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

Fri Oct 7 23:29:02 UTC 2022

I'm on an older commit of master branch (20 commits behind) and on that,
the pdf builds fine, If that helps you in any way.

thanks,

On Fri, 7 Oct 2022 at 23:19, Joel Sherrill <joel at rtems.org> wrote:

> 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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