[RFC] arm: Defer lookup of machine_type and vet of atags to setup.c

[Russell King - ARM Linux]

On Tue, Jan 11, 2011 at 08:36:30AM -0700, Grant Likely wrote:
> On Tue, Jan 11, 2011 at 10:40:51AM +0000, Russell King - ARM Linux wrote:
> > On Mon, Jan 10, 2011 at 07:15:53PM -0700, Grant Likely wrote:
> > > diff --git a/arch/arm/kernel/head.S b/arch/arm/kernel/head.S
> > > index 6bd82d2..9c0e938 100644
> > > --- a/arch/arm/kernel/head.S
> > > +++ b/arch/arm/kernel/head.S
> > > @@ -87,11 +87,6 @@ ENTRY(stext)
> > >  	movs	r10, r5				@ invalid processor (r5=0)?
> > >   THUMB( it	eq )		@ force fixup-able long branch encoding
> > >  	beq	__error_p			@ yes, error 'p'
> > > -	bl	__lookup_machine_type		@ r5=machinfo
> > > -	movs	r8, r5				@ invalid machine (r5=0)?
> > > - THUMB( it	eq )		@ force fixup-able long branch encoding
> > > -	beq	__error_a			@ yes, error 'a'
> > > -	bl	__vet_atags
> > >  #ifdef CONFIG_SMP_ON_UP
> > >  	bl	__fixup_smp
> > >  #endif
> > 
> > Don't forget to update the comments as well - there's two of them.
> 
> I'm not entirely clear on what you're referring to here.  Are you
> talking about the secondary cpu entry point?  I've fixed up that
> comment now as well as a s/__lookup_machine_type/__lookup_processor_type/
> typo right before the call to __enable_mmu.

In the above code, __lookup_machine_type is called, which to be
consistent with __lookup_processor_type, returns its value in r5.  This
is then copied to r8, which is the only point that r8 is initialized.

The remainder of the code used to make use of r8 to load various fields
from the machine record, and so there's a couple of comments indicating
that this is the case.  These comments are left behind after your patch
and so are misleading.

Shall I assume that you've already searched the head*.S files to make
sure that r8 isn't used before you removed its initialization? ;-)