[Buildroot] [PATCH v1] raspberrypi3: fix serial console (add enable_uart=1)

Khem Raj raj.khem at gmail.com
Fri Aug 12 04:14:59 UTC 2016


> On Aug 11, 2016, at 3:03 PM, Peter Seiderer <ps.report at gmx.net> wrote:
> 
> - enhance post-image.sh script to add 'enable_uart=1' to config.txt on request
> - add BR2_ROOTFS_POST_SCRIPT_ARGS="--add-rpi3-config-enable-uart" in raspberrypi3_defconfig
> 
> Signed-off-by: Peter Seiderer <ps.report at gmx.net>
> ---
> board/raspberrypi/post-image.sh | 13 +++++++++++++
> board/raspberrypi/readme.txt    |  6 +++++-
> configs/raspberrypi3_defconfig  |  1 +
> 3 files changed, 19 insertions(+), 1 deletion(-)
> 
> diff --git a/board/raspberrypi/post-image.sh b/board/raspberrypi/post-image.sh
> index 73ffd65..3dc5902 100755
> --- a/board/raspberrypi/post-image.sh
> +++ b/board/raspberrypi/post-image.sh
> @@ -5,6 +5,19 @@ BOARD_NAME="$(basename ${BOARD_DIR})"
> GENIMAGE_CFG="${BOARD_DIR}/genimage-${BOARD_NAME}.cfg"
> GENIMAGE_TMP="${BUILD_DIR}/genimage.tmp"
> 
> +case "${2}" in
> +	--add-rpi3-config-enable-uart)
> +	if ! grep -qE 'enable_uart=1' "${BINARIES_DIR}/rpi-firmware/config.txt"; then
> +		echo "Adding 'enable_uart=1' to config.txt."
> +		cat << __EOF__ >> "${BINARIES_DIR}/rpi-firmware/config.txt"
> +
> +# fixes rpi3 console
> +enable_uart=1
> +__EOF__
> +	fi
> +	;;
> +esac
> +
> # Mark the kernel as DT-enabled
> mkdir -p "${BINARIES_DIR}/kernel-marked"
> ${HOST_DIR}/usr/bin/mkknlimg "${BINARIES_DIR}/zImage" \
> diff --git a/board/raspberrypi/readme.txt b/board/raspberrypi/readme.txt
> index a170f8f..d101816 100644
> --- a/board/raspberrypi/readme.txt
> +++ b/board/raspberrypi/readme.txt
> @@ -58,7 +58,7 @@ After building, you should obtain this tree:
>     +-- rpi-firmware/
>     |   +-- bootcode.bin
>     |   +-- cmdline.txt
> -    |   +-- config.txt
> +    |   +-- config.txt              [3]
>     |   +-- fixup.dat
>     |   `-- start.elf
>     +-- sdcard.img
> @@ -69,6 +69,10 @@ After building, you should obtain this tree:
> 
> [2] This is the mkknlimg DT-marked kernel.
> 
> +[3] For Pi 3 an additional 'enable_uart=1' will be added to fix
> +    (serial) console output. Alternatives are 'dtoverlay=pi3-miniuart-bt'
> +    or 'dtoverlay=pi3-disable-bt'.
> +
> How to write the SD card
> ========================
> 
> diff --git a/configs/raspberrypi3_defconfig b/configs/raspberrypi3_defconfig
> index 4eb5333..62f47da 100644
> --- a/configs/raspberrypi3_defconfig
> +++ b/configs/raspberrypi3_defconfig
> @@ -34,3 +34,4 @@ BR2_TARGET_ROOTFS_EXT2_4=y
> # BR2_TARGET_ROOTFS_TAR is not set
> BR2_ROOTFS_POST_BUILD_SCRIPT="board/raspberrypi3/post-build.sh"
> BR2_ROOTFS_POST_IMAGE_SCRIPT="board/raspberrypi3/post-image.sh"
> +BR2_ROOTFS_POST_SCRIPT_ARGS="--add-rpi3-config-enable-uart”

This lowers the core clock speed to minimum, so if you are doing some high
definition video decode or interlace then you might want this disabled.
I would recommend keeping it disabled by default.

> --
> 2.8.1
> 
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