of ANN based controllers. This issue stems largely from the implementation strategies used within common neural network frameworks -- their underlying source code is often simply unsuitable for formal techniques such as static timing analysis. As a result, developers of safety-critical CPS must rely on informal techniques such as measurement based approaches to prove correctness, techniques that provide weak guarantees at best. In this work we address this challenge. We propose a design pipeline whereby neural networks trained using the popular deep learning framework Keras are compiled to functionally equivalent C code. This C code is restricted to simple constructs that may be analysed by existing static timing analysis tools. As a result, if compiled to a suitable time-predictable platform all execution bounds may be statically derived. To demonstrate the benefits of our approach we execute an ANN trained to drive an autonomous vehicle around a race track. We compile the ANN to the Patmos time-predictable controller, and show that we can derive worst case execution timings.Comment: 4 pages, 2 figures. IEEE Embedded Systems Letters, 202

Memory Mapped I/O Register Test Case Generator for Large Systems-on-Chip

This paper addresses automated testing of a massive number of Memory Mapped Input/Output (MMIO) registers in a real large-scale Systems-on-Chip (SoC). The golden reference is an IP-XACT hardware description that includes a global memory map. The memory addresses for peripheral registers are required by software developers to access the peripherals from software.However, frequent hardware changes occur during the HW design process, but the changes might not always propagate to the SW developers and an incorrect memory map can cause unexpected behaviour and critical errors. Our goal is to ensure that the memory map corresponds exactly to the HW description.The correctness of the memory map can be verified by writing software test cases that access all MMIO-registers. Writing them manually is time consuming and error prone, for which reason we present a test case generator. We use a Rust-based software stack, where the generator itself is written in Rust while the generator input is in CMSIS-SVD-format that is generated from IP-XACT. We have used the generator extensively in Tampere SoC Hub Ballast and Headsail SoCs and fixed several errors before the chips manufacturing. The test generator can be used with any IP-XACT based SoCs.Peer reviewe

Special Session: AutoSoC - A Suite of Open-Source Automotive SoC Benchmarks

The current demands for autonomous driving generated momentum for an increase in research in the different technologies required for these applications. Nonetheless, the limited access to representative designs and industrial methodologies poses a challenge to the research community. Considering this scenario, there is a high demand for an open-source solution that could support development of research targeting automotive applications. This paper presents the current status of AutoSoC, an automotive SoC benchmark suite that includes hardware and software elements and is entirely open-source. The objective is to provide researchers with an industrial-grade automotive SoC that includes all essential components, is fully customizable, and enables analysis of functional safety solutions and automotive SoC configurations. This paper describes the available configurations of the benchmark including an initial assessment for ASIL B to D configurations

Design and implementation of a bootrom in a Linux capable RISC-V processor

El moviment de codi obert promet revolucionar el món del maquinari igual que el programari ha revolucionat. Gràcies a l'arquitectura de conjunt d'instruccions o ISA (de l'anglès Instruction Set Architecture) RISC-V de codi obert, molts projectes s'estan obrint camí per oferir una alternativa a l'hermètic i privatiu món de l'arquitectura de computadors. En aquest context neix el projecte DRAC, les sigles del qual fan referència, de l'anglès, a Designing RISC-V-based Accelerators for next-generation Computers. Aquest projecte, liderat pel Barcelona Supercomputing Center (BSC), desenvolupa processadors i acceleradors basats en la tecnologia RISC-V, amb l'objectiu d'accelerar tasques de seguretat, medicina personalitzada i navegació autònoma. Aquesta tesi té com a propòsit dissenyar, implementar i verificar una bootrom pel SoC (de l'anglès System on Chip) de 64 bits DRAC 22 nm. Aquest SoC integra un processador RISC-V de 7 etapes anomenat Sargantana. El disseny del SoC, basat en l'anterior \textit{tape-out} anomenat PreDRAC, es divideix en dues parts. Una part conté tots els components orientats a l'ASIC; l'altra conté els elements orientats a la FPGA. Una de les raons principals d'aquesta divisió és que no existia una bootrom orientada a ASIC i, per tant, calia utilitzar la FPGA per arrencar el xip. Amb la integració de la bootrom desenvolupada en aquesta tesi, el SoC serà capaç d'arrencar per ell mateix, eliminant la part orientada a la FPGA del disseny del SoC.The open-source movement promises to revolutionize the hardware world just as it has revolutionized software. Thanks to the open-source RISC-V instruction set architecture (ISA), many projects are making their way to offer an alternative in the hermetic and proprietary world of computer architecture. The DRAC project, whose acronym refers to Designing RISC-V-based Accelerators for next-generation Computers, was created in this context. This project, led by the Barcelona Supercomputing Center (BSC), develops processors and accelerators based on RISC-V technology, and their purpose is to accelerate security tasks, personalized medicine and autonomous navigation. This thesis aims to design, implement and verify a bootrom for the 64-bit DRAC 22 nm System on Chip (SoC). This SoC integrates an in-order 7-stage RISC-V core called Sargantana. The SoC design, based on the previous tape-out PreDRAC, is divided into two parts. One part contains all the ASIC-oriented components; the other contains the FPGA-oriented components. One of the main reasons for this division is that there was no ASIC-oriented bootrom, and therefore, it was necessary to use the FPGA to boot the chip. With the integration of the bootrom developed in this thesis, the SoC will be able to boot by itself, eliminating the FPGA-oriented part of the SoC design