dtc: Add Kconfig option to pad device tree blob

This will allow arch(s) that use device tree blobs to pad the end of the
device tree so they can be modified by board files at run time. This will
help prevent errors such as FDT_ERR_NOSPACE from occurring.

Signed-off-by: Eric Schikschneit <eric.schikschneit@novatechautomation.com>
[trini: Change default order so that X86 && EFI_APP works correctly]

13 files changed, 26 insertions, 14 deletions

diff --git a/arch/Kconfig b/arch/Kconfig
index ea33d07c086..597b40ffd60 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -63,6 +63,13 @@ config SYS_CACHELINE_SIZE
 	default 64 if RISCV
 	default 32 if MIPS
 
+config SYS_DTC_PAD_BYTES
+	int "Size in bytes to pad device tree blob"
+	default 32768 if X86 && EFI_APP
+	default 4096 if ARC || ARM64 || M68K || MICROBLAZE || NIOS2 \
+		|| RISCV || SANDBOX || X86
+	default 0
+
 config LINKER_LIST_ALIGN
 	int
 	default 32 if SANDBOX
diff --git a/arch/arc/dts/Makefile b/arch/arc/dts/Makefile
index fe6ad7b849a..87c627c01c8 100644
--- a/arch/arc/dts/Makefile
+++ b/arch/arc/dts/Makefile
@@ -11,4 +11,4 @@ dtb-$(CONFIG_TARGET_IOT_DEVKIT) +=  iot_devkit.dtb
 include $(srctree)/scripts/Makefile.dts
 
 # Add any required device tree compiler flags here
-DTC_FLAGS += -R 4 -p 0x1000
+DTC_FLAGS += -R 4
diff --git a/arch/m68k/dts/Makefile b/arch/m68k/dts/Makefile
index 8b354b9c570..0f06109aa06 100644
--- a/arch/m68k/dts/Makefile
+++ b/arch/m68k/dts/Makefile
@@ -21,4 +21,4 @@ dtb-$(CONFIG_TARGET_STMARK2) += stmark2.dtb
 include $(srctree)/scripts/Makefile.dts
 
 # Add any required device tree compiler flags here
-DTC_FLAGS += -R 4 -p 0x1000
+DTC_FLAGS += -R 4
diff --git a/arch/microblaze/dts/Makefile b/arch/microblaze/dts/Makefile
index 9be902d3bb1..0f3a7472a67 100644
--- a/arch/microblaze/dts/Makefile
+++ b/arch/microblaze/dts/Makefile
@@ -5,4 +5,4 @@ dtb-y += $(shell echo $(CONFIG_DEFAULT_DEVICE_TREE)).dtb
 include $(srctree)/scripts/Makefile.dts
 
 # Add any required device tree compiler flags here
-DTC_FLAGS += -R 4 -p 0x1000
+DTC_FLAGS += -R 4
diff --git a/arch/nios2/dts/Makefile b/arch/nios2/dts/Makefile
index d77db9762a1..75951164978 100644
--- a/arch/nios2/dts/Makefile
+++ b/arch/nios2/dts/Makefile
@@ -5,4 +5,4 @@ dtb-y += $(CONFIG_DEFAULT_DEVICE_TREE:"%"=%).dtb
 include $(srctree)/scripts/Makefile.dts
 
 # Add any required device tree compiler flags here
-DTC_FLAGS += -R 4 -p 0x1000
+DTC_FLAGS += -R 4
diff --git a/arch/riscv/dts/Makefile b/arch/riscv/dts/Makefile
index cf1872f3fdc..2b10c2d6c01 100644
--- a/arch/riscv/dts/Makefile
+++ b/arch/riscv/dts/Makefile
@@ -19,4 +19,4 @@ dtb-$(CONFIG_TARGET_ASPEED_AST2700_IBEX) += ast2700-ibex.dtb
 include $(srctree)/scripts/Makefile.dts
 
 # Add any required device tree compiler flags here
-DTC_FLAGS += -R 4 -p 0x1000
+DTC_FLAGS += -R 4
diff --git a/arch/sandbox/dts/Makefile b/arch/sandbox/dts/Makefile
index 1c9fb4a4566..0d7b0b80e21 100644
--- a/arch/sandbox/dts/Makefile
+++ b/arch/sandbox/dts/Makefile
@@ -11,4 +11,4 @@ dtb-$(CONFIG_CMD_EXTENSION) += overlay0.dtbo overlay1.dtbo
 include $(srctree)/scripts/Makefile.dts
 
