How to modify u-boot device tree for a custom board based on iMX91 with yocto

[RD-airzone]

Hello NXP team,

I'm trying to build a custom image for my custom board. It is based on iMX91 so I've created a new machine copying configuration from evaluation board. I've also add a copy of the EV board device tree (named ws-hub.dts) to the u-boot-imx recipe and change the model name to something else, just to know it is using it. In addition, I've created succesfully a bbappend to add the custom DT to Makefile under "CONFIG_ARCH_IMX9" option.

Then I've created a "airzone_uboot_defconfig" file for my machine based on imx91_11x11_evk_defconfig and modify on my machine conf the variable "UBOOT_CONFIG_BASENAME" to "airzone_uboot". I can see that it is being compiled succesfully

If I leave it as it is, if flashs correctly and then loads kernel but it is not using my custom DT.

Then, I've modify "CONFIG_DEFAULT_FDT_FILE" from defconfig to ws-hub.dtb and it tells "Failed to load 'ws-hub.dtb' ".

I've checked the command "fdt list" on uboot to see the device tree but it show me this:

u-boot => fdt list
/ {
interrupt-parent = <0x00000001>;
#address-cells = <0x00000002>;
#size-cells = <0x00000002>;
model = "NXP i.MX91 11X11 EVK board";
compatible = "fsl,imx91-11x11-evk", "fsl,imx91";
aliases {
};
cpus {
};
clock-osc-32k {
};
clock-osc-24m {
};
clock-ext1 {
};
pmu {
};
thermal-zones {
};
psci {
};
timer {
};
interrupt-controller@48000000 {
};
usbphynop1 {
};
usbphynop2 {
};
soc@0 {
};
imx93-lpm {
};
se-fw2 {
};
chosen {
};
reserved-memory {
};
regulator-can2-stby {
};
regulator-adc-vref {
};
regulator-usdhc2 {
};
regulator-vdd-12v {
};
regulator-vrpi-3v3 {
};
binman {
};
firmware {
};
backlight {
};
panel {
};
signature {
};
__symbols__ {
};
};

So I don't know where that device tree comes from.

My question is how am I suppose to modify the u-boot to adapt it to my board? Am I on the right way or do I have to modify directly the evaluation board DT?

I post my machine.conf in case that you need for reference:

MACHINEOVERRIDES =. "mx91:"

require conf/machine/include/imx-base.inc

require conf/machine/include/arm/armv8-2a/tune-cortexa55.inc

DDR_FIRMWARE_NAME = " \

    lpddr4_dmem_1d_v202201.bin \

    lpddr4_dmem_2d_v202201.bin \

    lpddr4_imem_1d_v202201.bin \

    lpddr4_imem_2d_v202201.bin \

"

# Remove unused image types

IMAGE_FSTYPES:remove = "wic.bmap"

IMAGE_FSTYPES:remove = "tar.zst"

MACHINE_FEATURES += "pci wifi bluetooth"

MACHINE_FEATURES:append:use-nxp-bsp = " dpdk optee nxpwifi-all-sdio"

# No cares about kernel device tree right now

# KERNEL_DEVICETREE_BASENAME = "imx91-11x11-evk"

# KERNEL_DEVICETREE = "freescale/${KERNEL_DEVICETREE_BASENAME}.dtb"

# Select NXP U-Boot.

IMX_DEFAULT_BOOTLOADER:use-nxp-bsp = "u-boot-imx"

LOADADDR = ""

UBOOT_SUFFIX = "bin"

UBOOT_MAKE_TARGET = ""

SPL_BINARY = "spl/u-boot-spl.bin"

UBOOT_CONFIG ??= "sd"

#UBOOT_CONFIG_BASENAME = "imx91_11x11_evk"

UBOOT_CONFIG_BASENAME = "airzone_uboot"

UBOOT_CONFIG[sd]   = "${UBOOT_CONFIG_BASENAME}_defconfig,sdcard"

# Set ATF platform name

ATF_PLATFORM = "imx91"

IMXBOOT_TARGETS = "flash_singleboot"

IMX_BOOT_SOC_TARGET = "iMX91"

IMX_BOOT_SEEK = "32"

# We have to disable SERIAL_CONSOLE due to auto-serial-console

SERIAL_CONSOLES = "115200;ttyLP0"

IMX_DEFAULT_BSP = "nxp"

Thank you for your time.

[RD-airzone · Accepted solution]

Hi everyone,

I post what it actually happens just in case anyone has the same issue.

I had to change CONFIG_DEFAULT_DEVICE_TREE as @Manuel_Salas said but I had to include "imx91-11x11-evk-u-boot.dtsi" at the end of my device tree as it seems to do some configuration needed for u-boot.

Kind regards.

[Manuel_Salas]

Hello @RD-airzone 

I hope you are doing very well.

Could you please try changing the CONFIG_DEFAULT_DEVICE_TREE?

Best regards,

Salas.

[RD-airzone]

Hi @Manuel_Salas,

If I change that setting, I cannot even flash the uboot with:

./uuu -b emmc .\imx-boot-ws-hub-sd.bin-flash_singleboot

The same command works with the default value (imx91-11x11-evk-tianma-wvga-panel) for CONFIG_DEFAULT_DEVICE_TREE.

Best regards.