Banana pi custom Kernel (Part II, cross compiling)

Yann Dupont — Thu, 27 Aug 2015 11:05:00 +0200

I'm back ! Long time ago (March 2015) in banana pi custom kernel part I, I promised a follow-up to explain how to cleanly compile a kernel for such beasts. This part was delayed, but here it is at last ! So this article is the follow-up of previous article.

I maintain .config for my bestiary of exotic computers : ARM computers (Bananapi, Odroid, Raspberry pi, Dockstar), MIPS (nexx WT3020), Risc-V (qemu and spikes for the moment).

These .config are available on github : https://github.com/objoo/custom-linux-kernels

More on that later, for the moment, let's focus on bananapi.

Please note that this particular .config is based on vanilla kernel 4.1 and targeted for particular small server duties (samba, lxc, XFS and ceph/kRBD support). I personally use this for an ARM ceph cluster.

Nice professional looking ceph cluster, ehhh ?

Please note, there is NO video code on this kernel. Don't use it if you need a graphical environment.

Allwinner A20 chip powering bananapi is a quite capable processor and is able to compile a kernel, but it may take ages. A faster way is to use a more powerful machine, for example a X86 based PC, and use it to generate programs targeted for ARM. That's cross compilation.

Cross compilation is fast, but it's a complex and sometimes tricky process which requires the installation of lots of specific packages (when they're already available on the distribution and specific recompilations when they're not). A clean way to do this and not mess with the installed system is to use docker containers specially for this.

on the same github repository, there are scripts and Dockerfile to build all necessary parts.

On the building computer, git and docker need to be installed. Choose a clean directory, and check there is enough place for docker. Then :

1
2
3

git clone git://github.com/objoo/custom-Linux-kernels
cd custom-Linux-kernels/docker/DockerFiles/X86-64/cross/Debian
./build.sh

This will take lot of time for the first build, because this script creates a Debian Jessie docker image, with all cross-compile tools. When this image is run, it fetch uboot and Linux git repositories and compiles all with a pre-defined .config. uboot and linux kernel sources are installed on a persistant storage on the host computer, so next runs are far more speedier.

Upon termination of all these processes, you'll find the resulting files in :

../build/RESULT

uboot install is optional, it only need to be installed if the current version sd-card is too ancient.

Installation of uboot is :

dd if=u-boot-sunxi-with-spl.bin of of=DEVICE_OF_THE_SDCARD bs=1024 seek=8

Then, install the modules from / (they go to /lib/modules) and install uImage , sun7i-a20-bananapi.dtb in /boot and you're done. No need to build an Initrd.

If all goes well you'll see :

root@banana-one:~# uname -a
Linux banana-one 4.1.6YDoSHM #2 SMP Wed Aug 26 23:24:00 UTC 2015 armv7l GNU/Linux

Have a nice hack !

Banana pi custom Kernel (Part I)

Yann Dupont — Wed, 26 Aug 2015 11:00:00 +0200

Banana pi is a small ARM Board, quite cheap and capable. It's not the cheapest or fastest board around (I'll probably make an article about odroid C1 later), but it offers a good compromise. Being built around Allwinner A20, it offers some interesting features : a Native SATA port, and a gigabit ethernet.

In the sick tradition of lots of ARM Soc makers, Linux support is not stellar, and Lemaker only propose a custom 3.4 kernel. With these kernels, I encountered stability and performance problems. As I wanted to experiment Ceph on this kind of hardware it's problematic.

And that's where (http://linux-sunxi.org/Main_Page) Linux Sunix community comes to rescue. These guys (thanks A LOT to them) are leading Linuxmainlining effort (http://linux-sunxi.org/Linux_mainlining_effort) and this is paying off. Should I add it's really up to Allwinner to do this kind of job ?

Anyway. we now have all pieces for having a complete vanilla kernel support, at least for all server-relevant components.

--- I use these custom kernels on banana pi , for lxc & ceph (OSD , MON) usage. I promised a guide for compiling a complete kernel + uboot for bananapi.

This is explained in banana pi custom kernel part II

Exotic destinations

Banana pi custom Kernel (Part II, cross compiling)

Banana pi custom Kernel (Part I)