Michael Opdenacker – Page 9

Linux 2.6.30 – New features for embedded systems

Interesting features in Linux 2.6.30 for embedded system developers

Linux 2.6.30 has been released almost 1 month ago and it’s high time to write a little about it. Like every new kernel release, it contains interesting features for embedded system developers.

The first feature that stands out is support for fastboot. Today, most devices are initialized in a sequential way. As scanning and probing the hardware often requires waiting for the devices to be ready, a significant amount of cpu time is wasted in delay loops. The fastboot infrastructure allows to run device initialization routines in parallel, keeping the cpu fully busy and thus reducing boot time in a significant way. Fasboot can be enabled by passing the fastboot parameter in the kernel command line. However, unless your embedded system uses PC hardware, don’t be surprised if you don’t get any boot time reduction yet. If you look at the code, you will see that the async_schedule function is only used by 4 drivers so far, mainly for disk drives. You can see that board support code and most drivers still need to be converted to this new infrastructure. Let’s hope this will progress in future kernel releases, bringing significant boot time savings to everyone.

Linux 2.6.30 also features the inclusion of Tomoyo Linux, a lightweight Mandatory Access Control system developed by NTT. According to presentations I saw quite a long time ago, Tomoyo can be used as an alternative to SELinux, and it just consumes a very reasonable amount of RAM and storage space. It should interest people making embedded devices which are always connected to the network, and need strong security.

Another nice feature is support for kernel images compressed with bzip2 and lzma, and not just with zlib as it’s been the case of ages. The bzip2 and lzma compressors allow to reduce the size of a compressed kernel in a significant way. This should appeal to everyone interested in saving a few hundreds of kilobytes of storage space. Just beware that decompressing these formats requires more CPU resources, so there may be a price to pay in terms of boot time if you have a slow cpu, like in many embedded systems. On the other hand, if you have a fast cpu and rather slow I/O, like in a PC, you may also see a reduction in boot time. In this case, you would mainly save I/O time copying a smaller kernel to RAM, and with a fast cpu, the extra decompression cost wouldn’t be too high.

However, if you take a closer look at this new feature, you will find that it is only supported on x86 and blackfin. Alain Knaff, the author of the original patches, did summit a patch for the arm architecture, but it didn’t make it this time. Upon my request, Alain posted an update to this arm patch. Unfortunately, decompressing the kernel no longer works after applying this patch. There seems to be something wrong with the decompression code… Stay tuned on the LKML to follow up this issue. Note that the blackfin maintainers took another approach, apparently. They didn’t include any decompression code on this architecture. Instead, they relied on the bootloader to take care of decompression. While this is simpler, at least from the kernel code point of view, this is not a satisfactory solution. It would be best if the arm kernel bootstrap code took care of this task, which would then work with any board and any bootloader.

Another interesting feature is the inclusion of the Microblaze architecture, a soft core cpu on Xilinx FPGAs. This MMU-less core has been supported for quite a long time by uClinux, and it’s good news that it is now supported in the mainline kernel. This guarantees that this cpu will indeed be maintained for a long time, and could thus be a good choice in your designs.

Other noteworthy features are support for threaded interrupt handlers (which shows that work to merge the real-time preempt patches is progressing), ftrace support in 32 and 64 bit powerpc, new tracers, and of course, several new embedded boards and many new device drivers.

As usual, full details can be found on the Linux Kernel Newbies website.

The Bifferboard: tiny, low power embedded x86 board

A nice, cheap and tiny x86 embedded board that runs Linux and just consumes 1W. It has all the basic connectivity you need in an embedded system.

As you may already know, we maintain a list of attractive and Linux friendly embedded boards. Whenever we find a new board that is attractive and meets our strict criteria (supporting Linux or other free kernels, public pricelist, public documentation and website with an English version), we add this board to our list. This way, we don’t forget about any useful board, and we can offer useful guidance to our customers and to any embedded system developer looking for a suitable hardware platform.

