targets: derive ARM ISA features from CPU_TYPE

arm_v6 and arm_v7 are taken from the merged kernel config, which
describes the kernel and can differ from the userspace ISA:
sunxi/arm926ejs inherits CONFIG_CPU_V7=y from its target config and is
advertised as ARMv7 although it builds for arm926ej-s, and a promptless
symbol such as CPU_V7 cannot be unset in a subtarget config in a way
that survives kernel_oldconfig. Derive arm_v6, arm_v6k and arm_v7 from
CPU_TYPE, the core the toolchain targets, and keep ARMv6K, which has
ldrexd/strexd, apart from plain ARMv6.

Signed-off-by: Daniel Golle <daniel@makrotopia.org>

include/target.mk

@@ -238,6 +238,15 @@ ifeq ($(DUMP),1)
   endif
   ifneq ($(findstring arm,$(ARCH)),)
     CPU_TYPE ?= xscale
+    ifneq ($(filter arm1136j-s arm1136jf-s arm1156t2-s,$(CPU_TYPE)),)
+      FEATURES += arm_v6
+    endif
+    ifneq ($(filter arm1176jz-s arm1176jzf-s mpcore mpcorenovfp,$(CPU_TYPE)),)
+      FEATURES += arm_v6k
+    endif
+    ifneq ($(filter cortex-a% generic-armv7-a marvell-pj4,$(CPU_TYPE)),)
+      FEATURES += arm_v7
+    endif
   endif
   ifeq ($(ARCH),powerpc)
     CPU_CFLAGS_603e:=-mcpu=603e
@@ -330,15 +339,6 @@ ifeq ($(DUMP),1)
     ifneq ($(CONFIG_CPU_MIPS32_R2),)
       FEATURES += mips16
     endif
-    ifneq ($(CONFIG_CPU_V6),)
-      FEATURES += arm_v6
-    endif
-    ifneq ($(CONFIG_CPU_V6K),)
-      FEATURES += arm_v6
-    endif
-    ifneq ($(CONFIG_CPU_V7),)
-      FEATURES += arm_v7
-    endif
 
     # remove duplicates
     FEATURES:=$(sort $(FEATURES))

target/Config.in

@@ -152,6 +152,9 @@ config armeb
 config arm_v6
 	bool
 
+config arm_v6k
+	bool
+
 config arm_v7
 	bool