Hi,

I'm trying to automate the process of flashing a bootable emmc (NAND) on my 
beagle bone black. I've pin strapped the board to boot using bootp/dhcp - 
the kernel that gets loaded by the u-boot.img (that was pulled in via 
dhcp+tftp) uses an initramfs as the basis of writing the MLO, (a different) 
u-boot.img and root file system (containing zImage and uEnv.txt) to 
emmc/NAND. This all works and when I restart the beagle bone black it boots 
as I expect. Hooray for automated emmc flashing.

However my problem is that I can't seem to hand roll a version the the MLO 
and u-boot.img that I flash to NAND. What I'm using right now are copies I 
found of these two files in the debian images distributed here: 
https://beagleboard.org/latest-images (These images tend to contain 
filesystems with /opt/backup/uboot/MLO and /opt/back/uboot/u-boot.img files 
existing). If I use these two boot loader files, and craft my 
/boot/uEnv.txt just so (uuid needs to be specified), then I can boot a 
couple of kernels/filesystems I have lying around successfully.

But I can't seem to reproduce these two files (MLO and u-boot.img) for my 
NAND from source. I've tried these git repos:

git://git.denx.de/u-boot.git
git://git.ti.com/ti-u-boot/ti-u-boot.git

and even the u-boot source that that ships with the SDK:
~/ti-processor-sdk-linux-am335x-evm-04.00.00.04/board-support/u-boot-2017.01+gitAUTOINC+9fd60700db-g9fd60700db/

For each of those I'm running

make CROSS_COMPILE=arm-linux-gnueabihf- O=am335x_evm am335x_evm_defconfig 
&& make CROSS_COMPILE=arm-linux-gnueabihf- O=am335x_evm

And I've even tried a different config:

make CROSS_COMPILE=arm-linux-gnueabihf- O=am335x_boneblack 
am335x_boneblack_defconfig && make CROSS_COMPILE=arm-linux-gnueabihf- 
O=am335x_boneblack

This compilation process creates the MLO and u-boot.img files, but I can 
never seem to successfully boot anything if I use them regardless of which 
config I use.

If it helps with clarity, I am trying out MLO and u-boot.img files by 
booting from the SD card, copying over the new versions, and then running

dd if=MLO of=/dev/mmcblk1 conv=notrunc bs=128k count=1 seek=1
dd if=u-boot.img of=/dev/mmcblk1 conv=notrunc bs=384k count=2 seek=1

Note that I can always get back to the "bootable state" by writing the 
backup boot loader files that come with debian distro instead: (the sd card 
is running debian 8.7):

dd if=/opt/backup/uboot/MLO of=/dev/mmcblk1 conv=notrunc bs=128k count=1 
seek=1
dd if=/opt/backup/uboot/u-boot.img of=/dev/mmcblk1 conv=notrunc bs=384k 
count=2 seek=1


How can I build MLO and u-boot.img files in order to successfully boot a 
kernel and file system of my choosing on the emmc/NAND? Is there a page 
somewhere? Any help would be appreciated.

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