[PATCH v2 2/2] Makefile: Only build dtc if needed

[Heinrich Schuchardt]

Am April 27, 2020 12:29:29 AM UTC schrieb Simon Glass <sjg at chromium.org>:
>At present U-Boot always builds dtc if CONFIG_OF_CONTROL is defined.
>This
>is wasteful when the system already has a suitable version available.
>
>Update the Makefile logic to build dtc only if the version available is
>too old.
>
>This saves about 2.5 seconds of elapsed time on a clean build for me.
>
>- Add a patch to bring back the dtc-version.sh script
>- Update the check to make sure libfdt is available if needed

U -Boot has been set up to create reproducible builds. With this patch dtc will have to be made a build dependency to provide reproducibility. Cf. https://www.debian.org/doc/debian-policy/ch-source.html#reproducibility

This may require changes in the packaging of U-Boot in Linux distributions. Nothing to stop this patch, just something to keep in mind.

You presume that future versions of dtc will always be backward compatible with  U-Boot. Ok, we do the same for other tools like gcc too (with surprises at each new major release).

Cc: Vagrant

Best regards

Heinrich

>
>Signed-off-by: Simon Glass <sjg at chromium.org>
>---
>
> Makefile               | 21 ++++++++++++++++++---
> dts/Kconfig            |  4 ----
> scripts/Kbuild.include |  5 ++++-
> scripts/Makefile       |  1 -
> scripts/dtc-version.sh | 36 +++++++++++++++++++++++++++++++-----
> 5 files changed, 53 insertions(+), 14 deletions(-)
>
>diff --git a/Makefile b/Makefile
>index b8a4b5058a..90cb83ed32 100644
>--- a/Makefile
>+++ b/Makefile
>@@ -410,7 +410,12 @@ PERL		= perl
> PYTHON		?= python
> PYTHON2		= python2
> PYTHON3		= python3
>-DTC		?= $(objtree)/scripts/dtc/dtc
>+
>+# DTC is automatically built if the version of $(DTC) is older that
>needed.
>+# Use the system dtc if it is new enough.
>+DTC		?= dtc
>+DTC_MIN_VERSION	:= 010406
>+
> CHECK		= sparse
> 
> CHECKFLAGS     := -D__linux__ -Dlinux -D__STDC__ -Dunix -D__unix__ \
>@@ -1797,12 +1802,12 @@ include/config/uboot.release:
>include/config/auto.conf FORCE
> # version.h and scripts_basic is processed / created.
> 
> # Listed in dependency order
>-PHONY += prepare archprepare prepare0 prepare1 prepare2 prepare3
>+PHONY += prepare archprepare prepare0 prepare1 prepare2 prepare3
>prepare4
> 
># prepare3 is used to check if we are building in a separate output
>directory,
> # and if so do:
># 1) Check that make has not been executed in the kernel src $(srctree)
>-prepare3: include/config/uboot.release
>+prepare4: include/config/uboot.release
> ifneq ($(KBUILD_SRC),)
> 	@$(kecho) '  Using $(srctree) as source for U-Boot'
>	$(Q)if [ -f $(srctree)/.config -o -d $(srctree)/include/config ]; then
>\
>@@ -1812,6 +1817,14 @@ ifneq ($(KBUILD_SRC),)
> 	fi;
> endif
> 
>+# Checks for dtc and builds it if needed
>+prepare3: prepare4
>+	$(eval DTC := $(call
>dtc-version,010406,$(build_dtc),$(CONFIG_PYLIBFDT)))
>+	echo here $(DTC) $(build_dtc)
>+	if test "$(DTC)" = "$(build_dtc)"; then \
>+		$(MAKE) $(build)=scripts/dtc; \
>+	fi
>+
> # prepare2 creates a makefile if using a separate output directory
> prepare2: prepare3 outputmakefile cfg
> 
>@@ -1963,6 +1976,8 @@ SYSTEM_MAP = \
> System.map:	u-boot
> 		@$(call SYSTEM_MAP,$<) > $@
> 
>+build_dtc	:= $(objtree)/scripts/dtc/dtc
