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@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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