© 2011 Altera Corporation—Confidential Embedded Linux Hands-on Training For Embedded RSC and Specialists Nick Ni Embedded Applications Group

© 2011 Altera Corporation—Confidential

Embedded Linux Hands-on Training

For Embedded RSC and Specialists

Nick Ni

Embedded Applications Group


About me

Started at Altera (Embedded Applications) in May 2011- SoC FPGA Virtual Target + FPGA-In-the-Loop- Embedded software and SDK- OpenCL (after this trip)

Worked at Qualcomm as EDA consultant and Masters in University of Toronto Lived in 杭州 until 5 years old After that…

- 日本 : 10 years- Canada: 11 years- USA: Current

2


Let’s introduce yourself

Let’s briefly introduce yourself around the table

3


Objectives

To obtain basic Linux knowledge To feel comfortable with embedded Linux issues

with real silicon- Basic embedded Linux knowledge- Application development and debugging- Kernel driver development and debugging

4


Motivation

SoC FPGA soon shipping with Embedded Linux 3.3 kernel- Device drivers for all HPS hard IPs- Running Yocto for its build system- Android friendly

Expect customers to use Linux out-of-box

Write Linux drivers for their custom Ips Issues with driver/IP/silicon in context

of Linux

5


Requirements – NEEK Board

6


Requirements – Linux PC

7

Windows 7 PC- VirtualBox - VirtualBox image for CentOS 6

(provided) (~20GB)


Agenda

Agenda

Linux Basics

Introduction to embedded Linux

Building Linux Packages

Board Bring-up

Software Packages

Application development

Driver development

8


Linux Basics

9


What is Linux?

10

Linux – the kernel from www.kernel.org Linux Distribution – LOTS of packages (1000+)

- Mainly GNU Contribution

Linux Kernel

Linux Distribution

Perl

Make Toolchains

GCC/GDB

Media Libraries

Text Editor

http://www.kernel.org/


Why Customers choose Linux

Cost- Royalty free- Free tools- Free source code

Powerful Complete Modifiable Popular

- Huge Community

Portable

11


Embedded Linux Usage

12


Linux Distributions

Operating systems including a large collection of software applications such as word processors, spreadsheets, media players, and database applications.

consist of - the Linux kernel- a set of libraries and utilities from the GNU Project

Some distributions optimize for size (embedded)- use more compact libraries (i.e. GNU utilities, such as BusyBox, uClibc

, or newlib

Over 300 active distributions http://en.wikipedia.org/wiki/Comparison_of_Linux_dis

tributions13

http://en.wikipedia.org/wiki/Operating_system

http://en.wikipedia.org/wiki/Linux

http://en.wikipedia.org/wiki/GNU_Project

http://en.wikipedia.org/wiki/BusyBox

http://en.wikipedia.org/wiki/UClibc

http://en.wikipedia.org/wiki/Comparison_of_Linux_distributions

http://en.wikipedia.org/wiki/Comparison_of_Linux_distributions


Popular desktop distributions

14


uClinux

Used for Nios-II *was* a fork of the Linux kernel for

microcontrollers (in embedded systems) without a memory management unit (MMU).

Integrated in mainline kernel from 2.5.46 Consists of patches and tools for microcontrollers. Consists of small-size library packages

- busybox- dropbear- gdbserver- …

15

http://en.wikipedia.org/wiki/Fork_(software_development)

http://en.wikipedia.org/wiki/Linux_(kernel)

http://en.wikipedia.org/wiki/Microcontroller

http://en.wikipedia.org/wiki/Embedded_system

http://en.wikipedia.org/wiki/Memory_management_unit


Let’s play around with Linux!

You should already have VirtualBox installed

Load CentOS 6 VirtualBox Image

Right click and “open terminal”

16


Getting Help

Command manual- % man <command>- E.g. % man tar

Command help- % <command> --help

17


Command Options

-a = lists all the files and directories, even hidden ones (e.g. /home/user/.bashrc)

-l = lists the full detail about all the files and directories

-d = lists the directory -c = don’t create file if it already present -f = force -k = block Size -R = recursive -t = type -V = version.

18


Package Installation

Different distributions use different installers

19

Distribution

CentOS YUM

RedHut YUM

DEBIAN APT

UBUNTU APT

FEDORA YUM

Look at YUM Help to see how to use YUM


Linux File Properties

Each file has<dir><root rwx><group rxw><user rxw> <directories> <owner> <group> <size> <last

modified date> <filename>

20


User and Privileges

Variety of commands for user/privilege control

21

Command Functionality

Chmod Change Permission

Chown Change Owner

Chgrp Change Group

Su Switch User

Sudo “Root” Mode

e.g.Change permission to read/exec for user/group and full access to root% chmod 755 <file>Change the owner of file% chown <new user> <file>Switch current user to ROOT% sudo su -


File Access Commands


grep Search a string in a list of files

echo output a string (to console by default)

cat Read and output contents of a file (to console by default)

more File viewing

less File viewing with more features (better for large files)

touch Update timestamp of a file

find Find files

22

e.g.Search “integer” in any files in current directory (ignore subdirectories)% grep integer ./*Search “integer” in two files called “file1” and “file2”% grep integer file1 file2Output “hello world” to console% echo “hello world”Read file content of “file1”% cat file1


I/O Redirection


>> Redirect and append to another output target

< Redirect from another input source

| Pipe output of a command as input of another command

> Rediret to another output target

23

e.g.

