Clean up specifying build directory

Instead of setting the build directory unconditionally (which doesn't
entirely work anyway; U-Boot handles it well, but TFA and DT-rebasing do
not), by default let each project use it's own working directory.
However, if BUILD_BASE is set, then use that to create build directories
for the projects that support it.

Signed-off-by: Grant Likely <grant.likely@arm.com>

main.mk

@@ -19,7 +19,7 @@ include $(UBOOT_OUTPUT)/.config
 
 ifdef CONFIG_ROCKCHIP_RK3399
 TFA_PLAT := rk3399
-UBOOT_EXTRA := BL31=$(TFA_PATH)/build/$(TFA_PLAT)/release/bl31/bl31.elf
+UBOOT_EXTRA += BL31=$(TFA_PATH)/build/$(TFA_PLAT)/release/bl31/bl31.elf
 FLASH_IMAGE := $(UBOOT_OUTPUT)/flash_image.bin
 DTB_TARGET := src/arm64/$(CONFIG_DEFAULT_FDT_FILE)
 u-boot: tfa-bl31
@@ -41,9 +41,9 @@ endif
 
 # Grab the platform specific variables into generic versions
 
-#UBOOT_EXTRA ?= EXT_DTB=$(DT_PATH)/$(DTB_TARGET)
+#UBOOT_EXTRA ?= EXT_DTB=$(DT_OUTPUT)/$(DTB_TARGET)
 
-FLASH_IMAGE ?= $(TFA_PATH)/build/$(TFA_PLAT)/release/flash-image.bin
+FLASH_IMAGE ?= $(TFA_OUTPUT)/$(TFA_PLAT)/release/flash-image.bin
 
 ESP_SIZE ?= $$((64*1024*1024))
 ESP_OFFSET ?= $$((4*1024*1024))
@@ -54,12 +54,11 @@ SCT_VERSION:=UEFI2.6SCTII_Final_Release
 
 dtb:
 	${MAKE} -C ${DT_PATH} ${DTB_TARGET}
-	fdtput ${DT_PATH}/${DTB_TARGET} -t s / u-boot-ver `cd ${UBOOT_PATH} && git describe`
-	fdtput ${DT_PATH}/${DTB_TARGET} -t s / tfa-ver `cd ${TFA_PATH} && git describe`
-	fdtput ${DT_PATH}/${DTB_TARGET} -t s / dt-ver `cd ${DT_PATH} && git describe`
-	#fdtput ${DT_PATH}/${DTB_TARGET} -t x /ap806/config-space@f0000000/serial@512000 clock-frequency 0xbebc200
+	fdtput ${DT_OUTPUT}/${DTB_TARGET} -t s / u-boot-ver `cd ${UBOOT_PATH} && git describe`
+	fdtput ${DT_OUTPUT}/${DTB_TARGET} -t s / tfa-ver `cd ${TFA_PATH} && git describe`
+	fdtput ${DT_OUTPUT}/${DTB_TARGET} -t s / dt-ver `cd ${DT_PATH} && git describe`
+	#fdtput ${DT_OUTPUT}/${DTB_TARGET} -t x /ap806/config-space@f0000000/serial@512000 clock-frequency 0xbebc200
 
-u-boot: export KBUILD_OUTPUT=$(UBOOT_OUTPUT)
 u-boot: dtb
 	${MAKE} -C ${UBOOT_PATH} ${UBOOT_EXTRA} -j4
 
@@ -89,7 +88,7 @@ esp.tree/.done: scripts/main.mk Shell.efi $(SCT_VERSION).zip
 	mkdir -p esp.tree/efi/boot
 	cp Shell.efi esp.tree/efi/boot/bootaa64.efi
 
