Allow core code to request its cross compiler

Instead of having to pass in both the board and the arch used there
(which might be complicated in the light of different ECs with different
arches), allow passing in the board and a set of cross compilers.

The core/*/build.mk then pick the compiler that is responsible for them.
The current method works just the same: If you've already set
CROSS_COMPILE, no override happens. If you set neither CROSS_COMPILE nor
CROSS_COMPILE_$arch, the same default as before this CL is set.

BUG=none
BRANCH=none
TEST=emerge-{samus,kevin} chromeos-ec behave reasonably with adapted
ebuild

Change-Id: Icf1866f296412dd92ecfe134394224c49f7c3df5
Signed-off-by: Patrick Georgi <pgeorgi@google.com>
Reviewed-on: https://chromium-review.googlesource.com/549344
Commit-Ready: Patrick Georgi <pgeorgi@chromium.org>
Tested-by: Patrick Georgi <pgeorgi@chromium.org>
Reviewed-by: Stefan Reinauer <reinauer@google.com>

6 files changed, 24 insertions, 15 deletions

diff --git a/Makefile.rules b/Makefile.rules
index efc9c1e23e..2dae63a26e 100644
--- a/Makefile.rules
+++ b/Makefile.rules
@@ -456,19 +456,22 @@ endif
 help:
 	@echo "Google Chromium EC build"
 	@echo "Common Targets:"
-	@echo "  all   [BOARD=]     - Build a single board (Default target)"
-	@echo "  clean [BOARD=]     - Clean a single board"
-	@echo "  buildall           - Build and test all boards"
-	@echo "  clobber            - Clean all boards"
-	@echo "  proj-<boardname>   - Build a single board (similar to 'all BOARD=boardname')"
-	@echo "  savesizes          - Save the filesizes of currently built boards for comparison"
-	@echo "  newsizes           - Compare previously saved filesizes against new sizes"
+	@echo "  all   [BOARD=]       - Build a single board (Default target)"
+	@echo "  clean [BOARD=]       - Clean a single board"
+	@echo "  buildall             - Build and test all boards"
+	@echo "  clobber              - Clean all boards"
+	@echo "  proj-<boardname>     - Build a single board (similar to 'all BOARD=boardname')"
+	@echo "  savesizes            - Save the filesizes of currently built boards for comparison"
+	@echo "  newsizes             - Compare previously saved filesizes against new sizes"
 	@echo "Common Variables:"
-	@echo "  BOARD=             - Set the board name to build (Default is $(BOARD))"
-	@echo "  CROSS_COMPILE=     - Set the compiler for the board"
-	@echo "  V=1                - Show make output"
+	@echo "  V=1                  - Show make output"
+	@echo "  BOARD=               - Set the board name to build (Default is $(BOARD))"
+	@echo "  CROSS_COMPILE=       - Set the compiler for the board"
+	@echo "  CROSS_COMPILE_arch=  - Set the compiler for arch"
+	@echo "     The board picks its CROSS_COMPILE_arch if CROSS_COMPILE is not set."
+	@echo "     arch may be one of 'arm', 'i386', 'nds32'."
 	@echo "Example:"
-	@echo "  make BOARD=reef CROSS_COMPILE='arm-eabi-'"
+	@echo "  make BOARD=reef CROSS_COMPILE_arm='arm-eabi-'"
 
 .PHONY: savesizes
 savesizes:
diff --git a/Makefile.toolchain b/Makefile.toolchain
index 8bbac56dcd..1d1b458e3e 100644
--- a/Makefile.toolchain
+++ b/Makefile.toolchain
@@ -88,3 +88,9 @@ LDFLAGS=-nostdlib -Wl,-X -Wl,--gc-sections -Wl,--build-id=none $(LDFLAGS_EXTRA)
 BUILD_LDFLAGS=$(LIBFTDI_LDLIBS)
 HOST_TEST_LDFLAGS=-T core/host/host_exe.lds -lrt -pthread -rdynamic -lm\
 		  $(if $(TEST_COVERAGE),-fprofile-arcs,)
+
+# utility function to provide overridable defaults
+# $1: name of variable to set
+# $2: first default to use
+# $3: second default to use
+set-option = $(eval $1?=$$(if $(2),$(2),$(3)))
diff --git a/core/cortex-m/build.mk b/core/cortex-m/build.mk
index 5724a9ba39..cc323a2dca 100644
--- a/core/cortex-m/build.mk
+++ b/core/cortex-m/build.mk
@@ -7,7 +7,7 @@
 #
 
 # Select ARMv7-m bare-metal toolchain
-CROSS_COMPILE?=arm-none-eabi-
+$(call set-option,CROSS_COMPILE,$(CROSS_COMPILE_arm),arm-none-eabi-)
 
 # FPU compilation flags
 CFLAGS_FPU-$(CONFIG_FPU)=-mfpu=fpv4-sp-d16 -mfloat-abi=hard
diff --git a/core/cortex-m0/build.mk b/core/cortex-m0/build.mk
index f8f33aa2a3..6a0f44b367 100644
--- a/core/cortex-m0/build.mk
+++ b/core/cortex-m0/build.mk
@@ -7,7 +7,7 @@
 #
 
 # Select ARMv6-m compatible bare-metal toolchain
-CROSS_COMPILE?=arm-none-eabi-
+$(call set-option,CROSS_COMPILE,$(CROSS_COMPILE_arm),arm-none-eabi-)
 
 # CPU specific compilation flags
 CFLAGS_CPU+=-mthumb -Os -mno-sched-prolog
diff --git a/core/minute-ia/build.mk b/core/minute-ia/build.mk
index c58f5fff4e..4fae1ac107 100644
--- a/core/minute-ia/build.mk
+++ b/core/minute-ia/build.mk
@@ -7,7 +7,7 @@
 #
 
 # Select Minute-IA bare-metal toolchain
-CROSS_COMPILE=i686-pc-linux-gnu-
+$(call set-option,CROSS_COMPILE,$(CROSS_COMPILE_i386),i686-pc-linux-gnu-)
 
 # FPU compilation flags
 CFLAGS_FPU-$(CONFIG_FPU)=
diff --git a/core/nds32/build.mk b/core/nds32/build.mk
index 68dd1585ab..5b87d85b15 100644
--- a/core/nds32/build.mk
+++ b/core/nds32/build.mk
@@ -7,7 +7,7 @@
 #
 
 # Select Andes bare-metal toolchain
-CROSS_COMPILE?=nds32le-cros-elf-
+$(call set-option,CROSS_COMPILE,$(CROSS_COMPILE_nds32),nds32le-cros-elf-)
 
 # CPU specific compilation flags
 CFLAGS_CPU+=-march=v3m -Os