$ sudo apt-get install git gnupg flex bison gperf build-essential \
zip tar curl libc6-dev libncurses5-dev:i386 x11proto-core-dev \
libx11-dev:i386 libreadline6-dev:i386 libgl1-mesa-glx:i386 \
libgl1-mesa-dev g++-multilib mingw32 cmake tofrodos \
python-markdown libxml2-utils xsltproc zlib1g-dev:i386 lzop
$ sudo ln -s /usr/lib/i386-linux-gnu/mesa/libGL.so.1 /usr/lib/i386-linux-gnu/libGL.so

$ sudo apt-get install gcc-arm-linux-gnueabihf \
gcc-aarch64-linux-gnu device-tree-compiler lzop libncurses5-dev \
libssl1.0.0 libssl-dev

git clone -b firefly https://github.com/FireflyTeam/kernel.git

export ARCH=arm
export CROSS_COMPILE=arm-linux-gnueabihf-

make firefly_linux_defconfig
make rk3288-firefly-linux.img -j4

make rk3288-firefly-aio-linux.img -j4

make xxx.img -j4

CMDLINE:console=ttyS2,115200 root=/dev/mmcblk2p6 rw rootwait \
mtdparts=rk29xxnand:0x00002000@0x00002000(uboot),0x00002000@0x00004000(trust),\
0x00008000@0x00006000(resource),0x0000A000@0x0000E000(kernel),\
0x00002000@0x00018000(backup),-@0x0001A000(boot)

root=/dev/mmcblk2p6                             ---> rootfs partition
If the size of the root file partition is abnormal,
 resize2fs /dev/mmcblk2p6
 
 0x0000A000@0x0000E000(kernel)        ---> kernel partition
 kernel                                                        --->  partition name
 0x0000E000                                             --->  partition start address
 0x0000A000                                            --->  partition size, generally do not need to pay attention

sudo upgrade_tool di kernel kernel.img
sudo upgrade_tool di boot    rootfs.img
...
kernel                                                         --->  on the parameter partition name
kernel.img                                                 --->  Compiled production kernel.img partition image

1.1 Install Dev Packages

Install dev packages:

sudo apt-get install gcc-arm-linux-gnueabihf build-essential lzop libncurses5-dev libssl-dev
# If using 64 bits Ubuntu, you need also:
sudo apt-get install libc6:i386

1.2 Install mkbootimg utility

git clone https://github.com/neo-technologies/rockchip-mkbootimg.gitcd rockchip-mkbootimg
make && sudo make install

1.3 Get Kernel Source and Cross Compiling Toolchain

If you have already downloaded the Firefly-RK3288 Android SDK, the kernel source and cross compiling toolchain are in SDK/kernel and SDK/prebuilts respectively. Please skip to next step.

If not, please download the kernel source code and Android's arm-eabi-4.6 cross compiling toolchain.

Download the kernel source code：

git clone https://bitbucket.org/T-Firefly/firefly-rk3288-kernel.git

If you are using Firefly-RK3288-Reload board, please download the "lollipop" branch, and then checkout to "lollipop"

git fetch origin lollipop:lollipop
git checkout lollipop

Note: This is Linux kernel source code in separated source repository, which is extracted from Firefly-RK3288 Android SDK, for convenience of users who only want the kernel source code instead of the huge sdk.

For Android's arm-eabi-4.6 cross compiling toolchain, you may look around to see if any  local Android SDK has prebuilts/gcc/linux-x86/arm/arm-eabi-4.6. If there is, you can reuse it; otherwise download from here and extract it.

2 Compile Kernel

2.1 Compile Image

If you are not compiling kernel in the SDK, you need to specify ARCH and CROSS_COMPILE first:

export ARCH=arm
export CROSS_COMPILE=/path/to/prebuilts/gcc/linux-x86/arm/arm-eabi-4.6/bin/arm-eabi-

In the kernel source directory, execute:

make firefly-rk3288-linux_defconfig
make -j8 firefly-rk3288-linux.img

If you are using Firefly-RK3288-Reload board, executeː

make firefly-rk3288-reload-linux_defconfig
make -j8 firefly-rk3288-reload-linux.img

Note: if you are using the beta development board, please replace "firefly-rk3288.img" above with "firefly-rk3288_beta.img".

2.2 Compile Modules

Run:

make modules
mkdir modules_install
make INSTALL_MOD_PATH=./modules_install modules_insatll

Copy the kernel module files to the root file system:

rsync -av ./modules_install/ /path/to/your/rfs/

You can also copy to the development board, using ssh remote connection:

rsync -av ./modules_install/ root@:/

Clean up the module install directory (it  contains links which impact compilation of Android SDK):

rm -rf ./modules_install

3 Create boot.img

3.1 Create Initramfs

The kernel will load the initramfs as the first root file system. It is in charge of finding the actual root device, load it then finally switch to it. The development board use eMMC flash. There is no need of special kernel module file. Actually you can skip this step. But initramfs offers flexibility like multiple OS boot.

git clone -b for-kernel_4.4  
make -C initrd

3.2 Package Kernel and Initramfs

Package kernel and initramfs into boot.img:

# mkbootimg --kernel arch/arm/boot/zImage --ramdisk initrd.img -o boot.img
mkbootimg --kernel zImage --ramdisk initrd.img --second resource.img --output boot.img

4 Modify Parameter File

The root file system can reside on different partitions in different storage devices (eMMC, TF card or USB disk, etc). It must be specified in the kernel's command line. There is a CMDLINE in the paramter file:

CMDLINE:console=tty0 ... mtdparts=rk29xxnand:0x00002000@0x00002000(uboot),...,-@0x00394000(user)

Add one of below according to your need: (# and contents after are comments, no need to enter):

root=/dev/block/mtd/by-name/linuxroot        # flash partition named "linuxroot"
root=/dev/mmcblk0p1          # First partition of TF card
root=/dev/sda1               # First partition of USB disk
root=LABEL=linuxroot         # Partition whose label is "linuxroot"

5 Flash to Device

Please reference Flash image, choose the newly created boot.img and modified parameter files, flash to "boot" and "parameter" partitions respectively. Then the kernel update is done.

If the root filesystem image is not flashed yet, you can download the prebuilt image, or customize your own one, and flash it to the partition specified in parameter file.