ARM: enable Thumb build

Enable Thumb build and ARM-Thumb interworking based on the new
config flag CONFIG_SYS_THUMB_BUILD

Signed-off-by: Aneesh V <aneesh@ti.com>
Acked-by: Mike Frysinger <vapier@gentoo.org>

diff --git a/README b/README
index 79016e690ace8899488e54ee7a35e1715018e9a2..6919392dca82c142ea00d9281393ddcde33ae981 100644 (file)
--- a/README
+++ b/README
@@ -432,6 +432,14 @@ The following options need to be configured:
                Select high exception vectors of the ARM core, e.g., do not
                clear the V bit of the c1 register of CP15.
 
+               CONFIG_SYS_THUMB_BUILD
+
+               Use this flag to build U-Boot using the Thumb instruction
+               set for ARM architectures. Thumb instruction set provides
+               better code density. For ARM architectures that support
+               Thumb2 this flag will result in Thumb2 code generated by
+               GCC.
+
 - Linux Kernel Interface:
                CONFIG_CLOCKS_IN_MHZ
 

diff --git a/arch/arm/config.mk b/arch/arm/config.mk
index 3c5f9871671641f6dead045cd9238090cb215c0e..4cc99e7613747650227f0b54b952b6405b5906ca 100644 (file)
--- a/arch/arm/config.mk
+++ b/arch/arm/config.mk
@@ -33,25 +33,33 @@ endif
 
 PLATFORM_CPPFLAGS += -DCONFIG_ARM -D__ARM__
 
-# Explicitly specifiy 32-bit ARM ISA since toolchain default can be -mthumb:
-PF_CPPFLAGS_ARM := $(call cc-option,-marm,)
+# Choose between ARM/Thumb instruction sets
+ifeq ($(CONFIG_SYS_THUMB_BUILD),y)
+PF_CPPFLAGS_ARM := $(call cc-option, -mthumb -mthumb-interwork,\
+                       $(call cc-option,-marm,)\
+                       $(call cc-option,-mno-thumb-interwork,)\
+               )
+else
+PF_CPPFLAGS_ARM := $(call cc-option,-marm,) \
+               $(call cc-option,-mno-thumb-interwork,)
+endif
 
 # Try if EABI is supported, else fall back to old API,
 # i. e. for example:
 # - with ELDK 4.2 (EABI supported), use:
-#      -mabi=aapcs-linux -mno-thumb-interwork
+#      -mabi=aapcs-linux
 # - with ELDK 4.1 (gcc 4.x, no EABI), use:
-#      -mabi=apcs-gnu -mno-thumb-interwork
+#      -mabi=apcs-gnu
 # - with ELDK 3.1 (gcc 3.x), use:
-#      -mapcs-32 -mno-thumb-interwork
+#      -mapcs-32
 PF_CPPFLAGS_ABI := $(call cc-option,\
-                       -mabi=aapcs-linux -mno-thumb-interwork,\
+                       -mabi=aapcs-linux,\
                        $(call cc-option,\
                                -mapcs-32,\
                                $(call cc-option,\
                                        -mabi=apcs-gnu,\
                                )\
-                       ) $(call cc-option,-mno-thumb-interwork,)\
+                       )\
                )
 PLATFORM_CPPFLAGS += $(PF_CPPFLAGS_ARM) $(PF_CPPFLAGS_ABI)