[PATCH rtems-docs v4] raspberrypi4.rst: Documentation for the new AArch64 Raspberry pi 4B BSP

Fri Oct 7 17:48:50 UTC 2022

I pushed it but could only build html. See the other thread for issues
building PDF.

On Fri, Oct 7, 2022 at 8:38 AM Kinsey Moore <kinsey.moore at oarcorp.com>
wrote:

> Looks good to me. Thanks for sticking with this!
>
>
> Kinsey
>
> On 10/7/2022 00:00, Mohd Noor Aman 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 | 111 +++++++++++++++++++++++++++++
> >   user/bsps/bsps-aarch64.rst         |   1 +
> >   2 files changed, 112 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..b36d47b
> > --- /dev/null
> > +++ b/user/bsps/aarch64/raspberrypi4.rst
> > @@ -0,0 +1,111 @@
> > +.. 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 when compared with any
> ARM SoC.
> > +First the GPU initializes, loads the bootloader (Raspberry pi firmware)
> and then
> > +looks for the kernel img. This whole process is done by the GPU
> (VideoCore IV)
> > +till the kernel is loaded. More information can be found on the
> `Raspberry pi
> > +documentation page
> > +<
> https://www.raspberrypi.com/documentation/computers/raspberry-pi.html#boot-sequence
> >`_.
> > +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
> > +
> > +  # if user wants to enable GIC, uncomment the next line
> > +  # enable_gic=1
> > +  arm_64bit=1
> > +  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
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