dts: add property removal option CONFIG_OF_REMOVE_PROPS

This can be used for device tree size reduction similar as
CONFIG_OF_SPL_REMOVE_PROPS option. Some boards must pass the
built-in DTB unchanged to the kernel, thus we may not cut it
down unconditionally. Therefore enable the property removal
list option only if CONFIG_OF_DTB_PROPS_REMOVE is selected.

Signed-off-by: Anatolij Gustschin <agust@denx.de>

dts/Kconfig

@@ -314,6 +314,26 @@ config OF_SPL_REMOVE_PROPS
 	  can be discarded. This option defines the list of properties to
 	  discard.
 
+config OF_DTB_PROPS_REMOVE
+	bool "Enable removal of device tree properties"
+	depends on OF_CONTROL
+	help
+	  Some boards have restricted amount of storage for U-Boot image.
+	  If the generated binary doesn't fit into available image storage,
+	  the built-in device tree could probably be cut down by removing
+	  some not required device tree properties to reduce the image size.
+	  Enable this option and define the properties to be removed in the
+	  CONFIG_OF_REMOVE_PROPS list. Do not enable this option if you must
+	  pass the built-in DTB directly to the kernel!
+
+config OF_REMOVE_PROPS
+	string "List of device tree properties to drop"
+	depends on OF_DTB_PROPS_REMOVE
+	default "interrupt-parent interrupts" if PINCTRL
+	help
+	  Some properties are not used by U-Boot and can be discarded.
+	  This option defines the list of properties to discard.
+
 config SPL_OF_PLATDATA
 	bool "Generate platform data for use in SPL"
 	depends on SPL_OF_CONTROL

dts/Makefile

@@ -19,8 +19,13 @@ endif
 $(obj)/dt-spl.dtb: $(DTB) $(objtree)/tools/fdtgrep FORCE
 	$(call if_changed,fdtgrep)
 
+ifeq ($(CONFIG_OF_DTB_PROPS_REMOVE),y)
+$(obj)/dt.dtb: $(DTB) $(objtree)/tools/fdtgrep FORCE
+	$(call if_changed,fdt_rm_props)
+else
 $(obj)/dt.dtb: $(DTB) FORCE
 	$(call if_changed,shipped)
+endif
 
 targets += dt.dtb dt-spl.dtb
 

scripts/Makefile.lib

@@ -544,3 +544,11 @@ quiet_cmd_fdtgrep = FDTGREP $@
 	$(objtree)/tools/fdtgrep -r -O dtb - -o $@ \
 		-P u-boot,dm-pre-reloc -P u-boot,dm-spl -P u-boot,dm-tpl \
 		$(addprefix -P ,$(subst $\",,$(CONFIG_OF_SPL_REMOVE_PROPS)))
+
+# fdt_rm_props
+# ---------------------------------------------------------------------------
+# Pass the original device tree file through fdtgrep. This removes various
+# unused properties. The output is typically a smaller device tree file.
+quiet_cmd_fdt_rm_props = FDTGREP $@
+	cmd_fdt_rm_props = cat $< | $(objtree)/tools/fdtgrep -r -O dtb - -o $@ \
+			$(addprefix -P ,$(subst $\",,$(CONFIG_OF_REMOVE_PROPS)))