How to compile the device tree with the Developer Package

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1. Purpose[edit source]

This article explains how to update boot chain in case of use of a "customised" devicetree.
As exemple, CubeMX is able to generate "customised" devicetree.

This article describes how to update the DTB (devicetree compiled) part of the boot binaries.

Information

Even if STMicroelectronics strongly recommends to use a Linux^® environment, this article works in WSL2 (Windows Sub-system Linux 2) from Windows 10^® (builds 2019 or later)

2. Rationale[edit source]

The rationale to not use the devicetree provided by OpenSTLinux distribution and prefer a "customised" devicetree is various;

You made your own board
You need to swap some IPs from MCU side to MPU side (or reverse)
For any other reason...

3. Pre-requisites[edit source]

This article only need to update three software of the complete boot chain; Trusted Firmware A (TF-A), u-boot and the linux kernel.
Modifying those software need to handle :

Starter package :

need flashlayout and images to flash provided from file IMAGES-st-image-weston-openstlinux-weston-stm32mp1.tar.xz

Developer package :

Need components sources and patches of the the software to update provided in file SOURCES-st-image-weston-openstlinux-weston-stm32mp1.tar.xz
Need mkimage for stm32 and dtc utilities which could be provided by file SDK-x86_64-st-image-weston-openstlinux-weston-stm32mp1.tar.xz

Notice this is optional since 'dtc' and 'mkimage for stm32' could also be provided by your Linux distribution (as Ubuntu, even Ubuntu though WSL)

Host tools for binary manipulation : tar, patch, ssh/scp, dd and mount loop device

Those tools are very basic and available on any Linux distribution even on WSL.
In case of using WSL, mount loop device is only available from WSL2.

Programmer tool: the tool used to flash the images and binaries into target

4. Kernel device tree update[edit source]

#########################################
#########################################
######################################### KERNEL
#########################################
#########################################
###################
################### UNPACK + PATCH
###################
[frq09494@lmecxl0985 ~/views/DTC]
$ mkdir -p kernel
$ tar xf SOURCES-st-image-weston-openstlinux-weston-stm32mp1-openstlinux-4.19-thud-mp1-19-05-31/st-image-weston-openstlinux-weston-stm32mp1-openstlinux-4.19-thud-mp1-19-05-31/sources/arm-openstlinux_weston-linux-gnueabi/linux-stm32mp-4.19-r0/linux-4.19.43.tar.xz -C kernel
$ mv kernel/linux-* kernel/kernel-sources/
$ pushd kernel/kernel-sources/
for p in $(ls -1 ../../SOURCES-st-image-weston-openstlinux-weston-stm32mp1-openstlinux-4.19-thud-mp1-19-05-31/st-image-weston-openstlinux-weston-stm32mp1-openstlinux-4.19-thud-mp1-19-05-31/sources/arm-openstlinux_weston-linux-gnueabi/linux-stm32mp-4.19-r0/*.patch); do patch -p1 < $p; done
$ popd

###################
################### GENERATE DTB
###################
[frq09494@lmecxl0985 ~/views/DTC/kernel]
$ mkdir -p u-boot
$ pushd u-boot
$ cp -r ../MyDeviceTree_fromCubeMX/kernel dts
[frq09494@lmecxl0985 ~/views/DTC/kernel]
$ ll dts/
total 28
-rw-r--r-- 1 frq09494 frq09494 27156 Jun 17 17:10 stm32mp157c-mydevicetree-mx.dts

$ gcc -E -nostdinc -I kernel-sources/include/ -I kernel-sources/arch/arm/boot/dts -I dts -undef -D__DTS__ -x assembler-with-cpp -o stm32mp157c-mydevicetree-mx.dts.tmp dts/stm32mp157c-mydevicetree-mx.dts
$ dtc -I dts -O dtb -o stm32mp157c-mydevicetree-mx.dtb stm32mp157c-mydevicetree-mx.dts.tmp

###################
################### COPY DTB on target
###################
$ scp stm32mp157c-mydevicetree-mx.dtb root@<Target_IP>:/boot/

Then [#update extlinux] of target according this new dtb filename

5. U-Boot device tree update[edit source]

This operation depends on the use of a mkimage with stm32 support for Windows^® which is not officially available.

The usage of a a cross-compiler for Windows^® and mingw64, the latest mkimage version (provided by U-Boot) will allow you to generate a mkimage version
Upon request, STMicroelectronics may provide an executable binary, without warranty nor support.

Here a procedure to rebuild U-Boot with a new DTS (generated with CubeMX for exemple).