Write “hello” to “file1”

% echo “hello” > file1

Append “world” to “file1”

% echo “world” >> file1

Send stderr to stdout

% grep * 2>&1

Display the contents of a directory using “less” command

% ls | less


Other useful Information

% history- Shows you your command history

Bash start-up script- Located in ~/.bashrc- Add your commands to be run automatically when opening a console

% ifconfig- Networking information

% ps- View the processes currently running- e.g. ps aux | grep <user> = all <user>’s running processes

% kill- kill a process. (kill -9 if kill doesn’t work)

% top- View the CPU usage of processes

% dmesg- Displays kernel messages. Useful for driver development and kernel debugging

More info on http://www.systemverilog.in/pdf/LINUX-KACPER.pdf and google

24

http://www.systemverilog.in/pdf/LINUX-KACPER.pdf


Pop Quiz

25

What do the commands below do?% find . | xargs grep string

% grep int ./*/*.c 2> /tmp/log

% ls –l | grep “\.txt$”

% tar czvf /var/snapshot-$(date +%Y%m%d).tar.gz /home/devel

How do you list out all header files (.h) under current directory and sort them in ascending size


Linux File System

Three types of files- Regular Files contains a sequence of bytes that generally corresponds to

code or data.- Directory Files contains an entry for every file and subdirectory that it is

placed.- Device Files correspond to the printers or other devices connected to the

system.

26


Linux Directories

/bin = the binaries which are needed to run LINUX. /boot = all the files required for booting LINUX on

system. /dev = the devices for all the files. /etc = the configuration files of the various software. /home = like My Documents in Windows. /lib = the libraries required for the system files. /lost+found = files which are damaged or which are

not linked to any directory (e.g. due to the incorrect shutdown)

/mnt = where we mount the devices and other files /opt = optional softwares are installed. /root = The directory for the user root /proc = represent the current state of the kernel /sys = exports information about devices and drivers

from the kernel device model to user space, and is also used for configuration

27

http://en.wikipedia.org/wiki/User_space


Exercise: Installing GVIM

Search for the package “vim-X11” using YUM- % yum search <package name>

Install GVIM using YUM (with SUDO in the front)- % sudo yum install <package name>

Run GVIM

Uninstall GVIM- % sudo yum remove <package name>

Download GVIM Package from internet Install the downloaded Package locally using YUM

- % sudo yum –Uvh <package name>.rpm

Run GVIM28


Exercise: Write a Shell Script

Your file should begin with “#!/bin/sh”

Write a shell script that creates a file that looks like:

29

********************************************************** This file contains all files with .c extension under <current directory> containing word “string” **********************************************************<file 1><file 2>…


Agenda

Agenda

Linux Basics



Board Bring-up

Software Packages


Driver development

30


High-level Architecture

31

Hardware


Software Components

Cross-compiler- Compiler that runs on the development machine, but generates

code for the target

Bootloader- Started by the hardware, responsible for basic initialization,

loading and executing the kernel

Linux Kernel- Contains the process and memory management, network stack,

device drivers and provides services to userspace applications

C library- The interface between the kernel and the userspace applications

Libraries and applications

32


Device Tree

A data structure for describing hardware

No need to hard code every detail of a device into an OS

Hardware details are passed to OS at boot time

33


Root filesystem

several filesystems are mounted and create a global hierarchy of files and directories

A particular filesystem, the root filesystem, is mounted as / containing- all the libraries- applications- data

The kernel is usually kept separate Usually Root Filesystem is stored in non-

volatile storage (e.g. Flash) Ramdisk filesystem is also possible which

runs off memory- Changes do not get saved!

34


Developing Embedded Linux

Board Support Package development- A BSP contains a bootloader and kernel with the suitable device drivers

for the targeted hardware

System integration- Integrate all the components, bootloader, kernel, third-party libraries and

applications and in-house applications into a working system

Development of applications- Normal Linux applications, but using specifically chosen libraries

35


36

Power Cycle

read bootloader from a media (Flash) and copy to RAM

bootloader initializes HW and reads compressed kernel

Read Device Tree blob to decide how to initialize drivers

Mount root filesystem from a media (Flash)

Runs the program init based on /etc/inittab

Runs user init /etc/rc

Boot Sequences

Uncompress initialize kernel


Agenda

Agenda

Linux Basics



Board Bring-up

Software Packages


Driver development

37


uClinux

Linux distribution project Originally for non-MMU microcontrollers Now include

- Linux kernel 2.6+- User applications- Libraries- Toolchains

We build uClinux for Nios-II running on NEEK!

