confusions of boot sequence in MPC8572?

confusions of boot sequence in MPC8572?

[Michael.Kang]

I am reading the boot code in arch/powerpc/kernel/head_fsl_booke.S for
MPC8572( dual e500 core). The second core will encounter the following
code:

 319 #ifdef CONFIG_SMP
 320         /* Check to see if we're the second processor, and jump
 321          * to the secondary_start code if so
 322          */
 323         mfspr   r24,SPRN_PIR
 324         cmpwi   r24,0
 325         bne     __secondary_start
 326 #endif

And jump to __secondary_start -> call_setup_cpu,  source code in
call_setup_cpu as the following:
112 _GLOBAL(call_setup_cpu)
113         addis   r4,r3,cur_cpu_spec@ha
114         addi    r4,r4,cur_cpu_spec@l
115         lwz     r4,0(r4)
116         add     r4,r4,r3
117         lwz     r5,CPU_SPEC_SETUP(r4)
118         cmpwi   0,r5,0
119         add     r5,r5,r3
120         beqlr
121         mtctr   r5
122         bctr

here it seems cur_cpu_spec here is not a valid value since
cur_cpu_spec will only be set in identify_cpu() [
arch/powerpc/kernel/cputable.c: 1301] later.

So what is my mistake? Who responsible for initialize cur_cpu_spec
variable for second core??

Thanks
MK



-- 
www.skyeye.org

Re: confusions of boot sequence in MPC8572?

[Scott Wood]

On Thu, Sep 18, 2008 at 09:49:34PM +0800, Michael.Kang wrote:
> And jump to __secondary_start -> call_setup_cpu,  source code in
> call_setup_cpu as the following:
> 112 _GLOBAL(call_setup_cpu)
> 113         addis   r4,r3,cur_cpu_spec@ha
> 114         addi    r4,r4,cur_cpu_spec@l
> 115         lwz     r4,0(r4)
> 116         add     r4,r4,r3
> 117         lwz     r5,CPU_SPEC_SETUP(r4)
> 118         cmpwi   0,r5,0
> 119         add     r5,r5,r3
> 120         beqlr
> 121         mtctr   r5
> 122         bctr
> 
> here it seems cur_cpu_spec here is not a valid value since
> cur_cpu_spec will only be set in identify_cpu() [
> arch/powerpc/kernel/cputable.c: 1301] later.
> 
> So what is my mistake? Who responsible for initialize cur_cpu_spec
> variable for second core??

There is only one cur_cpu_spec for all cores, which is initialized by the
boot core before it releases the secondaries.

-Scott