[U-Boot-Users] PPC4xx OF Flat Tree Support

[U-Boot-Users] PPC4xx OF Flat Tree Support

[Darcy Watkins]

Hello,

I am investigating migration of our AMCC405EP embedded linux based
product from arch/ppc to arch/powerpc so that I can keep on top of real
time extensions and other things that have abandoned the arch/ppc tree.
I have just got to the point where I can compile linux kernel
2.6.24-rc3-git2 under arch/powerpc, but it will not boot.  Further
investigation leads to the boot process being different between the two
arch trees.

I read up on this open firmware (OF) flattened device tree (fdt) that
gets passed to the kernel and discover that there is no support for it
in the u-boot cpu support modules for the ppc4xx CPU family.

I know that there is work in progress going on out there to migrate the
Walnut (AMCC405GP) to arch/powerpc, and a new AMCC Kilauea board based
on the new AMCC405EX processor appears under arch/powerpc - but neither
of these appear to have board support or the OF fdt support in u-boot
yet.  I checked the latest release (1.3.0) and the git repository.

My requirement essential breaks out as follows:
 1.  I need OF fdt support for ppc4xx (at least I think I need it)
 2.  I need to implement a u-boot board support for our Taihushui board.
 3.  If possible, I would like to have u-boot be able to boot a linux
kernel
     built from either arch/ppc or arch/powerpc (with some form of
option in
     the bootm command to choose, or determine it from info in the
uImage).

If anyone has useful comments, suggestions and/or can point me to
work-in-progress, patches, etc that would help me further investigate
this, I'd appreciate it.

Thanks in advance!

Regards,

Darcy

[U-Boot-Users] PPC4xx OF Flat Tree Support

[Stefan Roese]

Hi Darcy,

On Friday 30 November 2007, Darcy Watkins wrote:
> I am investigating migration of our AMCC405EP embedded linux based
> product from arch/ppc to arch/powerpc so that I can keep on top of real
> time extensions and other things that have abandoned the arch/ppc tree.
> I have just got to the point where I can compile linux kernel
> 2.6.24-rc3-git2 under arch/powerpc, but it will not boot.  Further
> investigation leads to the boot process being different between the two
> arch trees.

Right.

> I read up on this open firmware (OF) flattened device tree (fdt) that
> gets passed to the kernel and discover that there is no support for it
> in the u-boot cpu support modules for the ppc4xx CPU family.
>
> I know that there is work in progress going on out there to migrate the
> Walnut (AMCC405GP) to arch/powerpc, and a new AMCC Kilauea board based
> on the new AMCC405EX processor appears under arch/powerpc - but neither
> of these appear to have board support or the OF fdt support in u-boot
> yet.  I checked the latest release (1.3.0) and the git repository.
>
> My requirement essential breaks out as follows:
>  1.  I need OF fdt support for ppc4xx (at least I think I need it)

Correct.

>  2.  I need to implement a u-boot board support for our Taihushui board.

Correct.

>  3.  If possible, I would like to have u-boot be able to boot a linux
> kernel
>      built from either arch/ppc or arch/powerpc (with some form of
> option in
>      the bootm command to choose, or determine it from info in the
> uImage).

That is possible.

> If anyone has useful comments, suggestions and/or can point me to
> work-in-progress, patches, etc that would help me further investigate
> this, I'd appreciate it.

Good news for you: Work-in-progress? Yes! Please take a look at 
the "for-1.3.1" branch of my u-boot-ppc4xx custodian repository:

http://www.denx.de/cgi-bin/gitweb.cgi?p=u-boot/u-boot-ppc4xx.git;a=shortlog;h=for-1.3.1

It has quite a bit of 4xx-fdt support already available. Tested right now only 
on Kilauea (405EX). But it should be possible to enable fdt support on other 
4xx board with little effort building on this code.

BTW: You may have noticed that the U-Boot fdt support is undergoing rapid 
changes right now (I'm having troubles keeping up here :)). So there may be 
some rework necessary to bring this new 4xx fdt support up-to-date. But this 
will happen in the next few weeks.

So if you still have a little time, I suggest you wait till the new stuff 
hit's the master U-Boot repository and you base you stuff on this version. 
But you are of course free to take a look at the already available fdt 
support in the "for-1.3.1" branch (yes, the name is not correct anymore, 
since 1.3.1 has no "real" merge window).

Best regards,
Stefan

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