Somebody at Bifferos.com has just contacted us to let us know about their Bifferboard product. Here are its announced features:

150MHz RDC CPU, Intel 486SX compatible
1 watt power consumption (200mA @5v)
68mm x 28mm x 19mm
32MB SDRAM/1MB Flash
OHCI/EHCI USB 2.0
10/100 Ethernet
Serial console 115200 baud
4-pin JTAG (can be used as GPIO)
2 GPIO (1 LED, 1 button)
Linux 2.6.27.5 + OpenWrt
29 UK pounds

The board has two components: the CPU board, and the I/O one, offering Ethernet and USB host connectivity. For a serial port, you can order a special cable from their shop, which connects to a USB port on your workstation.

Thanks to its low power consumption, the Bifferboard can even be powered by USB. According to its makers, the board can do anything a NSLU2 device can do. It is just cheaper (approximately 33 EUR at the time of this writing).

Last but not least, most Bifferboard hardware can be emulated with QEMU.

While it could also be suitable for mass production projects, it can be at least a nice platform for prototypes, hobby, research and educational projects.

Of course, if you know about other attractive boards that we could add to our list, please post a comment or send us e-mail.

Building Android on Beagle

Note: these instructions are now out of date and refer to URLs which no longer exist. See the elinux.org wiki for more recent instructions.

These instructions are derived from Embinux.org’s Android Porting Guide to Beagle Board (the corresponding web page no longer exists), based on their work to port Android on the Beagle board. They correct multiple inaccuracies in this guide, and also add many useful details.

These instructions were tested on xubuntu 9.04. There shouldn’t be many differences if you use other recent Ubuntu or Debian versions.

Install needed software packages

At the time of this writing, note that Android requires Sun’s Java5 JDK, and doesn’t support the Java6 one.

apt-get update
apt-get dist-upgrade
apt-get install git-core bison sun-java5-jdk flex g++ zlib1g-dev
apt-get install  libx11-dev libncurses5-dev gperf uboot-mkimage

Android also uses its own repo script as a git front-end:

mkdir -p ~/bin
cd ~/bin
curl https://dl-ssl.google.com/dl/googlesource/git-repo/repo > repo
chmod +x repo

We are also going to need a 2007q3 toolchain from Code Sourcery

cd
wget http://www.codesourcery.com/sgpp/lite/arm/portal/package1787/public/arm-none-linux-gnueabi/arm-2007q3-51-arm-none-linux-gnueabi-i686-pc-linux-gnu.tar.bz2
cd /opt
sudo tar jxf arm-2007q3-51-arm-none-linux-gnueabi-i686-pc-linux-gnu.tar.bz2

You could also get this toolchain from our website:

cd
wget /pub/demos/beagleboard/android/arm-2007q3-51-arm-none-linux-gnueabi-i686-pc-linux-gnu.tar.lzma
cd /opt
sudo tar --lzma -xf ~/arm-2007q3-51-arm-none-linux-gnueabi-i686-pc-linux-gnu.tar.lzma

Download sources

Our instructions create a directory in your home directory, but of course, it can be placed anywhere!

 mkdir ~/beagledroid
 cd ~/beagledroid
 repo init -u git://labs.embinux.org/repo/android/platform/beaglemanifest.git/
 repo sync

Caution: this can take a lot of time, as this downloads and extracts 2.4 GB of data. On a fast workstation with a 500KB/s Internet connection, it took about 90 minutes.

Building Android

make

If your workstation has multiple CPUs, you could save a lot of time by running multiple jobs in parallel:

make -j 4

On our machine, this took about 4 hours!

