1. git clone git://git.freescale.com/imx/uboot-imx.git

2. cd uboot-imx
git checkout -b imx_v2009.08_3.0.35_4.1.0 --track remotes/origin/imx_v2009.08_3.0.35_4.1.0

3. make ARCH=arm CROSS_COMPILE=arm-wrs-linux-gnueabi- mx6q_sabresd_config

4. make ARCH=arm CROSS_COMPILE=arm-wrs-linux-gnueabi-

5. the newly generated u-boot.bin is dd to sd card
sudo dd if=u-boot.bin of=/dev/sdb bs=512 seek=2 skip=2 conv=fsync

6. boot the board with this u-boot.bin