[PATCH 1/9] arm: select different compiler flags for ARM CortexM3

[Paul Osmialowski <pawelo@king.net.pl>]

This one is inspired by two commits published on Emcraft git repo:

https://github.com/EmcraftSystems/linux-emcraft.git

1) 6302b692f570ff9d5645a6e72c11f87b0c1aa409
 RT #62654. Fixed kernel crashes while running httpd by enabling
 "-mfix-cortex-m3-ldrd" compiler option, which prevents compiler from
 generating code like 'ldrd Ra, Rb, [Ra, #Imm]' - according to the 602117
 Cortex-M3 Errata it may result in incorrect base register when interrupted
 or faulted.

by: Yuri Tikhonov <yur@emcraft.com>

2) 359d3cda84c01c0f3fae1a519b97a31f318f57ab
 RT #62654. Removed "--march=..." leaving only "-mcpu=cortex-m3" to make
 sure only the correct instructions will be generated.

by: Sergei Poselenov <sposelenov@emcraft.com>

I reworked these patches to make them less intrusive.

Signed-off-by: Paul Osmialowski <pawelo@king.net.pl>
---
 arch/arm/Kconfig    |  2 +-
 arch/arm/Makefile   |  1 +
 arch/arm/mm/Kconfig | 11 ++++++++++-
 3 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index a750c14..8e3a833 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -32,7 +32,7 @@ config ARM
 	select HANDLE_DOMAIN_IRQ
 	select HARDIRQS_SW_RESEND
 	select HAVE_ARCH_AUDITSYSCALL if (AEABI && !OABI_COMPAT)
-	select HAVE_ARCH_BITREVERSE if (CPU_32v7M || CPU_32v7) && !CPU_32v6
+	select HAVE_ARCH_BITREVERSE if (CPU_32v7M || CPU_32v7M3 || CPU_32v7) && !CPU_32v6
 	select HAVE_ARCH_JUMP_LABEL if !XIP_KERNEL && !CPU_ENDIAN_BE32
 	select HAVE_ARCH_KGDB if !CPU_ENDIAN_BE32
 	select HAVE_ARCH_SECCOMP_FILTER if (AEABI && !OABI_COMPAT)
diff --git a/arch/arm/Makefile b/arch/arm/Makefile
index 07ab3d2..a7e1007 100644
--- a/arch/arm/Makefile
+++ b/arch/arm/Makefile
@@ -58,6 +58,7 @@ endif
 # Note that GCC does not numerically define an architecture version
 # macro, but instead defines a whole series of macros which makes
 # testing for a specific architecture or later rather impossible.
+arch-$(CONFIG_CPU_32v7M3)	=-D__LINUX_ARM_ARCH__=7 -mcpu=cortex-m3 -Wa,-mcpu=cortex-m3
 arch-$(CONFIG_CPU_32v7M)	=-D__LINUX_ARM_ARCH__=7 -march=armv7-m -Wa,-march=armv7-m
 arch-$(CONFIG_CPU_32v7)		=-D__LINUX_ARM_ARCH__=7 $(call cc-option,-march=armv7-a,-march=armv5t -Wa$(comma)-march=armv7-a)
 arch-$(CONFIG_CPU_32v6)		=-D__LINUX_ARM_ARCH__=6 $(call cc-option,-march=armv6,-march=armv5t -Wa$(comma)-march=armv6)
diff --git a/arch/arm/mm/Kconfig b/arch/arm/mm/Kconfig
index 7c6b976..d19cb4d 100644
--- a/arch/arm/mm/Kconfig
+++ b/arch/arm/mm/Kconfig
@@ -401,12 +401,18 @@ config CPU_V7
 # ARMv7M
 config CPU_V7M
 	bool
-	select CPU_32v7M
+	select CPU_32v7M if !CPU_CORTEXM3
+	select CPU_32v7M3 if CPU_CORTEXM3
 	select CPU_ABRT_NOMMU
 	select CPU_CACHE_NOP
 	select CPU_PABRT_LEGACY
 	select CPU_THUMBONLY
 
+# ARM CortexM3
+config CPU_CORTEXM3
+	bool
+	select CPU_V7M
+
 config CPU_THUMBONLY
 	bool
 	# There are no CPUs available with MMU that don't implement an ARM ISA:
@@ -457,6 +463,9 @@ config CPU_32v7
 config CPU_32v7M
 	bool
 
+config CPU_32v7M3
+	bool
+
 # The abort model
 config CPU_ABRT_NOMMU
 	bool
-- 
2.3.6