Building the code for the Element 14 Cirrus audio card

Last updated : Tuesday, 10 March 2015

This tutorial shows how to build a Raspberry PI kernel and install it on to your device. This tutorial assumes that you are building on a Linux machine as building on the Raspberry PI nativily is very slow.

Note: This has been tested with the lastest updates to Raspian as of the time of writing. Download Raspian from here. To install Raspian follow the instructions here.

1. Download the Raspberry PI cross-compilers:

cd ~/bin
mkdir raspberrypi
cd raspberrypi
git clone https://github.com/raspberrypi/tools

2. Set CCPREFIX environment variable:

For 32 bit tools

export CCPREFIX=~/bin/raspberrypi/tools/arm-bcm2708/gcc-linaro-arm-linux-gnueabihf-raspbian/bin/arm-linux-gnueabihf-
${CCPREFIX}gcc -v

For 64 bit tools

export CCPREFIX=~/bin/raspberrypi/tools/arm-bcm2708/gcc-linaro-arm-linux-gnueabihf-raspbian-x64/bin/arm-linux-gnueabihf-
${CCPREFIX}gcc -v

3. Download the Cirrus Raspberry PI kernel

cd ~
mkdir code
cd code
git clone https://github.com/CirrusLogic/rpi-linux.git
cd rpi-linux
git checkout -b rpi-3.18.y origin/rpi-3.18.y

4. Create a .config file that includes the audio card code.

when the target platform is bcm2708 i.e. Raspberry Pi boards

make ARCH=arm bcmrpi_defconfig

when the target platform is bcm2709 i.e. Raspberry Pi 2 boards

make ARCH=arm bcm2709_defconfig

You could be asked a lot of questions but you can answer the default to all of these.

5. Build the kernel and kernel modules

ARCH=arm CROSS_COMPILE=${CCPREFIX} make -j <num-cores>
ARCH=arm CROSS_COMPILE=${CCPREFIX} INSTALL_MOD_PATH=../modules make modules_install

Note : Where <num-cores> is the number of processor cores dedicated to the build

6. Upload the new kernel, modules and dtb file to the Raspberry PI

cd ~/bin/raspberrypi/tools/mkimage
./mkknlimg  ~/code/rpi-linux/arch/arm/boot/zImage <kernel_img>
scp <kernel_img> pi@<ip-addr>:/tmp
cd ~/code/rpi-linux/modules
tar czf modules.tgz *
scp modules.tgz pi@<ip-addr>:/tmp
scp ~/code/rpi-linux/arch/arm/boot/dts/rpi-cirrus-wm5102-overlay.dtb pi@<ip-addr>:/tmp

Note : Where <kernel_img> is kernel.img for bcm2708, kernel7.img for bcm2709

7. Install the kernel, modules and dtb file on the Raspberry PI. Connect to your Raspberry PI over SSH and do the following:

cd /
sudo mv /tmp/<kernel_img> /boot/
sudo tar xzf /tmp/modules.tgz
sudo mv /tmp/rpi-cirrus-wm5102-overlay.dtb /boot/overlays/
rm /tmp/modules.tgz

8. Device tree configuration for cirrus audio card Open the config.txt file and add entry for dtoverlay

sudo nano /boot/config.txt
dtoverlay=rpi-cirrus-wm5102-overlay

9. Dependancies between modules: There are certain modules those should be loaded before loading of other modules. Connect to the Raspberry PI over SSH and do the following:

sudo nano /etc/modprobe.d/raspi-blacklist.conf

Note : create raspi-blacklist.conf if it is not existed

Add the following lines to the file

softdep arizona-spi pre: arizona-ld
softdep spi-bcm2708 pre: fixed

10. Restart the Raspberry PI

sudo shutdown -r now

11. When the Raspberry PI reboots connect over SSH and run:

uname -a

This will display the new kernel version.