Articles tagged with USB
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Some time ago I acquired a BeagleBone Black, a hard-float ARM-based embedded mini PC, quite similar to the widely popular Raspberry Pi. Mainly I did this because I was disappointed in the Raspberry Pi for its need of non-free firmware to boot it up and because you had to rely on third-party maintained Linux distributions of questionable security maintenance for it to function.
Because some people gave me the impression that you could easily install an unmodified, official Debian operating system on it, I chose to take a look at the BeagleBone Black.
After tinkering a bit with the device, I realized that this is not true at all. There are some third-party maintained Debian-based distributions available, but at their peak of security awareness, they offer MD5 fingerprints from a non-HTTPS-accessible website for image validation. I’d rather not trust in that.When installing an official Debian Wheezy, the screen stays black. When using Jessie (testing) or Sid (unstable), the system seems to boot up correctly, but the USB host port malfunctions and I’m unable to attach a keyboard. Now while I was looking for a way to get the USB port to work, some people hinted to me, that it might be possible to fix this problem by changing some Linux kernel configuration parameters. Sadly I cannot say whether this actually works or not, because it seems to work only for boards of revision C and higher. My board, from the third-party producer element14 seems to be a revision B.
Still I would like to share with the world, how I managed to cross-compile the armmp kernel in Debian Sid with a slightly altered configuration on a
x86_64Debian Jessie system. -
Creating a clean Sid environment for building
First of all, I created a fresh building environment using
debootstrap:sudo debootstrap sid sid sudo chroot sid /bin/bash
Further instructions are what I did while being inside the
chrootenvironmentThen I added some decent package sources, and especially made sure there is a line for source packages. You might want to exchange the URL with some repository close to your location, the Debian CDN sometimes leads to strange situations in my experience.
cat <<FILE > /etc/apt/source.list deb http://cdn.debian.net/debian sid main deb-src http://cdn.debian.net/debian sid main FILE
Then I added the foreign armhf architecture to this environment, so I could acquire packages from that:
dpkg --add-architecture armhf apt-get update
Next, I installed basic building tools and the building dependencies for the Linux kernel itself:
apt-get install build-essential fakeroot gcc-arm-linux-gnueabihf libncurses5-dev apt-get build-dep linux
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Configuring the Linux kernel package source
Still within the earlier created chroot environment I then prepared to build the actual package.
I reset the locale settings to have no dependency on actual installed locale definitions:
export LANGUAGE=C export LANG=C export LC_ALL=C unset LC_PAPER LC_ADDRESS LC_MONETARY LC_NUMERIC LC_TELEPHONE LC_MESSAGES LC_COLLATE LC_IDENTIFICATION LC_MEASUREMENT LC_CTYPE LC_TIME LC_NAME
I then acquired the kernel source code:
cd /tmp apt-get source linux cd linux-3.16.7-ckt2
I configured the name prefix for the cross-compiler executable to be used:
export CROSS_COMPILE=arm-linux-gnueabihf-
Now in the file
debian/config/armhf/config.armmp, I changed the Linux kernel configuration. In my case I just did change the following line:CONFIG_TI_CPPI41=y
You might need completely different changes here.
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Building the kernel package
Because for some reason this package expects the compiler executable to be
gcc-4.8and I couldn’t find out how to teach it otherwise, I just created a symlink to the cross-compiler:ln -s /usr/bin/arm-linux-gnueabihf-gcc /usr/local/bin/arm-linux-gnueabihf-gcc-4.8
Afterwards, the build process was started by the following command:
dpkg-buildpackage -j8 -aarmhf -B -d
The
-jflag defines the maximum amount of tasks that will be done in parallel. The optimal setting for fastest compilation should be the amount of CPU cores and/or hyper-threads you’ve got on your system.The
-dflag ignores if some dependencies aren’t installed. In my case, the process complained aboutpythonandgcc-4.8not being installed before, even though they actually were installed. I guess it meantpython:armhfandgcc-4.8:armhfthen, but installing these is not even possible on myx86_64system, even with multiarch enabled. So in the end I decided to ignore these dependencies and the compilation went fine by the looks of it.Now that compilation process takes quite a while and outputs a lot of
.deband.udebpackage into the/tmpdirectory. The actual kernel package I needed was namedlinux-image-3.16.0-4-armmp_3.16.7-ckt2-1_armhf.debin my case. -
Creating a bootable image using the new kernel
For this, I left the Sid chroot environment again. I guess you don’t even have to.
