[U-Boot] RFC: i.MX6 write U-Boot to NAND

[Heiko Schocher <hs@denx.de>]

Hello Sergey,

add Stefano to Cc as he is the imx6 custodian,

Am 25.04.2016 um 22:29 schrieb Sergey Kubushyn:
> Hi everybody,
>
> It looks like using kobs-ng utility is the only way to make a bootable NAND
> for i.MX6 and their siblings. There might be other utilities I'm not aware
> of but that doesn't change anything -- you need Linux (or whatever that
> utility runs on) running on your board to create and write all those FCB and
> other parts onto a virgin raw NAND device.

Yes, I stumbled over that too recently ...

> This makes initial programming a cumbersome and complicated operation. One
> can not program NAND on a development machine as it is easy to do with e.g.
> SD Card -- the OS must run on the same board where that NAND is because NAND
> is not removable.
>
> It is possible, of course, to assemble something on an SD Card and use that
> to program NAND but that assumes there is an SD Card slot on a target system
> and some means to tell it to boot off of SD Card. However it is not always a
> case -- there might be boards with NAND as only storage device available.
> That leaves only Serial/USB boot as only options for initial boot on a
> virgin board. However it does not provide means for writing the NAND U-Boot
> into actual NAND.
>
> There are many different varieties of NAND chips so those FCB and other
> structures are not generic i.e. they can not be defined beforehead and just
> prepended to the actual U-Boot image. Even if we have made those a
> configuration parameters there are still bad block tables that are chip
> specific so they should be discovered first i.e. FCB should be built
> dynamically based on NAND scanning results.
>
> Sure, one can write a custom first stage SPL that would've booted the actual
> U-Boot via the same Serial/USB interface and run it but then what? Let's
> assume the target board doesn't have ethernet so it would make it impossible
> to mount rootfs over NFS and no other storage devices available. It is still
> possible to load Linux kernel and bare minimal rootfs in initramfs image but
> that's a lot of serial downloading just for initializing NAND...
>
> It would be nice to have a U-Boot command that would've allowed initial NAND
> setup and writing NAND U-Boot image to it properly updating the headers.

Yes, that would be great!

> There might be other ways to do this that I might've overlooked...
>
> Does anybody knows a ready-made solution or works on something suitable for
> this purpose? I don't want to re-invent the wheel starting my own solution
> so it would've been good to hear from other guys who might've solved this
> dilemma.

Sorry, I do not know another way.

> Any thoughts?

I think, an U-Boot command which writes the headers into the nand would
be a good thing.

tools/imximage.c is may the wrong place, as the infos in FCB and DBBT
are dependend on the boards nand.

bye,
Heiko
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