Garbage UART output on RPI 4 with upstream kernel DTB

[Stefan Wahren]

Hi,

i tried to run current U-Boot (rpi_4_32b_defconfig) on my RPi 4 with
bcm2711-rpi-4-b.dtb from the upstream kernel. Unfortunately i only see
garbage on the debug UART (pin 14 & 15). Using the DTB from the
downstream kernel has a proper UART output. The config.txt contains
debug_uart=1

I compared both and identified an offending Linux commit:
ARM: dts: bcm283x: Remove brcm,bcm2835-pl011 compatible

Unfortunately reverting this patch still doesn't fix the issue. Any ideas?

Best regards
Stefan