[FE training-materials-updates] Start first Buildroot lab
Thomas Petazzoni
thomas.petazzoni at free-electrons.com
Tue Apr 21 18:21:11 CEST 2015
Repository : git://git.free-electrons.com/training-materials.git
On branch : master
Link : http://git.free-electrons.com/training-materials/commit/?id=b72aca7b19e5a2cf8edb49305a25b62465122d49
>---------------------------------------------------------------
commit b72aca7b19e5a2cf8edb49305a25b62465122d49
Author: Thomas Petazzoni <thomas.petazzoni at free-electrons.com>
Date: Tue Apr 21 18:20:43 2015 +0200
Start first Buildroot lab
Signed-off-by: Thomas Petazzoni <thomas.petazzoni at free-electrons.com>
>---------------------------------------------------------------
b72aca7b19e5a2cf8edb49305a25b62465122d49
.../beaglebone-black-serial-connection.jpg | Bin
labs/buildroot-basic/buildroot-basic.tex | 309 ++++++++++++++++++++-
2 files changed, 308 insertions(+), 1 deletion(-)
diff --git a/labs/kernel-board-setup/beaglebone-black-serial-connection.jpg b/labs/buildroot-basic/beaglebone-black-serial-connection.jpg
similarity index 100%
copy from labs/kernel-board-setup/beaglebone-black-serial-connection.jpg
copy to labs/buildroot-basic/beaglebone-black-serial-connection.jpg
diff --git a/labs/buildroot-basic/buildroot-basic.tex b/labs/buildroot-basic/buildroot-basic.tex
index 487b463..a42130b 100644
--- a/labs/buildroot-basic/buildroot-basic.tex
+++ b/labs/buildroot-basic/buildroot-basic.tex
@@ -1,4 +1,311 @@
\subchapter
{Basic Buildroot usage}
-{Objectives:}
+{Objectives:
+ \begin{itemize}
+ \item Configure a minimal system with Buildroot for the BeagleBone Black
+ \item Do the build
+ \item Prepare the BeagleBone Black for usage
+ \item Flash and test the generated system
+ \end{itemize}
+}
+\section{Setup}
+
+Go to the \code{$HOME/buildroot-labs/} directory.
+
+As specified in the Buildroot
+manual\footnote{\url{http://buildroot.org/downloads/manual/manual.html\#requirement-mandatory}},
+Buildroot requires a few packages to be installed on your
+machine. Let's install them using Ubuntu's package manager:
+
+\begin{verbatim}
+sudo apt-get install which sed make binutils gcc g++ bash patch \
+ gzip bzip2 perl tar cpio python unzip rsync wget libncurses-dev
+\end{verbatim}
+
+\section{Download Buildroot}
+
+Since we're going to do Buildroot development, let's clone the
+Buildroot source code from its Git repository:
+
+\begin{verbatim}
+git clone git://git.busybox.net/buildroot
+\end{verbatim}
+
+Go into the newly created \code{buildroot} directory.
+
+We're going to start a branch from the {\em 2015.02} Buildroot
+release, with which this training has been tested.
+
+\begin{verbatim}
+git checkout -b felabs 2015.02
+\end{verbatim}
+
+\section{Configuring Buildroot}
+
+If you look under \code{configs/}, you will see that there is a file
+named \code{beaglebone_defconfig}, which is a ready-to-use Buildroot
+configuration file to build a system for the BeagleBone Black
+platform. However, since we want to learn about Buildroot, we'll start
+our own configuration from scratch!
+
+Start the Buildroot configuration utility:
+
+\begin{verbatim}
+make menuconfig
+\end{verbatim}
+
+Of course, you're free to try out the other configuration utilities
+\code{nconfig}, \code{xconfig} or \code{gconfig}.
+
+Now, let's do the configuration:
+
+\begin{itemize}
+
+\item \code{Target Options} menu
+
+ \begin{itemize}
+
+ \item It is quite well known that the BeagleBone Black is an ARM based
+ platform, so select \code{ARM (little endian)} as the target
+ architecture.
+
+ \item According to the BeagleBone Black website at
+ \url{http://beagleboard.org/BLACK}, it uses a Texas Instruments
+ AM335x, which is based on the ARM Cortex-A8 code. So select
+ \code{cortex-A8} as the \code{Target Architecture Variant}.
+
+ \item On ARM two {\em Application Binary Interfaces} are available:
+ \code{EABI} and \code{EABIhf}. Unless you have backward
+ compatibility concerns with pre-built binaries, \code{EABIhf} is
+ more efficient, so make this choice as the \code{Target ABI}.
