linux-kernel - Re: [PATCH] ARM: berlin: add CPU hotplug support

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Date:	Tue, 12 May 2015 16:03:46 +0100
From:	Mark Rutland <mark.rutland@....com>
To:	Antoine Tenart <antoine.tenart@...e-electrons.com>
Cc:	"sebastian.hesselbarth@...il.com" <sebastian.hesselbarth@...il.com>,
	"zmxu@...vell.com" <zmxu@...vell.com>,
	"jszhang@...vell.com" <jszhang@...vell.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] ARM: berlin: add CPU hotplug support

On Tue, May 12, 2015 at 03:16:26PM +0100, Antoine Tenart wrote:
> Adds CPU hotplug support for Berlin SoCs (currently BG2 and BG2Q). The
> CPUs are put in WFI after disabling the coherency.

This is _not_ CPU hotplug (given the CPUs are still sat on kernel text,
and could be woken at any point), so this is simply broken anywhere it
really matters (e.g. kexec).

So NAK, as the same style of pseudo-hotplug has received repeatedly in
the past for other platforms.

Thanks,
Mark.

> 
> Signed-off-by: Antoine Tenart <antoine.tenart@...e-electrons.com>
> ---
>  arch/arm/mach-berlin/platsmp.c | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
> 
> diff --git a/arch/arm/mach-berlin/platsmp.c b/arch/arm/mach-berlin/platsmp.c
> index 702e7982015a..d9c62057be76 100644
> --- a/arch/arm/mach-berlin/platsmp.c
> +++ b/arch/arm/mach-berlin/platsmp.c
> @@ -14,6 +14,7 @@
>  #include <linux/of_address.h>
>  
>  #include <asm/cacheflush.h>
> +#include <asm/cp15.h>
>  #include <asm/smp_plat.h>
>  #include <asm/smp_scu.h>
>  
> @@ -92,8 +93,20 @@ unmap_scu:
>  	iounmap(scu_base);
>  }
>  
> +#ifdef CONFIG_HOTPLUG_CPU
> +static void berlin_cpu_die(unsigned int cpu)
> +{
> +	v7_exit_coherency_flush(louis);
> +	while (1)
> +		cpu_do_idle();
> +}
> +#endif
> +
>  static struct smp_operations berlin_smp_ops __initdata = {
>  	.smp_prepare_cpus	= berlin_smp_prepare_cpus,
>  	.smp_boot_secondary	= berlin_boot_secondary,
> +#ifdef CONFIG_HOTPLUG_CPU
> +	.cpu_die		= berlin_cpu_die,
> +#endif
>  };
>  CPU_METHOD_OF_DECLARE(berlin_smp, "marvell,berlin-smp", &berlin_smp_ops);
> -- 
> 2.4.0
> 
> 
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
> 
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