linux-kernel - Re: [PATCH 3/9] ARM: tegra: # of CPU cores detection w/ & w/o HAVE_ARM

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Message-ID: <20121220181818.GA26861@arwen.pp.htv.fi>
Date:	Thu, 20 Dec 2012 20:18:18 +0200
From:	Felipe Balbi <balbi@...com>
To:	Hiroshi Doyu <hdoyu@...dia.com>
CC:	"balbi@...com" <balbi@...com>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
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	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 3/9] ARM: tegra: # of CPU cores detection w/ & w/o
 HAVE_ARM_SCU

Hi,

On Thu, Dec 20, 2012 at 12:21:36PM +0100, Hiroshi Doyu wrote:
> Felipe Balbi <balbi@...com> wrote @ Thu, 20 Dec 2012 11:06:25 +0100:
> ...
> > > @@ -149,7 +154,26 @@ done:
> > >   */
> > >  static void __init tegra_smp_init_cpus(void)
> > >  {
> > > -	unsigned int i, ncores = scu_get_core_count(scu_base);
> > > +	unsigned int i, cpu_id, ncores;
> > > +	u32 l2ctlr;
> > > +	phys_addr_t pa;
> > > +
> > > +	cpu_id = read_cpuid(CPUID_ID) & CPU_MASK;
> > > +	switch (cpu_id) {
> > > +	case CPU_CORTEX_A15:
> > > +		asm("mrc p15, 1, %0, c9, c0, 2\n" : "=r" (l2ctlr));
> > > +		ncores = ((l2ctlr >> 24) & 3) + 1;
> > > +		break;
> > > +	case CPU_CORTEX_A9:
> > > +		/* Get SCU physical base */
> > > +		asm("mrc p15, 4, %0, c15, c0, 0" : "=r" (pa));
> > > +		scu_base = IO_ADDRESS(pa);
> > > +		ncores = scu_get_core_count(scu_base);
> > > +		break;
> > > +	default:
> > > +		BUG();
> > 
> > instead of bugging out, how about setting ncores to 1 instead ?
> 
> Maybe that would be useful in the case of adding new ARM core in the
> future.

right, kernel would at least boot in that case.

-- 
balbi

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