MTK平台DTBO如何生成的以及DWS生成DTS

一、MTK平台最初就是使用DWS來配置GPIO，非常友善、直覺；但随着kernel版本更新使用裝置樹之後，硬體資訊都由DTS來描述，但MTK仍然保留了DWS，下面看看MTK如何将DWS轉換為DTSI的。

kernel使用的DWS路徑：drivers/misc/mediatek/dws/mt6752/mt6752_64.dws
雖然vendor\mediatek\proprietary\custom\mt6752_64\kernel\dct\dct\codegen.dws也存在但預設不用這個
DWS轉換為DTSI的工具kernel-4.14/scripts/drvgen/drvgen.mk
核心代碼：
.PHONY: drvgen
drvgen: $(DRVGEN_FILE_LIST)
$(DRVGEN_FILE_LIST): $(DRVGEN_TOOL) $(DWS_FILE) $(DRVGEN_FIG) $(PROJ_DTS_FILES)
        for i in $(PROJ_DTS_FILES); do \
                base_prj=`grep -m 1 '#include [<\"].*\/cust\.dtsi[>\"]' $$i | sed 's/#include [<"]//g'\
                | sed 's/\/cust\.dtsi[>"]//g' | sed 's/\/\*//g' | sed 's/\*\///g' | sed 's/ //g'`\
                prj_path=$(DRVGEN_OUT)/$$base_prj ;\
                dws_path=$(srctree)/$(DRVGEN_PATH)/$$base_prj.dws ;\
                if [ -f $$dws_path ] ; then \
                        mkdir -p $$prj_path ;\
                        $(python) $(DRVGEN_TOOL) $$dws_path $$prj_path $$prj_path cust_dtsi;\
                fi \
        done


最終生成的DTSI檔案路徑obj\KERNEL_OBJ\arch\arm64\boot\dts\mt6752_64\cust_dtsi
           

具體怎麼生成的可以看這個drvgen.mk以及它所依賴的工具

二、MTK DTBO的生成，它使用的哪個DTS檔案

相關檔案：scripts/drvgen/drvgen.mk
相關代碼
my_dtbo_id := 0
define mk_dtboimg_cfg
echo $(1) >>$(2);\
echo " id=$(my_dtbo_id)" >>$(2);\
$(eval my_dtbo_id:=$(shell echo $$(($(my_dtbo_id)+1))))
endef

dtbs: $(objtree)/dtboimg.cfg
$(objtree)/dtboimg.cfg: FORCE
        rm -f [email protected]
        $(foreach f,$(ABS_DTB_FILES),$(call mk_dtboimg_cfg,$(f),[email protected]))
        if ! cmp -s [email protected] [email protected]; then \
                mv [email protected] [email protected]; \
        else \
                rm [email protected]; \
        fi
由此可見這裡生成了一個dtboimg.cfg檔案，路徑：obj\KERNEL_OBJ\dtboimg.cfg

這個檔案指定了DTBO由哪個DTS檔案生成

DTBO生成：
device/mediatek/build/tasks/dtbo.mk

.KATI_RESTAT: $(KERNEL_OUT)/dtboimg.cfg
$(KERNEL_OUT)/dtboimg.cfg: $(KERNEL_ZIMAGE_OUT) ;

# mkdtimg is from system/libufdt/utils/src
$(BOARD_PREBUILT_DTBOIMAGE): PRIVATE_TOOL := $(HOST_OUT_EXECUTABLES)/mkdtimg
$(BOARD_PREBUILT_DTBOIMAGE): PRIVATE_CFG := $(KERNEL_OUT)/dtboimg.cfg
$(BOARD_PREBUILT_DTBOIMAGE): $(HOST_OUT_EXECUTABLES)/mkdtimg
$(BOARD_PREBUILT_DTBOIMAGE): $(KERNEL_OUT)/dtboimg.cfg
        $(hide) mkdir -p $(dir [email protected])
        $(PRIVATE_TOOL) cfg_create [email protected] $(PRIVATE_CFG)

ifeq ($(strip $(MTK_DTBO_UPGRADE_FROM_ANDROID_O)), yes)
droidcore: $(PRODUCT_OUT)/$(notdir $(BOARD_PREBUILT_DTBOIMAGE))
odmdtboimage: $(PRODUCT_OUT)/$(notdir $(BOARD_PREBUILT_DTBOIMAGE))
else
droidcore: $(PRODUCT_OUT)/dtbo.img
dtboimage: $(PRODUCT_OUT)/dtbo.img
endif
$(PRODUCT_OUT)/recovery.img: $(BOARD_PREBUILT_DTBOIMAGE)

