The easy way:
# Download the binaries from here:
sha1sum kernelAndFirmware_wolfson_rt.tar.bz2 is
76c3b38f588f09ae6a557f3065ce9dc30674615b kernelAndFirmware_wolfson_rt.tar.bz2
mkdir kernelAndFirmware_wolfson_rt
Extract:
tar -xvjf kernelAndFirmware_wolfson_rt.tar.bz2 -C kernelAndFirmware_wolfson_rt
and copy to root of the Raspberry pi.
sudo nano /boot/config.txt
change
kernel=kernel.img
to
# kernel=kernel.img
kernel=kernel_new.img
sudo sync
sudo reboot
or do it the hard way 😉
Read Compile and install as described here -> http://elinux.org/RPi_Kernel_Compilation
# Download the sources
# RPI-Kernel
Download rpi-3.12.y_rt_wlfsn.tar.bz2
sha1sum rpi-3.12.y_rt_wlfsn.tar.bz2 is
523f06ab89088e9cf8384c7dd9551c2fc74b2598 rpi-3.12.y_rt_wlfsn.tar.bz2
tar -xvjf rpi-3.12.y_rt_wlfsn.tar.bz2 -C rpi-3.12.y_rt_wlfsn
cd rpi-3.12.y_rt_wlfsn
Download rpi-3.12.y_rt_wlfsn.config into rpi-3.12.y_rt_wlfsn directory and change it to .config
export ARCH=arm
export CROSS_COMPILE=/path/to/your/tools/arm-bcm2708/gcc-linaro-arm-linux-gnueabihf-raspbian/bin/arm-linux-gnueabihf-
export INSTALL_MOD_PATH=/your/modules/dir/path
mv config.txt .config
make -j4 ARCH=arm CROSS_COMPILE=${CROSS_COMPILE} mrproper
make -j4 ARCH=arm CROSS_COMPILE=${CROSS_COMPILE} xconfig
# make your changes here
make -j4 ARCH=arm CROSS_COMPILE=${CROSS_COMPILE}
make -j4 ARCH=arm CROSS_COMPILE=${CROSS_COMPILE} modules
make -j4 ARCH=arm CROSS_COMPILE=${CROSS_COMPILE} modules_install
# Have fun.