 # Add any required device tree compiler flags here
-DTC_FLAGS += -R 4 -p 0x1000
+DTC_FLAGS += -R 4
diff --git a/arch/x86/dts/Makefile b/arch/x86/dts/Makefile
index 9a46726e026..725991e2629 100644
--- a/arch/x86/dts/Makefile
+++ b/arch/x86/dts/Makefile
@@ -24,4 +24,4 @@ dtb-y += bayleybay.dtb \
 
 include $(srctree)/scripts/Makefile.dts
 
-DTC_FLAGS += -R 4 -p $(if $(CONFIG_EFI_APP),0x8000,0x1000)
+DTC_FLAGS += -R 4
diff --git a/doc/board/broadcom/bcm7xxx.rst b/doc/board/broadcom/bcm7xxx.rst
index f1994d9f975..f559d5c290a 100644
--- a/doc/board/broadcom/bcm7xxx.rst
+++ b/doc/board/broadcom/bcm7xxx.rst
@@ -149,10 +149,8 @@ and with a generic ARMv7 root file system.
 				 * to the Linux source tree as a .dts file.
 				 *
 				 * To support modifications to the device tree
-				 * in-place in U-Boot, add to Linux's
-				 * arch/arm/boot/dts/Makefile:
-				 *
-				 * DTC_FLAGS ?= -p 4096
+				 * in-place in U-Boot, set the config variable
+				 * CONFIG_SYS_DTC_PAD_BYTES as needed.
 				 *
 				 * This will leave some padding in the DTB and
 				 * thus reserve room for node additions.
diff --git a/doc/develop/makefiles.rst b/doc/develop/makefiles.rst
index 37a7deaca92..593556f4dd5 100644
--- a/doc/develop/makefiles.rst
+++ b/doc/develop/makefiles.rst
@@ -1430,10 +1430,13 @@ When kbuild executes, the following steps are followed (roughly):
 	A central rule exists to create `$(obj)/%.dtb` from `$(src)/%.dts`;
 	architecture Makefiles do no need to explicitly write out that rule.
 
+        The device tree can now be padded by the specified number of bytes
+        by setting CONFIG_SYS_DTC_PAD_BYTES instead of explicitly setting
+        DTC_FLAGS with the -p option.
+
 	Example::
 
 		targets += $(dtb-y)
-		DTC_FLAGS ?= -p 1024
 
 7.9 Preprocessing linker scripts
 --------------------------------
diff --git a/dts/upstream/src/arm64/Makefile b/dts/upstream/src/arm64/Makefile
index b6db0dc6b26..01a5265114e 100644
--- a/dts/upstream/src/arm64/Makefile
+++ b/dts/upstream/src/arm64/Makefile
@@ -6,5 +6,5 @@ include $(srctree)/scripts/Makefile.dts
 DTC_FLAGS += -a 0x8
 
 ifdef CONFIG_RCAR_64
-DTC_FLAGS += -R 4 -p 0x1000
+	DTC_FLAGS += -R 4
 endif
diff --git a/dts/upstream/src/riscv/Makefile b/dts/upstream/src/riscv/Makefile
index 980617e6de3..43351f801db 100644
--- a/dts/upstream/src/riscv/Makefile
+++ b/dts/upstream/src/riscv/Makefile
@@ -2,5 +2,5 @@
 
 include $(srctree)/scripts/Makefile.dts
 
-DTC_FLAGS += -R 4 -p 0x1000
+DTC_FLAGS += -R 4
 
diff --git a/scripts/Makefile.dts b/scripts/Makefile.dts
index 685e3371bc6..3871a4ad412 100644
--- a/scripts/Makefile.dts
+++ b/scripts/Makefile.dts
@@ -16,6 +16,10 @@ dtb-y += $(subst $(dt_dir)/,,$(dtb-vendor_dts))
 
 endif
 
+ifneq ($(CONFIG_SYS_DTC_PAD_BYTES),0)
+DTC_FLAGS += -p $(CONFIG_SYS_DTC_PAD_BYTES)
+endif
+
 targets += $(dtb-y)
 
 PHONY += dtbs