[U-Boot] [PATCH] mpc83xx: Make it boot again

[Scott Wood]

On Wed, 17 Nov 2010 20:15:01 +0100
Joakim Tjernlund <joakim.tjernlund at transmode.se> wrote:

> Scott Wood <scottwood at freescale.com> wrote on 2010/11/17 20:03:25:
> > The "load, conditional branch, isync" sequence is documented in the
> > architecture manual (1.7.1), "even if the effects of the 'dependency'
> > are independent of the value loaded".
> 
> So it doesn't matter what address you do twi on?
> Still, it would make a little more sense if
> it read twi 0,r3,0

It's not an address, it's data that is being compared with zero.  And it
has to be r4, since that's what you want to create the data dependency
on.

The architecture suggests a similar but slightly longer sequence (but
I don't think the wording rules out using twi), which may make the
intent clearer:

lwz	r4, ...
cmpw	r4, r4
beq	1f
1: isync

-Scott