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

[Will Deacon]

On Tue, Aug 09, 2011 at 12:48:05PM +0100, Sergei Shtylyov wrote:
> Hello.
> 
> On 08-08-2011 21:10, Will Deacon wrote:
> 
> > On ARM, Linux assumes that the boot CPU has ID 0. If this ends up being
> > out of sync with the hardware CPU number, we will configure the GIC
> > incorrectly and route interrupts to the CPU with hardware ID 0.
> 
> > This patch implements smp_setup_processor_id for ARM, using the MPIDR to
> > set the CPU of the boot thread.
> 
> > Signed-off-by: Will Deacon<will.deacon at arm.com>
> > ---
> >   arch/arm/kernel/smp.c |   16 ++++++++++++++++
> >   1 files changed, 16 insertions(+), 0 deletions(-)
> 
> > diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
> > index d88ff02..8e60a4f 100644
> > --- a/arch/arm/kernel/smp.c
> > +++ b/arch/arm/kernel/smp.c
> > @@ -259,6 +259,22 @@ void __ref cpu_die(void)
> >   }
> >   #endif /* CONFIG_HOTPLUG_CPU */
> >
> > +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));
> > +
> > +	current_thread_info()->cpu = mpidr&  0xff;
> > +	printk("Booting Linux on CPU %d\n", current_thread_info()->cpu);
> 
>     printk() should have the KERN_* logging facility.

There's an echo around here :) This patch is pretty much dead anyway after
the discussion with Russell. I'll post some other guys soon.

Will