Building the kernel

export CC_PATH=/opt/arm-2007q3/bin/arm-none-linux-gnueabi-
cd ~/beagledroid/kernel
../vendor/embinux/support-tools/beagle_build_kernel.sh

Copying the Android root filesystem

Android’s root file system is generated in ~/beagledroid/out/target/product/generic

cd ~/beagledroid/out/target/product/generic
mkdir ~/beagledroid/rootfs
cp -a root/* ~/beagledroid/rootfs/
cp -a system/* ~/beagledroid/rootfs/system/
cd ~/beagledroid/rootfs
sudo chown -R root.root .
sudo chmod -R a+rwX data system

Formatting an MMC/SD card

First connect your card reader to your workstation, with the MMC/SD card inside. Type the dmesg command to see which device is used by your workstation. Let’s assume that this device is /dev/sdb

Type the mount command to check your currently mounted partitions. If MMC/SD partitions are mounted, unmount them.

In a terminal edit partitions with fdisk:

sudo fdisk /dev/sdb

Delete any existing partition with the d command.

Now, create the boot partition:

Command (m for help): n 
Command action 
   e   extended 
   p   primary partition (1-4) 
p 
Partition number (1-4): 1 
First cylinder (1-239, default 1): 1 
Last cylinder, +cylinders or +size{K,M,G} (1-239, default 239): +64M

Change its type to FAT32:

Command (m for help): t
Selected partition 1
Hex code (type L to list codes): c
Changed system type of partition 1 to c (W95 FAT32 (LBA))

Using the n command again, create a second partition filling up the rest of your card (just accept default values).

Now, format the partitions in your card:

sudo mkfs.vfat -n beagleboot -F 32 /dev/sdb1
sudo mkfs.ext3 /dev/sdb2

Remove and insert your card again. Your new partitions should be mounted automatically.

Copying data to the MMC/SD card

Start by copying the X-loader and U-boot on the first partition.

cd /media/beagleboot
wget /pub/demos/beagleboard/android/MLO
/pub/demos/beagleboard/android/u-boot.bin
cp ~/beagledroid/kernel/arch/arm/boot/uImage .

Now copy the Android root filesystem to the second partition (assuming it is mounted on /media/disk:

sudo rsync -a ~/beagledroid/rootfs/ /media/disk/

Finish by unmounting your MMC/SD partitions:

sudo umount /media/beagleboot
sudo umount /media/disk

Boot setup

The last thing left to do is to specify how the board boots Linux.

Plug the Beagle board on your computer, and also connect it to a DVI-D monitor. Start minicom (corresponding to Hyperterminal in Windows) on /dev/ttyS0, or on /dev/ttyUSB0 if you are using a serial to USB adapter. Power up the board.

First, stop Minicom from truncating long lines by typing [Ctrl] [a] followed by z and w.

In the U-boot prompt, make the board boot automatically on the MMC/SD card:

setenv bootcmd 'mmc init;fatload mmc 0 80000000 uImage;bootm 80000000'
saveenv

Now set the kernel command line arguments:

setenv bootargs console=ttyS2,115200n8 noinitrd root=/dev/mmcblk0p2 video=omapfb.mode=dvi:1280x720MR-24@50 init=/init rootfstype=ext3 rw rootdelay=1 nohz=off androidboot.console=ttyS2

You may need to adapt the video settings to the capabilities of your DVI display. You should now see Android boot!

Beagle board MMC boot myths?

Booting a Beagle board from an MMC/SD should be easier than what people tell you

At the time of this writing, most documentation that you can find on the web about the Beagle board will tell you that you need to take special preparation steps if you wish to boot your board on an MMC/SD card:

The card requires a special geometry: 255 heads and 63 sectors per track
The first partition on the card, with a FAT type, must be marked as bootable
The X-loader (MLO file), must be copied to the first sectors of the first partition. As a consequence, you should copy this file first.

As my colleague Florent Peyraud and TI engineers started to suspect, all this is not always required. I’ve just made tests with my Rev C2 Beagle board:

I took a brand new MMC/SD card. fdisk showed that it had 57 heads and 56 sectors per track.
I created the partitions again, and didn’t flag the first one as bootable.
After formatting the first partition in FAT32 format, I first copied the u-boot.bin and uImage files, and then the MLO one.

After all this, I had no problem booting my Beagle board on the MMC/SD card. At least with my Rev C2 board, what TI engineers expected was true: the board romcode understood the FAT format, and therefore just needed a file with the MLO name, whatever its physical location on the card.

