nuttx/boards/arm/stm32f7/nucleo-144
Xiang Xiao 92f156c969 boards: Change the linker generated symbols from uint32_t to uint8_t array
since the symbol generated by linker is always used as an address not a value.

Signed-off-by: Xiang Xiao <xiaoxiang@xiaomi.com>
2022-10-05 14:24:47 +02:00
..
configs libc/stdio: Enable LIBC_FLOATINGPOINT by default if ARCH_FPU is enabled 2022-07-21 09:53:09 -04:00
include
scripts
src boards: Change the linker generated symbols from uint32_t to uint8_t array 2022-10-05 14:24:47 +02:00
Kconfig
README.txt arch/arm/toolchain: migrate the toolchain define to arch/arm/Kconfig 2022-09-16 14:47:27 +08:00

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README
======

This README discusses issues unique to NuttX configurations for the STMicro
Nucleo-144 board.  See ST document STM32 Nucleo-144 boards (UM1974):

https://www.st.com/resource/en/user_manual/dm00244518.pdf

Contents
========

  - Nucleo-144 Boards
  - Nucleo F722ZE
  - Nucleo F746ZG
  - Nucleo F767ZI
  - Development Environment
  - IDEs
  - Basic configuration & build steps
  - Hardware
    - Button
    - LED
    - U[S]ARTs and Serial Consoles
    - SPI
    - SDIO - MMC
  - SPI Test
  - Configurations
     f7xx-nsh
     f7xx-evalos

Nucleo-144 Boards:
=================

The Nucleo-144 is a standard board for use with several STM32 parts in the
LQFP144 package.  Variants include

  STM32 Part     Board Variant Name
  -------------  ------------------
  STM32F207ZGT6  NUCLEO-F207ZG
  STM32F303ZET6  NUCLEO-F303ZE
  STM32F429ZIT6  NUCLEO-F429ZI
  STM32F446ZET6  NUCLEO-F446ZE
  STM32F722ZET6  NUCLEO-F722ZE
  STM32F746ZGT6  NUCLEO-F746ZG
  STM32F756ZGT6  NUCLEO-F756ZG
  STM32F767ZIT6  NUCLEO-F767ZI
  STM32L496ZGT6  NUCLEO-L496ZG
  STM32L496ZGT6P NUCLEO-L496ZG-P
  STM32L4A6ZGT6  NUCLEO-L4A6ZG
  STM32L4R5ZIT6  NUCLEO-L4R5ZI
  STM32L4R5ZIT6P NUCLEO-L4R5ZI-P
  ------------- ------------------

This directory is intended to support all STM32F7 Nucleo-144 variants since
the boards are identical, differing only in the installed part.  This common
board design provides uniformity in the documentation from ST and should
allow us to quickly change configurations by just cloning a configuration
and changing the CPU choice and board initialization.  Unfortunately for
the developer, the CPU specific information must be extracted from the
common information in the documentation.

The NUCLEO-L496ZG and NUCLEO-L496ZG-P boards are not supported by this
directory, but by boards/arm/stm32l4/nucleo-l496zg. Any other STM32L4
Nucleo-144 boards are also not supported by this directory.

Please read the User Manual UM1727: Getting started with STM32 Nucleo board
software development tools and take note of the Powering options for the
board (6.3 Power supply and power selection) and the Solder bridges based
hardware configuration changes that are configurable (6.11 Solder bridges).

Common Board Features:
---------------------

  Peripherals:    8 leds, 2 push button (3 LEDs, 1 button) under software
                  control
  Debug:          STLINK/V2-1 debugger/programmer Uses a STM32F103CB to
                  provide a ST-Link for programming, debug similar to the
                  OpenOcd FTDI function - USB to JTAG front-end.

  Expansion I/F:  ST Zio and Extended Arduino and Morpho Headers

Nucleo F746ZG
=============

ST Nucleo F746ZG board from ST Micro is supported.  See

http://www.st.com/content/st_com/en/products/evaluation-tools/product-evaluation-tools/mcu-eval-tools/stm32-mcu-eval-tools/stm32-mcu-nucleo/nucleo-f746zg.html

The Nucleo F746ZG order part number is NUCLEO-F746ZG. It is one member of
the STM32 Nucleo-144 board family.