Now I used the vmdebootstrap tool to create an image that can then be put onto an SD card.
First of all I had to install the tool from the experimental repositories, because the versions in Sid and Jessie were bugged somehow. That might not be needed anymore in the future.
So I added the experimental repository to the package management system:
cat <<FILE > /etc/apt/sources.list.d/experimental.list deb http://ftp.debian.org/debian experimental main contrib non-free deb-src http://ftp.debian.org/debian experimental main contrib non-free FILE
And afterwards I did the installation:
apt-get update apt-get -t experimental vmdebootstrap
I created a script named
customise.shthat sets the bootloader up inside the image, with the following content (many thanks to Neil Williams):#!/bin/sh set -e rootdir=$1 # copy u-boot to the boot partition cp $rootdir/usr/lib/u-boot/am335x_boneblack/MLO $rootdir/boot/MLO cp $rootdir/usr/lib/u-boot/am335x_boneblack/u-boot.img $rootdir/boot/u-boot.img # Setup uEnv.txt kernelVersion=$(basename `dirname $rootdir/usr/lib/*/am335x-boneblack.dtb`) version=$(echo $kernelVersion | sed 's/linux-image-\(.*\)/\1/') initRd=initrd.img-$version vmlinuz=vmlinuz-$version # uEnv.txt for Beaglebone # based on https://github.com/beagleboard/image-builder/blob/master/target/boot/beagleboard.org.txt cat >> $rootdir/boot/uEnv.txt <<EOF mmcroot=/dev/mmcblk0p2 ro mmcrootfstype=ext4 rootwait fixrtc console=ttyO0,115200n8 kernel_file=$vmlinuz initrd_file=$initRd loadaddr=0x80200000 initrd_addr=0x81000000 fdtaddr=0x80F80000 initrd_high=0xffffffff fdt_high=0xffffffff loadkernel=load mmc \${mmcdev}:\${mmcpart} \${loadaddr} \${kernel_file} loadinitrd=load mmc \${mmcdev}:\${mmcpart} \${initrd_addr} \${initrd_file}; setenv initrd_size \${filesize} loadfdt=load mmc \${mmcdev}:\${mmcpart} \${fdtaddr} /dtbs/\${fdtfile} loadfiles=run loadkernel; run loadinitrd; run loadfdt mmcargs=setenv bootargs console=tty0 console=\${console} root=\${mmcroot} rootfstype=\${mmcrootfstype} uenvcmd=run loadfiles; run mmcargs; bootz \${loadaddr} \${initrd_addr}:\${initrd_size} \${fdtaddr} EOF mkdir -p $rootdir/boot/dtbs cp $rootdir/usr/lib/linux-image-*-armmp/* $rootdir/boot/dtbsAfterwards the image was built using the following command:
Note that you might want to change the Debian mirror here as well.
sudo -H \ vmdebootstrap \ --owner `whoami` \ --log build.log \ --log-level debug \ --size 2G \ --image beaglebone-black.img \ --verbose \ --mirror http://cdn.debian.net/debian \ --arch armhf \ --distribution sid \ --bootsize 128m \ --boottype vfat \ --no-kernel \ --no-extlinux \ --foreign /usr/bin/qemu-arm-static \ --package u-boot \ --package linux-base \ --package initramfs-tools \ --custom-package [INSERT PATH TO YOUR SID CHROOT]/tmp/linux-image-3.16.0-4-armmp_3.16.7-ckt2-1_armhf.deb \ --enable-dhcp \ --configure-apt \ --serial-console-command '/sbin/getty -L ttyO0 115200 vt100' \ --customize ./customise.sh
The result is a file called beaglebone-black.img that can easily be put onto an SD card by using the
ddcommand. -
After I put that image on my SD card and booted it, it didn’t solve the USB problem, maybe it isn’t working at all, or maybe it just doesn’t work on my hardware revision. At least it did boot like a regular Sid image I tried before and now I have the knowledge to conduct further experiments.
It was a hell of a job to find out how to do it, involving tons of guides and howtos giving contradicting instructions and being outdated in different grades. In the end, what helped the most was talking to a lot of people on IRC.
So I hope this is helpful for someone else and should you be aware of a way to actually fix the USB host problem, please send me a comment.
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