[PATCH 2/2] doc: add Arm Juno board documentation

[Sudeep Holla]

On Tue, Dec 14, 2021 at 05:55:39PM +0000, Andre Przywara wrote:
> 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 at arm.com>
> ---
>  doc/board/armltd/index.rst |   1 +
>  doc/board/armltd/juno.rst  | 117 +++++++++++++++++++++++++++++++++++++
>  2 files changed, 118 insertions(+)
>  create mode 100644 doc/board/armltd/juno.rst
> 
> diff --git a/doc/board/armltd/index.rst b/doc/board/armltd/index.rst
> index caa6fd2bb0..68d938c647 100644
> --- a/doc/board/armltd/index.rst
> +++ b/doc/board/armltd/index.rst
> @@ -8,3 +8,4 @@ ARM Ltd. boards and emulated systems
>     :maxdepth: 2
>  
>     fvp64
> +   juno
> diff --git a/doc/board/armltd/juno.rst b/doc/board/armltd/juno.rst
> new file mode 100644
> index 0000000000..f37bc2c78e
> --- /dev/null
> +++ b/doc/board/armltd/juno.rst
> @@ -0,0 +1,117 @@
> +.. SPDX-License-Identifier: GPL-2.0
> +.. Copyright (C) 2021 Arm Ltd.
> +
> +Arm Juno board
> +==============
> +
> +The `Juno development board`_ is an open, vendor-neutral, Armv8-A
> +development platform, made by Arm Ltd. It is based on the former Versatile
> +Express series.
> +There are three revisions of the board:
> +
> +* Juno r0, with two Cortex-A57 and four Cortex-A53 cores, without PCIe.
> +* Juno r1, with two Cortex-A57 and four Cortex-A53 cores, in later silicon
> +  revisions, and with PCIe slots, Gigabit Ethernet and two SATA ports.
> +* Juno r2, with two Cortex-A72 and four Cortex-A53 cores, otherwise the
> +  same as r1.
> +
> +Among other things, the motherboard contains a management controller (MCP),

IIRC the MCP is new and inside the SoC. You may refer [1], [2] and use the
terminologies from there to be consistent with the documentation. IIRC this
one is referred as MCC. So I would prefer s/MCP/MCC or MB throughout this
document.

> +an FPGA providing I/O interfaces (IOFPGA) and 64MB of NOR flash. The provided
> +platform devices resemble the VExpress peripherals.
> +The actual SoC also contains a Cortex-M3 based System Control Processor (SCP).
> +
> +U-Boot build
> +------------
> +There is only one defconfig and one binary build that covers all three board
> +revisions, so to generate the needed ``u-boot.bin``:
> +
> +.. code-block:: bash
> +
> +    $ make vexpress_aemv8a_juno_defconfig
> +    $ make
> +
> +The automatic distro boot sequence looks for UEFI boot applications and
> +``boot.scr`` scripts on various boot media, starting with USB, then on disks
> +connected to the two SATA ports, PXE, DHCP and eventually on the NOR flash.
> +
> +U-Boot installation
> +-------------------
> +This assumes there is some firmware on the SD card or NOR flash (see below
> +for more details). The U-Boot binary is included in the Trusted Firmware
> +FIP image, so after building U-Boot, this needs to be repackaged or recompiled.
> +
> +The NOR flash will be updated by the MCP, based on the content of a micro-SD
> +card, which will be exported as a USB mass storage device via the rear USB-B
> +socket. So to access that SD card, connect a USB-A->USB-B cable between some
> +host computer and the board, and mount the FAT partition on the UMS device.
> +If there is no device, check the upper serial port for a prompt, and
> +explicitly enable the USB interface::
> +
> +    Cmd> usb_on
> +    Enabling debug USB...
> +

Not sure if you need these details(above one paragraph) here if we can direct
to one of the pages I have pointed out or specifically [3]. I guess you can
add other topics from there and links to those subsections if you need more
details. I am fine either way.

Otherwise looks good. Thanks for doing this.

-- 
Regards,
Sudeep

[1] https://developer.arm.com/documentation/100113/0000
[2] https://developer.arm.com/documentation/dui0928/e/firmware/firmware-components
[3] https://developer.arm.com/documentation/dui0928/e/configuration/connecting-to-a-host-computer?lang=en