U-Boot notes

Porting u-boot

Just some simple guidelines for start porting u-boot to a new board. I'm using an NXP imx8mp as example.

Using u-boot-2021.04 as example. This is not at all a detailed report but just the initial basic steps.

Board files

Copy board/freescale/imx8mp_evk as board/freescale/imx8mp_my_board/

$ ls board/freescale/imx8mp_my_board/

boot.cmd  ddr4_timing.c  imx8mp_evk.c  Kconfig  lpddr4_timing.c  lpddr4_timing_ndm.c  MAINTAINERS  Makefile  spl.c

Rename

board/freescale/imx8mp_my_board/imx8mp_evk.c

to

board/freescale/imx8mp_my_board/imx8mp_my_board.c

Update Kconfig and Makefile

board/freescale/imx8mp_my_board/Kconfig

if TARGET_IMX8MP_MY_BOARD
config SYS_BOARD
default "imx8mp_my_board"
config SYS_VENDOR
default "freescale"
config SYS_CONFIG_NAME
default "imx8mp_my_board"
source "board/freescale/common/Kconfig"
endif

board/freescale/imx8mp_my_board/Makefile

obj-y += imx8mp_my_board.o
ifdef CONFIG_SPL_BUILD
obj-y += spl.o
ifdef CONFIG_IMX8M_LPDDR4_FREQ0_3200MTS
obj-y += lpddr4_timing_ndm.o
else
obj-$(CONFIG_IMX8M_LPDDR4) += lpddr4_timing.o
obj-$(CONFIG_IMX8M_DDR4) += ddr4_timing.o
endif
endif

Update arch/arm/mach-imx/imx8m/Kconfig to include the board files

+config TARGET_IMX8MP_MY_BOARD
+       bool "imx8mp LPDDR4 my board"
+       select IMX8MP
+       select SUPPORT_SPL
+       select IMX8M_LPDDR4
+       select FSL_CAAM
+       select FSL_BLOB
+       select MISC
+       select SPL_CRYPTO_SUPPORT if SPL
+
+source "board/freescale/imx8mp_my_board/Kconfig"

Board dts files

$ cp arch/arm/dts/imx8mp-evk.dts arch/arm/dts/imx8mp-my-board.dts

$ cp arch/arm/dts/imx8mp-evk-u-boot.dtsi arch/arm/dts/imx8mp-my-board-u-boot.dtsi

Update dts makefile arch/arm/dts/Makefile to add our new dt

+       imx8mp-my-board.dtb

Board config file

Take a copy of configs/imx8mp_evk_defconfig as configs/imx8mp_my_board_defconfig

Then make following changes

CONFIG_TARGET_IMX8MP_EVK=y  ->  CONFIG_TARGET_IMX8MP_MY_BOARD=y

replace whatever dt files, or you can just use existing ones for now

CONFIG_DEFAULT_DEVICE_TREE="imx8mp-evk" -> CONFIG_DEFAULT_DEVICE_TREE="imx8mp-my-board"

CONFIG_DEFAULT_FDT_FILE="imx8mp-evk.dtb"    ->  CONFIG_DEFAULT_FDT_FILE="imx8mp-my-board.dtb"

Board header file

$ cp include/configs/imx8mp_evk.h include/configs/imx8mp_my_board.h