RPI_USE_U_BOOT on raspberry pi 5 without ENABLE_UART

[tjallingt]

https://meta-raspberrypi.readthedocs.io/en/latest/extra-build-config.html#boot-to-u-boot

Says that the raspberry pi 5 does not require ENABLE_UART ="1".

However the in rpi-config_git.bb there is a check that makes sure that ENABLE_UART ="1" when setting RPI_USE_U_BOOT ="1".

meta-raspberrypi/recipes-bsp/bootfiles/rpi-config_git.bb

Lines 189 to 201 in 046a238

	# U-Boot requires "enable_uart=1" for various boards to operate correctly
	# cf https://source.denx.de/u-boot/u-boot/-/blob/v2023.04/arch/arm/mach-bcm283x/Kconfig?ref_type=tags#L65
	if [ "${RPI_USE_U_BOOT}" = "1" ] && [ "${ENABLE_UART}" != "1" ]; then
	case "${UBOOT_MACHINE}" in
	rpi_0_w_defconfig|rpi_3_32b_config|rpi_4_32b_config|rpi_arm64_config)
	if [ "${ENABLE_UART}" = "0" ]; then
	bbfatal "Invalid configuration: RPI_USE_U_BOOT requires to enable the UART in config.txt for ${MACHINE}"
	fi
	echo "# U-Boot requires UART" >>$CONFIG
	echo "enable_uart=1" >>$CONFIG
	;;
	esac
	fi

This checks for rpi_arm64_config which is also used for the raspberry pi 5:

meta-raspberrypi/conf/machine/raspberrypi5.conf

Line 36 in 046a238

UBOOT_MACHINE = "rpi_arm64_config"

I think the documentation is correct and u-boot works on raspberry pi 5 without enable_uart=1. This means the check in rpi-config_git.bb should be updated to not error for raspberry pi 5.