由此可見，此處使用mkdtimg工具根據dtboimg.cfg來生成dtbo.img
           

三、MTK DTB  DTBO使用哪個DTS檔案

檔案：kernel-4.14/scripts/drvgen/drvgen.mk

ifeq ($(strip $(CONFIG_ARM64)), y)
MAIN_DT_NAMES := $(subst $\",,$(CONFIG_BUILD_ARM64_APPENDED_DTB_IMAGE_NAMES))
else
MAIN_DT_NAMES := $(subst $\",,$(CONFIG_BUILD_ARM_APPENDED_DTB_IMAGE_NAMES))
endif

ifeq ($(strip $(CONFIG_ARM64)), y)
PROJ_DT_NAMES := $(subst $\",,$(CONFIG_BUILD_ARM64_DTB_OVERLAY_IMAGE_NAMES))
else
PROJ_DT_NAMES := $(subst $\",,$(CONFIG_BUILD_ARM_DTB_OVERLAY_IMAGE_NAMES))
endif

檔案：kernel 的config檔案
CONFIG_BUILD_ARM64_APPENDED_DTB_IMAGE_NAMES="mediatek/mt6752"
CONFIG_BUILD_ARM64_DTB_OVERLAY_IMAGE_NAMES="mediatek/mt6752_64"

mt6752_64.dts用來生成DTBO，mt6752.dts用來生成dtb

但是drvgen.mk下面生成的DTB依賴檔案是mtk.dtb，那mtk.dtb哪裡來的呢？

ABS_DTB_FILES := $(abspath $(addsuffix .dtb,$(addprefix $(objtree)/arch/$(SRCARCH)/boot/dts/,$(PROJ_DT_NAMES))))
ABS_DTB2_FILES := $(abspath $(addprefix $(objtree)/arch/$(SRCARCH)/boot/,mtk.dtb))


$(objtree)/dtbimg.cfg: FORCE
        rm -f [email protected]
        $(foreach f,$(ABS_DTB2_FILES),$(call mk_dtbimg_cfg,$(f),[email protected]))
        if ! cmp -s [email protected] [email protected]; then \
                mv [email protected] [email protected]; \
        else \
                rm [email protected]; \
fi
這個dtbimg.cfg檔案内容就是mtk.dtb的路徑

其他地方關于mtk.dtb的定義
kenv.mk:109:    KERNEL_DTB_FILE := $(KERNEL_OUT)/arch/$(KERNEL_TARGET_ARCH)/boot/mtk.dtb
Android.mk
### DTB
ifdef BOARD_PREBUILT_DTBIMAGE_DIR
INSTALLED_MTK_DTB_TARGET := $(BOARD_PREBUILT_DTBIMAGE_DIR)/mtk_dtb
$(shell if [ ! -f $(INSTALLED_MTK_DTB_TARGET) ]; then mkdir -p $(dir $(INSTALLED_MTK_DTB_TARGET)); touch $(INSTALLED_MTK_DTB_TARGET);fi)
$(INSTALLED_MTK_DTB_TARGET): $(INSTALLED_KERNEL_TARGET)
        @mkdir -p $(dir [email protected])
        @cp -f $(KERNEL_DTB_FILE) [email protected]
endif

dtbimg.cfg路徑
"out\target\product\mt6752_64\obj\KERNEL_OBJ\dtbimg.cfg"
mtk.dtb路徑
"out\target\product\mt6752_64\obj\PACKAGING\dtb\mtk.dtb"


mtk.dtb來源：

檔案：arch/arm64/boot/Makefile

DTB_NAMES := $(subst $\",,$(CONFIG_BUILD_ARM64_APPENDED_DTB_IMAGE_NAMES))
ifneq ($(DTB_NAMES),)
DTB_LIST := $(addsuffix .dtb,$(DTB_NAMES))
else
DTB_LIST := $(dtb-y)
endif
DTB_OBJS := $(addprefix $(obj)/dts/,$(DTB_LIST))


$(obj)/mtk.dtb: $(DTB_OBJS) FORCE
        $(call if_changed,cat)