microblaze: Support simpleImage.dts make target

Instead of remembering to specify DTB= on the make commandline, this commit
allows the much friendlier make simpleImage.<dts>
where <dts>.dts is expected to be found in arch/microblaze/boot/dts/
The resulting vmlinux, with the compiled DTS linked in, will be copied to
boot/simpleImage.<dts>

This mirrors the same functionality as on PowerPC,
albeit achieving it in a slightly different way.

+ strip simpleImage file
The size of output file is very similar to linux.bin.

vmlinux - full elf without fdt blob
simpleImage.<dtb name>.unstrip - full elf with fdt blob
simpleImage.<dtb name> - stripped elf with fdt blob

Add symlink to generic system.dts in platform folder

Signed-off-by: John Williams <john.williams@petalogix.com>
Signed-off-by: Michal Simek <monstr@monstr.eu>

arch/microblaze/boot/Makefile

@@ -2,10 +2,24 @@
 # arch/microblaze/boot/Makefile
 #
 
-targets := linux.bin linux.bin.gz
+obj-y += linked_dtb.o
+
+targets := linux.bin linux.bin.gz simpleImage.%
 
 OBJCOPYFLAGS_linux.bin  := -O binary
 
+# Where the DTS files live
+dtstree         := $(srctree)/$(src)/dts
+
+# Ensure system.dtb exists
+$(obj)/linked_dtb.o: $(obj)/system.dtb
+
+# Generate system.dtb from $(DTB).dtb
+ifneq ($(DTB),system)
+$(obj)/system.dtb: $(obj)/$(DTB).dtb
+	$(call if_changed,cp)
+endif
+
 $(obj)/linux.bin: vmlinux FORCE
 	[ -n $(CONFIG_INITRAMFS_SOURCE) ] && [ ! -e $(CONFIG_INITRAMFS_SOURCE) ] && \
 	touch $(CONFIG_INITRAMFS_SOURCE) || echo "No CPIO image"
@@ -16,4 +30,27 @@ $(obj)/linux.bin.gz: $(obj)/linux.bin FORCE
 	$(call if_changed,gzip)
 	@echo 'Kernel: $@ is ready' ' (#'`cat .version`')'
 
-clean-kernel += linux.bin linux.bin.gz
+quiet_cmd_cp = CP      $< $@$2
+	cmd_cp = cat $< >$@$2 || (rm -f $@ && echo false)
+
+quiet_cmd_strip = STRIP   $@
+      cmd_strip = $(STRIP) -K _start -K _end -K __log_buf -K _fdt_start vmlinux -o $@
+
+$(obj)/simpleImage.%: vmlinux FORCE
+	$(call if_changed,cp,.unstrip)
+	$(call if_changed,strip)
+	@echo 'Kernel: $@ is ready' ' (#'`cat .version`')'
+
+# Rule to build device tree blobs
+DTC = $(objtree)/scripts/dtc/dtc
+
+# Rule to build device tree blobs
+quiet_cmd_dtc = DTC     $@
+	cmd_dtc = $(DTC) -O dtb -o $(obj)/$*.dtb -b 0 -p 1024 $(dtstree)/$*.dts
+
+$(obj)/%.dtb: $(dtstree)/%.dts FORCE
+	$(call if_changed,dtc)
+
+clean-kernel += linux.bin linux.bin.gz simpleImage.*
+
+clean-files += *.dtb

arch/microblaze/boot/dts/system.dts

@@ -0,0 +1 @@
+../../platform/generic/system.dts

arch/microblaze/boot/linked_dtb.S

@@ -0,0 +1,3 @@
+.section __fdt_blob,"a"
+.incbin "arch/microblaze/boot/system.dtb"
+