+
+ \item The other parameters can be left to their default value:
+ \code{ELF} is the only available \code{Target Binary Format},
+ \code{VFPv3-D16} is a sane default for the {\em Floating Point
+ Unit}, and using the \code{ARM} instruction set is also a good
+ default (we could use the \code{Thumb-2} instruction set for
+ slightly for compact code).
+
+ \end{itemize}
+
+\item We don't have anything special to change in the
+ \code{Build options} menu, but take nonetheless this opportunity to
+ visit this menu, and look at the available options. Each option has
+ a help text that tells you more about the option.
+
+\item \code{Toolchain} menu
+
+ \begin{itemize}
+
+ \item By default, Buildroot builds its own toolchain. This takes
+ quite a bit of time, and for \code{ARMv7} platforms, there is a
+ nicely pre-built toolchain provided by Linaro. We'll use it
+ through the {\em external toolchain} mechanism of
+ Buildroot. Select \code{External toolchain} as the
+ \code{Toolchain type}. Do not hesitate however to look at the
+ available options when you select \code{Buildroot toolchain} as
+ the \code{Toolchain type}.
+
+ \item Select \code{Linaro 2014.09} as the
+ \code{Toolchain}. Buildroot can either use pre-defined toolchains
+ such as the Linaro one, or custom toolchains (either downloaded
+ from a given location, or pre-installed on your machine).
+
+ \end{itemize}
+
+\item \code{System configuration} menu
+
+ \begin{itemize}
+
+ \item For our basic system, we don't need a lot of custom {\em
+ system configuration} for the moment. So take some time to look
+ at the available options, and put some custom values for the
+ \code{System hostname}, \code{System banner} and \code{Root
+ password}.
+
+ \end{itemize}
+
+\item \code{Kernel} menu
+
+ \begin{itemize}
+
+ \item We obviously need a Linux kernel to run on our platform, so
+ enable the \code{Linux kernel} option.
+
+ \item By default, the most recent Linux kernel version available at
+ the time of the Buildroot release is used. In our case, we want to
+ use a specific version: \code{4.0}. So select \code{Custom
+ version} as the \code{Kernel version}, and enter \code{4.0} in
+ the \code{Kernel version} text field that appears.
+
+ \item Now, we need to define which kernel configuration to
+ use. We'll start by using a default configuration provided within
+ the kernel sources themselves, called a {\em defconfig}. To
+ identify which {\em defconfig} to use, you can look in the kernel
+ sources directly, at
+ \url{http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/arch/arm/configs/?id=v4.0}. In
+ practice, for this platform, it is not trivial to find which one
+ to use: the AM335x processor is supported in the Linux kernel as
+ part of the support for many other Texas Instruments processors:
+ OMAP2, OMAP3, OMAP4, etc. So the appropriate {\em defconfig} is
+ named \code{omap2plus_defconfig}. You can open up this file in the
+ Linux kernel Git repository viewer, and see it contains the line
+ \code{CONFIG_SOC_AM33XX=y}, which is a good indication that it has
+ the support for the processor used in the BeagleBone Black. Now
+ that we have identified the {\em defconfig} name, enter
+ \code{omap2plus} in the \code{Defconfig name} option.
+
+ \item The \code{Kernel binary format} is the next option. Since we
+ are going to use a recent U-Boot bootloader, we'll select the
+ \code{zImage} format. The \code{uImage} format used to be the norm
+ on ARM platforms, but everybody is now transitioning to the
+ \code{zImage} format.
+
+ \item On ARM, most of the platforms now use the {\em Device Tree} to
+ describe the hardware. The BeagleBone Black is in this situation,
+ so you'll have to enable the \code{Build a Device Tree Blob}
+ option. At
+ \url{http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/arch/arm/boot/dts/?id=v4.0},
+ you can see the list of all Device Tree files available in the 4.0
+ Linux kernel (note: the Device Tree files for boards use the
+ \code{.dts} extension). The one for the BeagleBone Black is
+ \code{am335x-boneblack.dts}. Even if talking about Device Tree is
+ beyond the scope of this training, feel free to have a look at
+ this file to see what it contains. Back in Buildroot, use the
+ option \code{Use a device tree present in the kernel}, and type
+ \code{am335x-boneblack} as the \code{Device Tree Source file
+ names}.
+
+ \end{itemize}
+
+\item \code{Target packages} menu. This is probably the most important
+ menu, as this is the one where you can select amongst the 1500
+ available Buildroot packages which ones should be built and
+ installed in your system. For our basic system, enabling
+ \code{Busybox} is sufficient, but feel free to explore the available
+ packages. We'll have the opportunity to enable some more packages in
+ the next labs.