38


Images you will build

Linux kernel image- vmImage (Gunzip’ed binary for U-

boot booting)- vmlinux (ELF)

U-Boot Bootloader image

- u-boot (elf)- u-boot.bin (binary)

Root filesystem- rootfs.jffs2 (JFFS2 Filesystem)- rootfs.initramfs (Raw)- rootfs.initramfs.gz (Gunzip’ed raw)

39


40

Configure uClinux with- vendor- processor- platform

Configure Linux Kernel

Configure User Applications/Library

Build all images *except* u-boot

Re-Build Linux Kernel with ramdisk-initramfs_data.cpio-linux.initramfs.gz

Build User app/lib-rootfs.initramfs-rootfs.initramfs.gz-rootfs.jffs2

Build linux kernel- vmlinux- vmlinux.bin- vmlinux.gz- vmImage

uClinux Build Flow

Generate and customize device tree from .sopcinfo

Under the hood


U-Boot Build Flow

U-Boot needs to be built independently from Linux Kernel and Root filesystem

41

Generate and Customize U-Boot header file from sopcinfo

Build u-boot


Cross-Compiler

Need to build cross-compiler for Nios-II- Runs on x86 PC- Outputs Nios-II instructions

Already set up in the Vbox image- Try % which nios2-linux-gnu-gcc- Try % echo $PATH

42


Exercise: Generate Device Tree

A tools from Nios-II community called sopc2dts can convert “most of” .sopcinfo to device tree and header files- % cd ~/nios2-linux/tools/sopc2dts- % java -jar sopc2dts.jar --gui- In the GUI, choose file: <eth_std_main_system.sopcinfo file from ethernet

standard Quartus II project for NEEK> - Select following in the GUI:

43

BoardinfoGeneral

Select master: cpu:cpuMemory nodes: select both memory (CTRL key)

Click ApplyKernel Bootargs: debug console=ttyJ0,115200

Click ApplyEthernet

Highlight tse_macEdit MAC-address

Click ApplyOutput

Save As: <your choice of name>.dts


Exercise: Customize Device Tree

Fix the following bold parts in generated .dts manually to fix the tool bug

44

ext_flash: flash@0x100000 { #address-cells = < 1 >; #size-cells = < 1 >; compatible = "ALTR,cfi_flash-altera_generic_tristate_controller", "cfi-flash"; reg = < 0x00100000 0x00b00000 >; bank-width = < 2 >; device-width = < 1 >; }; //end flash@0x0 (ext_flash)…

ethernet_subsystem_ethernet_bridge: bridge@0x800a000 {compatible = "ALTR,avalon-12.0","simple-bus";reg = < 0x800a000 0x3000>;#address-cells = <1>;#size-cells = <1>;ranges = <0x00000000 0x0800A000 0x00000400

0x00000440 0x0800A440 0x000000400x00000400 0x0800A400 0x000000400x00002000 0x0800C000 0x00001000>;

ethernet_subsystem_tse_mac: ethernet@0x0 {

compatible = "ALTR,tse-12.0","ALTR,tse-1.0";reg = < 0x0 0x400 0x400 0x40 0x440 0x40 0x2000 0x1000>;interrupt-parent = < &cpu >;interrupts = < 1 6 >;


Exercise: Configure uClinux

Go to uClinux directory and start configuration tool- % cd ~/nios2-linux/uClinux-dist- % make menuconfig- Select “Vendor/Product Selection”- Select Altera for Vendor and nios2 for Products- Press “Exit” to go back one level and Select “Kernel/Library/Defaults”- Select “Customize kernel Settings” and “App/Lib Settings”- Exit and save when prompted

45


Exercise: Configure Linux Kernel

Menuconfig of linux kernel should appear soon after Select the followings

46

Platform OptionsMem base: 0x10000000Compile and link device tree into kernel imageAdd path to Device tree source fileEnable MUL/ DIV instruction

Processor Type and FeaturesUnselect “Ignore kernel command string from DTB”

Device DriversNetwork device support

Ethernet driver supportAltera DeviceAltera Triple-Speed Ethernet Mac support

Character devicesEnable /dev/kmem virtual device supportSerial drivers

Altera JTAG UART supportAltera JTAG UART console support

Memory Technology Device (MTD) supportMapping drivers for chip access

Flash device in physical memory map based on OF description

Exit and save. If asked for any questions, just enter for default choice


Exercise: Configure Filesystem

uClinux Distribution Configuration menuconfig will appear

Select BusyBox -> Networking Utilities -> httpd Exit and Save

47


Exercise: Build Linux Kernel and Filesystem Simply type “make” in uClinux-dist directory to

kick-off the build process On VirtualBox, it will take 30-60 min Native box would be much faster (~10min)

48


Exercise: Building U-Boot

U-Boot needs to be built separately Use sopc2dts to generate Header file instead of .dts file (No need to

do this for this lab) U-Boot is already configured and .h generated in the Vbox image

- u-boot/include/configs/3c25_eth_std_main_system.h- u-boot/board/altera/nios2-generic/3c25_eth_std_main_system.h

Simply build for now- % cd ~/nios2-linux/u-boot- % make CROSS_COMPILE=nios2-linux-gnu- 3c25_eth_std_main_system_config- % make CROSS_COMPILE=nios2-linux-gnu-

You should see U-boot and U-boot.bin built

49


Exercise: You are ready to bring-up NEEK with Linux! You should have:

50


Agenda

Agenda

Linux Basics



Board Bring-up

Software Packages


Driver development

51


52

Convert U-Boot image to a BootROM image and program to CFI flash

Boot U-Boot and set up ethernet and erase sections of CFI flash

Fetch RootFS, Kernel and device tree from TFTP server and program them to CFI

Hit reset and linux boot up!

