How to use engineering and production modes

Applicable for STM32MP15x lines

1 Introduction[edit]

To simplify the development of the STM32MP1 ecosystem coprocessor firmware, the Cortex®-M4 firmware can be developed in a stand-alone « MCU Single Core like » way called « Engineering mode». It removes the complexity of multiprocessor system development such as inter processor communication, system resources management...; and focuses on « real-time » application development.
An application can dynamically detect if the STM32MP1 is running in engineering or production mode through the SYSCFG_BOOTR register.

  • A macro IS_ENGINEERING_BOOT_MODE() is provided in CMSIS device file for that purpose.
  • Most of available projects support both engineering and production modes.

This article describes how to initialize the STM32CubeMP1 Arm® Cortex®-M4 Software in Engineering mode and when ready move to Production mode.
Finally, detailed description of each step is given together with sample code.

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2 Boot modes[edit]

The STM32MP1 can be run in 2 different boot modes : Production boot mode (default mode) and Engineering boot mode

2.1 Production boot mode[edit]

Firmware is loaded into the coprocessor by the master processor (Cortex-A7 - Flash Memory boot mode), this means:

  • System resources are managed directly by OpenSTLinux (clocks, regulators, and so on)
  • the pre-built pieces of firmware are provided/downloaded in an OpenSTLinux image or file system
  • the pre-built firmware is launched on the coprocessor through the Linux Remote Proc component
  • Cortex-A firmware (Linux OS) is in charge of loading the Cortex-M firmware
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Notes: At boot time, you can select 3 kernel configurations:
  • Configuration 1 (<board_name>-sdcard): All IPs are assigned to Cortex-A7 for Linux drivers, Cortex-M4 coprocessor firmware TTY executed by default
  • This is the configuration activated by default
  • Configuration 2 (<board_name>-a7-examples-sdcard): Some IPs are assigned to Cortex-A7 to execute Cortex-A7 delivered examples on the board (EVAL or DISCO).
  • Configuration 3 (<board_name>-m4-examples-sdcard): Some IPs are assigned to Cortex-M4 to execute Cortex-M4 delivered examples on the board (EVAL or DISCO).

Example for STM32MP157C-DK2 board:

Select the boot mode
1:      stm32mp157c-dk2-sdcard
2:      stm32mp157c-dk2-a7-examples-sdcard
3:      stm32mp157c-dk2-m4-examples-sdcard

2.2 Engineering boot mode[edit]

The engineering boot mode is used specifically for firmware testing directly on the coprocessor, this means:

  • all resources are managed directly in the example source code (clocks, regulators, and so on)
  • the firmware can be loaded directly from your favorite IDE

Most of the examples can be used in Engineering boot mode (except those that require firmware running on a Cortex-A7, such as the OpenAMP examples)

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3 Arm® Cortex®-M4 startup in engineering mode (“MCU Single Core like”)[edit]

The Engineering mode allows the user to connect a debugger on an open chip, load and debug the Arm® Cortex®-M4 firmware in an “MCU like world”. In this mode, STM32CubeMP1 initialization steps are similar to a single CPU MCU device.
There are some rules that need to be followed in order to develop in engineering mode:

  • Peripheral assignment request (ResMgr_Request) is a multicore instruction and can be integrated into the code when developing the engineering mode firmware.
ResMgr_Request is based on an ETZPC peripheral features. In engineering mode, ETZPC configuration makes all resources accessible to the Arm® Cortex®-M4 and therefore ResMgr_Request will return True in any case.
  • OpenAMP_Init for RPMsg service (MX_OPENAMP_Init) is NOT executed in engineering mode as there are blocking step in RPMsg framework initialization code running on the Arm® Cortex®-A7 (rproc_virtio_wait_remote_ready). The call to MX_OPENAMP_Init can masked by the macro call if (!IS_ENGINEERING_BOOT_MODE())


4 Arm® Cortex®-M4 startup in production mode[edit]

The Arm® Cortex®-M4 STM32CubeMP1 firmware is started by running OpenSTLinux on Arm® Cortex®-A7.
It can be started by a U-Boot with the remoteproc feature (rproc command) or, later, by Linux remoteproc framework, depending on the application startup time targets.
In order to move the Arm® Cortex®-M4 application from engineering to production mode, the following 4 items need to be addressed:

  • System clock configuration (SystemClock_Config()) is "done" by running the FSBL on Arm® Cortex®-A7. Beware, this function call shall NOT be executed in production mode. SystemClock_Config() shall be under if(IS_ENGINEERING_BOOT_MODE()).
  • Clock source of each peripheral is also done by running the FSBL on Arm® Cortex®-A7 and the function call (HAL_RCCEx_PeriphCLKConfig()) shall be done under if(IS_ENGINEERING_BOOT_MODE()).
  • GPIO configuration PERIPH_LOCK service (hardware semaphore) can be used to protect the (HAL_GPIO_Init/HAL_GPIO_DeInit()).
If the GPIO bank is used by both Arm® Cortex®-A7 and Arm® Cortex®-M4, this GPIO bank is seen as a shared resource. Some GPIO registers are not designed to support concurrent core accesses and they need be protected by hardware semaphore.
  • EXTI configuration (HAL_EXTI_SetConfigLine()) for configurable events shall be protected by PERIPH_LOCK service (hardware semaphore).
EXTI is a shared resource and registers used for configurable events are not designed to support concurrent core accesses and they have to be protected by hardware semaphore.


5 How to log in production mode[edit]

On top of all the different tools supporting STM32CubeMP1 debugging, the different examples have integrated in a way to log STM32CubeMP1 firmware visible from Linux (so, only valid for production mode).
A resource table entry is dedicated for that, see: How to add trace for the log buffer.
The principle:

  • "__LOG_TRACE_IO_" preprocessor flag needs to be defined
  • The logs done with log_info() or log_err() functions will be available in Linux sysfs file: "/sys/kernel/debug/remoteproc/remoteproc0/trace0"

These logs can be retrieved after a firmware crash: refer to How to retrieve Cortex-M4 logs after crash for more information.