NUCLEO-F746ZG Features:
----------------------

  Microprocessor: STM32F746ZGT6 Core: ARM 32-bit Cortex®-M7 CPU with FPU,
                  L1-cache: 4KB data cache and 4KB instruction cache, up to
                  216 MHz, MPU, and DSP instructions.
  Memory:         1024 KB Flash 320KB of SRAM (including 64KB of data TCM RAM)
                  + 16KB of instruction TCM RAM + 4KB of backup SRAM
  ADC:            3×12-bit, 2.4 MSPS ADC: up to 24 channels and 7.2 MSPS in
                  triple interleaved mode
  DMA:            2 X 16-stream DMA controllers with FIFOs and burst support
  Timers:         Up to 18 timers: up to thirteen 16-bit (1x 16-bit low power),
                  two 32-bit timers, 2x watchdogs, SysTick
  GPIO:           114 I/O ports with interrupt capability
  LCD:            LCD-TFT Controller with (DMA2D), Parallel interface
  I2C:            4 × I2C interfaces (SMBus/PMBus)
  U[S]ARTs:       4 USARTs, 4 UARTs (27 Mbit/s, ISO7816 interface, LIN, IrDA,
                  modem control)
  SPI/12Ss:       6/3 (simplex) (up to 50 Mbit/s), 3 with muxed simplex I2S
                  for audio class accuracy via internal audio PLL or external
                  clock
  QSPI:           Dual mode Quad-SPI
  SAIs:           2 Serial Audio Interfaces
  CAN:            2 X CAN interface
  SDMMC interface
  SPDIFRX interface
  USB:            USB 2.0 full-speed device/host/OTG controller with on-chip
                  PHY
  10/100 Ethernet: MAC with dedicated DMA: supports IEEE 1588v2 hardware,
                   MII/RMII
  Camera Interface: 8/14 Bit
  CRC calculation unit
  TRG:            True random number generator
  RTC

See https://developer.mbed.org/platforms/ST-Nucleo-F746ZG  for additional
information about this board.

Nucleo F767ZI
=============

ST Nucleo F7467ZI board from ST Micro is supported.  See

http://www.st.com/content/st_com/en/products/evaluation-tools/product-evaluation-tools/mcu-eval-tools/stm32-mcu-eval-tools/stm32-mcu-nucleo/nucleo-f767zi.html

The Nucleo F767ZI order part number is NUCLEO-F767ZI. It is one member of
the STM32 Nucleo-144 board family.

NUCLEO-F767ZI Features:
----------------------

  Microprocessor: STM32F767ZIT6 Core: ARM 32-bit Cortex®-M7 CPU with DPFPU,
                  L1-cache: 16KB data cache and 16KB instruction cache, up to
                  216 MHz, MPU, and DSP instructions.
  Memory:         2048 KB Flash 512KB of SRAM (including 128KB of data TCM RAM)
                  + 16KB of instruction TCM RAM + 4KB of backup SRAM
  ADC:            3×12-bit, 2.4 MSPS ADC: up to 24 channels and 7.2 MSPS in
                  triple interleaved mode
  DMA:            2 X 16-stream DMA controllers with FIFOs and burst support
  Timers:         Up to 18 timers: up to thirteen 16-bit (1x 16-bit low power),
                  two 32-bit timers, 2x watchdogs, SysTick
  GPIO:           114 I/O ports with interrupt capability
  LCD:            LCD-TFT Controller with (DMA2D), Parallel interface
  I2C:            4 × I2C interfaces (SMBus/PMBus)
  U[S]ARTs:       4 USARTs, 4 UARTs (27 Mbit/s, ISO7816 interface, LIN, IrDA,
                  modem control)
  SPI/12Ss:       6/3 (simplex) (up to 50 Mbit/s), 3 with muxed simplex I2S
                  for audio class accuracy via internal audio PLL or external
                  clock
  QSPI:           Dual mode Quad-SPI
  SAIs:           2 Serial Audio Interfaces
  CAN:            3 X CAN interface
  SDMMC interface
  SPDIFRX interface
  USB:            USB 2.0 full/High-speed device/host/OTG controller with on-chip
                  PHY
  10/100 Ethernet: MAC with dedicated DMA: supports IEEE 1588v2 hardware,
                   MII/RMII
  Camera Interface: 8/14 Bit
  CRC calculation unit
  TRG:            True random number generator
  RTC             subsecond accuracy, hardware calendar

For pinout and details Check NUCLEO-F767ZI page on developer.mbed.org:
https://os.mbed.com/platforms/ST-Nucleo-F767ZI/

Also https://developer.mbed.org/platforms/ST-Nucleo-F746ZG
may contain some related useful information.