Board Bring-up Flow


CFI Flash Partitioning

BootROM / U-Boot (0x0)

RootFS (0x100000)

U-Boot Env (0xC00000)

Device Tree(0xD00000)

Linux Kernel (0xE00000)

53

U-Boot View

Linux View


Exercise: Set up a Shared Folder

To pass software images to Windows 7

In VirtualBox menu, go to, Devices -> Shared Folders- Change folder path to “shared_folder” in the

distributed package

In Linux, mount the shared drive to /mnt- % sudo mount –t vboxsf shared_folder /mnt

Copy the built images to /mnt- uClinux-dist/images/*- u-boot/u-boot*- uClinux-dist/linux-2.6.x/arch/nios2/boot/

system.dtb

54


Exercise: Install TFTP server

TFTPD64 http://tftpd32.jounin.net/tftpd32_downl

oad.html

Set your “shared_folder” as TFTP directory

IMPORTANT: Your host Windows machine may have firewall that prevents tftp access from outside

If it does NOT work, try allow “tftpd” to go through firewall in “Windows Firewalls”55

http://tftpd32.jounin.net/tftpd32_download.html

http://tftpd32.jounin.net/tftpd32_download.html


Exercise: Program U-Boot asBootROM image

56

In NiosII Command Shell,- Program FPGA with SOF file in shared_folder\niosii-ethernet-

standard-3c25\niosii-ethernet-standard-3c25.sof- % nios2-configure-sof <.sof>

- Convert U-Boot as BootROM dataGo to shared_folder% elf2flash --input u-boot --output u-boot.flash --base 0xe0000000 --end

0xe0ffffff --reset 0xe0000000 --boot=<path to nio2eds>/components/altera_nios2/boot_loader_cfi.srec

- Download into Flash% ../nios2-flash-programmer --base=0xe0000000 u-boot.flash

- Start Nios2-terminal and hit “CPU reset” on the board- You should see U-Boot booted up


Exercise: Program Flash Contents

In U-Boot- Set environmental variables

% setenv ipaddr <NEEK IP> % setenv serverip <Host IP> % setenv ethaddr <NEEK MAC> % setenv bootcmd 'set bootargs root=/dev/mtdblock0 rootfstype=jffs2 rw; cp.b e0d00000 d1000000 20000;

bootm e0e00000 – d1000000'

- Program RootFS % protect off all % erase e0100000 +00f00000 % tftp d1000000 rootfs.jffs2 % cp.b d1000000 e0100000 $filesize

- Program Kernel and Device Tree % tftp d1000000 system.dtb % cp.b d1000000 e0d00000 $filesize % tftp d1000000 vmImage % cp.b d1000000 e0e00000 $filesize

- Save U-Boot environments % saveenv

57

http://alterawiki.com/uploads/c/c4/Rootfs.jffs2-3c1120


Exercise: Cross your fingers!

Hit “CPU reset” on the board and… Hope Linux boots completely!

58


Agenda

Agenda

Linux Basics



Board Bring-up

Software Packages


Driver development

59


Software Packages

Pre-built Application and Library codes

Access hardware through Linux Kernel System Call API

Thousands of packages already exist by the Open-Source community- Busybox- Web browser- Text editor- SSH - Development tools (e.g. gcc/gdb)- Compression- Graphics- Audio- …

60


Busybox

The Swiss Army Knife of Embedded Linux Tiny versions of many common UNIX utilities Replacements for most of the utilities in GNU fileutils,

shellutils, etc. Generally have fewer options than their full-featured

GNU cousins Provides a fairly complete environment for any small

or embedded system. Designed for size-optimization and limited resources

in mind. http://busybox.net/

61

http://busybox.net/


Methods to build software packages

Option 1: Build manually from source files- Download the source files- Configure to cross-compile into the target hardware- Build it- Install it- Copy it to the filesystem

Option 2: Use distribution to automatically build it- Configure uClinux to include the package- Build uClinux (automatically configure/build/install/copy to FS for

you)

62


Exercise: Build SSH server

Go to nios2-linux/dropbear Create and go into a new dir called

build-dropbear-0.52 Configure/build/install dropbear to

cross compile for Nios-II% cd build-dropbear-0.52% ../dropbear-0.52/configure --host=nios2-

linux-gnu --with-zlib=/home/student/nios2-linux/uClinux-dist/lib/zlib prefix=/home/student/linux-labs/dropbear/install-dropbear-0.52

% make% make install

63


Exercise: Build SSH server (cont’d)

Copy install-dropbear-0.52 to /mnt On NEEK

- Set up ethernet with an static IP% ifconfig eth0 <NEEK IP given to you in the class>- fetch the all the files in install-dropbear-0.52/bin and /sbin

to /bin and /sbin in Nios-II linux filesystem% tftp -g <tftp server ip> -r <file name> -l

</bin/dropbear or /bin/dropbearkey>- Generate Host RSA key% mkdir -p /etc/dropbear% dropbearkey -t rsa -f

/etc/dropbear/dropbear_rsa_host_key- Set root password since SSH server needs one% passwd- Start SSH server% dropbear

Now use a SSH client program on your workstation (e.g. Putty) and connect to:- root@<NEEK IP>

64


Exercise: Use Distribution to build

Go to uClinux-dist and select “dropbear” in menuconfig- % cd uClinux-dist- Select “Kernel/Library/Def Sel” -> Customize App/Lib Settings”- Save and Exit- Select “Network App” -> “dropbear”- Save and Exit- % make

Once finished, look into romfs/etc/dropbear and romfs/etc/inetd.conf to see what got generated

65


Exercise: Use Distribution to build SSH (Cont’d)