Does anyone know whether the requirements used to be true with earlier Beagle board romcode releases, or in special cases?

ELC Europe in Grenoble

Just a quick note after the announcement that has just been made at the Embedded Linux Conference (ELC) in San Francisco…

Tim Bird has just announced that the next European edition of ELC will be in Grenoble, France, on October 15-16. As the new conference home page says, it will be colocated with ESWEEK.

We are very excited about this news, as Grenoble is a not only a beautiful place, but also a very dynamic city full of universities and high-tech companies. We will do our best to incite people to attend the conference, and of course to speak about their projects and propose demos.

Bootlin at ELC

My colleague Thomas Petazzoni and I will participate to the Embedded Linux Conference on April 6-8 in San Francisco.

This is an exciting conference with a very interesting program, and we are proud to be part of it:

Monday, April 6, 7:30-9:00 pm
System size BOF (Michael)
Tuesday, April 7, 11:00-11:50 am
Update on filesystems for flash storage (Michael)
Tuesday, April 7, 4:40-5:30 pm
Building Embedded Linux Systems with Buildroot (Thomas)
Wednesday, April 8, 1:00-1:45 pm
Build tools BOF (Thomas)

If participate to this conference too, and if you are interested in the above topics, or in topics we covered in this blog, don’t hesitate to come and chat with us. We will both arrive on Saturday afternoon, so we could even meet before the conference starts.

If you can’t make it to this conference, we will also shoot and share videos as usual, so at least you won’t miss the technical contents. You will just miss the beer together…

USB-Ethernet device for Linux

Useful device when you work with an embedded development board

For our Embedded Linux training sessions, I was looking for a USB to Ethernet device. Since Linux supported devices are often difficult to find, I’m glad to share my investigations here.

When you use an embedded development board, you must connect it to your computer with an Ethernet cable, for example to transfer a new kernel image to U-boot through tftp, or to make your board boot on a directory on your workstation, exported with NFS.

You could connect both the board and computer to your local network, which would still allow your computer to connect to the Internet while you work with the board. However, you may create conflicts on your local network if you don’t use DHCP to assign an IP address to your board (if your DHCP server even accepts this new device on the network). In a training environment, you are also likely to run out of Ethernet outlets in the training room if you have to connect 8 such boards. Hence, a direct connection between the board and your workstation’s Ethernet port is often the most convenient solution.

If you can’t use WIFI to keep your computer connected to the outside world, a good solution is to add an extra Ethernet port to your computer by using an USB-to-Ethernet device.

My colleague Thomas and I started looking for such devices that would be supported by Linux. Here are a few that we found:

D-Link DUB-E100. Supported by the USB_NET_AX8817X driver. However, this product is bulky and quite heavy (at least 100 grams).
TRENDnet TU2-E100. Supported by the same driver, but still bulk (August 2015 update: now replaced by a more recent version, now almost as small as the Apple one, and supported out of the box in Linux. See the comment about this device.)
Linksys USB 200m. Supported by the same Linux driver and has a much more acceptable size, but customer reviews complain that its connector can break easily.
Apple USB Ethernet Adapter. This should be working out of the box in Linux. At least the MB442Z/A or MC704ZM/A references did, but Apple now sells a new reference that might have a different chipset. It is beautiful, small and light. Support for this device (at least the references I mentioned) was added to Linux 2.6.26 through the same driver. You should be able to use it in recent distros.

So, I recommend the Apple device. I event posted a comment on the Apple Store, titled “Perfect for Linux”! I hope the Apple droids won’t censor it. Don’t hesitate to buy it, so that we can confirm that the latest reference is supported too.

I can’t tell whether this could happen with Apple. This was the first Apple device I ever bought…

Public session changes

New agenda, sessions in Grenoble, and walking away with an embedded board

Did you notice? We’ve made significant changes to our next public training sessions.