Development Environment
=======================

  Either Linux or Cygwin on Windows can be used for the development environment.
  The source has been built only using the GNU toolchain (see below).  Other
  toolchains will likely cause problems.

  All testing has been conducted using the GNU toolchain from ARM for Linux.
  found here https://developer.arm.com/open-source/gnu-toolchain/gnu-rm/4.9/4.9-2015-q3-update/+download/gcc-arm-none-eabi-4_9-2015q3-20150921-linux.tar.bz2

  If you change the default toolchain, then you may also have to modify the
  PATH environment variable to include the path to the toolchain binaries.

IDEs
====

  NuttX is built using command-line make.  It can be used with an IDE, but some
  effort will be required to create the project.

  Makefile Build
  --------------
  Under Eclipse, it is pretty easy to set up an "empty makefile project" and
  simply use the NuttX makefile to build the system.  That is almost for free
  under Linux.  Under Windows, you will need to set up the "Cygwin GCC" empty
  makefile project in order to work with Windows (Google for "Eclipse Cygwin" -
  there is a lot of help on the internet).

Basic configuration & build steps
==================================

  A GNU GCC-based toolchain is assumed.  The PATH environment variable should
  be modified to point to the correct path to the Cortex-M7 GCC toolchain (if
  different from the default in your PATH variable).

   - Configures nuttx creating .config file in the nuttx directory.
     $ tools/configure.sh nucleo-f746zg:nsh
   - Refreshes the .config file with the latest available configurations.
     $ make oldconfig
   - Select the features you want in the build.
     $ make menuconfig
   - Builds NuttX with the features you selected.
     $ make

Hardware
========

  GPIO - there are 144 I/O lines on the STM32F7xxZxT6 with various pins pined out
  on the Nucleo 144.

  See https://developer.mbed.org/platforms/ST-Nucleo-F746ZG/ for slick graphic
  pinouts.

  Keep in mind that:
   1) The I/O is 3.3 Volt not 5 Volt like on the Arduino products.
   2) The Nucleo-144 board family has 3 pages of Solder Bridges AKA Solder
      Blobs (SB) that can alter the factory configuration. We will note SB
      in effect but will assume the factory default settings.

  Our main concern is establishing a console and LED utilization for
  debugging. Because so many pins can be multiplexed with so many functions,
  the above mentioned graphic may be helpful in identifying a serial port.

  There are 5 choices that can be made from the menuconfig:

  CONFIG_NUCLEO_CONSOLE_ARDUINO or CONFIG_NUCLEO_CONSOLE_MORPHO or
  CONFIG_NUCLEO_CONSOLE_MORPHO_UART4 or CONFIG_NUCLEO_CONSOLE_VIRTUAL or
  CONFIG_NUCLEO_CONSOLE_NONE

  The CONFIG_NUCLEO_CONSOLE_NONE makes no preset for the console. You should still
  visit the U[S]ART selection and Device Drivers to disable any U[S]ART remaining.

  The CONFIG_NUCLEO_CONSOLE_ARDUINO configurations assume that you are using a
  standard Arduino RS-232 shield with the serial interface with RX on pin D0 and
  TX on pin D1 from USART6:

            -------- ---------------
                        STM32F7
            ARDUIONO FUNCTION  GPIO
            -- ----- --------- -----
            DO RX    USART6_RX PG9
            D1 TX    USART6_TX PG14
            -- ----- --------- -----

  The CONFIG_NUCLEO_CONSOLE_MORPHO configurations uses Serial Port 8 (USART8)
  with TX on PE1 and RX on PE0.

            Serial
            ------
            SERIAL_RX         PE_0
            SERIAL_TX         PE_1

  The CONFIG_NUCLEO_CONSOLE_MORPHO_UART4 configurations uses Serial Port 4 (UART4)
  with TX on PA1 and RX on PA0. Zero Ohm resistor / solder short at
  SB13 must be removed/open. (Disables Ethernet MII clocking.)

