Tools
upgrade_tool is rockchip offical tool, you can find it under rkbin/tools.
rkflashtool is opensource flash tool.
git clone https://github.com/ARM-software/arm-trusted-firmware.git
git clone https://github.com/rockchip-linux/rkbin
git clone https://github.com/rockchip-linux/rkflashtool
cd ../rkflashtool
make
make install