66

Copy the built images to /mnt- uClinux-dist/images/*- uClinux-dist/linux-2.6.x/arch/nios2/boot/system.dtb

In NiosII Command Shell,- Start Nios2-terminal and hit “CPU reset” on the board- You should see U-Boot booted up, press any key to interrupt U-Boot

In U-Boot- Program RootFS

% protect off all% erase e1000000 +00b00000% tftp d1000000 rootfs.jffs2% cp.b d1000000 e0100000 $filesize

Hit “CPU Reset” on the board and linux should boot up with SSH server automatically started

http://alterawiki.com/uploads/c/c4/Rootfs.jffs2-3c1120


Agenda

Agenda

Linux Basics



Board Bring-up

Software Packages


Driver development

67


Application

Uses In-house/third-party Libraries and Standard C Library

No direct access to Hardware Resources

Talk to drivers through file interface- /dev/mtdblock0 = 1st partition of a Storage device- /dev/ttyS0 = 1st UART- /dev/ttyJ0 = 1st JTAG UART- …

68


Pop Quiz: Use JTAG UART driver

Use nios-terminal and a SSH client connected to Nios-II to talk to each other using /dev/ttyJ0

69


Pop Quiz: Simplest Solution

nios2-terminal -> SSH client- In SSH client

% cat /dev/ttyJ0- In nios2-terminal

% echo “<string>” > /dev/ttyJ0

SSH client -> nios2-terminal- In SSH client

% echo “<string>” > /dev/ttyJ0

70


Linux Application

What you write- Source files .c- Header files .h- Makefile

What are provided- Standard C libraries .a or .so

Usually located inside the toolchain ~/nios2-linux/toolchain-mmu/x86-linux2/nios2-linux-gnu/libc Compiler will look for headers and libraries to link to in the directory by

default- User libraries

Configured and built by user (manually or with distribution) Usually located in some user specified location For uClinux, it’s in uClinux-dist/user Need to explicitly specify the header and library location in Makefile

71


Linux Application Build Flow

72

.c/.h

.a/.so

.o

.a/.so

GCC

.c/.h

.o

GCC

.c/.h

.o

GCC

.c/.h

.o

GCC

AR

Binary / ELF

GCC GCC GCC

User Library Application

Standard C Lib


Compiler and Useful Tools

Tool Description

GCC Compiler

GDB Debugger

DDD GDB with GUI

OBJDUMP Display information from object files

NM List symbols from object files

AR Create, modify, and extract from archives

OBJCOPY Copy and Translate object files

STRIP Discard symbols from object files

73

Native desktop tools without any prefix Cross-compiler adds prefix

e.g. nios2-linux-gnu-gcc e.g. arm-none-linux-gnueabi-objdump


I/O Libraries in Standard C

74

API Description API Descriptionfopen opens a file vfscanf a file stream or a buffer using variable argument listfreopen opens a different file with an existing stream vsscanffflush synchronizes an output stream with the actual file printf prints formatted byte/wchar_t output to stdout,fclose closes a file fprintf a file stream or a buffersetbuf sets the buffer for a file stream sprintfsetvbuf sets the buffer and its size for a file stream snprintf

fwideswitches a file stream between wide character I/O and narrow character I/O vprintf prints formatted byte/wchar_t output to stdout,

fread reads from a file vfprintf a file stream, or a buffer using variable argument listfwrite writes to a file vsprintffgetc

reads a byte/wchar_t from a file streamvsnprintf

getc ftell returns the current file position indicatorfgets reads a byte/wchar_t string from a file stream fgetpos gets the file position indicatorfputc

writes a byte/wchar_t to a file streamfseek moves the file position indicator to a specific location in a file

putc fsetpos moves the file position indicator to a specific location in a filefputs writes a byte/wchar_t string to a file stream rewind moves the file position indicator to the beginning in a filegetchar reads a byte/wchar_t from stdin clearerr clears errorsgets reads a byte string from stdin feof checks for the end-of-fileputchar writes a byte/wchar_t to stdout ferror checks for a file error

puts writes a byte string to stdout perrordisplays a character string corresponding of the current error to stderr

ungetc puts a byte/wchar_t back into a file stream remove erases a filescanf reads formatted byte/wchar_t input from stdin, rename renames a filefscanf a file stream or a buffer tmpfile returns a pointer to a temporary filesscanf tmpnam returns a unique filenamevscanf reads formatted input byte/wchar_t from stdin, strcmp compares two c strings.

