Android Customizing U-Boot

Toolchain setup for manual U-Boot build

$ export ARCH=arm
Setup the toolchain path to point to arm-eabi- tools in prebuilts/gcc/linux-x86/arm/arm-eabi-4.6/bin
$ export CROSS_COMPILE=//prebuilts/gcc/linux-x86/arm/arm-eabi-4.8/bin/arm-eabi-

Manual build Bootloader 

Change directory to U-Boot

$ cd //bootable/bootloader/uboot-imx

Execute following commands:

clean tree:
$ make mrproper

Choose build for SD card or NAND flash:
$ make mx6var_som_sd_android_defconfig
or
$ make mx6var_som_nand_android_defconfig

Build U-Boot:
$ make -j4

This command will generate the U-Boot images 'SPL' and 'u-boot'.

Flash newly created bootloader

To flash the newly created SPL and u-boot images, replace the following files in the recovery SD card image.

SPL Images:

SPL-nand ---------------- NAND SPL
SPL-sd ------------------ eMMC / SD SPL

U-boot Images:

u-boot-var-imx6-nand.img - NAND U-boot
u-boot-var-imx6-sd.img --- eMMC / SD U-boot

Path Where to Replace Android Image: /opt/images/Android/

Sync and safely remove the SD card after replacing image.

Boot And Flash new updated bootloader

1. Change the DIP switch settings to SD boot mode depending upon your HW.
2. Flash the Android images. (Be careful this will wipe out your Android partitions and re-create it) on eMMC / NAND