How to compile the device tree with the Developer Package

Warning

This page need to be renamed. Do you have any suggestion ? My proposal is: HowTo update devicetree of bootchain

1. Purpose

This article explains how to update boot chain (trusted mode) 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.

2. Rationale

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

Information

Even if STMicroelectronics strongly recommends to use a Linux® environment, this article works in WSL2 (Windows Sub-system Linux 2) environment. WSL2 is available on Windows 10® since builds 18917.

This article only need to update three software of the complete boot chain (trusted mode); 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 which are provided by file SOURCES-st-image-weston-openstlinux-weston-stm32mp1.tar.xz
  • Need SDK toolchain which is provided by file SDK-x86_64-st-image-weston-openstlinux-weston-stm32mp1.tar.xz
• (optionnal) STM32CubeProgrammer: the tool used to flash the images and binaries into target

• Custom devicetree sources:
  • For the rest of document the custom devicetree are considered generated by STM32CubeMX and stored in a tarball MyDeviceTree_fromCubeMX.tar.xz with following file tree:

MyDeviceTree_fromCubeMX
|-- kernel
|   |-- stm32mp157c-mydevicetree-mx.dts
|-- tf-a
|  |-- stm32mp15-mx.h
|  |-- stm32mp157c-mydevicetree-mx.dts
|-- u-boot
|  |-- stm32mp15-mx.h
|  |-- stm32mp157c-mydevicetree-mx-u-boot.dtsi
|  |-- stm32mp157c-mydevicetree-mx.dts

• Make sure PC_Prerequisite#Linux PC have been run (even with a WSL2 setup)

4. Prepare your environnement

As seen in #Pre-requisites, there are numerus inputs so here a proposition to organize your environment.
Better is to create a dedicated WORKDIR somewhere in your HOME. Then copy all inputs quoted in #Pre-requisites in that just created WORKDIR:

cd

mkdir WORKDIR

cd WORKDIR

export WORKDIR="$PWD"

tar --strip-components=1 -xf <IMAGES-st-image-weston-openstlinux-weston-stm32mp1.tar.xz> -C $WORKDIR/

tar --strip-components=1 -xf <SOURCES-st-image-weston-openstlinux-weston-stm32mp1.tar.xz> -C $WORKDIR/

tar --strip-components=1 -xf <SDK-st-image-weston-openstlinux-weston-stm32mp1.tar.xz> -C $WORKDIR/

tar xf <MyDeviceTree_fromCubeMX.tar.xz> -C $WORKDIR/

Then proceed in the SDK installation.

Commands of the rest of the document should be run in a SDK environment context (Starting_up_the_SDK).

5. Kernel device tree update

Updating the devicetree of kernel only needs to replace the 'dtb' file of '/boot' partition.
Indeed 'extlinux.conf' explicitly points on the dtb the kernel should use (something like '/boot/<devicetree>.dtb'). Below the procedure to generate and then copy new DTB in target:

5.1. Kernel : unpack and patch sources

Run following command into a shell:

pushd $WORKDIR

mkdir -p kernel

tar xf sources/arm-openstlinux_weston-linux-gnueabi/linux-stm32mp-4.19-r0/linux-4.19.*.tar.xz -C kernel

mv kernel/linux-* kernel/kernel-sources/

pushd kernel/kernel-sources/

for p in $(ls -1 ../../sources/arm-openstlinux_weston-linux-gnueabi/linux-stm32mp-4.19-r0/*.patch); do patch -p1 < $p; done

popd

popd

5.2. Kernel : generate DTB

pushd $WORKDIR

cp -r MyDeviceTree_fromCubeMX/kernel kernel/dts

ls kernel/dts/

stm32mp157c-mydevicetree-mx.dts

pushd $WORKDIR

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

Template:Highlight3

popd

popd

5.3. Kernel : copy DTB into bootfs

First of all update bootfs with the just new DTB to take it into account on next boot of the target.

Then if needed update extlinux of target according this new dtb filename. This is only needed if the filename of the dtb generated is diferent from the one used by extlinux to boot.

