Fwd: [RFC][PATCH] kbuild: Produce diff between base DT and U-Boot augmented DT if DEVICE_TREE_DEBUG=1

[Heinrich Schuchardt]

Hello Hal, hello Minda,

Marek created the patch below, to find differences between Linux 
device-tree and what U-Boot uses.

For all JH7110 boards I find these differences which are due to 
arch/riscv/dts/starfive-visionfive2-u-boot.dtsi. Could you, please, 
check if these are still intended:

@@ -533,7 +617,7 @@
  			#clock-cells = <0x1>;
  			#reset-cells = <0x1>;
  			assigned-clock-parents = <0x28 0x0 0x28 0x2 0x28 0x2 0x3 0x59>;
-			assigned-clock-rates = <0x0 0x0 0x0 0x0 0x1dcd6500 0x59682f00>;
+			assigned-clock-rates = <0x0>;
  			assigned-clocks = <0x3 0x0 0x3 0x5 0x3 0x4 0x3 0x5a 0x3 0x1 0x28 0x0>;
  			bootph-pre-ram;
  			clock-names = "osc", "gmac1_rmii_refin", "gmac1_rgmii_rxin", 
"i2stx_bclk_ext", "i2stx_lrck_ext", "i2srx_bclk_ext", "i2srx_lrck_ext", 
"tdm_ext", "mclk_ext", "pll0_out", "pll1_out", "pll2_out";
@@ -996,6 +1080,7 @@

  		memory-controller at 15700000 {
  			bootph-pre-ram;
+			clock-frequency = <0x855>; // 2133 MHz
  			clock-names = "pll";
  			clocks = <0x3 0x1>;
  			compatible = "starfive,jh7110-dmc";

Best regards

Heinrich


-------- Forwarded Message --------
Subject: [RFC][PATCH] kbuild: Produce diff between base DT and U-Boot 
augmented DT if DEVICE_TREE_DEBUG=1
Date: Thu,  6 Nov 2025 22:08:18 +0100
From: Marek Vasut <marek.vasut+renesas at mailbox.org>
To: u-boot at lists.denx.de
CC: Marek Vasut <marek.vasut+renesas at mailbox.org>, Adriano Cordova 
<adrianox at gmail.com>, Heinrich Schuchardt <xypron.glpk at gmx.de>, Ilias 
Apalodimas <ilias.apalodimas at linaro.org>, Peter Robinson 
<pbrobinson at gmail.com>, Sam Edwards <cfsworks at gmail.com>, Tom Rini 
<trini at konsulko.com>

In case DEVICE_TREE_DEBUG is set, produce a diff between the base DT and
DT with U-Boot extras, to show how much does the U-Boot DT differ from
the base DT. This is particularly useful together with OF_UPSTREAM, to
minimize the diff between upstream DTs and U-Boot DTs.

Example usage:
$ make r8a779g3_sparrowhawk_defconfig && make DEVICE_TREE_DEBUG=1
$ cat ./dts/upstream/src/arm64/renesas/r8a779g3-sparrow-hawk.dtb.diff

This still has a downside. Even 'dtc -I dts -O dts ...' applied on
base DT and U-Boot augmented DT can produce different phandle IDs
for the same node in those two DTs, which results in a lot of noise
in the resulting diff. The only way I can think of is to patch DTC
to emit full paths in those phandles instead, something like a
phandle = <&{/full/path/to/remote/end} ...>;

Signed-off-by: Marek Vasut <marek.vasut+renesas at mailbox.org>
---
Cc: Adriano Cordova <adrianox at gmail.com>
Cc: Heinrich Schuchardt <xypron.glpk at gmx.de>
Cc: Ilias Apalodimas <ilias.apalodimas at linaro.org>
Cc: Peter Robinson <pbrobinson at gmail.com>
Cc: Sam Edwards <cfsworks at gmail.com>
Cc: Tom Rini <trini at konsulko.com>
Cc: u-boot at lists.denx.de
---
  scripts/Makefile.lib | 24 +++++++++++++++++++++++-
  1 file changed, 23 insertions(+), 1 deletion(-)

diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index 5db2fbc418a..2d8bf3c04f4 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -386,10 +386,31 @@ ifeq ($(CONFIG_OF_LIBFDT_OVERLAY),y)
  DTC_FLAGS += -@
  endif
  +# In case DEVICE_TREE_DEBUG is set, produce a diff between the base 
DT and
+# DT with U-Boot extras, to show how much does the U-Boot DT differ from
+# the base DT. This is particularly useful together with OF_UPSTREAM, to
+# minimize the diff between upstream DTs and U-Boot DTs.
+ifdef DEVICE_TREE_DEBUG
+cmd_dtc_diff = \
+	$(HOSTCC) -E $(dtc_cpp_flags) -I$(obj) -x assembler-with-cpp -o 
$(dtn-tmp) $< ; \
+	$(DTC) -s -O dts -o $@.clean.dts -b 0 \
+		-i $(dir $<) $(DTC_FLAGS) $(dtn-tmp) || \
+		(echo "Check $(shell pwd)/$< for errors" && false); \
+	$(DTC) -s -O dts -o $@.full.dts -b 0 \
+		-i $(dir $<) -i $(u_boot_dtsi_loc) $(DTC_FLAGS) $(dtc-tmp) || \
+		(echo "Check $(shell pwd)/$(pre-tmp) for errors" && false); \
+	(diff -Naru $@.clean.dts $@.full.dts > $@.diff || true)
+
+dtn-tmp = $(subst $(comma),_,$(dot-target).dtn.tmp)
+else
+cmd_dtc_diff =
+endif
+
  quiet_cmd_dtc = DTC     $@
  # Modified for U-Boot
  # Bring in any U-Boot-specific include at the end of the file
  # And finally any custom .dtsi fragments specified with 
CONFIG_DEVICE_TREE_INCLUDES
+
  cmd_dtc = mkdir -p $(dir ${dtc-tmp}) ; \
  	(cat $< > $(pre-tmp)); \
  	$(foreach f,$(subst $(quote),,$(dtsi_include_list) 
$(CONFIG_DEVICE_TREE_INCLUDES)), \
@@ -400,7 +421,8 @@ cmd_dtc = mkdir -p $(dir ${dtc-tmp}) ; \
  		-d $(depfile).dtc.tmp $(dtc-tmp) || \
  		(echo "Check $(shell pwd)/$(pre-tmp) for errors" && false) \
  		; \
-	sed "s:$(pre-tmp):$(<):" $(depfile).pre.tmp $(depfile).dtc.tmp > 
$(depfile)
+	sed "s:$(pre-tmp):$(<):" $(depfile).pre.tmp $(depfile).dtc.tmp > 
$(depfile) ; \
+	$(cmd_dtc_diff)
   dtsi_include_list_deps := $(addprefix $(u_boot_dtsi_loc),$(subst 
$(quote),,$(dtsi_include_list)))
  -- 2.51.0