Agnostic Device Drivers

Heiko J Schick <[email protected]> 04/09/23 © 2004 IBM Corporation

Agnostic Device Drivers (ADD)

Concept, Design, and Implementation of a Slimline Boot Firmware for Linux on Power Architecture

IBM Deutschland Entwicklung GmbHSchoenaicherstr. 22071032 Boeblingen

Agnostic Device Drivers

© 2004 IBM Corporation2 Heiko J Schick <[email protected]> 04/09/23

Contents

1. Open Firmware Standard

2. Existing Hardware Abstraction Concepts

3. Agnostic Device Drivers (ADD)

4. Further Opportunities



Is Hardware Abstraction necessary?



Open Firmware Standard

IEEE StandardIEEE Std. 1275-1994 Standard for Boot (Initialization Configuration) Firmware

– Device Interface

– User Interface

– Client Interface

Device-Tree

Operating System

Open Firmware

Low-LevelFirmware

Hardware Hardware

Operating System

BOOT-TIME RUN-TIME

Device-Tree



Existing Hardware Abstraction Concepts(based on Open Firmware)

Operating System

Open Firmware

Low-LevelFirmware

Hardware Hardware

Operating System

BOOT-TIME RUN-TIME

RTAS

Device-TreeRTAS

Open Firmware

Device-Tree

Operating System

Low-LevelFirmware

Hardware Hardware

Operating System

BOOT-TIME RUN-TIME

PE

PE Platform Expert

Platform Expert Code

PEC

PED Platform Expert Data

PED

PEC

PE PEC

PED

Common Hardware Reference Platform: Apple:



Comparison

RTAS Platform Expert

Performance: - ++

Flexibility: - +/-

Packaging: - --

High-Level Language Facilities:

- -



Agnostic Device Drivers (ADD)– Concept and Basics

Operating System

Open Firmware

Low-LevelFirmware

Hardware Hardware

Operating System

BOOT-TIME RUN-TIME

Device-TreeByte-Code

Device-TreeByte-Code

1

ADD -Virtual

Machine

Byte-Code

2

I2CGPIO

3



Agnostic Device Drivers (ADD)– Packaging Options

1: ADD byte-code program taken from Device-Tree– Packaged with the Firmware Code.

– Additional Device-Tree properties can include control or execution information.

2: ADD byte-code program inserted during run-time (via user transaction)– Fast development of ADD byte-code

programs.

– Flexible packaging.

Operating System

Open Firmware

Low-LevelFirmware

Hardware Hardware

Operating System

BOOT-TIME RUN-TIME

AgnosticDeviceDrivers

Front-End1

2

Byte-Code

Byte-Code



Agnostic Device Drivers (ADD)– Virtual Machine

Front-End:Loads Byte-Code (from different sources)

Virtual Machine:Executes ADD Byte-Code

Back-End:Implements I2C and GPIO Binding to the Operating System

Virtual MachineFront-End

ADD byte-code over

Device Driver

ADD byte-code over

Device-Tree

InnerInterpreter

OuterInterpreter

Data Stack

Return Stack Build-InTokens

VendorTokens

LocalTokens

Doers(for Constants,Variables, etc.)

Back-End

Byte-CodeVerifier I2C

Interface

GPIOInterface

Token-Tables

PowerManagment



Agnostic Device Drivers (ADD)– Functionality

Small footprint virtual machine

Controlling of low-bandwidth devices (e.g. I2C or GPIO) is possible

Controlling of the policy and the logic of a device is possible

– Control Structures

– Defining Words

Extended Debug Facilities

– Virtual Machine runs in hosted mode

– Virtual Machine runs as kernel thread (root user can interrupt it)

– I2C Drivers can debugged via I2C Emulation Host Adapter

– Rebooting during development is not necessary

– Single execution is not difficult to implement



Agnostic Device Drivers (ADD)– Summary

RTAS Platform Expert Agnostic Device Drivers

Performance: - ++ ++

Flexibility: - - ++

Packaging: - -- ++

High-Level Language Facilities:

- - ++



Questions ???



Further Opportunities

Real-Time / Performance– ADD is an asynchronous interface / hardware abstraction.

– Functionality can implemented as primitive (for real-time applications).

Scheduling– Scheduling (once, every 5 sec., etc.) can controlled via a Device-Tree property.

– Thread Support is not difficult to implement (instruction pointer and token-table pointer must saved).

Multi-OS– Only vendor token-table entries changed.

ADD Virtual Machine can integrated into the firmware– ADD driver could then used in the firmware and the operating system.

Extended Debug Facilities– Realizes fast program development and debugging.



