linux-kernel - Re: [PATCH 4/9] powerpc/85xx: support CPU hotplug for e500mc and e5500

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Date:	Tue, 11 Mar 2014 18:48:13 -0500
From:	Scott Wood <scottwood@...escale.com>
To:	Chenhui Zhao <chenhui.zhao@...escale.com>
CC:	<linuxppc-dev@...ts.ozlabs.org>, <linux-kernel@...r.kernel.org>,
	<leoli@...escale.com>, <Jason.Jin@...escale.com>
Subject: Re: [PATCH 4/9] powerpc/85xx: support CPU hotplug for e500mc and
 e5500

On Fri, 2014-03-07 at 12:58 +0800, Chenhui Zhao wrote:
> diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
> index ac2621a..f3f4401 100644
> --- a/arch/powerpc/kernel/smp.c
> +++ b/arch/powerpc/kernel/smp.c
> @@ -405,8 +405,12 @@ void generic_cpu_die(unsigned int cpu)
>  
>  	for (i = 0; i < 100; i++) {
>  		smp_rmb();
> -		if (per_cpu(cpu_state, cpu) == CPU_DEAD)
> +		if (per_cpu(cpu_state, cpu) == CPU_DEAD) {
> +#ifdef CONFIG_PPC64
> +			paca[cpu].cpu_start = 0;
> +#endif

Why wasn't this needed by previous ppc64 machines?

> diff --git a/arch/powerpc/platforms/85xx/smp.c b/arch/powerpc/platforms/85xx/smp.c
> index 2e5911e..0047883 100644
> --- a/arch/powerpc/platforms/85xx/smp.c
> +++ b/arch/powerpc/platforms/85xx/smp.c
> @@ -19,6 +19,7 @@
>  #include <linux/kexec.h>
>  #include <linux/highmem.h>
>  #include <linux/cpu.h>
> +#include <linux/smp.h>
>  
>  #include <asm/machdep.h>
>  #include <asm/pgtable.h>
> @@ -46,6 +47,17 @@ static u64 timebase;
>  static int tb_req;
>  static int tb_valid;
>  
> +#ifdef CONFIG_PPC_E500MC
> +/* specify the cpu PM state when cpu dies, PH15/NAP is the default */
> +int qoriq_cpu_die_state = E500_PM_PH15;
> +#endif

static?  Is there any way to modify this other than modifying source
code?

BTW, QorIQ doesn't imply an e500mc derivative.

> @@ -125,6 +138,34 @@ static void mpc85xx_take_timebase(void)
>  }
>  
>  #ifdef CONFIG_HOTPLUG_CPU
> +#ifdef CONFIG_PPC_E500MC
> +static void qoriq_cpu_die(void)
> +{
> +	unsigned int cpu = smp_processor_id();
> +
> +	local_irq_disable();
> +#ifdef CONFIG_PPC64
> +	__hard_irq_disable();
> +#endif

Why this instead of one call to hard_irq_disable() (no leading
underscores)?

-Scott


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