RPI CM4 - I2C BUS and Device Tree

[Romain Crausaz]

Hi all,



I am currently facing an issue with U-Boot and a raspberry pi CM4. Here is
the setup:



1. Yocto Scarthgap

2. U-Boot 2024.01

3. rpi_arm64_defconfig



I am trying to access the i2c bus from U-Boot. I have been trying to modify
the device tree which is referenced as
“CONFIG_DEFAULT_DEVICE_TREE="bcm2711-rpi-4-b”” in the defconfig without
success. I can remove everything, set all nodes to disabled and I see no
change in U-Boot (I am using dm commands to check the status of the
peripherals).



It seems that with the rpi, U-Boot will only configure itself against the
device tree passed by the bootloader of RPI. Could someone confirm this ?



Is there a way to configure / modify U-Boot to use its own devicetree and
simply pass the device tree generated by the rpi bootloader to the kernel ?



Because the second issue is that the i2c driver defined in the device tree
passed to u-boot is not available in u-boot.



Thanks for your help



Best regards

Romain