Add the following line in your source file- #include <stdio.h>

See the detailed API syntax- % man <API>

http://c-p-p.net/c/stdio.h/fopen

http://en.cppreference.com/w/cpp/io/c/vfscanf

http://c-p-p.net/c/stdio.h/freopen

http://en.cppreference.com/w/cpp/io/c/vsscanf

http://c-p-p.net/c/stdio.h/fflush

http://c-p-p.net/c/stdio.h/printf

http://c-p-p.net/c/stdio.h/fclose

http://c-p-p.net/c/stdio.h/fprintf

http://c-p-p.net/c/stdio.h/setbuf

http://c-p-p.net/c/stdio.h/sprintf

http://c-p-p.net/c/stdio.h/setvbuf

http://en.cppreference.com/w/cpp/io/c/snprintf

http://c-p-p.net/c/stdio.h/fwide

http://en.cppreference.com/w/cpp/io/c/vprintf

http://c-p-p.net/c/stdio.h/fread

http://en.cppreference.com/w/cpp/io/c/vfprintf

http://c-p-p.net/c/stdio.h/fwrite

http://en.cppreference.com/w/cpp/io/c/vsprintf

http://c-p-p.net/c/stdio.h/fgetc

http://en.cppreference.com/w/cpp/io/c/vsnprintf

http://c-p-p.net/c/stdio.h/getc

http://c-p-p.net/c/stdio.h/ftell

http://c-p-p.net/c/stdio.h/fgets

http://c-p-p.net/c/stdio.h/fgetpos

http://c-p-p.net/c/stdio.h/fputc

http://c-p-p.net/c/stdio.h/fseek

http://c-p-p.net/c/stdio.h/putc

http://c-p-p.net/c/stdio.h/fsetpos

http://c-p-p.net/c/stdio.h/fputs

http://c-p-p.net/c/stdio.h/rewind

http://c-p-p.net/c/stdio.h/getchar

http://c-p-p.net/c/stdio.h/clearerr

http://c-p-p.net/c/stdio.h/gets

http://c-p-p.net/c/stdio.h/feof

http://c-p-p.net/c/stdio.h/putchar

http://c-p-p.net/c/stdio.h/ferror

http://c-p-p.net/c/stdio.h/puts

http://c-p-p.net/c/stdio.h/perror

http://c-p-p.net/c/stdio.h/ungetc

http://c-p-p.net/c/stdio.h/remove

http://c-p-p.net/c/stdio.h/scanf

http://c-p-p.net/c/stdio.h/rename

http://en.wikipedia.org/wiki/Rename_(computing)

http://c-p-p.net/c/stdio.h/fscanf

http://c-p-p.net/c/stdio.h/tmpfile

http://c-p-p.net/c/stdio.h/sscanf

http://c-p-p.net/c/stdio.h/tmpnam

http://en.cppreference.com/w/cpp/io/c/vscanf

http://c-p-p.net/c/stdio.h/strcmp


Application Driver Interface

/* Open UART device at /dev/ttyAL0 */

fd = fopen("/dev/ttyAL0", "r+w”);

/* Write a char* prompt to UART */

count = fwrite(prompt, 1, strlen(prompt), fd);

/* Read a line from UART device */

fgets(input, size, fd);

/* Print to debug console. Default to JTAG Uart */

printf(%s: Read %s\n”, __func__, input);

/* Close UART device */

fclose(fd)

75


Makefile

CC = nios2-linux-gnu-gccCFLAGS = -gTARGET = uart_appobjs = uart_app.o

all: $(TARGET)

uart_app: $(objs) $(CC) $(CFLAGS) $(objs) -o $@

.c.o: $(CC) $(CFLAGS) $< -c -o $@

clean: rm -rf $(objs) $(TARGET)

76

Target

TAB


Application Debugging

Use a debug server to run your application under development

Use GDBSERVER for debugging using GDB Through TCP/IP protocol Already built into the root filesystem Often called “Run-Mode Debugging”

77


Exercise: Write a UART Console

Use /dev/ttyAL0 Use Standard C I/O libraries Write an shell application that

- prompt “##UART Shell>>” and wait for user input into JTAG UART- Start parsing the user input string upon a newline ‘\n’- Implement following functions:

##UART Shell>> keyfind <dir> <keyword>- where <dir> is absolute path to a parent directory where you start you search

from- <keyword> is a string you are looking for

##UART Shell>> exit- End application and go back to standard linux console

Write a Makefile for building the final application ELF/Binary

78


Exercise: Write a UART application (Cont’d) Upload the ELF to running Linux via TFTP Run “gdbserver” on Nios-II linux

- % gdbserver host:2345 <ELF file>

Use DDD to debug from your VirtualBox- % ddd –debugger nios2-linux-gnu-gdb <ELF file>- In DDD console:

% target remote <NEEK IP>:2345

Use Putty as host receiver with - Serial/115200/8-N-1/No HW Flow Ctrl

…and Good luck!

79


Agenda

Agenda

Linux Basics



Board Bring-up

Software Packages


Driver development

80


User space and Kernel space

Kernel space- Linux manages the machine's

hardware, offering the user a System Call Interface

- Any subroutines or functions forming part of the kernel (modules and device drivers, for example)

User space- End-user programs, like the UNIX

shell or other GUI based applications

- Do not directly interact with Hardware but through the System Call Interface

81


System Call Interface

Hardware devices are seen as device files from user space- /dev/ttyJ0- /dev/sda1 …

Basic System Call interface are like file operations

82

System Call Description

Insmod (system) Load driver module

Open Open device

Read Read from device

Write Write to device

Close Close device

Rmmod (system) Unregister driver module


System Call Interface in Driver

These functions will be called by user application - Like the one you wrote in the UART application

83

int uart_open(struct inode *inode, struct file *filp); int uart_release(struct inode *inode, struct file *filp); ssize_t uart_read(struct file *filp, char *buf, size_t count, loff_t *f_pos); ssize_t uart_write(struct file *filp, char *buf, size_t count, loff_t *f_pos); void uart_exit(void); int uart_init(void);

/* Structure that declares the usual file */ struct file_operations uart_fops = { read: uart_read, write: uart_write, open: uart_open, release: uart_release };


