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

[Peter Seiderer]

Hello Khem Raj,

On Thu, 11 Aug 2016 21:14:59 -0700, Khem Raj <raj.khem at gmail.com> wrote:

> 
> > 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.

Is this (maybe) a vote for my initial proposed patch ([1]) to add
dtoverlay=pi3-miniuart-bt?

The current situation for Pi 3 (no dtoerlay, no enable_uart) is no serial console
and an unusable default console on HDMI (with a doubled (but unusable) login prompt)...

Regards,
Peter

> 
> > --
> > 2.8.1
> > 
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