6. U-Boot device tree update

Updating the devicetree of u-boot needs to replace the 'dtb' part of the u-boot binary.
By adding new devicetree to u-boot source code, the Makefile will regenerate a new u-boot.stm32 containing the new 'dts'

6.1. U-boot : unpack and patch sources

pushd $WORKDIR

mkdir -p u-boot

tar xf st-image-weston-openstlinux-weston-stm32mp1/sources/arm-openstlinux_weston-linux-gnueabi/u-boot-stm32mp-*/v*.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 ../../st-image-weston-openstlinux-weston-stm32mp1/sources/arm-openstlinux_weston-linux-gnueabi/u-boot-stm32mp-*/*.patch); do patch -p1 < $p; done

popd

6.2. U-boot : copy DTS in u-boot source code

pushd $WORKDIR/u-boot/u-boot-sources

cp ../../MyDeviceTree_fromCubeMX/u-boot/* arch/arm/dts/

popd

6.3. U-boot : regenerate u-boot.stm32

pushd $WORKDIR/u-boot/u-boot-sources

make stm32mp15_<config>_defconfig

<config> : could be trusted or basic according the boot type

make DEVICE_TREE=<device tree> all

<device tree> : is the devicetree just copied, i.e.: stm32mp157c-mydevicetree-mx

popd

ls -l $WORKDIR/u-boot/u-boot-sources/u-boot.stm32

6.4. U-boot : copy u-boot on target

• Because of 'extlinux' and before flashing the new u-boot.stm32, make sure #extlinux update is done according the 'compatible' value in DTS file.
  

• Then flash the u-boot.stm32 into 'ssbl' partition of the target with STM32CubeProgrammer else using 'dd' as following :

dd if=u-boot.stm32 of=Template:Highlight3 conv=fdatasync

Information

The '/dev/mmcblk0p3' is in case of the sdcard is inserted in dedicated drive of the PC, using an USB sdcard reader will probably create /dev/sdb3 entry.

7. TF-A device tree update

Updating the devicetree of TF-A needs to replace the 'dtb'part of the TF-A binary.
TF-A binary allocates just after the 'mkimage" headers a 'fixed' zone for DTB. DTB is smaller than the reserved zone, padding is done with zero.

Below the procedure to generate TF-A with a new DTB and then flash it on target:

7.1. TF-A : unpack and patch sources

Information

The procedure below is equivalent to chapter 3 of the README_HOWTO.txt file available in $WORKDIR/st-image-weston-openstlinux-weston-stm32mp1/sources/arm-openstlinux_weston-linux-gnueabi/tf-a-stm32mp-*

pushd $WORKDIR

mkdir -p tf-a

tar xf st-image-weston-openstlinux-weston-stm32mp1/sources/arm-openstlinux_weston-linux-gnueabi/tf-a-stm32mp-*/v*.tar.gz -C tf-a

mv tf-a/arm-trusted-firmware-* tf-a/tf-a-sources

pushd tf-a/tf-a-sources

for p in $(ls -1 ../../st-image-weston-openstlinux-weston-stm32mp1/sources/arm-openstlinux_weston-linux-gnueabi/tf-a-stm32mp-*/*.patch); do patch -p1 < $p; done

popd

popd

7.2. TF-A : copy dts into source code

pushd $WORKDIR/tf-a

cp -r ../MyDeviceTree_fromCubeMX/tf-a tf-a-sources/fdts/

popd

7.3. TF-A : regenerate TF-A.stm32

Information

The procedure below is equivalent to chapter 5 of the README_HOWTO.txt file available in $WORKDIR/st-image-weston-openstlinux-weston-stm32mp1/sources/arm-openstlinux_weston-linux-gnueabi/tf-a-stm32mp-*

pushd $WORKDIR/tf-a/tf-a-sources

make -f $PWD/../Makefile.sdk TFA_DEVICETREE=<device tree> TF_A_CONFIG=<config> all

<config> : could be trusted or basic according the boot type

<device tree> : is the devicetree just copied, i.e.: stm32mp157c-mydevicetree-mx

popd

ls -l $WORKDIR/tf-a/build/<config>/tf-a-<device tree>-<config>.stm32

7.4. TF-A : copy DTB on target/bootfs

Then flash the tf-a-*.stm32 into the 'fsbl1' and 'fsbl2' partitions of the target with STM32CubeProgrammer else use 'dd' as follow:

dd if=tf-a.stm32 of=Template:Highlight3 conv=fdatasync

dd if=tf-a.stm32 of=Template:Highlight3 conv=fdatasync

Warning

'fsbl1' and 'fsbl2' are two redondant partitions and so, they should have same content

Information

The '/dev/mmcblk0pX' are in case of the sdcard is inserted in dedicated drive of the PC, using an USB sdcard reader will probably create /dev/sdbX entries.