Sysfs Interface

RAM-based filesystem Provides a means to export

- Kernel data structures- Attributes- Linkages between them to userspace

Some devices allow you to control HW directly by writing to sysfs- E.g. echo 1 > /sys/devices/platform/asus_laptop/wlan - E.g. echo file > /sys/devices/platform/usb-otg/gadget/file

84


Sysfs Interface in Driver

static ssize_t irqgen_show_interval(struct device *dev, struct device_attribute *attr, const char *buf);static ssize_t irqgen_store_interval(struct device *dev, struct device_attribute *attr, const char *buf, size_t size);

static struct class *irqgen_class;static struct device *dev;

static DEVICE_ATTR(interval, 0644, irqgen_show_interval, irqgen_store_interval);

static int __init custom_irqgen_driver_init(void){

irqgen_class = class_create(THIS_MODULE, "irqgen");

dev = device_create(irqgen_class, NULL, MKDEV(MAJOR, MINOR), NULL, "irqgen");

result = device_create_file(dev, &dev_attr_interval);

return 0;}

static void __exit custom_irqgen_driver_exit(void){

device_remove_file(dev, &dev_attr_interval);device_unregister(dev);class_destroy(irqgen_class);

}

85


/dev/mem Interface

/dev/mem- a special file that provides access to the physical memory of the computer.

/dev/kmem- a special file that provides access to the virtual address space of the

operating system kernel, excluding memory that is associated with an I/O device.

/dev/allkmem- a special file that provides access to the virtual address space of the

operating system kernel, including memory that is associated with an I/O device.

Use to examine and modify the system Warning: BAD THINGS can happen if you are NOT

careful. Use with CARE.

86


/dev/mem usage example

fd = open(/dev/mem”, O_RDWR|O_SYNC);

// Map physical memory range of a peripheral memory map (0xE8000080 – 0xE800017f) to userspace memorymem = mmap(NULL, 0x100, PROT_READ|PROT_WRITE, MAP_SHARED, \ fd, 0xE8000080);

// Write to E8000084 in Peripheral register map*(mem+4) = 0x2f

// Read from E8000088 in Peripheral register mapvalue = *(mem+8);

87


Data passing

Never access data from userspace directly in kernel

Use following functions to copy to kernel space- unsigned long copy_from_user (void * to, const void __user *

from, unsigned long n);- unsigned long copy_to_user (void __user * to, const void * from,

unsigned long n);

88


Device Files

Usually sit in /dev type

- block (b)- character (c)- unbuffered character (u)- FIFO (p)

Major number Minor number Use “mknod” to create a

device file- % mknod /dev/irqgen0 c 251 0

89


Allocating kernel resource

Reserve a major/minor number Register System Call Interface

90

struct file_operations irqgen_fops = {read: irqgen_read,write: irqgen_write,open: irqgen_open,release: irqgen_release

};

Int irqgen_major = 251; // Set to 0 for auto-allocation

result = register_chrdev(irqgen_major, "irqgen", &irqgen_fops);if(result < 0){

printk(KERN_ALERT "irqgen: cannot obtain major number %d\n", irqgen_major);

return result;}


Interrupt Registration

91

Register interrupt service routine with a IRQ line

static irqreturn_t irqgen_interrupt_handler(int irq, void* dev_id){…return IRQ_RETVAL(1);

}

request_irq(IRQ_NUM, irqgen_interrupt_handler, 0, “irqgen0”, NULL);


Hardware Access

Remap physical memory mapped I/O base to Virtual Address- virt_addr = ioremap(base, size)

Low-level hardware access- writel(data, virt_addr+offset)- readl(virt_addr+offset)

92


Building Kernel Driver

Loadable Kernel Module- Build as a loadable module (.ko)- Select (M) instead of (*) in menuconfig for a driver OR- Build it externally with Makefile pointing to the kernel source- Prefered during development!

Statically build into the kernel image- Add a driver to kernel source- Include the driver in menuconfig- Re-build linux kernel image

93


Loadable Kernel Module

obj-m := <your driver source file>.o …

CROSS_COMPILE = nios2-linux-gnu-KDIR := <dir to linux-2.6.x>ARCH := nios2

all:$(MAKE) ARCH=$(ARCH) CROSS_COMPILE=$(CROSS_COMPILE) -C $(KDIR)

M=`pwd` modules

clean:rm $(obj-m)rm *.korm *.mod.*rm *.symversrm *.order

94

Makefile points to kernel source Generate a .ko file Load .ko file in running Linux using “insmod”


Debugging Kernel Code

Printk()! (Most Common) Nios II GDB Server

- Uses JTAG to debug in instruction set level- Uses “nios2-gdb-server”

Lauterbach Trace32- Uses JTAG and MICTOR connectors- Able to capture “Instruction Trace”

KGDB- Source level debugger for kernel- Uses serial port (RS232) to communicate with host- Intrusive to the kernel source (need to add package)

Often called “Stop-Mode Debugging”

95


Debugging using Nios II GDB Server

Compile Linux kernel with “Compile the kernel with debug info” (already done for you in your vmlinux)- (menuconfig) Kernel hacking ->

Boot Linux on Nios II In Host, start with

- % nios2-gdb-server –tcpport <port>

In Linux VirtualBox, start GDB with vmlinux built in uClinux/linux-2.6.x- % nios2-linux-gnu-gdb vmlinux- (GDB) % target remote <host IP>:<port>

