[U-Boot] mpc512x: Trouble migrating from 2012.07 to 2013.01

[Joakim Tjernlund]

Joakim Tjernlund/Transmode wrote on 2013/01/24 09:40:45:

> From: Joakim Tjernlund/Transmode
> To: Mats Kärrman <Mats.Karrman at tritech.se>, 
> Cc: "u-boot at lists.denx.de" <u-boot at lists.denx.de>, Wolfgang Denk 
<wd at denx.de>
> Date: 2013/01/24 09:40
> Subject: RE: [U-Boot] mpc512x: Trouble migrating from 2012.07 to 2013.01
> 
> Mats Kärrman <Mats.Karrman at tritech.se> wrote on 2013/01/23 22:58:56:
> > 
> > Dear Wolfgang Denk,
> > 
> > >> Found that it was looping endlessly in 
arch/powerpc/lib/ticks.S::wait_ticks
> > (). Reverting commit "ppc: Create a stack frame for wait_ticks()" made 

> > everything work again.
> > > 
> > > This makes no sense to me  - especially as it works on all other
> > > systems.
> > 
> 
> Me neither, there is not a lot details. I do recall having other 
problems with
> wait_ticks from time to time, sometimes the TB counter(mtfbu, mftb in 
get_ticks)
> would not increment so one would just loop forever in wait_ticks. This 
problem
> had nothing to do with my patch though.
> Never got around to finding out what caused it, we ended up blaming 
unstable HW.
> 
> Some ideas though:
> - Perhaps you have some alignment problem, try adding nop's here and 
there.
> - My patch uses r0(which is what one should use to make gdb happy) 
instead of r8
>   to stash the LR. Possibly you have some odd dependency on r0, try 
using r8 again.

Try getting LR from stack instead of trusting r0 to be valid:
-       mtlr    r0              /* restore link register */
+       lwz     r0, 20(r1)      /* restore link register */
+       mtlr    r0
This is what one should do but as we have complete control of r0 here we 
don't need to.

hmm, do you have WATCHDOG_RESET defined? does it use r0?
I guess the above patch would make wait_ticks safer from accidental use by 
WATCHDOG_RESET,
if it works for you, please send a proper patch to u-boot.

 Jocke