First of all, partnering with CALAO Systems, we are opening new public sessions in Grenoble.

In the upcoming sessions, we also offer a new training agenda, covering embedded Linux system development in full detail. Until recently, our public trainings dedicated approximately 3 days to kernel integration and device driver development, and only 2 days to real-time and to developing the system itself. The new sessions will still cover kernel configuration, (cross)compiling and usage, but will leave Linux kernel and driver development to dedicated sessions.

The new training sessions will thus cover the below topics:

Introduction to embedded Linux
Bootloaders
Configuring, (cross)compiling and booting a Linux kernel
Block filesystems
Flash filesystems – Manipulating flash partitions
C library and cross-compiling toolchains
Embedded system development tools
BusyBox and other lightweight tools for embedded systems. Graphical toolkits
Debugging and profiling tools
Implementing realtime requirements
Udev and hotplugging
System optimizations
Practical lab: implementing a multimedia system

For the first time too, each participant will walk away with an embedded board from CALAO systems. After the training sessions, you will then be able to go on practicing with the new technologies that you discovered, and to build your own system prototypes.

You will find more details in the description of our public training sessions.

If there is enough demand, we will propose other public sessions in September 2009, this time on Linux kernel and device driver development. Don’t hesitate to contact us if you are interested in such a session. We could even make it earlier if enough people are interested.

Real hardware in our training sessions

At last, real hardware in our training sessions

If you haven’t had a look at our new training agendas, you may not have noticed that we now use real hardware in our embedded Linux and kernel training sessions. For 4 years, we had been using the QEMU emulator on the x86, arm and mips platforms. While this simplified training session logistics, and avoided any trouble due to hardware failures, this was not close enough to the real world situations that our customers face.

We chose the nifty boards from Calao Systems. They have great features that make them very attractive for training and prototyping purposes

AT91SAM9263 ARM CPU from ATMEL, running at 200 MHz
64 MB of RAM and 256 MB of flash, which are more than enough for any embedded system we can think of.
Small and light (30 g), with a USB connector replacing power, serial and JTAG connectors, making it easy to travel with several of these devices without having to carry many heavy accessories. Carrying convenience was a key decision factor.
100 Mbit Ethernet port, allowing to practice with root filesystems on NFS, and with tftp from the U-boot command line.
2 USB 2.0 host ports, allowing to connect any type of device. In particular, we are thinking about USB mass storage and webcam devices.
1 USB device port, allowing to experiment with Linux USB gadget drivers.
Very affordable price (less than 160 €).

On the software side, this board is also very attractive:

It is supported by the mainline Linux kernel, since version 2.6.27.
A bricked board can be reflashed without ever needing to use Windows, thanks the Linux version of Atmel’s SAM-BA utility.
It will soon be supported by the mainline version of U-boot. We are contributing to this.
It should also be directly supported in the mainline version of Buildroot in the next months, making it easy to build complete root filesystems for it. We will also work on this.

We will also soon offer training cost options that include these boards. This way, customers can walk away with their own device and easily continue to practice with the training hardware and make prototypes, without having to go through an extra purchasing process.

Embedded Linux Conference Europe 2008 videos

Together with the announcement of our free mainlining offer in our Linux kernel and bsp development services, we are pleased to announce the availability of new conference videos.

The CELF Embedded Linux Conference Europe (ELCE) and the NLUUG Autumn Conference on Mobile Computing took place last November in Ede, in the Netherlands.

For those who don’t know them yet, the Embedded Linux Conference (ELC) and ELCE are in our opinion the most interesting conferences for embedded Linux system developers. They cover only interesting topics, such as power management, boot time, flash storage, security, graphics, mobile applications and many more.

This time, four people shot videos: Ruud Derwig (NXP), Tim Bird (Sony), Thomas Petazzoni and Michael Opdenacker (both from Bootlin). Then, Thomas took care of reading the tapes and DVDs, and encoding them to Ogg/Theora, all this in just a few minutes of manual intervention, thanks to his super automated scripts.

Here are all the videos: