[U-Boot] [PATCH v5 1/3] Add README for the "Falcon" mode

[Stefan Roese <stefan.roese@gmail.com>]

On 12.02.2013 12:48, Andreas Bie?mann wrote:

<big snip>

> The spl export command does not write to a storage media. The user is
> responsible to transfer the gathered information (assembled ATAGS list
> or prepared FDT) from temporary storage in RAM into persistant storage
> after each run of 'spl export'. Unfortunately the position of temporary
> storage can not be predicted nor provided at commandline, it depends
> highly on your system setup and your provided data (ATAGS or FDT).
> However at the end of an succesful 'spl export' run it will print the
> RAM address of temporary storage.
> Now the user have to save the generated BLOB from that printed address
> to the pre-defined address in persistent storage
> (CONFIG_CMD_SPL_NAND_OFS in case of NAND).
> The following example shows how to prepare the data for Falcon Mode on
> twister board with ATAGS BLOB.
> --->8---
> 
> Would be nice to have some FDT example too (in future).

I used FDT with SPL already on the a3m071 board. Please take a look at
the README (board/a3m071/README):

...
Preparing Linux image(s) for booting from SPL U-Boot:
-----------------------------------------------------
To boot the Linux kernel from the SPL, the DT blob (fdt) needs to get
prepard/patched first. U-Boot usually inserts some dynamic values into
the DT binary (blob), e.g. autodetected memory size, MAC addresses,
clocks speeds etc. To generate this patched DT blob, you can use
the following command:

1. Load fdt blob to SDRAM:
=> tftp 1800000 a3m071/a3m071.dtb

2. Set bootargs as desired for Linux booting (e.g. flash_mtd):
=> run mtdargs addip2 addtty

3. Use "fdt" commands to patch the DT blob:
=> fdt addr 1800000
=> fdt boardsetup
=> fdt chosen

4. Display patched DT blob (optional):
=> fdt print

5. Save fdt to NOR flash:
=> erase fc060000 fc07ffff
=> cp.b 1800000 fc060000 10000
...

So all we need for DT based booting (compared to ATAG booting) is the
"fdt" command.

Stefano, perhaps you could integrate this into this README as well.

Thanks,
Stefan