[meta-xilinx] Zynq NAND Flash support in U-Boot SPL

[Oleg K Dzhimiev]

Hi,

Within my krogoth/yocto build I get several files and it is confusing
> which to use.
> I have a boot.bin (fsbl/bit/u-boot.elf) I generate/program in SDK and
> that works fine.

If I'd like to program NAND from within u-boot via say booting from an
> SD card, do you have a recommendation for which files to use? I've
> patched u-boot with my ps7 files and have CONFIG_SPL=y. Should I use
> SPL or is there a way to program my existing boot.bin directly?
>

1. If you are able to load the full u-boot then it doesn't matter what was
used - fsbl or spl.
To be able to write to NAND, you might need to include into the full u-boot
image:
* a driver that supports the flash chip.
* flash commands support  - example: elphel393.h
<https://github.com/Elphel/ezynq/blob/master/u-boot-tree/include/configs/elphel393.h>.
For the commands, see UBootCmdGroupNand
<http://www.denx.de/wiki/DULG/UBootCmdGroupNand>.

With our 10393 board <http://wiki.elphel.com/wiki/10393> I tried NAND
reading/writing a while ago but since then we program flash from OS (booted
from SD or NAND) only.
To be able to do this - make sure the required applications are included in
the rootfs - our current rootfs recipe
<https://github.com/Elphel/meta-elphel393/blob/master/recipes-core/images/core-image-elphel393.bb>.
Commands examples <http://wiki.elphel.com/wiki/NAND_flash_boot_rootfs>.

2. If your goal is to put the bootloaders to NAND flash and eventually boot
from it:
fsbl:
* Haven't used it for a while - don't know whether it can load the full
u-boot from flash.
spl:
* Make sure it comes with a driver to read from flash - we had to make our
own <https://github.com/Elphel/ezynq/tree/master/u-boot-tree>.

Best regards,
Oleg Dzhimiev
Electronics Engineer
phone: +1 801 783 5555 x124
Elphel, Inc.
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