linux-kernel - Re: [PATCH] keystone: adds cpu

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Message-ID: <20150629175223.GC19863@leverpostej>
Date:	Mon, 29 Jun 2015 18:52:23 +0100
From:	Mark Rutland <mark.rutland@....com>
To:	Vitaly Andrianov <vitalya@...com>
Cc:	"linux@....linux.org.uk" <linux@....linux.org.uk>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"ssantosh@...nel.org" <ssantosh@...nel.org>,
	Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>,
	"grygorii.strashko@...com" <grygorii.strashko@...com>
Subject: Re: [PATCH] keystone: adds cpu_die implementation

On Mon, Jun 29, 2015 at 06:52:32PM +0100, Vitaly Andrianov wrote:
> This commit add cpu_die implementation
> 
> Signed-off-by: Vitaly Andrianov <vitalya@...com>
> ---
> 
> The discussion of the "keystone: psci: adds cpu_die implementation" commit
> shows that if PCSI is enabled platform code doesn't need that implementation
> at all. Having PSCI commands in DTB should be sufficient. Unfortunately 
> Keystone with LPAE enable requires some additional development.

I don't follow.

What do you need to implement for LPAE?

Why not implement that rather than adding more platform code that you'll
likely want to remove later anyway?

Thanks,
Mark.

> To support HOTPLUG_CPU w/o PSCI we need platform implementation of
> the cpu_die(), which is added by this patch.
> 
>  arch/arm/mach-keystone/keystone.h |  1 +
>  arch/arm/mach-keystone/platsmp.c  | 24 ++++++++++++++++++++++++
>  2 files changed, 25 insertions(+)
> 
> diff --git a/arch/arm/mach-keystone/keystone.h b/arch/arm/mach-keystone/keystone.h
> index cd04a1c..93549cf 100644
> --- a/arch/arm/mach-keystone/keystone.h
> +++ b/arch/arm/mach-keystone/keystone.h
> @@ -12,6 +12,7 @@
>  #define __KEYSTONE_H__
>  
>  #define KEYSTONE_MON_CPU_UP_IDX		0x00
> +#define KEYSTONE_MON_CPU_DIE_IDX	0x84000002
>  
>  #ifndef __ASSEMBLER__
>  
> diff --git a/arch/arm/mach-keystone/platsmp.c b/arch/arm/mach-keystone/platsmp.c
> index 5f46a7c..4e5bdde 100644
> --- a/arch/arm/mach-keystone/platsmp.c
> +++ b/arch/arm/mach-keystone/platsmp.c
> @@ -51,7 +51,31 @@ static inline void __cpuinit keystone_smp_secondary_initmem(unsigned int cpu)
>  {}
>  #endif
>  
> +
> +#ifdef CONFIG_HOTPLUG_CPU
> +static void keystone_cpu_die(unsigned int cpu)
> +{
> +	int error;
> +
> +	pr_debug("keystone-smp: cpu_die %d\n", cpu);
> +
> +	error = keystone_cpu_smc(KEYSTONE_MON_CPU_DIE_IDX, cpu, 0);
> +	if (error)
> +		pr_err("CPU %d die failed with %d\n", cpu, error);
> +
> +	/*
> +	 * we shouldn't come here. But in case something went
> +	 * wrong the code below prevents kernel from crush
> +	 */
> +	while (1)
> +		cpu_do_idle();
> +}
> +#endif
> +
>  struct smp_operations keystone_smp_ops __initdata = {
>  	.smp_boot_secondary	= keystone_smp_boot_secondary,
>  	.smp_secondary_init     = keystone_smp_secondary_initmem,
> +#ifdef CONFIG_HOTPLUG_CPU
> +	.cpu_die		= keystone_cpu_die,
> +#endif
>  };
> -- 
> 1.9.1
> 
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