[U-Boot-Users] builtin OF tree dtb gone

Joakim Tjernlund joakim.tjernlund at transmode.se
Sun Dec 17 16:40:09 CET 2006

> -----Original Message-----
> From: glikely at gmail.com [mailto:glikely at gmail.com] On Behalf 
> Of Grant Likely
> Sent: den 17 december 2006 16:11
> To: Joakim Tjernlund
> Cc: wd at denx.de; u-boot-users at lists.sourceforge.net
> Subject: Re: [U-Boot-Users] builtin OF tree dtb gone
> On 12/17/06, Joakim Tjernlund <joakim.tjernlund at transmode.se> wrote:
> >
> > "in some setups", that's the point. Our setup works fine with
> > an embedded OF tree in u-boot. If I am to adapt to this new
> > method of supplying the OF tree, not only will I have to repartion
> > the flash to fit the tree in there, I also need to make sure
> > that some 15-20 people learns this new concept for no real gain.
> >
> > It is nothing wrong with having the ability provide a OF tree
> > at boot time, but forcing everyone to do so is. The
> > most flexible way is to have both.
> This shouldn't be too big a deal.  Add the code back for linking the
> .dtb into the image.  Look in common/boot.c and add a check for if the
> third bootm parameter is '-'.  If it is, then use the builtin section
> for the .dtb address.  Then you can either use the builtin version, or
> pass a new one.  We're not talking a lot of code here.

I am looking at this now. I have a DTB linked into uboot at address
0xffc9d90(near end of my 256MB RAM when u-boot has relocated itself).
Passing this address to bootm $loadaddr - 0xffc9d90 makes the
kernel SEGV because the kernel can't access data that high up in RAM
early in the boot process.
Seems to that the u-boot should copy the DTB to an address that 
the kernel can access before passing control the kernel. How
else is one supposed to have a DTB in flash that is even higher up
in the address space?

Maybe I have misunderstood something, but I can't se what presently.

> Alternately; your u-boot image does not totally fill the sectors you
> have allocated for it.  Since your plan is to update u-boot and the
> .dtb at the same time; modify your u-boot build procedure (I think by
> using objcopy) to link your .dtb to a known address within the unused
> part of the u-boot sectors (so that u-boot+dtb are in a single file)
> and make sure the update procedure also changes the default bootm
> command to include the known dtb address.

This option does not really suit me, but thanks for the suggestion.


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