Agnostic Device Drivers (ADD)– Example: Byte Code

FMT CHKSUM LENGTH0xF1

0xCA 0x05 0x77 0x6F 0x72 0x6C 0x64 0x08

0x00 0xB7 0x12 0x05 0x68 0x65 0x6C 0x6C

0xC20x330x67 0x90 0xA5 0x08 0x00 0x00

add-version1headers

external: world " hello" type 0 exit ;

headers

world

add-end

Header

Defining Words

Local ADD Byte-Code Numbers

Functions

Strings



Agnostic Device Drivers (ADD)– Example: Linux Kernel I2C Interface

I2C algorithm driver used by the I2C bus driver to talk to the I2C bus.

I2C chip driver controls the process of talking to an individual I2C device that lives on an I2C bus.

Adapters /Bus Driver Chip DriverChip DriverChip Driver

AlgorithmDriver

I2C over Parallel PortApple KeywestAMD 8111...

LM75 Temperature SensorEEPROM

i2c_smbus_read_bytei2c_smbus_write_bytei2c_smbus_read_byte_datai2c_smbus_write_byte_datai2c_smbus_read_word_datai2c_smbus_write_word_datai2c_smbus_read_block_datai2c_smbus_write_block_datai2c_smbus_read_i2c_block_datai2c_smbus_write_i2c_block_data

i2c-newi2c-deletei2c-pingi2c-b@i2c-w@i2c-l@i2c-b!i2c-w!i2c-l!

Linux Kernel 2.6 ADD Byte-Code

AgnosticDevice Driver



Overview of available Options – CHRP (Common Hardware Reference Platform)

Based on Open Firmware

RTAS(Run-Time Abstraction Service)Hides machine dependent operations behind a machine independent interface, which the operating system can call synchronous.

System Firmware =LLFW + Open Firmware + RTAS

Operating System

Open Firmware

Low-LevelFirmware

Hardware Hardware

Operating System

BOOT-TIME RUN-TIME

RTAS



Overview of available Options – RPA (RISC Platform Architecture)

Based on CHRP

Hypervisor– partitions machine resources

– enables multiple operating systems

– space for hardware dependent patches

– only one Hypervisor instance exitsfor all operating systems

Partition Firmware =Open Firmware + RTAS

Hypervisor

OperatingSystem

(A)

OpenFirmware

Low-LevelFirmware

Hardware Hardware

Operating System(A)

BOOT-TIME RUN-TIME

RTAS

OpenFirmware

OperatingSystem

(B)

Hypervisor

Operating System(B)

RTAS

Hypervisor



LinuxBIOS

Hardware

Bootstrap / Startup Code

LinuxBIOS

Linux

ADLO

Linux

Bochs Bios

Boot Manager

Operating System(Win2k, BSD, Linux)

ELF Loader ELF Loader

Boot Manageror OpenBIOS

Linux Kernel(over Ethernet or

raw disk i/o)

Linux

Linux Kernel

ELF Loader

Linux Kernel

Linux Kernel

ELF Loader

kexec, LOBOS,2 kernel monte

T

T

O

T

T

T

O optional

T transient



OpenBIOS

MaintainerStefan Reinauer and Patrick Mauritz

Main GoalTo get a 100% compliant Open Firmware boot firmware.

Current FunctionOpenBIOS could be executed under a boot manager or LinuxBIOS.

File System SupportSupport adopted from Grub and libhfs.

PPC SupportRudimentary available from the Mac-On-Linux project.

Operating System

OpenBIOS(100% Open Firmware compliant)

Low-LevelFirmware

Hardware Hardware

Operating System

BOOT-TIME RUN-TIME



Complete Boot Process- Phase 1

Phase 1Service Processor

Phase 2Low-Level Firmwareand Open Firmware

Time

IBM JS20 specificHardware initialization

Processor StartupSequence andinitialization of

Processors in SMP Mode

U3 (Memory controller)initialization, inclusive

setup of theElastic Interface

C Program-Code

PPC 970 PPC 970

U3

AMD 8131AMD 8111SIO

PC87417

GbitBCM5704S

Memory

IDE

IDE

Flash

ServiceProcessor

H8 C



Complete Boot Process - Phase 2


Phase 3Linux Boot-Process

ClientInterface

Time

createDevice-Tree

I/O setup andinitialization

Configurationsetup

Boot Deviceconfiguration

Network

Harddisk

initiatesOS Boot

C Program-Code

PPC 970 PPC 970

U3

AMD 8131AMD 8111SIO

PC87417

GbitBCM5704S

Memory

IDE

IDE

Flash

ServiceProcessor

H8 C



Complete Boot Process - Phase 3


Phase 3Linux Boot-Process

ClientInterface

initiatesOS Boot

Low-LevelSetup

copyDevice-Tree

relocate LinuxKernel from

higher to lowerMemory

(OF is notlonger

available)

Time

Initiate runtimeroutines

C Program-Code

PPC 970 PPC 970

U3

AMD 8131AMD 8111SIO

PC87417

GbitBCM5704S

Memory

IDE

IDE

Flash

ServiceProcessor

H8 C

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