>+
>#########################################################################
> 
> # ARM relocations should all be R_ARM_RELATIVE (32-bit) or
>diff --git a/dts/Kconfig b/dts/Kconfig
>index 046a54a173..f8b808606c 100644
>--- a/dts/Kconfig
>+++ b/dts/Kconfig
>@@ -5,9 +5,6 @@
> config SUPPORT_OF_CONTROL
> 	bool
> 
>-config DTC
>-	bool
>-
> config PYLIBFDT
> 	bool
> 
>@@ -24,7 +21,6 @@ menu "Device Tree Control"
> 
> config OF_CONTROL
> 	bool "Run-time configuration via Device Tree"
>-	select DTC
> 	select OF_LIBFDT if !OF_PLATDATA
> 	help
> 	  This feature provides for run-time configuration of U-Boot
>diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include
>index b34dedade7..8c167cef2d 100644
>--- a/scripts/Kbuild.include
>+++ b/scripts/Kbuild.include
>@@ -151,8 +151,11 @@ cc-fullversion = $(shell $(CONFIG_SHELL) \
>cc-ifversion = $(shell [ $(cc-version) $(1) $(2) ] && echo $(3) || echo
>$(4))
> 
> # added for U-Boot
>+# $1: min_version
>+# 32: build_dtc
>+# $3: need_pylibfdt
>binutils-version = $(shell $(CONFIG_SHELL)
>$(srctree)/scripts/binutils-version.sh $(AS))
>-dtc-version = $(shell $(CONFIG_SHELL)
>$(srctree)/scripts/dtc-version.sh $(DTC))
>+dtc-version = $(shell $(CONFIG_SHELL)
>$(srctree)/scripts/dtc-version.sh $(DTC) $1 $2 $3)
> 
> # cc-ldoption
> # Usage: ldflags += $(call cc-ldoption, -Wl$(comma)--hash-style=both)
>diff --git a/scripts/Makefile b/scripts/Makefile
>index e7b353f77f..cfe9fef804 100644
>--- a/scripts/Makefile
>+++ b/scripts/Makefile
>@@ -10,4 +10,3 @@ always		:= $(hostprogs-y)
> 
> # Let clean descend into subdirs
> subdir-	+= basic kconfig
>-subdir-$(CONFIG_DTC)	+= dtc
>diff --git a/scripts/dtc-version.sh b/scripts/dtc-version.sh
>index 0744c39eb0..75ba82830d 100755
>--- a/scripts/dtc-version.sh
>+++ b/scripts/dtc-version.sh
>@@ -1,12 +1,26 @@
> #!/bin/sh
> #
>-# dtc-version dtc-command
>+# dtc-version dtc_command min_version build_dtc need_pylibfdt
> #
>-# Prints the dtc version of `dtc-command' in a canonical 6-digit form
>-# such as `010404'  for dtc 1.4.4
>+# Selects which version of dtc to use
>+#
>+# If need_pylibfdt is non-empty then the script first checks that the
>Python
>+# libfdt library is available. If not it outputs $build_dtc and exits
>+#
>+# Otherwise, if the version of dtc_command is < min_version, prints
>build_dtc
>+# else prints dtc_command. The min_version is in the format MMmmpp
>where:
>+#
>+#   MM is the major version
>+#   mm is the minor version
>+#   pp is the patch level
>+#
>+# For example 010406 means 1.4.6
> #
> 
>-dtc="$*"
>+dtc="$1"
>+min_version="$2"
>+build_dtc="$3"
>+need_pylibfdt="$4"
> 
> if [ ${#dtc} -eq 0 ]; then
> 	echo "Error: No dtc command specified."
>@@ -14,8 +28,20 @@ if [ ${#dtc} -eq 0 ]; then
> 	exit 1
> fi
> 
>+if [ -n "${need_pylibfdt}" ]; then
>+	if ! echo "import libfdt" | python3 2>/dev/null; then
>+		echo $build_dtc
>+		exit 0
>+	fi
>+fi
>+
> MAJOR=$($dtc -v | head -1 | awk '{print $NF}' | cut -d . -f 1)
> MINOR=$($dtc -v | head -1 | awk '{print $NF}' | cut -d . -f 2)
>PATCH=$($dtc -v | head -1 | awk '{print $NF}' | cut -d . -f 3 | cut -d
>- -f 1)
> 
>-printf "%02d%02d%02d\\n" $MAJOR $MINOR $PATCH
>+version="$(printf "%02d%02d%02d" $MAJOR $MINOR $PATCH)"
>+if test $version -lt $min_version; then \
>+	echo $build_dtc
>+else
>+	echo $dtc
>+fi