[PATCH rtems-docs v3] raspberrypi4.rst: Documentation for the new AArch64 Raspberry pi 4B BSP

Thu Oct 6 21:58:32 UTC 2022

Hey Alan,

I've addressed the changes. TF-A is not required as of now. I thought
earlier that TF-A is required for enabling GIC but without it, it just work
fine. Now for SMP, TF-A might be crucial as SMP in the xilinx zync is
handled using TF-A, so it might be the same case for Raspberry pi 4? Not
sure about it. Overall, TF-A is NOT required as of now.

Now for ethernet driver, libbsd can be used but not sure. Either way, it's
still a long way. PCIe needs to be managed first, then the ethernet as
"BCM54213PE" Ethernet controller which is directly connected through the
PCIe bridge, unlike the previous generations where the ethernet was
connected using the USB hub controller.

On Thu, 6 Oct 2022 at 21:47, Mohd Noor Aman <nooraman5718 at gmail.com> wrote:

> This patch adds the relevant documentations required for booting the new
> BSP.
> JTAG support is added for debugging. I have built the HTML docs and
> verified
> them.
> ---
>  user/bsps/aarch64/raspberrypi4.rst | 104 +++++++++++++++++++++++++++++
>  user/bsps/bsps-aarch64.rst         |   1 +
>  2 files changed, 105 insertions(+)
>  create mode 100644 user/bsps/aarch64/raspberrypi4.rst
>
> diff --git a/user/bsps/aarch64/raspberrypi4.rst
> b/user/bsps/aarch64/raspberrypi4.rst
> new file mode 100644
> index 0000000..274ade9
> --- /dev/null
> +++ b/user/bsps/aarch64/raspberrypi4.rst
> @@ -0,0 +1,104 @@
> +.. SPDX-License-Identifier: CC-BY-SA-4.0
> +
> +.. Copyright (C) 2022 Mohd Noor Aman
> +
> +.. _BSP_aarch64_Raspberrypi_4:
> +
> +Raspberry Pi 4B
> +===============
> +
> +The 'raspberrypi4b' BSP currently supports only the LP64 ABI. ILP32 is not
> +supported. Raspberry pi 4B all variants and Raspberry Pi 400  are
> supported. The
> +default bootloader which is used by the Raspbian OS or other OS can be
> used to
> +boot RTEMS. SMP is currently not supported.
> +
> +Raspberry Pi 4B has 2 types of interrupt controller, GIC-400 (GICv2) and
> ARM
> +legacy generic controller. Both are supported. By default, raspberrypi 4B
> uses
> +ARM legacy generic controller. Set ``enable_gic=1`` in the ``config.txt``
> file
> +to enable GIC.
> +
> +Clock Driver
> +------------
> +
> +The clock driver uses the `ARM Generic Timer`.
> +
> +Console Driver
> +--------------
> +
> +Raspberry pi 4B has 2 types of UARTs, ARM PL011 and Mini-uart. The PL011
> is a
> +capable, broadly 16550-compatible UART, while the mini UART has a reduced
> +feature set. The console driver supports the default Qemu emulated ARM
> PL011
> +PrimeCell UART as well as the physical ARM PL011 PrimeCell UART in the
> +raspberrypi hardware. Mini-uart is not supported.
> +
> +Preparing to boot
> +------------------
> +
> +Raspberry Pi uses a different mechanism to boot. First the GPU
> initializes,
> +loads the bootloader and then looks for the kernel img. By default the
> arm64
> +mode looks for the ``kernel8.img``. Any other kernel can be loaded by
> adding
> +``kernel=<img_name>`` to the ``config.txt`` file.
> +
> +The Firmware files are required in order to boot RTEMS. The latest
> firmware can
> +be downloaded from the `Raspberry Pi Firmware Repository
> +<https://github.com/raspberrypi/firmware/>`_. USB boot is supported. All
> the
> +files (Firmwares and kernel) must be place in the FAT32 partition only.
> Add
> +``arm_64bit=1`` in the ``config.txt`` file in order to boot the BSP in
> 64bit
> +kernel mode.
> +
> +
> +UART Setup
> +^^^^^^^^^^
> +
> +Connect your serial device to the GPIO15 and GPIO14. Add the following to
> the
> +``config.txt`` file in order to use the PL011 UART0 and thus disabling the
> +default Mini-uart.
> +
> +.. code-block:: none
> +
> +  dtoverlay = disable-bt
> +  enable_uart=1
> +
> +.. note::
> +  The Raspberry Pi 4B and 400 have an additional four PL011 UARTs. They
> are not
> +  supported.
> +
> +Generating kernel image
> +^^^^^^^^^^^^^^^^^^^^^^^
> +
> +The following steps show how to run ``hello.exe`` on the BSP. Other
> executables
> +can be processed in a similar way.
> +
> +To create the kernel image:
> +
> +.. code-block:: shell
> +
> +  $ aarch64-rtems at rtems-ver-major@-objcopy -Obinary hello.exe kernel8.img
> +
> +Copy the kernel image to the SD card.
> +
> +JTAG Setup
> +----------
> +
> +The Raspberry Pi 4 doesn't have dedicated JTAG pins. Instead, you must
> configure
> +the GPIO pins (GPIO22-GPIO27) to activate the JTAG functionality. The RPi
> 4
> +documentation refers to this as Alt4 functions of those pins. Alt5 does
> exist
> +too, which goes from GPIO4, 5, 6, 12 and 13. you can check this out from
> +`pinout.xyz <https://pinout.xyz/pinout/jtag#>`_ or `eLinux
> +<https://elinux.org/RPi_BCM2835_GPIOs>`_
> +
> +One more thing to note on JTAG with Raspberry pi 4B is that, by default,
> All the
> +GPIO pins are pulled down, according to the `BCM2711 documentation
> +<https://datasheets.raspberrypi.com/bcm2711/bcm2711-peripherals.pdf>`_.
> This
> +wasn't the case in the earlier models. So in order to let the data flow
> freely,
> +we will have to disable them.
> +
> +.. code-block:: none
> +
> +  # Disable pull downs
> +  gpio=22-27=np
> +
> +  # Enable jtag pins (i.e. GPIO22-GPIO27)
> +  enable_jtag_gpio=1
> +
> +
> diff --git a/user/bsps/bsps-aarch64.rst b/user/bsps/bsps-aarch64.rst
> index 933370f..f3aa15c 100644
> --- a/user/bsps/bsps-aarch64.rst
> +++ b/user/bsps/bsps-aarch64.rst
> @@ -9,3 +9,4 @@ aarch64 (AArch64)
>  .. include:: aarch64/a72.rst
>  .. include:: aarch64/xilinx-versal.rst
>  .. include:: aarch64/xilinx-zynqmp.rst
> +.. include:: aarch64/raspberrypi4.rst
> \ No newline at end of file
> --
> 2.38.0
>
>
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