Warning

Please notice only trusted mode is supported

inputs: u-boot sources + patches, u-boot-nodtb.bin, u-boot dts
host tools required: tar, patch, gcc (anyone), mkimage (with stm32 support), dtc

Here a zipfile with all inputs files used for testing Below the procedure with a mkimage with support of stm32image:

U-Boot trusted

#########################################
#########################################
######################################### UBOOT
#########################################
#########################################
###################
################### UNPACK + PATCH
###################
[frq09494@lmecxl0985 ~/views/DTC]
$ mkdir -p u-boot
$ tar xf SOURCES-st-image-weston-openstlinux-weston-stm32mp1-openstlinux-4.19-thud-mp1-19-05-31/st-image-weston-openstlinux-weston-stm32mp1-openstlinux-4.19-thud-mp1-19-05-31/sources/arm-openstlinux_weston-linux-gnueabi/u-boot-stm32mp-2018.11-r0/v2018.11.tar.gz -C u-boot
$ mv u-boot/u-boot* u-boot/u-boot-sources/
$ pushd u-boot/u-boot-sources
for p in $(ls -1 ../../SOURCES-st-image-weston-openstlinux-weston-stm32mp1-openstlinux-4.19-thud-mp1-19-05-31/st-image-weston-openstlinux-weston-stm32mp1-openstlinux-4.19-thud-mp1-19-05-31/sources/arm-openstlinux_weston-linux-gnueabi/u-boot-stm32mp-2018.11-r0/*.patch); do patch -p1 < $p; done
$ popd

###################
################### GENERATE DTB
###################
[frq09494@lmecxl0985 ~/views/DTC/u-boot]
$ mkdir -p u-boot
$ pushd u-boot
$ cp -r ../MyDeviceTree_fromCubeMX/u-boot dts
[frq09494@lmecxl0985 ~/views/DTC/u-boot]
$ ll dts
total 36
-rw-r--r-- 1 frq09494 frq09494 25968 Jun  7 17:32 stm32mp157c-mydevicetree-mx.dts
-rw-r--r-- 1 frq09494 frq09494  3642 Jun  7 17:32 stm32mp157c-mydevicetree-mx-u-boot.dtsi
-rw-r--r-- 1 frq09494 frq09494  3511 Jun  7 17:32 stm32mp15-mx.h

## include dtsi u-boot file into dts of u-boot
$ echo '#include "stm32mp157c-mydevicetree-mx-u-boot.dtsi"' >> dts/stm32mp157c-mydevicetree-mx.dts

$ gcc -E -nostdinc -I u-boot-sources/include/ -I u-boot-sources/arch/arm/dts -I dts -undef -D__DTS__ -x assembler-with-cpp -o stm32mp157c-mydevicetree-mx.dts.tmp dts/stm32mp157c-mydevicetree-mx.dts
$ dtc -I dts -O dtb -o u-boot.dtb stm32mp157c-mydevicetree-mx.dts.tmp

###################
################### REBUILD UBOOT.stm32
###################
[frq09494@lmecxl0985 ~/views/DTC/u-boot]
$ cat SOURCES-st-image-weston-openstlinux-weston-stm32mp1-openstlinux-4.19-thud-mp1-19-05-31/st-image-weston-openstlinux-weston-stm32mp1-openstlinux-4.19-thud-mp1-19-05-31/sources/arm-openstlinux_weston-linux-gnueabi/u-boot-stm32mp-2018.11-r0/intermediate-binaries/trusted/u-boot-nodtb.bin u-boot.dtb > u-boot-dtb.bin
## SYS_TEXT_BASE=0xC0100000 is the addr of u-boot in memory (should never change)
$ export SYS_TEXT_BASE=0xC0100000
$ mkimage -T stm32image -a $SYS_TEXT_BASE -e $SYS_TEXT_BASE -d u-boot-dtb.bin u-boot.stm32

Because of 'extlinux' before flashing the new u-boot.stm32, an extlinux entry should be add in bootfs to be able to boot on new devicetree

First get the 'compatible' of the devicetree from dts file. At the head of the file, look for the 'compatible = ' line. The compatible should looks like something as : "st,stm32mp157c-mydevicetree-mx"

* Add a new entry in extlinux.conf file located in /boot/mmc0_stm32mp157c-dk2_extlinux/.
:If the mmc0_<something> directory is not available, add the new entry in /boot/extlinux/extlinux.conf.

 menu title Select the boot mode
 MENU BACKGROUND ../splash.bmp
 TIMEOUT 20
 DEFAULT stm32mp157c-mydevicetree-mx
 LABEL stm32mp157c-dk2-sdcard
         KERNEL /uImage
         FDT /stm32mp157c-dk2.dtb
         APPEND root=/dev/mmcblk0p6 rootwait rw console=ttySTM0,115200
 LABEL stm32mp157c-dk2-a7-examples-sdcard
         KERNEL /uImage
         FDT /stm32mp157c-dk2-a7-examples.dtb
         APPEND root=/dev/mmcblk0p6 rootwait rw console=ttySTM0,115200
 LABEL stm32mp157c-dk2-m4-examples-sdcard
         KERNEL /uImage
         FDT /stm32mp157c-dk2-m4-examples.dtb
         APPEND root=/dev/mmcblk0p6 rootwait rw console=ttySTM0,115200
 LABEL stm32mp157c-mydevicetree-mx
        KERNEL /uImage
        FDT /stm32mp157c-mydevicetree-mx.dtb
        APPEND root=/dev/mmcblk0p6 rootwait rw console=ttySTM0,115200

Warning

Do not forget to synchronize the file system before rebooting the board
sync

6. TF-A device tree update[edit source]

This operation is not supported. It is currently not possible to modify TF-A device tree without recompiling TF-A module.