kinetis: Add watchdog disable code snippet

cpu/kinetis_common/Makefile.include

@@ -9,3 +9,10 @@ export UNDEF += $(BINDIR)kinetis_common/startup.o
 
 # add the CPU specific fault handlers for the linker
 export UNDEF += $(BINDIR)kinetis_common/fault_handlers.o
+
+# Define a recipe to build the watchdog disable binary, used when flashing
+$(RIOTCPU)/kinetis_common/dist/wdog-disable.bin: $(RIOTCPU)/kinetis_common/dist/wdog-disable.s
+	$(AD)$(MAKE) -C $(RIOTCPU)/kinetis_common/dist/ $(notdir $@)
+
+# Reset the default goal to not make wdog-disable.bin the default target.
+.DEFAULT_GOAL :=

cpu/kinetis_common/dist/Makefile

@@ -0,0 +1,9 @@
+wdog-disable.bin: wdog-disable.o
+	arm-none-eabi-objcopy -O binary -j .text.wdog_disable -S -g $^ $@
+
+wdog-disable.o: wdog-disable.s
+	arm-none-eabi-as -mthumb -o $@ $^
+
+.PHONY: clean
+clean:
+	@rm wdog-disable.o

cpu/kinetis_common/dist/README.md

@@ -0,0 +1,15 @@
+K60 tools
+=========
+
+This directory contains tools for working with K60 CPUs.
+
+Watchdog disable
+----------------
+
+wdog-disable.bin is a location-independent watchdog disable function with a breakpoint instruction at the end. Useful for disabling the watchdog directly from OpenOCD.
+
+Usage:
+
+    openocd -c 'reset halt' \
+      -c 'load_image wdog-disable.bin 0x20000000 bin' \
+      -c 'resume 0x20000000' # watchdog is disabled and core halted

cpu/kinetis_common/dist/wdog-disable.s

@@ -0,0 +1,33 @@
+/*
+ * Copyright (C) 2015 Eistec AB
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/* GCC ARM assembler */
+
+    .text
+    .thumb
+    .align 2
+
+/* Public functions declared in this file */
+    .global  wdog_disable
+
+.section .text.wdog_disable
+.thumb_func
+.func
+wdog_disable:
+    movw r0, #0x200e
+    movw r1, #0xc520
+    movt r0, #0x4005
+    strh r1, [r0, #0]
+    movw r1, #0xd928
+    strh r1, [r0, #0]
+    movw r0, #0x2000
+    movs r1, #0xd2
+    movt r0, #0x4005
+    strh r1, [r0, #0]
+    bkpt #0
+.endfunc