-	cp $(DT_PATH)/$(DTB_TARGET) \
+	cp $(DT_OUTPUT)/$(DTB_TARGET) \
 	   $(UBOOT_OUTPUT)/lib/efi_selftest/efi_selftest_miniapp_return.efi \
 	   $(UBOOT_OUTPUT)/lib/efi_selftest/efi_selftest_miniapp_exception.efi \
 	   $(UBOOT_OUTPUT)/lib/efi_selftest/efi_selftest_miniapp_exit.efi \

top.mk

 # SPDX-License-Identifier: GPL-2.0+
 #
 # Copyright (C) Arm Limited, 2020
+#
+# Makefile Conventions:
+# Variable names:
+# TARGET:   U-Boot configuration name; TFA, OP-TEE, and other target
+#           configuration names key off the U-Boot configuration; this is a
+#           U-Boot oriented tool after all.
+# *_PATH:   Full path to project source directories or other assets
+# *_OUTPUT: Build directories for each of the sub projects
+# *_EXTRA:  Extra parameters to the make call. Gets added to make targets, e.g.
+#           "$(MAKE) -C ${PROJECT_PATH} ... ${PROJECT_EXTRA} ..."
 
 ifndef TARGET
   $(error TARGET is not set)
@@ -8,27 +18,38 @@ endif
 
 # Set some defaults that can be overridden by the target  makefile include
 export DT_PATH    := $(CURDIR)/devicetree-rebasing
+export DT_OUTPUT  := $(DT_PATH)
 export TFA_PATH   := $(CURDIR)/arm-trusted-firmware
 export UBOOT_PATH := $(CURDIR)/u-boot
-export UBOOT_OUTPUT := $(CURDIR)/u-boot/build-$(TARGET)
+
+# Give the option of building in a separate directory
+ifdef BUILD_OUTPUT
+  __BUILD := $(realpath $(BUILD_OUTPUT))
+  export TFA_OUTPUT := $(__BUILD)/tfa
+  export TFA_EXTRA += BUILD_BASE=$(TFA_OUTPUT)
+  export UBOOT_OUTPUT := $(__BUILD)/u-boot
+  export UBOOT_EXTRA += KBUILD_OUTPUT=$(UBOOT_OUTPUT)
+else
+  export TFA_OUTPUT := $(TFA_PATH)/build
+  export UBOOT_OUTPUT := $(UBOOT_PATH)
+endif
 
 all: tfa-fip
 
 clean:
-	cd $(UBOOT_PATH) && make mrproper
-	cd $(UBOOT_PATH) && make KBUILD_OUTPUT=$(UBOOT_OUTPUT) clean
+	$(MAKE) -C $(UBOOT_PATH) $(UBOOT_EXTRA) mrproper
 	cd $(TFA_PATH) && git clean -fdx
 	cd $(CURDIR)/mv-ddr && git clean -fdx
 
 $(UBOOT_OUTPUT)/.config:
 	mkdir -p $(UBOOT_OUTPUT)
-	$(MAKE) -C $(UBOOT_PATH) KBUILD_OUTPUT=$(UBOOT_OUTPUT) $(TARGET)_defconfig
+	$(MAKE) -C $(UBOOT_PATH) $(UBOOT_EXTRA) $(TARGET)_defconfig
 	echo CONFIG_CMD_BOOTEFI_HELLO=y >> $(UBOOT_OUTPUT)/.config
 	echo CONFIG_CMD_BOOTEFI_SELFTEST=y >> $(UBOOT_OUTPUT)/.config
 	echo CONFIG_CMD_NVEDIT_EFI=y >> $(UBOOT_OUTPUT)/.config
 	echo CONFIG_CMD_EFIDEBUG=y >> $(UBOOT_OUTPUT)/.config
 	echo CONFIG_CMD_GPT=y >> $(UBOOT_OUTPUT)/.config
-	$(MAKE) -C $(UBOOT_PATH) KBUILD_OUTPUT=$(UBOOT_OUTPUT) olddefconfig
+	$(MAKE) -C $(UBOOT_PATH) $(UBOOT_EXTRA) olddefconfig
 
 %: $(UBOOT_OUTPUT)/.config
 	$(MAKE) -f scripts/main.mk TARGET=$(TARGET) $@