RPi3: serial console

[Heinrich Schuchardt]

Hello Matthias,

I have upgraded the Raspberry 3 firmware from raspi3-firmware
(1.20190215-1+deb10u4) to raspi-firmware (1.20200601-3)
[https://packages.debian.org/bullseye/raspi-firmware].

After the upgrade the output of U-Boot on the serial console is complete
gibberish as if the baudrate were incorrect. The output from the Linux
kernel is fine at 115200 baud.

I observe this both with rpi_3_defconfig and rpi_arm64_defconfig,
v2020.10 and current origin/master.

config.txt:

arm_control=0x200
enable_uart=1
upstream_kernel=1
kernel=u-boot.bin

boot.scr:
setenv autoload no
dhcp
load mmc 0:1 $fdt_addr_r bcm2710-rpi-3-b-plus.dtb
load mmc 0:2 $kernel_addr_r EFI/debian/grubaa64.efi
bootefi $kernel_addr_r $fdt_addr_r

Best regards

Heinrich