Now you can debug any STATICALLY COMPILED kernel code/drivers

96


Debugging Loadable Kernel Module

It’s tricky because - the module gets loaded to a dynamic memory address during run-

time- Need to re-map all code/data segments in ELF file

Linux provides /sys filesystem which provide you the info- /sys/module/<driver name>/sections/

97


Debugging Loadable Kernel Module (cont’d) In VirtualBox

- Start GDB without ELF% nios2-linux-gnu-gdb

- Connect to nios2_linux_server- Remap ELF filePrai

(GDB) % add-file-symbol <your driver>.ko <.text address> -s .data <.data address> -s …

- Now GDB can debug the driver like other part of kernel

98


Debugging with KGDB

Warning! Very unstable with Virtual I/O RS232 to VirtualBox

Compile Linux kernel with KGDB - (menuconfig) kernel hacking -> KGDB: kernel debugger -> KGDB: use

kgdb over the serial console- (Already Done for you in the vmlinux image)

Reset the board and interrupt U-boot Modify U-Boot environments

- (U-boot) % setenv bootcmd 'set bootargs debug kgdboc=ttyAL0,115200 kgdbwait console=ttyJ0,115200 root=/dev/mtdblock0 rootfstype=jffs2 rw; cp.b e0d00000 d1000000 20000; bootm e0e00000 - d1000000‘

- (U-boot) % saveenv

Reset the board and let Linux Boot

99


Debugging with KGDB (cont’d)

Linux booting should pause at- ttyAL0 at MMIO 0x6000000 (irq = 2) is a Altera UART kgdb: Registered I/O

driver kgdboc. kgdb: Waiting for connection from remote gdb...

Quit any serial program like Putty On VirtualBox GUI, plug in the Serial-USB device On VirtualBox,

- Check which device file the serial cable is registered to (should be /dev/ttyUSB0)

- % dmesg- Run GDB- % nios2-linux-gnu-gdb –b 115200- (GDB) % target remote /dev/ttyUSB0- (GDB) % symbol-file linux-2.6.x/vmlinux

Now the GDB should work the same way

100


Final and Ultimate Exercise: Write Complete Software for a custom IP Programmable-interval interrupt generator IP

- See HDL file to find out how it works

Write a kernel driver Write an application which

- Change interrupt interval uniformly% irqgen_app uniform <interval in clk cycle>

- Change interrupt interval incre/decrementally% irqgen_app var <start interval> <end interval>

Also change interrupt interval using sysfs Debug application and driver and HW

(SignalTap)

101


Final and Ultimate Exercise Steps:

Programmable-interval interrupt generator IP- Open Qsys system “eth_std_main_system”- Look at IP called “ramdom_number_generator.v”- See HDL file to find out:

Software accessible register offsetsBit field definition IP base address (+0xE0000000 for Virtual Address)

102



Write a kernel driver- Initialize the interrupt interval and enable interrupts- write function to write new interval value- Implement sysfs interface- Start from template found in ~/linux-labs/linux-irqgen-driver/- Fill in all “TODO:” sections- Take a look at other drivers in ~/nios2-linux/linux-2.6/drivers for

examples- Search on web for examples or references

Build driver- Simply hit %make in ~/linux-labs/linux-irqgen-driver/- if successful, copy custom-irqgen-driver.ko to /mnt so TFTP

server can host the file

103



Load driver- TFTP to running linux on Nios-II

(nios2-linux) % tftp –g <host IP> -r custom-irqgen-driver.ko- Load the driver

(nios2-linux) % insmod custom-irqgen-driver.ko- If not yet exist, create /dev/irqgen0

(nios2-linux) % mknod /dev/irqgen0 c 251 0- When finished unload the driver

(nios2-linux) % rmmod custom-irqgen-driver

Test the interval modification using sysfs(nios2-linux) % echo <interval> > /sys/class/irqgen/irqgen/interval- Try 12500000 as interval and you should see a number printed on

screen every second

Debug Driver using nios2-gdb-server and printk()

104



Write an application which- Change interrupt interval uniformly

% irqgen_app uniform <interval in clk cycle>- Change interrupt interval incre/decrementally

% irqgen_app var <start interval> <end interval>- Start with templates found in ~/linux-labs/irqgen_app- Fill in all “TODO”- simply hit “make” in ~/linux-labs/irqgen_app- copy irqgen_app to /mnt so TFTP server can host it

Test application- TFTP to running Nios-II Linux- Run the two commands for irqgen_app shown above- Try 12500000 as interval for uniform and you should see a number printed on screen

every second- Try 12500 and 12500000 as intervals for var and you should see a number printed on

screen in changing interval

Debug application using “run-mode” gdbserver in nios-II linux

105


Optional Exercise: If you finish too fast and nothing better to do Add read interface to the IP

- Read 4KB RAM from 0x0 to 0xFFF

Enhance the kernel driver- read function to read current interval- add 2 more files in sysfs for reading “start” and “end” interval

Enhance the application which- Read current start/end interval

% irqgen_app status (example output) >> (Start – End) = (125000000 – 12500) clocks

Enhance the custom IP by adding “read” interface to read the RAM which stores interval values

106

© 2011 Altera Corporation—Confidential ALTERA, ARRIA, CYCLONE, HARDCOPY, MAX, MEGACORE, NIOS, QUARTUS and STRATIX words and logos are trademarks of Altera Corporation and registered in the United States and are trademarks or registered trademarks in other countries.

Thank You