Elprotronic’s GangFlasher-ST provides convenient procedures for programming custom boards with ST MPUs inside. Within this procedure called the User-Defined boards programming it is possible to automatically adapt user Device Trees (DT) memory nodes into Elprotronic device bootloaders. These bootloaders provide programming access to peripherals and external devices during the GangFlasher’s programming process. The bootloaders are resident only in volatile memory, so they do not affect board state after a power-cycle. One of the key functionalities of the GangFlasher-ST is the ability to run custom boards designed by the client. The GangFlasher-ST has an automatic method of integrating the custom DT into its boot process. As an alternative to this automated process, there is also the possibility for the user to control the boot DT with their own corrections. Th minimal Device Tree (DTmin) and direct user corrections can be combined using a DT configuration file.

As an example, let us consider a 3rd party MPU board from an external vendor, in this case it will be the Karo TXMP-1570 board. This board will not boot using any default ST MPU board configurations (like DK1/DK2, EV1, etc.).

1. GangFlasher-CLI example

Firstly compile GF-CLI with F_LoadOS() functionality (argument cmdcmd equal 3). GF-CLI functionalities are described in details in GF-CLI tutorial. To setup Karo in GF User-Defined mode please set Karo board in configuration file and load this file with usage of function F_LoadTargetConfig():

Compile and run this configuration, in UART console there will be shown log:

In this particular setup (environment is ST Toolkit version 4, and board Karo TXMP-1570 with STM32MP157C MPU) the problem lies in HSE configuration. Documentation could be found in STM32MP157 Reference Manual (RM0436 Rev 6, pp.526) and Trusted Firmware ARM (TFA) synchronized with ST Toolkit version 4 (Developer Package v4 TFA/plat/st/stm32mp1/bl2_plat_setup.c l. 322 provide details about probable problem with clock). It is quite easy to figure out where lies source of problem - in clock or uart configuration.

2. Karo environment

Secondly please analyze Karo documentation and build environment with Karo build tutorial. Then build image with usage of provided instructions and analyze board TFA source code. Find board Device Tree and analyze clock and uart nodes.

3. DTmin analysis

Thirdly export minimal Device Tree used in GangFlasher-ST. For doing this there is special DLL function. In GF-CLI use function F_SaveDTmin(DTMIN_TYPE_FSBL, (char*)"DTmin.dtb")to save processed DTmin. Exported file must be recompiled with usage od Device Tree Compiler (DTC) dtc -I dtb -O dts -o DTmin.dts DTmin.dtb. Open recompiled DTmin source file and compare it with recompiled Karo source code. Recompilation means that firstly there must be available binary version of DT and then it is recompiled with DTC to human-readable source version. It could be ease to compare two recompiled source files with source comparison tool for example Meld.

Open

DTmin TFA recompiled source on left and Karo TFA recompiled source on right.

It is obvious that clocks node could differ in HSE Digital clock source bypass mode. It is possible to edit GangFlasher minimal Device Tree with usage of DTmin configuration file.

4. DTmin configuration file

It is possible to provide user fine-tuning of GangFlasher minimal Device Tree. Functionalities consist of:

• add/remove node (ADD/RM),

• add/remove subnode,

• add/remove node/subnode property.

In case of Karo TXMP board this will be as easy as removal of subnode property:

Provided changes are automatically included in FSBL and SSBL Device Trees (TFA DT; TFA-OPTEE DT; UBOOT DT; LINUX DT which is the same as UBOOT DT). Load DTmin config file before run functions (f.e. F_AutoProgram() or F_LoadOS() via function F_LoadDTminConfig("/home/UserXX/Karo/DTmin_config.cfg"). After reset Karo TXMP board boots normally.