[PATCH 4/6] ARM: smp: set thread_info->cpu to hardware CPU number for boot thread

[Will Deacon]

On Mon, Aug 08, 2011 at 06:33:38PM +0100, Stephen Boyd wrote:
> On 08/08/2011 10:10 AM, Will Deacon wrote:
> >
> >  
> > +void __init smp_setup_processor_id(void)
> > +{
> > +	u32 mpidr;
> > +
> > +	/* Read the MPIDR to find the hardware ID of the current CPU. */
> > +	asm("1:		mrc	p15, 0, %0, c0, c0, 5\n"
> > +	    "		.pushsection \".alt.smp.init\", \"a\"\n"
> > +	    "		.long	1b\n"
> > +	    "		mov	%0, #0\n"
> > +	    "		.popsection"
> > +	    : "=r" (mpidr));
> 
> Would it be a good idea to put this into asm/cputype.h? I suppose the
> smp alternatives part would need to be written in C.
> 
>     mpidr = is_smp() ? read_cpuid_mpidr() : 0;

Yes, that's much better. We used to have asm/smp_mpidr.h which did this, so I
lifted the code from there but doing it in C is easier to read.

> >
> > +
> > +	current_thread_info()->cpu = mpidr & 0xff;
> > +	printk("Booting Linux on CPU %d\n", current_thread_info()->cpu);
> > +}
> > +
> 
> Should there be a KERN_INFO there?

Can be. I just followed suit with secondary_start_kernel, but smp.c doesn't
seem to be consistent anyway so I'll add the specifier.

Thanks for the comments,

Will