8. Update methods

8.1. bootfs update

• Template:DarkBlue

scp stm32mp157c-mydevicetree-mx.dtb root@<Target_IP>:/boot/

• Template:DarkBlue

This method doesn't need to have a target up and running but only need the "st-image-bootfs-openstlinux-weston-stm32mp1.ext4" file. To modify a 'ext4' file, a loopback mount tool is need which is avaible in any Linux Distribution (even through Windows 10 via WSL2):

mkdir -p $WORKING/bootfs

mount -o loop Template:Highlight3 $WORKING/bootfs

##Then copy the new dtb file at the root of $WORKING/bootfs

umount $WORKING/bootfs

sync

dd if=Template:Highlight3 of=Template:Highlight3 conv=fdatasync

Information

The '/dev/mmcblk0p4' is in case of the sdcard is inserted in dedicated drive of the PC, using an USB sdcard reader will probably create /dev/sdb4 entry.

8.2. extlinux update

8.2.1. extlinux : basics

'extlinux' is a collection of scripts/config files describing how u-boot should boots. Updating extlinux consists in updating the extlinux.conf.

• As exemple by using a DK-2 board and booting on sdcard, then the extlinux.conf file is located in "/boot/mmc0_stm32mp157c-dk2_extlinux/".

  If "mmc0_Template:Highlight3_extlinux" directory is not available, please use "/boot/extlinux/extlinux.conf" file instead.

'extlinux.conf' is the description of a boot menu with one or several entries, 'DEFAULT' selects the one to use by default .
Below an exemple of file:

menu title Select the boot mode
MENU BACKGROUND ../splash.bmp
TIMEOUT 5
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

In example above the highlighted lines may need to be updated/added by this wiki page:

• DEFAULT: This is the default 'LABEL' to boot
• LABEL : The entry 'LABEL' is the value of 'compatible' of the DTS file compiled with u-boot.

  The 'compatible' value is at head of the DTS file and looks like : "st,stm32mp157c-mydevicetree-mx"

• FDT : The path from /boot of the kernel DTB to use

8.2.2. extlinux : updating

Updating 'extlinux' consists into modifying the extlinux.conf. There are 2 ways to proceed:

• Template:DarkBlue

Open a ssh connection to the target or directly with tty terminal, and then use an editor as 'vi' to modify the extlinux.conf file.

Do not forget to synchronize the file system before rebooting the target:

sync

• Template:DarkBlue

This method doesn't need to have a target up and running but only need the "st-image-bootfs-openstlinux-weston-stm32mp1.ext4" file. To modify a 'ext4' file, a loopback mount tool is need which is avaible in any Linux Distribution (even through Windows 10 via WSL2):

mkdir -p $WORKING/bootfs

mount -o loop Template:Highlight3 $WORKING/bootfs

##Then edit the extlinux.conf file (for WSL2 use a 'Linux' type editor; vi, ...)

##Once extlinux.conf up-to-date, umount loopback and flash the bootfs into sdcard with STM32CubeProgrammer or 'dd' :

umount $WORKING/bootfs

sync

dd if=Template:Highlight3 of=Template:Highlight3 conv=fdatasync

Information

The '/dev/mmcblk0p4' is in case of the sdcard is inserted in dedicated drive of the PC, using an USB sdcard reader will probably create /dev/sdb4 entry.

Device tree binary (or Blob)

Microcontroller unit (MCUs have internal flash memory and are intended to operate with a minimum amount of external support ICs. They commonly are a self-contained, system-on-chip (SoC) designs.)

Microprocessor unit

Linux^® is a registered trademark of Linus Torvalds.

Trusted firmware for Arm^® Cortex^®-A

Software development kit (A programming package that enables a programmer to develop applications for a specific platform.)

Device tree source (in software context) or digital temperature sensor (in peripheral context)

Das U-Boot -- the universal boot loader (see U-Boot)