Makefile: Only build dtc if needed
At present U-Boot always builds dtc if CONFIG_OF_CONTROL is defined, even
when DTC is provided. The built dtc is not actually used, so this is a
waste of time.
Update the Makefile logic to build dtc only if one is not provided to the
build with the DTC variable. Add documentation to explain this.
This saves about 3.5 seconds of elapsed time on a clean build of
sandbox_spl for me.
Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/Makefile b/Makefile
index f911f70..32d29b8 100644
--- a/Makefile
+++ b/Makefile
@@ -415,7 +415,13 @@
PYTHON ?= python
PYTHON2 = python2
PYTHON3 ?= python3
-DTC ?= $(objtree)/scripts/dtc/dtc
+
+# The devicetree compiler and pylibfdt are automatically built unless DTC is
+# provided. If DTC is provided, it is assumed the pylibfdt is available too.
+DTC_INTREE := $(objtree)/scripts/dtc/dtc
+DTC ?= $(DTC_INTREE)
+DTC_MIN_VERSION := 010406
+
CHECK = sparse
CHECKFLAGS := -D__linux__ -Dlinux -D__STDC__ -Dunix -D__unix__ \
@@ -1954,9 +1960,29 @@
endif
+# Check dtc and pylibfdt, if DTC is provided, else build them
PHONY += scripts_dtc
scripts_dtc: scripts_basic
- $(Q)$(MAKE) $(build)=scripts/dtc
+ $(Q)if test "$(DTC)" = "$(DTC_INTREE)"; then \
+ $(MAKE) $(build)=scripts/dtc; \
+ else \
+ if ! $(DTC) -v >/dev/null; then \
+ echo '*** Failed to check dtc version: $(DTC)'; \
+ false; \
+ else \
+ if test "$(call dtc-version)" -lt $(DTC_MIN_VERSION); then \
+ echo '*** Your dtc is too old, please upgrade to dtc $(DTC_MIN_VERSION) or newer'; \
+ false; \
+ else \
+ if [ -n "$(CONFIG_PYLIBFDT)" ]; then \
+ if ! echo "import libfdt" | $(PYTHON3) 2>/dev/null; then \
+ echo '*** pylibfdt does not seem to be available with $(PYTHON3)'; \
+ false; \
+ fi; \
+ fi; \
+ fi; \
+ fi; \
+ fi
# ---------------------------------------------------------------------------
quiet_cmd_cpp_lds = LDS $@