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The Juno Arm development board is an open, vendor-neutral, Armv8-A development platform. Add documentation that briefly outlines the hardware, and describes building and installation of U-Boot. Signed-off-by: Andre Przywara <andre.przywara@arm.com> Reviewed-by: Sudeep Holla <sudeep.holla@arm.com> Reviewed-by: Linus Walleij <linus.walleij@linaro.org> Reviewed-by: Simon Glass <sjg@chromium.org>
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4.8 KiB
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114 lines
4.8 KiB
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.. SPDX-License-Identifier: GPL-2.0
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.. Copyright (C) 2021 Arm Ltd.
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Arm Juno development platform
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=============================
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The `Juno development board`_ is an open, vendor-neutral, Armv8-A development
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platform, made by Arm Ltd. It is part of the Versatile Express family.
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There are three revisions of the board:
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* Juno r0, with two Cortex-A57 and four Cortex-A53 cores, without PCIe.
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* Juno r1, with two Cortex-A57 and four Cortex-A53 cores, in later silicon
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revisions, and with PCIe slots, Gigabit Ethernet and two SATA ports.
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* Juno r2, with two Cortex-A72 and four Cortex-A53 cores, otherwise the
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same as r1.
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Among other things, the motherboard contains a management controller (MCC),
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an FPGA providing I/O interfaces (IOFPGA) and 64MB of NOR flash. The provided
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platform devices resemble the VExpress peripherals.
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The actual SoC also contains a Cortex-M3 based System Control Processor (SCP).
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The `V2M-Juno TRM`_ contains more technical details.
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U-Boot build
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------------
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There is only one defconfig and one binary build that covers all three board
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revisions, so to generate the needed ``u-boot.bin``:
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.. code-block:: bash
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$ make vexpress_aemv8a_juno_defconfig
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$ make
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The automatic distro boot sequence looks for UEFI boot applications and
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``boot.scr`` scripts on various boot media, starting with USB, then on disks
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connected to the two SATA ports, PXE, DHCP and eventually on the NOR flash.
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U-Boot installation
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-------------------
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This assumes there is some firmware on the SD card or NOR flash (see below
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for more details). The U-Boot binary is included in the Trusted Firmware
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FIP image, so after building U-Boot, this needs to be repackaged or recompiled.
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The NOR flash will be updated by the MCC, based on the content of a micro-SD
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card, which is exported as a USB mass storage device via the rear USB-B
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socket. So to access that SD card, connect a cable to some host computer, and
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mount the FAT16 partition of the UMS device.
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If there is no device, check the upper serial port for a prompt, and
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explicitly enable the USB interface::
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Cmd> usb_on
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Enabling debug USB...
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Repackaging an existing FIP image
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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To prevent problems, it is probably a good idea to backup the existing firmware,
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for instance by just copying the entire ``SOFTWARE/`` directory, or at least
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the current ``fip.bin``, beforehand.
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To just replace the BL33 image in the exising FIP image, you can use
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`fiptool`_ from the Trusted Firmware repository, on the image file:
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.. code-block:: bash
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git clone https://git.trustedfirmware.org/TF-A/trusted-firmware-a.git
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cd trusted-firmware-a
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make fiptool
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tools/fiptool/fiptool update --nt-fw=/path/to/your/u-boot.bin /mnt/juno/SOFTWARE/fip.bin
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Unmount the USB mass storage device and reboot the board, the new ``fip.bin``
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will be automatically written to the NOR flash and then used.
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Rebuilding Trusted Firmware
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^^^^^^^^^^^^^^^^^^^^^^^^^^^
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You can also generate a new FIP image by compiling Arm Trusted Firmware,
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and providing ``u-boot.bin`` as the BL33 file. For that you can either build
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the required `SCP firmware`_ yourself, or just extract the existing
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version from your ``fip.bin``, using `fiptool`_ (see above):
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.. code-block:: bash
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mkdir /tmp/juno; cd /tmp/juno
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fiptool unpack /mnt/juno/SOFTWARE/fip.bin
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Then build TF-A:
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.. code-block:: bash
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git clone https://git.trustedfirmware.org/TF-A/trusted-firmware-a.git
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cd trusted-firmware-a
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make CROSS_COMPILE=aarch64-linux-gnu- PLAT=juno DEBUG=1 \
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SCP_BL2=/tmp/juno/scp-fw.bin BL33=/path/to/your/u-boot.bin fiptool all fip
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cp build/juno/debug/bl1.bin build/juno/debug/fip.bin /mnt/juno/SOFTWARE
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Then umount the USB device, and reboot, as above.
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Device trees
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------------
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The device tree files for the boards are maintained in the Linux kernel
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repository. They end up in the ``SOFTWARE/`` directory of the SD card, as
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``juno.dtb``, ``juno-r1.dtb``, and ``juno-r2.dtb``, respectively. The MCC
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firmware will look into the images.txt file matching the board revision, from
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the ``SITE1/`` directory. Each version there will reference its respective DTB
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file in ``SOFTWARE/``, and so the correct version will end in the NOR flash, in
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the ``board.dtb`` partition. U-Boot picks its control DTB from there, you can
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pass this on to a kernel using ``$fdtcontroladdr``.
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You can update the DTBs anytime, by building them using the ``dtbs`` make
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target from a Linux kernel tree, then just copying the generated binaries
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to the ``SOFTWARE/`` directory of the SD card.
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.. _`Juno development board`: https://developer.arm.com/tools-and-software/development-boards/juno-development-board
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.. _`V2M-Juno TRM`: https://developer.arm.com/documentation/100113/latest
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.. _`fiptool`: https://github.com/ARM-software/arm-trusted-firmware/tree/master/tools/fiptool
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.. _`SCP firmware`: https://github.com/ARM-software/SCP-firmware.git
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