linux-kernel - Re: [PATCH v5 2/5] powerpc/85xx: add HOTPLUG

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Message-ID: <20120604110444.GA20676@localhost.localdomain>
Date:	Mon, 4 Jun 2012 19:04:44 +0800
From:	Zhao Chenhui <chenhui.zhao@...escale.com>
To:	Scott Wood <scottwood@...escale.com>
CC:	<linuxppc-dev@...ts.ozlabs.org>, <linux-kernel@...r.kernel.org>,
	<galak@...nel.crashing.org>, <leoli@...escale.com>
Subject: Re: [PATCH v5 2/5] powerpc/85xx: add HOTPLUG_CPU support

On Fri, Jun 01, 2012 at 04:27:27PM -0500, Scott Wood wrote:
> On 05/11/2012 06:53 AM, Zhao Chenhui wrote:
> \> +#if defined(CONFIG_FSL_BOOKE) || defined(CONFIG_6xx)
> > +extern void __flush_disable_L1(void);
> > +#endif
> 
> Prototypes aren't normally guarded by ifdefs.

OK. Thanks.

> 
> > +static void __cpuinit smp_85xx_mach_cpu_die(void)
> > +{
> > +	unsigned int cpu = smp_processor_id();
> > +	u32 tmp;
> > +
> > +	local_irq_disable();
> > +	idle_task_exit();
> > +	generic_set_cpu_dead(cpu);
> > +	mb();
> > +
> > +	mtspr(SPRN_TCR, 0);
> > +
> > +	__flush_disable_L1();
> > +	tmp = (mfspr(SPRN_HID0) & ~(HID0_DOZE|HID0_SLEEP)) | HID0_NAP;
> > +	mtspr(SPRN_HID0, tmp);
> > +
> > +	/* Enter NAP mode. */
> > +	tmp = mfmsr();
> > +	tmp |= MSR_WE;
> > +	mb();
> > +	mtmsr(tmp);
> > +	isync();
> 
> Need isync after writing to HID0.
> 
> > +		/*
> > +		 * We don't set the BPTR register here upon it points
> > +		 * to the boot page properly.
> > +		 */
> > +		mpic_reset_core(hw_cpu);
> 
> That comment's wording is hard to follow -- maybe s/upon it points/since
> it already points/
> 
> > +		/* wait until core is ready... */
> > +		if (!spin_event_timeout(in_be32(&spin_table->addr_l) == 1,
> > +						10000, 100)) {
> > +			pr_err("%s: timeout waiting for core %d to reset\n",
> > +							__func__, hw_cpu);
> > +			ret = -ENOENT;
> > +			goto out;
> > +		}
> 
> We need to fix U-Boot to write addr_l last (with an msync beforehand).

I agree.

> 
> > -#ifdef CONFIG_KEXEC
> > +#if defined(CONFIG_KEXEC) || defined(CONFIG_HOTPLUG_CPU)
> 
> Let's not grow lists like this.  Is there any harm in building it
> unconditionally?
> 
> -Scott

We need this ifdef. We only set give_timebase/take_timebase
when CONFIG_KEXEC or CONFIG_HOTPLUG_CPU is defined.

-Chenhui

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