-# 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,) \
+ $(call cc-option,-mno-thumb-interwork,)
+endif
+
+# Only test once
+ifneq ($(CONFIG_SPL_BUILD),y)
+ALL-$(CONFIG_SYS_THUMB_BUILD) += checkthumb
+endif