linux-kernel - Re: [RFC PATCH v2] ARM hardcoded instruction causes cpu-hotplug fail to work on big-endian platfrom

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Date:	Mon, 22 Oct 2012 19:01:00 +0800
From:	Fei Yang <yangfei.kernel@...il.com>
To:	Dave Martin <dave.martin@...aro.org>, linux@....linux.org.uk,
	lethal@...ux-sh.org, magnus.damm@...il.com, kgene.kim@...sung.com,
	linux-arm-kernel@...ts.infradead.org
Cc:	Mikael Pettersson <mikpe@...uu.se>,
	"linux-assembly@...r.kernel.org" <linux-assembly@...r.kernel.org>,
	linux-hotplug@...r.kernel.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	yangfei.kernel@...il.com, "Yangfei (Felix)" <felix.yang@...wei.com>
Subject: Re: [RFC PATCH v2] ARM hardcoded instruction causes cpu-hotplug fail
 to work on big-endian platfrom

2012/10/17 Fei Yang <yangfei.kernel@...il.com>:
> <cut>
>
>> Not handling the Thumb case is a definite bug for any file which may
>> run on v7, since the kernel could be built in Thumb for that case.
>> For example, the existing code is mach-realview/hotplug.c is broken
>> when building an SMP Thumb-2 kernel for the Realview PBX-A9.
>>
>> Cheers
>> ---Dave
>
> Thanks for pointing this out. I think we just cannot make any
> assumption about the versions of the tools used. Based on this, I have
> made a v2 of the patch against linux-3.7-rc1. I am not touching the
> CFLAGS in the patch as I am not familiar with the three ARM boards
> here.
> Can the respective board maintainers
> (mach-exynos/mach-realveiw/mach-shmobile) give any comments about v2
> of the patch?
>
> Thanks.
> ---Fei
>
> v2: Define opcode of the ARM "WFI" instruction in the right way.
>
> Signed-off-by: Fei Yang<yangfei.kernel@...il.com>
>
> diff -urN linux-3.7-rc1/arch/arm/mach-exynos/hotplug.c
> linux/arch/arm/mach-exynos/hotplug.c
> --- linux-3.7-rc1/arch/arm/mach-exynos/hotplug.c        2012-10-15
> 05:41:04.000000000 +0800
> +++ linux/arch/arm/mach-exynos/hotplug.c        2012-10-17 19:25:49.000000000 +0800
> @@ -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 @@
>                 /*
>                  * here's the WFI
>                  */
> -               asm(".word      0xe320f003\n"
> +               asm(__WFI
>                     :
>                     :
>                     : "memory", "cc");
> diff -urN linux-3.7-rc1/arch/arm/mach-realview/hotplug.c
> linux/arch/arm/mach-realview/hotplug.c
> --- linux-3.7-rc1/arch/arm/mach-realview/hotplug.c      2012-10-15
> 05:41:04.000000000 +0800
> +++ linux/arch/arm/mach-realview/hotplug.c      2012-10-17 19:25:20.000000000 +0800
> @@ -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 @@
>                 /*
>                  * here's the WFI
>                  */
> -               asm(".word      0xe320f003\n"
> +               asm(__WFI
>                     :
>                     :
>                     : "memory", "cc");
> diff -urN linux-3.7-rc1/arch/arm/mach-shmobile/hotplug.c
> linux/arch/arm/mach-shmobile/hotplug.c
> --- linux-3.7-rc1/arch/arm/mach-shmobile/hotplug.c      2012-10-15
> 05:41:04.000000000 +0800
> +++ linux/arch/arm/mach-shmobile/hotplug.c      2012-10-17 19:25:34.000000000 +0800
> @@ -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 @@
>                 /*
>                  * here's the WFI
>                  */
> -               asm(".word      0xe320f003\n"
> +               asm(__WFI
>                     :
>                     :
>                     : "memory", "cc");
> --
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>
>

Hi,

    Any comments on this patch? It is posted last week. Please let me
know if I missed anything.
    Thanks.

    ---Fei
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