Ensimag, Amphi E
18 November 2011 - 14h00
Contributions to Transaction-Level Modeling of Systems-on-a-Chip (Phd Defense)
by Giovanni Funchal from Verimag/STMicroelectronics
Abstract: This thesis deals with modeling of Systems-on-a-Chip (SoC) at the Transactional Level (TLM), an approach also known as virtual prototyping. Virtual prototypes are of special industrial interest because they allow some activities (such as embedded software development) to start earlier in the design flow. Because this approach is relatively new, several modeling issues are still open. In particular, there is an increasing need for understanding how close a given model is to the hypothetical system it is intended to represent. This is a difficult problem specially because we lack a way to perform an objective comparison, since the modeling activity is prior to the physical existence of the modeled system. A methodology is required to address these concerns, going beyond classical objective and functional quality requirements. In this context, the industry searches for clear modeling guidelines based on experience and the identification of the current modeling practices and known recurring problems.
In this thesis, we present a comprehensive study of a range of technical considerations involved in the design flow of the hardware and software that constitutes a typical SoC. We use this knowledge to identify one particular source of divergence between the model and the modeled system. We show that this divergence causes some software bugs to become hidden in the virtual prototype and we correlate this situation to the corresponding modeling practice.
Secondly, we attempt to identify language-dependency issues in the modeling practices. We claim that it is only by confronting with an alternative language that we could measure the extent to which common modeling issues were caused by mixing up conceptual transaction-level modeling with its implementation in the current industry standard language. Therefore, we propose a complete experimentation framework specifically designed to help in the study of fundamental concepts beneath TLM. Amongst other features, this framework introduces a novel approach to modeling time in discrete-event simulators that distinguishes between instantaneous actions and tasks that take time. We show that this notion can be exploited to enrich trace visualization tools; to derive a clear definition of overlapping tasks; to effortlessly achieve an important simulation speedup by enabling parallel execution of actions occurring at different simulation times; and to expose subtle bugs by removing the constraint that actions at different simulation times are necessarily synchronized.
Composition du Jury :
Robert DE SIMONE INRIA Sophia-Antipolis Rapporteur
Reinhard VON HANXLEDEN Christian-Albrechts-University Kiel Rapporteur
Matthieu MOY Grenoble INP Directeur de thèse
Florence MARANINCHI Grenoble INP Directeur de thèse
Emmanuel CASSEAU ENSSAT - IRISA/INRIA Examinateur
Laurent MAILLET-CONTOZ STMicroelectronics Examinateur