boot BBB from u-boot (no initramfs, no overlays)

# this is for booting from eMMC;
# to boot from SD card use "mmc 0:1" instead of "mmc 1:1" and "mmcblk0p1" instead of "mmcblk1p1"

# set defaults
run findfdt ; setenv dtb $fdtfile

# load settings from /boot/uEnv.txt
load mmc 1:1 $loadaddr /boot/uEnv.txt
env import -t $loadaddr $filesize

# this is the right time to customize if needed, e.g. to
# reset the dtb to its default:
#setenv dtb $fdtfile

# load kernel
load mmc 1:1 $loadaddr /boot/vmlinuz-$uname_r

# load DT (try two locations):
load mmc 1:1 $fdtaddr /boot/dtbs/$uname_r/$dtb || load mmc 1:1 $fdtaddr /boot/dtbs/$dtb

# set kernel parameters
setenv bootargs console=$console root=/dev/mmcblk1p1 ro rootfstype=ext4 rootwait $cmdline

# go!
bootz $loadaddr - $fdtaddr