linux-kernel - Re: [PATCH] ARM: Fix the "WFI" instruction opcode definition.

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Date:	Wed, 31 Oct 2012 20:32:43 -0500
From:	Rob Herring <robherring2@...il.com>
To:	"Yangfei (Felix)" <felix.yang@...wei.com>
CC:	Russell King <linux@....linux.org.uk>,
	Kukjin Kim <kgene.kim@...sung.com>,
	Paul Mundt <lethal@...ux-sh.org>,
	Magnus Damm <magnus.damm@...il.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-samsung-soc@...r.kernel.org" 
	<linux-samsung-soc@...r.kernel.org>,
	"linux-sh@...r.kernel.org" <linux-sh@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ARM: Fix the "WFI" instruction opcode definition.

On 10/31/2012 08:24 PM, Yangfei (Felix) wrote:
> The current "WFI" opcode definiton causes CPU hot-plug feature fails to work
> if the kernel is built with CONFIG_THUMB2_KERNEL/CONFIG_CPU_ENDIAN_BE8 being
> defined. An invalid instruction exception will be generated.
> 
> Signed-off-by: yangfei.kernel@...il.com
> ---
>  arch/arm/mach-exynos/hotplug.c   |    8 +++++++-
>  arch/arm/mach-realview/hotplug.c |    8 +++++++-
>  arch/arm/mach-shmobile/hotplug.c |    8 +++++++-
>  3 files changed, 21 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/arm/mach-exynos/hotplug.c b/arch/arm/mach-exynos/hotplug.c
> index f4d7dd2..823a0e4 100644
> --- a/arch/arm/mach-exynos/hotplug.c
> +++ b/arch/arm/mach-exynos/hotplug.c
> @@ -18,11 +18,17 @@
>  #include <asm/cacheflush.h>
>  #include <asm/cp15.h>
>  #include <asm/smp_plat.h>
> +#include <asm/opcodes.h>
>  
>  #include <mach/regs-pmu.h>
>  
>  #include "common.h"
>  
> +/*
> + * Define opcode of the WFI instruction.
> + */
> +#define __WFI __inst_arm_thumb16(0xe320f003, 0xbf30)
> +
>  static inline void cpu_enter_lowpower(void)
>  {
>  	unsigned int v;
> @@ -72,7 +78,7 @@ static inline void platform_do_lowpower(unsigned int cpu, int *spurious)
>  		/*
>  		 * here's the WFI
>  		 */
> -		asm(".word	0xe320f003\n"
> +		asm(__WFI

Wouldn't using the actual wfi instruction fix this. There is a wfi() macro.

Or just call cpu_do_idle() which will do any other things needed before
wfi like a dsb instruction.

Rob
>  		    :
>  		    :
>  		    : "memory", "cc");
> diff --git a/arch/arm/mach-realview/hotplug.c b/arch/arm/mach-realview/hotplug.c
> index 53818e5..5271a1a 100644
> --- a/arch/arm/mach-realview/hotplug.c
> +++ b/arch/arm/mach-realview/hotplug.c
> @@ -15,6 +15,12 @@
>  #include <asm/cacheflush.h>
>  #include <asm/cp15.h>
>  #include <asm/smp_plat.h>
> +#include <asm/opcodes.h>
> +
> +/*
> + * Define opcode of the WFI instruction.
> + */
> +#define __WFI __inst_arm_thumb16(0xe320f003, 0xbf30)
>  
>  static inline void cpu_enter_lowpower(void)
>  {
> @@ -64,7 +70,7 @@ static inline void platform_do_lowpower(unsigned int cpu, int *spurious)
>  		/*
>  		 * here's the WFI
>  		 */
> -		asm(".word	0xe320f003\n"
> +		asm(__WFI
>  		    :
>  		    :
>  		    : "memory", "cc");
> diff --git a/arch/arm/mach-shmobile/hotplug.c b/arch/arm/mach-shmobile/hotplug.c
> index b09a0bd..0d7b7d1 100644
> --- a/arch/arm/mach-shmobile/hotplug.c
> +++ b/arch/arm/mach-shmobile/hotplug.c
> @@ -20,6 +20,12 @@
>  #include <mach/emev2.h>
>  #include <asm/cacheflush.h>
>  #include <asm/mach-types.h>
> +#include <asm/opcodes.h>
> +
> +/*
> + * Define opcode of the WFI instruction.
> + */
> ++#define __WFI __inst_arm_thumb16(0xe320f003, 0xbf30)
>  
>  static cpumask_t dead_cpus;
>  
> @@ -39,7 +45,7 @@ void shmobile_cpu_die(unsigned int cpu)
>  		/*
>  		 * here's the WFI
>  		 */
> -		asm(".word	0xe320f003\n"
> +		asm(__WFI
>  		    :
>  		    :
>  		    : "memory", "cc");
> --
> 
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
> 

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