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

[Stefan Roese <sr@denx.de>]

Hi Sergey, Hi Heiko,

On 26.04.2016 07:43, Heiko Schocher wrote:
> 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.

I've missed such a tool a few years ago while porting U-Boot & Linux
to a i.MX6 based NAND booting board as well. And noticed since then
that barebox has included such a tool:

http://lists.infradead.org/pipermail/barebox/2014-March/018202.html

Perhaps its not too much work to port this tool over to U-Boot?
Just an idea...

Thanks,
Stefan