            Serial
            ------
            SERIAL_RX         PA_1  CN11 30
            SERIAL_TX         PA_0  CN11 28

  The CONFIG_NUCLEO_CONSOLE_VIRTUAL configurations uses Serial Port 3 (USART3)
  with TX on PD8 and RX on PD9.

            Serial
            ------
            SERIAL_RX         PD9
            SERIAL_TX         PD8

  These signals are internally connected to the on board ST-Link.

  Of course if your design has used those pins you can choose a completely
  different U[S]ART to use as the console. In that Case, you will need to edit
  the include/board.h to select different U[S]ART and / or pin selections.

  Buttons
  -------
  B1 USER: the user button is connected to the I/O PC13 (Tamper support, SB173
           ON and SB180 OFF)

  LEDs
  ----
  The Board provides a 3 user LEDs, LD1-LD3
  LED1 (Green)      PB_0  (SB120 ON and SB119 OFF)
  LED2 (Blue)       PB_7  (SB139 ON)
  LED3 (Red)        PB_14 (SP118 ON)

    - When the I/O is HIGH value, the LEDs are on.
    - When the I/O is LOW, the LEDs are off.

  These LEDs are not used by the board port unless CONFIG_ARCH_LEDS is
  defined.  In that case, the usage by the board port is defined in
  include/board.h and src/stm32_autoleds.c. The LEDs are used to encode OS
  related events as follows when the LEDs are available:

  SYMBOL                Meaning                  RED  GREEN BLUE
  -------------------  -----------------------   ---  ----- ----

  LED_STARTED          NuttX has been started    OFF  OFF   OFF
  LED_HEAPALLOCATE     Heap has been allocated   OFF  OFF   ON
  LED_IRQSENABLED      Interrupts enabled        OFF  ON    OFF
  LED_STACKCREATED     Idle stack created        OFF  ON    ON
  LED_INIRQ            In an interrupt           NC   NC    ON  (momentary)
  LED_SIGNAL           In a signal handler       NC   ON    OFF (momentary)
  LED_ASSERTION        An assertion failed       ON   NC    ON  (momentary)
  LED_PANIC            The system has crashed    ON   OFF   OFF (flashing 2Hz)
  LED_IDLE             MCU is is sleep mode      ON   OFF   OFF

OFF -    means that the OS is still initializing. Initialization is very fast
         so if you see this at all, it probably means that the system is
         hanging up somewhere in the initialization phases.

GREEN -  This means that the OS completed initialization.

BLUE  -  Whenever and interrupt or signal handler is entered, the BLUE LED is
         illuminated and extinguished when the interrupt or signal handler
         exits.

VIOLET - If a recovered assertion occurs, the RED and blue LED will be
         illuminated briefly while the assertion is handled.  You will
         probably never see this.

Flashing RED - In the event of a fatal crash, all other LEDs will be
          extinguished and RED LED will FLASH at a 2Hz rate.

  Thus if the GREEN LED is lit, NuttX has successfully booted and is,
  apparently, running normally.  If the RED LED is flashing at
  approximately 2Hz, then a fatal error has been detected and the system has
  halted.

Serial Consoles
===============

  USART6 (CONFIG_NUCLEO_CONSOLE_ARDUINO)
  ------
                STM32F7
    ARDUINO FUNCTION  GPIO
    -- ----- --------- -----
    DO RX    USART6_RX PG9
    D1 TX    USART6_TX PG14
    -- ----- --------- -----

  You must use a 3.3 TTL to RS-232 converter or a USB to 3.3V TTL

    Nucleo 144           FTDI TTL-232R-3V3
    -------------       -------------------
    TXD - D1-TXD   -    RXD - Pin 5 (Yellow)
    RXD - D0-RXD   -    TXD - Pin 4 (Orange)
    GND   GND      -    GND   Pin 1  (Black)
    -------------       -------------------

    *Note you will be reverse RX/TX

  Use make menuconfig to configure USART6 as the console:

    CONFIG_STM32F7_USART6=y
    CONFIG_USARTs_SERIALDRIVER=y
    CONFIG_USARTS_SERIAL_CONSOLE=y
    CONFIG_USART6_RXBUFSIZE=256
    CONFIG_USART6_TXBUFSIZE=256
    CONFIG_USART6_BAUD=115200
    CONFIG_USART6_BITS=8
    CONFIG_USART6_PARITY=0
    CONFIG_USART6_2STOP=0

