[U-Boot] [RFC] powerpc/lib: unsafe register handling in wait_ticks

[Joakim Tjernlund]

Wolfgang Denk <wd at denx.de> wrote on 2013/01/24 20:27:26:
> 
> Dear Joakim Tjernlund,
> 
> In message <OF52C94A3D.C3BD2E6F-ONC1257AFD.005BAFE0-C1257AFD.
> 006736C5 at transmode.se> you wrote:
> > 
> > This adds some extra churn to the code that my patch didn't do.
> > On the other hand your patch makes the function look more
> > like how gcc would have done so I am fine with that.
> > However, I am not sure r14 is a good fit, I cannot remember if there 
is
> > some
> > special purpose for r14. Hopefully somebody on the list knows.
> 
> This is documented in the README:
> 
> | For PowerPC, the following registers have specific use:
> |    R1:   stack pointer
> |    R2:   reserved for system use
> |    R3-R4:   parameter passing and return values
> |    R5-R10: parameter passing
> |    R13:   small data area pointer
> |    R30:   GOT pointer
> |    R31:   frame pointer
> | 
> |    (U-Boot also uses R12 as internal GOT pointer. r12
> |    is a volatile register so r12 needs to be reset when
> |    going back and forth between asm and C)
> | 
> |     ==> U-Boot will use R2 to hold a pointer to the global data
> | 

Right, then I think the patch is good:

Acked-by: Joakim Tjernlund <joakim.tjernlund at transmode.se>