+
+\item \code{Filesystem images} menu. For now, keep only the \code{tar
+ the root filesystem} option enabled. We'll take care separately of
+ flashing the root filesystem on the SD card.
+
+\item \code{Bootloaders} menu.
+
+ \begin{itemize}
+
+ \item We'll use the most popular ARM bootloader, {\em U-Boot}, so
+ enable it in the configuration.
+
+ \item Look at
+ \url{http://git.denx.de/?p=u-boot.git;a=tree;f=configs} to
+ identify the available U-Boot configuration. The one matching the
+ BeagleBone Black is \code{am335x_boneblack_defconfig}, so type
+ \code{am335x_boneblack} in \code{U-Boot board name}.
+
+ \item Use \code{2015.04} as the U-Boot version, by using the
+ \code{Custom version} option.
+
+ \item U-Boot on AM335x is split in two parts: the first stage
+ bootloader called \code{MLO} and the second stage bootloader
+ called \code{u-boot.img}. So, select \code{u-boot.img} as the
+ \code{U-Boot binary format}, enable \code{Install U-Boot SPL
+ binary image} and use \code{MLO} as the \code{U-Boot SPL binary
+ image name}.
+
+ \end{itemize}
+
+\end{itemize}
+
+You're now done with the configuration!
+
+\section{Building}
+
+You could simply run \code{make}, but since we would like to keep a
+log of the build, we'll redirect both the standard and error outputs
+to a file, as well as the terminal by using the \code{tee} command:
+
+\begin{verbatim}
+make 2>&1 | tee build.log
+\end{verbatim}
+
+While the build is on-going, please go through the following sections
+to prepare what will be needed to test the build results.
+
+\section{Prepare the BeagleBone Black}
+
+The BeagleBone Black is powered via the USB-A to mini-USB cable,
+connected to the mini-USB connector labeled \code{P4} on the back of
+the board.
+
+The Beaglebone serial connector is exported on the 6 male pins close
+to one of the 48 pins headers. Using your special USB to Serial
+adapter provided by your instructor, connect the ground wire (blue) to
+the pin closest to the power supply connector (let's call it pin 1),
+and the \code{TX} (red) and \code{RX} (green) wires to the pins 4
+(board \code{RX}) and 5 (board \code{TX}). \footnote{See
+ \url{https://www.olimex.com/Products/Components/Cables/USB-Serial-Cable/USB-Serial-Cable-F/}
+ for details about the USB to Serial adapter that we are using.}
+
+You always should make sure that you connect the \code{TX} pin of the
+cable to the \code{RX} pin of the board, and vice-versa, whatever the
+board and cables that you use.
+
+\begin{center}
+\includegraphics[width=8cm]{labs/buildroot-basic/beaglebone-black-serial-connection.jpg}
+\end{center}
+
+Once the USB to Serial connector is plugged in, a new serial port
+should appear: \code{/dev/ttyUSB0}. You can also see this device
+appear by looking at the output of \code{dmesg}.
+
+To communicate with the board through the serial port, install a
+serial communication program, such as \code{picocom}:
+
+\begin{verbatim}
+sudo apt-get install picocom
+\end{verbatim}
+
+If you run \code{ls -l /dev/ttyUSB0}, you can also see that only
+\code{root} and users belonging to the \code{dialout} group have read
+and write access to this file. Therefore, you need to add your user to
+the \code{dialout} group:
+
+\begin{verbatim}
+sudo adduser $USER dialout
+\end{verbatim}
+
+You now need to log out and log in again to make the new group visible
+everywhere.
+
+Now, you can run \code{picocom -b 115200 /dev/ttyUSB0}, to start
+serial communication on \code{/dev/ttyUSB0}, with a baudrate of
+\code{115200}. If you wish to exit \code{picocom}, press
+\code{[Ctrl][a]} followed by \code{[Ctrl][x]}.
+
+There should be nothing on the serial line so far, as the board is not
+powered up yet.
+
+\section{Prepare the SD card}
+
+Our SD card needs to be formatted in two partitions:
+
+\begin{itemize}
+
+\item The first partition for the bootloader. It needs to comply with
+ the requirements of the AM335x so that it can find the bootloader in
+ this partition. It should be a FAT16 partition. We will store the
+ bootloader (\code{MLO} and \code{u-boot.img}), the kernel image
+ (\code{zImage}), the Device Tree (\code{am335x-boneblack.dtb}) and a
+ special U-Boot script for the boot.
+
+\item The second partition for the root filesystem. It can use
+ whichever filesystem type you want, but for our system, we'll use
+ {\em ext4}.
+
+\end{itemize}
+
+\section{Flash the system}
+
+\section{Boot the system}
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