linux-kernel - Re: [RFC PATCH v2] Hardcoded instruction causes cpu-hotplug fail on be8 big-endian ARM platfrom

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Message-ID: <CAKw8HL3+=4JXTQ+nphM5XjN_yaVUy55fzytGX=83P+P2n=qvnw@mail.gmail.com>
Date:	Wed, 17 Oct 2012 20:00:51 +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 (Felix)" <felix.yang@...wei.com>
Subject: Re: [RFC PATCH v2] Hardcoded instruction causes cpu-hotplug fail on
 be8 big-endian ARM platfrom

<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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