[PATCH] ARM: berlin: add CPU hotplug support

[PATCH] ARM: berlin: add CPU hotplug support

[Antoine Tenart]

Adds CPU hotplug support for Berlin SoCs (currently BG2 and BG2Q). The
CPUs are put in WFI after disabling the coherency.

Signed-off-by: Antoine Tenart <antoine.tenart@free-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

Re: [PATCH] ARM: berlin: add CPU hotplug support

[Mark Rutland]

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@free-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@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
> 

Re: [PATCH] ARM: berlin: add CPU hotplug support

[Russell King - ARM Linux]

On Tue, May 12, 2015 at 04:16:26PM +0200, Antoine Tenart wrote:
> Adds CPU hotplug support for Berlin SoCs (currently BG2 and BG2Q). The
> CPUs are put in WFI after disabling the coherency.
> 
> Signed-off-by: Antoine Tenart <antoine.tenart@free-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>

I don't see anything being added by this patch which would need this
include.

>  #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@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

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Re: [PATCH] ARM: berlin: add CPU hotplug support

[Antoine Tenart]

On Wed, May 13, 2015 at 12:23:22AM +0100, Russell King - ARM Linux wrote:
> On Tue, May 12, 2015 at 04:16:26PM +0200, Antoine Tenart wrote:
> > Adds CPU hotplug support for Berlin SoCs (currently BG2 and BG2Q). The
> > CPUs are put in WFI after disabling the coherency.
> > 
> > Signed-off-by: Antoine Tenart <antoine.tenart@free-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>
> 
> I don't see anything being added by this patch which would need this
> include.

v7_exit_coherency_flush(..) needs CR_C to be defined, which is done in
asm/cp15.h. Is there a better way to get this defined here?

> >  
> > +#ifdef CONFIG_HOTPLUG_CPU
> > +static void berlin_cpu_die(unsigned int cpu)
> > +{
> > +	v7_exit_coherency_flush(louis);
> > +	while (1)
> > +		cpu_do_idle();
> > +}
> > +#endif
> > +

Antoine

-- 
Antoine Ténart, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com