arm: Switch to -mno-unaligned-access when supported by the compiler
When we tell the compiler to optimize for ARMv7 (and ARMv6 for that
matter) it assumes a default of SCTRL.A being cleared and unaligned
accesses being allowed and fast at the hardware level. We set this bit
and must pass along -mno-unaligned-access so that the compiler will
still breakdown accesses and not trigger a data abort.
To better help understand the requirements of the project with respect
to unaligned memory access, the
Documentation/unaligned-memory-access.txt file has been added as
doc/README.unaligned-memory-access.txt and is taken from the v3.14-rc1
tag of the kernel.
Cc: Albert ARIBAUD <albert.u.boot@aribaud.net>
Cc: Mans Rullgard <mans@mansr.com>
Signed-off-by: Tom Rini <trini@ti.com>
diff --git a/arch/arm/cpu/armv7/config.mk b/arch/arm/cpu/armv7/config.mk
index d01f3d9..c048531 100644
--- a/arch/arm/cpu/armv7/config.mk
+++ b/arch/arm/cpu/armv7/config.mk
@@ -10,9 +10,12 @@
PF_CPPFLAGS_ARMV7 := $(call cc-option, -march=armv7-a, -march=armv5)
PLATFORM_CPPFLAGS += $(PF_CPPFLAGS_ARMV7)
-# SEE README.arm-unaligned-accesses
+# On supported platforms we set the bit which causes us to trap on unaligned
+# memory access. This is the opposite of what the compiler expects to be
+# the default so we must pass in -mno-unaligned-access so that it is aware
+# of our decision.
PF_NO_UNALIGNED := $(call cc-option, -mno-unaligned-access,)
-PLATFORM_NO_UNALIGNED := $(PF_NO_UNALIGNED)
+PLATFORM_CPPFLAGS += $(PF_NO_UNALIGNED)
ifneq ($(CONFIG_IMX_CONFIG),)
ifdef CONFIG_SPL
diff --git a/arch/arm/cpu/armv8/config.mk b/arch/arm/cpu/armv8/config.mk
index 027a68c..f5b9559 100644
--- a/arch/arm/cpu/armv8/config.mk
+++ b/arch/arm/cpu/armv8/config.mk
@@ -6,10 +6,7 @@
#
PLATFORM_RELFLAGS += -fno-common -ffixed-x18
-# SEE README.arm-unaligned-accesses
-PF_NO_UNALIGNED := $(call cc-option, -mstrict-align)
-PLATFORM_NO_UNALIGNED := $(PF_NO_UNALIGNED)
-
PF_CPPFLAGS_ARMV8 := $(call cc-option, -march=armv8-a)
+PF_NO_UNALIGNED := $(call cc-option, -mstrict-align)
PLATFORM_CPPFLAGS += $(PF_CPPFLAGS_ARMV8)
PLATFORM_CPPFLAGS += $(PF_NO_UNALIGNED)