[U-Boot] [PATCH 6/6] powerpc: Add LINK_OFF calls in early C-code.

[Scott Wood]

On Wed, 24 Nov 2010 22:36:27 +0100
Joakim Tjernlund <joakim.tjernlund at transmode.se> wrote:

> Scott Wood <scottwood at freescale.com> wrote on 2010/11/24 18:16:56:
> >
> > On Wed, 24 Nov 2010 12:04:15 +0100
> > Joakim Tjernlund <joakim.tjernlund at transmode.se> wrote:
> >
> > > >
> > > > Scott Wood <scottwood at freescale.com> wrote on 2010/11/23 23:32:04:
> > > > >
> > > > > On Tue, 23 Nov 2010 23:14:06 +0100
> > > > > Joakim Tjernlund <joakim.tjernlund at transmode.se> wrote:
> > > > >
> > > > > > Scott Wood <scottwood at freescale.com> wrote on 2010/11/23 22:20:58:
> > > > > > > "load address" being pre-relocation?  Currently these must be equal
> > > > > > > (which doesn't seem particularly burdensome).
> > > > > >
> > > > > > Yes, but in our case we update the boot in the field and we want to
> > > > > > make that safer by having two uboot areas but we don't want to carry around
> > > > > > two u-boot images.
> > > > >
> > > > > How about playing with BATs before entering C code, so that the image
> > > > > always appears at the same effective address?
> > > >
> > > > hmm, never thought of that. The extra bonus would be that LINK_OFF should
> > > > not be needed either.
> > >
> > > After sleeping on it I realize that all direct accesses to the flash
> > > such as getting the env. will need to be adjusted instead.
> >
> > You could have one small mapping for the U-Boot image, and another
> > larger unchanging mapping that covers the whole flash.
> 
> Played a little with this but it seems like two BATs cannot overlap?

They can't overlap in effective address space.  They can have
overlapping physical addresses (make sure the WIMG bits are the same).

-Scott