  USART8 (CONFIG_NUCLEO_CONSOLE_MORPHO)
  ------

  Pins and Connectors:
    FUNC GPIO  Connector
                   Pin NAME
    ---- ---   ------- ----
    TXD: PE1   CN11-61, PE1
    RXD: PE0   CN12-64, PE0
               CN10-33, D34
    ---- ---   ------- ----

  You must use a 3.3 TTL to RS-232 converter or a USB to 3.3V TTL

    Nucleo 144           FTDI TTL-232R-3V3
    -------------       -------------------
    TXD - CN11-61   -   RXD - Pin 5 (Yellow)
    RXD - CN12-64   -   TXD - Pin 4 (Orange)
    GND   CN12-63   -   GND   Pin 1  (Black)
    -------------       -------------------

    *Note you will be reverse RX/TX

  Use make menuconfig to configure USART8 as the console:

    CONFIG_STM32F7_UART8=y
    CONFIG_UART8_SERIALDRIVER=y
    CONFIG_UART8_SERIAL_CONSOLE=y
    CONFIG_UART8_RXBUFSIZE=256
    CONFIG_UART8_TXBUFSIZE=256
    CONFIG_UART8_BAUD=115200
    CONFIG_UART8_BITS=8
    CONFIG_UART8_PARITY=0
    CONFIG_UART8_2STOP=0

  Virtual COM Port (CONFIG_NUCLEO_CONSOLE_VIRTUAL)
  ----------------
  Yet another option is to use USART3 and the USB virtual COM port.  This
  option may be more convenient for long term development, but is painful
  to use during board bring-up.

  Solder Bridges.  This configuration requires:

    PD8 USART3 TX SB5 ON and SB7 OFF (Default)
    PD9 USART3 RX SB6 ON and SB4 OFF (Default)

  Configuring USART3 is the same as given above but add the S and #3.

  Question:  What BAUD should be configure to interface with the Virtual
  COM port?  115200 8N1?

  Default
  -------
  As shipped, SB4 and SB7 are open and SB5 and SB6 closed, so the
  virtual COM port is enabled.

SPI
---
  Since this board is so generic, having a quick way to set the SPI
  configuration seams in order. So the board provides a quick test
  that can be selected vi CONFIG_NUCLEO_SPI_TEST that will initialize
  the selected buses (SPI1-SPI3) and send some text on the bus at
  application initialization time board_app_initialize.

SDIO
----
  To test the SD performance one can use a SparkFun microSD Sniffer
  from https://www.sparkfun.com/products/9419 or similar board
  and connect it as follows:

          VCC    V3.3 CN11  16
          GND    GND  CN11-8
          CMD    PD2  CN11-4
          CLK    PC12 CN11-3
          DAT0 - PC8  CN12-2
          DAT1 - PC9  CN12-1
          DAT2   PC10 CN11-1
          CD     PC11 CN11-2

SPI Test
========

  The builtin SPI test facility can be enabled with the following settings:

    +CONFIG_STM32F7_SPI=y
    +CONFIG_STM32F7_SPI1=y
    +CONFIG_STM32F7_SPI2=y
    +CONFIG_STM32F7_SPI3=y

    +# CONFIG_STM32F7_SPI_INTERRUPTS is not set
    +# CONFIG_STM32F7_SPI1_DMA is not set
    +# CONFIG_STM32F7_SPI2_DMA is not set
    +# CONFIG_STM32F7_SPI3_DMA is not set
     # CONFIG_STM32F7_CUSTOM_CLOCKCONFIG is not set

    +CONFIG_NUCLEO_SPI_TEST=y
    +CONFIG_NUCLEO_SPI_TEST_MESSAGE="Hello World"
    +CONFIG_NUCLEO_SPI1_TEST=y
    +CONFIG_NUCLEO_SPI1_TEST_FREQ=1000000
    +CONFIG_NUCLEO_SPI1_TEST_BITS=8
    +CONFIG_NUCLEO_SPI1_TEST_MODE3=y

    +CONFIG_NUCLEO_SPI2_TEST=y
    +CONFIG_NUCLEO_SPI2_TEST_FREQ=12000000
    +CONFIG_NUCLEO_SPI2_TEST_BITS=8
    +CONFIG_NUCLEO_SPI2_TEST_MODE3=y

