[U-Boot] Download the u-boot from flash back to PC

[Jason]

On Wed, Jun 08, 2011 at 09:25:42AM -0400, Rishi Dhupar wrote:
> I have a board which has a version of u-boot on it that I would like
> to save before overwriting. I did not flash this version so I do not
> have the source code for it.

funny how often that happens... :-(
 
> I am trying to figure out is there away to essentially do a 'tftp get'
> of the u-boot.bin that was originally written to flash.  I do not see
> any methods to "read" data from U-boot back to the PC.  Is there any
> method to do this?

Here's what I've done in the past.

WARNING: read everything _before_ you start!

1.) On the device, in U-Boot, zero out some memory (1MB at 0x0800000)

$ mw.b 0x0800000 0x00 0x100000

2.) Read the bootloader into RAM at 0x0800000, size 1MB, offset into
nand, 0x300. 

$ nand read 0x0800000 0x300 0x100000

3.) close your minicom/screen/whatever that you are using to talk to the
serial port.  On your desktop, run the following:

$ printf "md.b 0x0800000 0x100000\r\r" | \
socat - /dev/ttyUSB0,raw,echo=0,crnl >u-boot.ascii 2>&1

This will take a while (10 - 20 minutes!), in another terminal, setup a
watch:

$ watch -n3 "ls -l u-boot.ascii"

4.) prep the ascii file for conversion to binary.
	a.) remove the first and last lines
	b.) start the address numbers (first column) at 0, eg

$ sed -i.bak -r -e 's/^008/000/' -e 's/^009/001/' u-boot.ascii

5.) Convert ascii to binary

$ xxd -r u-boot.ascii u-boot.bin

Notes: Obviously, your addresses and sizes are going to be different,
you may need to use 'sudo socat' for step 3.  This is from memory, I
just did it a week ago though.  You could always replace xxd with some
sort of sed/awk script.

hth,

Jason.