[PATCH] powerpc: make the padding for the device tree a configurable option

[Timur Tabi]

Add the DTS_PADDING Kconfig option, which allows users and board defconfig
files to specify a padding value when compiling device trees.

When a device tree source (DTS) is compiled into a binary (DTB), a hard-coded
padding of 1024 bytes is used (i.e. dtc command-line parameter "-p 1024").
Although this has worked so far, it may not be sufficient in the future for
some boards.  Newer versions of U-boot perform more and more fixup on the
device tree, and eventually it will run out.

So to accommodate future boards where more padding is needed, we make the
option for the -p parameter configurable.

Signed-off-by: Timur Tabi <timur at freescale.com>
---
 arch/powerpc/boot/Makefile     |    4 ++--
 arch/powerpc/platforms/Kconfig |   13 +++++++++++++
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/boot/Makefile b/arch/powerpc/boot/Makefile
index bb2465b..750fa6b 100644
--- a/arch/powerpc/boot/Makefile
+++ b/arch/powerpc/boot/Makefile
@@ -35,7 +35,7 @@ endif
 
 BOOTCFLAGS	+= -I$(obj) -I$(srctree)/$(obj)
 
-DTS_FLAGS	?= -p 1024
+DTS_FLAGS	?= -p ${CONFIG_DTS_PADDING}
 
 $(obj)/4xx.o: BOOTCFLAGS += -mcpu=405
 $(obj)/ebony.o: BOOTCFLAGS += -mcpu=405
@@ -331,7 +331,7 @@ $(obj)/treeImage.%: vmlinux $(obj)/%.dtb $(wrapperbits)
 # Rule to build device tree blobs
 DTC = $(objtree)/scripts/dtc/dtc
 
-$(obj)/%.dtb: $(dtstree)/%.dts
+$(obj)/%.dtb: $(dtstree)/%.dts $(srctree)/.config
 	$(DTC) -O dtb -o $(obj)/$*.dtb -b 0 $(DTS_FLAGS) $(dtstree)/$*.dts
 
 # If there isn't a platform selected then just strip the vmlinux.
diff --git a/arch/powerpc/platforms/Kconfig b/arch/powerpc/platforms/Kconfig
index d1663db..2b0a9c3 100644
--- a/arch/powerpc/platforms/Kconfig
+++ b/arch/powerpc/platforms/Kconfig
@@ -41,6 +41,19 @@ config PPC_OF_BOOT_TRAMPOLINE
 
 	  In case of doubt, say Y
 
+config DTS_PADDING
+	int "Padding for the device tree binary"
+	default 1024
+	help
+	  Specify the padding value to be used when compiling a DTS (device
+	  tree source) file into a DTB (device tree binary).  The padding is
+	  used to ensure enough space for any additional nodes and properties
+	  that the boot loader adds during fix-up.  If your boot loader
+	  complains about lack of space during fix-up, try increasing this
+	  value.
+
+	  If unsure, leave this value at the default.
+
 config UDBG_RTAS_CONSOLE
 	bool "RTAS based debug console"
 	depends on PPC_RTAS
-- 
1.6.5