    +CONFIG_NUCLEO_SPI3_TEST=y
    +CONFIG_NUCLEO_SPI3_TEST_FREQ=40000000
    +CONFIG_NUCLEO_SPI3_TEST_BITS=8
    +CONFIG_NUCLEO_SPI3_TEST_MODE3=y

    +CONFIG_BOARDCTL=y
    +CONFIG_NSH_ARCHINIT=y

Configurations
==============

f7xx-nsh:
---------

  Configures the NuttShell (nsh) located at apps/examples/nsh for the
  Nucleo-144 boards.  The Configuration enables the serial interfaces
  on USART6.  Support for builtin applications is enabled, but in the base
  configuration no builtin applications are selected (see NOTES below).

  NOTES:

  1. This configuration uses the mconf-based configuration tool.  To
     change this configuration using that tool, you should:

     a. Build and install the kconfig-mconf tool.  See nuttx/README.txt
        see additional README.txt files in the NuttX tools repository.

     b. If this is the initial configuration then execute

           ./tools/configure.sh nucleo-144:nsh

        in nuttx/ in order to start configuration process.
        Caution: Doing this step more than once will overwrite .config with
        the contents of the nucleo-144/nsh/defconfig file.

     c. Execute 'make oldconfig' in nuttx/ in order to refresh the
        configuration.

     d. Execute 'make menuconfig' in nuttx/ in order to start the
        reconfiguration process.

     e. Save the .config file to reuse it in the future starting at step d.

  2. By default, this configuration uses the ARM GNU toolchain
     for Linux.  That can easily be reconfigured, of course.

     CONFIG_HOST_LINUX=y                     : Builds under Linux
     CONFIG_ARM_TOOLCHAIN_GNU_EABI=y      : ARM GNU for Linux

  3. The serial console may be configured to use either USART3 (which would
     correspond to the Virtual COM port) or with the console device
     configured for USART6 to support an Arduino serial shield (see
     instructions above under "Serial Consoles).  You will need to check the
     defconfig file to see how the console is set up and, perhaps, modify
     the configuration accordingly.

     To select the Virtual COM port:

       -CONFIG_NUCLEO_CONSOLE_ARDUINO
       +CONFIG_NUCLEO_CONSOLE_VIRTUAL=y
       -CONFIG_USART6_SERIAL_CONSOLE=y
       +CONFIG_USART3_SERIAL_CONSOLE=y

     To select the Arduino serial shield:

       -CONFIG_NUCLEO_CONSOLE_VIRTUAL=y
       +CONFIG_NUCLEO_CONSOLE_ARDUINO
       -CONFIG_USART3_SERIAL_CONSOLE=y
       +CONFIG_USART6_SERIAL_CONSOLE=y

     Default values for other settings associated with the select USART should
     be correct.

f7xx-evalos:
------------

  This configuration is designed to test the features of the board.
    - Configures the NuttShell (nsh) located at apps/examples/nsh for the
      Nucleo-144 boards. The console is available on serial interface USART3,
      which is accessible over the USB ST-Link interface.
    - Configures nsh with advanced features such as autocompletion.
    - Configures the on-board LEDs to work with the 'leds' example app.
    - Configures the 'helloxx' example app.
    - Adds character device for i2c1
    - Tries to register mpu60x0 IMU to i2c1

  NOTES:

  1. This configuration uses the mconf-based configuration tool.  To
    change this configuration using that tool, you should:

    a. Build and install the kconfig-mconf tool.  See nuttx/README.txt
       see additional README.txt files in the NuttX tools repository.

    b. If this is the initial configuration then execute

          ./tools/configure.sh nucleo-144:evalos

       in nuttx/ in order to start configuration process.
       Caution: Doing this step more than once will overwrite .config with
       the contents of the nucleo-144/evalos/defconfig file.

    c. Execute 'make oldconfig' in nuttx/ in order to refresh the
       configuration.

    d. Execute 'make menuconfig' in nuttx/ in order to start the
       reconfiguration process.

    e. Save the .config file to reuse it in the future starting at step d.

  2. By default, this configuration uses the ARM GNU toolchain
    for Linux.  That can easily be reconfigured, of course.

    CONFIG_HOST_LINUX=y                     : Builds under Linux
    CONFIG_ARM_TOOLCHAIN_GNU_EABI=y      : ARM GNU for Linux