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Requirements and Solutions for Timing Analysis of Automotive Systems. Saoussen Anssi 1 , Sébastien Gérard 2 , Arnaud Albinet 1 , François Terrier 2 1 Continental Automotive France SAS, PowerTrain E IPP {saoussen.ansi, arnaud.albinet}@continental-corporation.com

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requirements and solutions for timing analysis of automotive systems

Requirements and Solutions for Timing Analysis of Automotive Systems

Saoussen Anssi1, Sébastien Gérard2, Arnaud Albinet1, François Terrier2

1Continental Automotive France SAS, PowerTrain E IPP

{saoussen.ansi, arnaud.albinet}@continental-corporation.com

2CEA LIST, Laboratory of model driven engineering for embedded systems,

{françois.terrier,sebastien.gerard}@cea.fr

slide2

Timing Analysis in Automotive Software Design

Timing Verification in automotive software design

Automotive Applications

  • Increasing Complexity
  • Limited Resources
  • Timing Constraints
  • Safety Requirements
  • Performed Late after the implementation
  • Addressed by means of measuring & testing
  • No formal / systematic analysis
  • No methodological support
  • Design mistakes detected late
  • High design cost
  • Long time-to-market

Necessity to integrate timing verification in the automotive development process

Requirements and Solutions for Timing Analysis of Automotive Systems

  • 2
work context
Work Context
  • Part of a study to define a model based scheduling analysis process for automotive systems
    • Q.1: how well scheduling analysis can be used for automotive applications?
        • Evaluate the usability of scheduling theory
        • Evaluate the capability of scheduling analysis tools
    • Q.2: how to integrate scheduling analysis in the development process ? (when/how?, confidence level, refinement,...)
  • Current work (Q.1): Evaluate the capability of two scheduling analysis tools
    • MAST
    • Cheddar

Requirements and Solutions for Timing Analysis of Automotive Systems

scheduling analysis needs for automotive applications
Scheduling Analysis Needs for Automotive Applications

Necessity to consider the distributed aspect when analyzing the system, consider the hardware platform impact

Necessity to evaluate processor load & Needed memory size

Distributed Architecture

Multiple ECUs, Multiple communication protocols, CAN, LIN, Flexray, etc.

Limited hardware resources

CPU Load, RAM/ROM consumption

Necessity to verify if those constraints are met or not

Automotive Applications

Necessity to support this tasks models & consider task dependency

Timing constraints

Deadlines, Max activation/output jitters, data synchronization constraints, end-to-end constraints

Task dependency and concurrency

Dependent tasks, data exchange, shared resources, preemptive/non-preemptive/cooperative tasks, same priority level

Necessity to account for this triggering diversity when analyzing the system

Various triggering paradigms

Time triggered/event triggered, periodic/sporadic/singular tasks, timing recurrence/angular recurrence

Property protection

Systems with black box components

Necessity to consider the black box aspect when analyzing the system

Requirements and Solutions for Timing Analysis of Automotive Systems

scheduling analysis tools requirements 1 2
Scheduling Analysis Tools Requirements (1/2)

Requirements and Solutions for Timing Analysis of Automotive Systems

slide6

Scheduling Analysis Tools Requirements (2/2)

Requirements and Solutions for Timing Analysis of Automotive Systems

slide7

Scheduling Analysis Tools Capabilities (1/2)

Limited hardware resources

Timing Constraints

  • Cheddar:

REQ2 & 3:Deadlines on tasks

REQ4: No activation jitter specification

REQ5 & 9: No data synchronization constraints specification/verification

REQ6: No end-to-end constraints specification

REQ7 & 8: Response times calculated for tasks

  • Cheddar:

REQ1: Calculation of processor utilization factor only for periodic tasks

  • MAST:

REQ2 & 3: Timing requirement: operation deadlines & max output jitter

REQ4: External event: max activation jitter (only for periodic)

REQ5 & 9 : No data synchronization constraints specification/verification

REQ6: End-to-end-constraints on transaction output event

REQ7 & 8: Response times for operation and transactions

  • MAST:

REQ1: Calculation of Processor utilization & processor slack

Triggering patterns

  • MAST:

REQ11: External events may be periodic, sporadic, unbounded, bursty

REQ12: No angular event specification

  • Cheddar:

REQ11: No triggering event concept but rather task kind (periodic, sporadic & aperiodic)

REQ12: No angular event specification

Requirements and Solutions for Timing Analysis of Automotive Systems

slide8

Scheduling Analysis Tools Capabilities (2/2)

Distributed Architecture

Task concurrency and dependency

  • Cheddar:

REQ17, 18 & 19 : Description and analysis of systems with shared buffers, data exchange not supported, task precedence constraints description

REQ20: possibility to use FIFO for tasks with same priority levels

REQ22: only preemtive/non-preemptive tasks, no cooperative tasks

  • Cheddar:

REQ13 & 14: Possibility to describe and analyze multiprocessor systems

REQ15: No dedicated techniques for CAN, LIN or Flexray

REQ16: Context switch overhead for task activation, no network overhead description

  • MAST:

REQ17& 18: Description and analysis of systems with shared resources, data exchange through internal event concept

REQ19: No joins/ forks supported, only linear transactions

REQ20: No dedicated techniques for tasks with same priority levels

REQ22: only preemtive/non-preemptive tasks, no cooperative tasks

  • MAST:

REQ13 & 14: Possibility to describe and analyze multiprocessor systems

REQ15: No dedicated techniques for CAN, LIN or Flexray

REQ16: Context switch overhead description, packet overheads

Property protection

  • Cheddar:

REQ22: No techniques for systems with black box components

  • MAST:

REQ22: No techniques for systems with black box components

Requirements and Solutions for Timing Analysis of Automotive Systems

slide9

Scheduling Analysis of an Automotive Application

Use case: knock system

Knock Processor

TASK_knk_kw

TASK_E1_SEG

TASK_T1_100ms

Knk_100ms

Periodic activation

WCET: 85µs

D: 600µs

Knk_kw

Sporadic activation

WCET: 200µs

D: 500µs

Knk_seg

Angular activation

WCET: 250µs

D: 600µs

Requirements and Solutions for Timing Analysis of Automotive Systems

slide10

Analysis Results

  • Results are quite close to each other
  • MAST results are more precise
  • No possibility to describe allocation of functions to tasks with cheddar
  • Processor utilization with MAST: 97.66%
  • No possibility to calculate processor utilization with Cheddar, because of sporadic tasks
  • Results graphical display is interesting in Cheddar

Requirements and Solutions for Timing Analysis of Automotive Systems

slide11

Conclusion

  • Open source aspect is interesting for the two tools  possibility to integrate new automotive analysis techniques
  • MAST model is closer to concrete systems / Cheddar model is closer to scheduling theory
  • MAST seems to be more mature than Cheddar
  • Mast can be used for detailed scheduling analysis at implementation phase
  • Cheddar can be used for timing analysis in earlier development phases

Requirements and Solutions for Timing Analysis of Automotive Systems