Re: booting BeagleBoneGreen

["John D. Baker" <jdbaker%mylinuxisp.com@localhost>]

Getting closer yet.  After figuring out the MLO/u-boot.img magic, I
watched the startup more carefully and determined that U-Boot was, in
fact, reading the "uEnv.txt" file from the DOS partition on the microSD
card.

It seems to ignore the "loaduimage" command variable, so it falls through,
looking for "zImage" as the kernel image file.  When it can't find it, it
switches to the eMMC and repeats the process where it finds the Linux
install.

So, renaming "netbsd-BEAGLEBONE.ub" to "zImage" (although NOT compressed),
U-Boot now loads and starts the NetBSD kernel from the microSD card.

The resulting "bootargs" setting prompts the BBG to panic complaining
of no console.

Setting "bootargs=root=ld0a console=com0" in uEnv.txt (instead of
"console=fb") uses the proper console.

It does process "uenvcmd".  Inserting the instructions to disable the
watchdog at the beginning of the "uenvcmd" variable allows fully automated
boot.

These same procedures will be also be needed to prepare the eMMC.

Write "MLO" starting at sector 256 (offset 0x00020000).
Write "u-boot.img" starting at sector 768 (offset 0x00060000).
MBR partition starting at sector 2048 (offset 0x00100000) or later.
Disklabel partitions as desired following MBR partition.
Kernel file in MBR partition must be uncompressed and named "zImage".
Omit "console=*" or explicitly set "console=com0" in "bootargs".
Insert "mw 44e35048 aaaa ; sleep 1 ; mw 44e35048 5555 ;" at beginning
of "uenvcmd" variable to disable watchdog.

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