Embedding Linux For An Automotive Environment

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Name of Presentation
Embedding Linux For An Automotive Environment
 Who is I, Anders Arnholm, What is Mecel
 What differs an embedded system to a conventional desktop
 What differs automotive from other embedded systems
 Some example automotive solutions
 Kernel start up optimizations, an example
 Don’t forget to ask

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Me, Myself and I

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Mecel

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Embedded vs Desktop
 What is an embedded system
 How does embedded differ
 Some words on requirements for Embedded and real-time computing

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Embedded system
An embedded system is a computer system designed to perform one or a
few dedicated functions often with real-time computing constraints. It
is embedded as part of a complete device often including hardware and
mechanical parts. By contrast, a general-purpose computer, such as
a personal computer (PC), is designed to be flexible and to meet a wide
range of end-user needs. Embedded systems control many devices in
common use today.
From Wikipedia, the free encyclopedia

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Few functions, Similar/Same Hardware
 Solves one or a few problems
 Mobile phone, smart phones moves into general computing
 GPS Navigator
 Engine Control Module
 Hardware and Software one bundle
 Can test on all hardware
 Can test all software configurations
 Expected to always work

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Real Time Myth? Or Fact?
 Real time
 Real-time computing, have a fixed deadline. An event in the
system need to have an answer within a fixed time. The
idea is that the result must arrive in time or the result is
invalid. This have to happened regardless of system load
 Often one know it’s a real time constraint but not the real
limit
 Many system run worst case scenario all the time
 Jitter problems
 Jitter are small variations of a periodic signal. Many
embedded systems work on tasks where the jitter have big
effects on the result. Often the results of jitter can be bigger
than the real time needs
 Effects audio
 Communications networks and busses

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Automotive vs Embedded
 The automotive industry designs,
develops, manufactures, markets, and
sells motor vehicles, and is one of the
world's most important economic
sectors by revenue.
 Usually, Cars, Light Commercial
Vehicles, Heavy Commercial Vehicles
and Busses.
 All cars are an embedded systems
 Automotive industry are conservative
 Automotive industry are regulated
 Electronic Control Unit (ECU)

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Example System, Gauge Cluster
 Main CPU Freescale i.MX51 600 MHz
Cortex-A8 + Linux
 GPU
 Renesas V850 + embedded system for
communication
 Media Oriented Systems Transport (MOST)
Connecting to mediaplayer to show some
information for the driver in the cluster and hud
display.
 CAN
Input for car information such as speed, RPM, etc
 Local Interconnect Network (LIN)
To connect with the physical keys for user
interaction such as button on the steering wheel.

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Example System, Communications node
 Automotive communications busses are limited
 Either slow or expensive
 All systems use a mix of busses
 Node connected to communications busses, and transfers messages mostly
to and from the HMI for the driver.
 AutoSAR with a small real time OS

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Zodiac Infotainment platform
 2009 Demo platform
 Based on Genivi IVI – Russellville
 Using Mecel Populus
 Using Mecel Betula
 Youtube video player
 Internet radio
 Podcast support
 Speech recognition

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Demo - Autonomy
 CPU: Freescale (PowerPC) - MPC5121e
 128 Mb RAM
 64 MB Flash
 Touch screen
 Bluetooth
 GPS
 Can interface

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Embedded solutions for Automotive
 AUTOSAR
 Linux
 Genivi Alliance – Delphi is Founding and Charter member
 LTIB – Linux Target Image Builder, Used by Freescale
 Buildroot – Also commonly used
 Windows Embedded Automotive
 QNX
 Custom software

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Optimizing Linux start-up time
 Focus on kernel start up
 We like to have a one cpu solution
 For CAN communication start up time
critical target < 100 ms
 Low end system
 OMAP OSK5912
 ARM9 – 192 Mhz
 32 Mb NOR Flash
 32 Mb RAM

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Optimize the kernel
 Quiet output
 Pre-calculate bogomips
 Remove Legacy PTY
 Remove Hotplug
 Remove MTD
 Remove Init
 Select filesystem

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Flash Filesystems
 JFFS2
 Compressed filesystem
 Standard fs for flash drives
 Supports NAND flash devices
 Cramfs
 Can be used without decompression
 Linear Cramfs support application XIP
 AXFS
 Supports XIP
 Read only

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Execute in Place
 Don’t copy the code into ram memory
 Optimize code for speed not size
 Flash slower that ram
 For applications need special filesystem, Linear CRAMFS or AXFS
 Read only FS

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Boot times
Conguration
Before shell
is started
After shell is
started
Shell start
time
Unoptimized
with JFFS2
5.428 100% 6.207 100% 0.779
Optimized with
JFFS2
2.771 51% 2.964 47% 0.193
Optimized with
Cramfs
2.627 48% 2.814 45% 0.187
Optimized with
AXFS
1.451 27% 1.576 25% 0.125
Optimized XIP
with AXFS
0.189 3% 0.360 6% 0.171

Embedding Linux For An Automotive Environment

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