[U-Boot] [PATCH] armv7: Fix infinite loop for the spl boot

[Albert ARIBAUD <albert.u.boot@aribaud.net> (by way of Albert ARIBAUD <albert.u.boot@aribaud.net>]

Hi Zhong Hongbo,

On Thu, 05 Jul 2012 19:53:46 +0800, Zhong Hongbo <bocui107@gmail.com>
wrote:
> Hi Albert,
> 
> Could you applied the patch to the arm tree?
> 
> Thanks,
> hongbo
> On 07/03/2012 07:46 AM, Zhong Hongbo wrote:
> > From: Zhong Hongbo <bocui107@gmail.com>
> > 
> > In the spl booting step, When __bss_start is equal to __bss_end__,
> > The loop will clear all the things in CPU space. If there are have
> > the same address for this symbol, To skip the clear bss section.
> > 
> > Signed-off-by: Hongbo Zhong <bocui107@gmail.com>
> > ---
> >  arch/arm/cpu/armv7/start.S |    3 +++
> >  1 files changed, 3 insertions(+), 0 deletions(-)
> > 
> > diff --git a/arch/arm/cpu/armv7/start.S b/arch/arm/cpu/armv7/start.S
> > index 76ccef1..c72f337 100644
> > --- a/arch/arm/cpu/armv7/start.S
> > +++ b/arch/arm/cpu/armv7/start.S
> > @@ -258,6 +258,8 @@ clear_bss:
> >  	/* No relocation for SPL */
> >  	ldr	r0, =__bss_start
> >  	ldr	r1, =__bss_end__
> > +	cmp	r0, r1
> > +	beq	skip_clbss
> >  #else
> >  	ldr	r0, _bss_start_ofs
> >  	ldr	r1, _bss_end_ofs
> > @@ -271,6 +273,7 @@ clbss_l:str	r2, [r0]		/*
> > clear loop...		    */ add	r0, r0, #4
> >  	cmp	r0, r1
> >  	bne	clbss_l
> > +skip_clbss:

Clearly the loop was wrong in that it should implement a "for (r0 =
start; r0 < end; r0++)" but actually implements a "for (r0 =
start; r0 != end; r0++)".

I'd rather the loop be fixed to match the intended implementation
rather than worked around. Please rewrite your patch to turn:

> clbss_l:str     r2, [r0]  /* clear loop...*/
>         add     r0, r0, #4
>         cmp     r0, r1
>         bne     clbss_l

Into something like

> clbss_l:cmp     r0, r1
>         blo     clbss_d
>         str     r2, [r0]  /* clear loop...*/
>         add     r0, r0, #4
>         b       clbss_l
> clbss_d:

Also, as Andreas points out, make sure the same fix is applied to all ARM start.S files which need it.

Thanks in advance.

Amicalement,
-- 
Albert.