Customizing device tree

[MSele.1]

Help on customizing the device tree

I installed my starter package according to instructions at https://wiki.st.com/stm32mpu/wiki/STM32MP15_Discovery_kits_-_Starter_Package

And the developer package following instructions at  https://wiki.st.com/stm32mpu/wiki/STM32MP1_Developer_Package

Then on developing my projects, I realized that I need a different device tree than what was provided in those two packages, because the CAN bus is not  defined in those installations, and that is the core of my project.

Then I read this blog

https://wiki.st.com/stm32mpu/wiki/How_to_cross-compile_with_the_Developer_Package

Somewhere, it requires to navigate to "Device Drivers - Generic Driver Options"

• select "Size in Megabytes"
• modify its value to 256
• exit and save the new configuration

The problem is: if you follow those instructions, there is no option to select “Size in Megabytes,�? which left in darkness!!

Somewhere in the next page it advises to change directory to the <Linux kernel build directory> as

PC $> cd <Linux kernel build directory>

 

Problem is that no clear information on what this <Linux kernel build directory> is!

 

Again, on the next page there is this instruction

 

PC $> cd <Linux kernel source directory>

The following several pages keep jumping between <Linux kernel source directory> which is not clearly defined, and the <Linux kernel build directory> and then comes

 

PC $> cd <tag>/sources/arm-<distro>-linux-gnueabi

Where the so called <tag> and <distro> are not clearly defined

On modifying u-boot, there is the command

PC $> cd <U-Boot source directory>

and I have no idea what the <U-Boot source directory> directory is. I believe If I gent into that directory, the following instructions should be easy to fulfil, but I don’t know where that directory is. Finally there is this command with a similar problem about <TF-A source directory>

PC $> cd <TF-A source directory>

Another document I read is this

https://wiki.st.com/stm32mpu/wiki/How_to_compile_the_device_tree_with_the_Developer_Package

Section 3 states the prerequisistes which are in agreement with my prior process of installing of the Starter package and Developer package. However, Section 4 suggests something that I have to reinstall the developer package again, which is what I fail to understand why if I have already met the prerequisites of Section 3. If I skip Section 4, then it seems that Section 5 does not work at all.

This document relies on WORKDIR, which in my case (following instructions at https://wiki.st.com/stm32mpu/wiki/STM32MP1_Developer_Package) would be

$HOME/STM32MPU_workspace/STM32MP15-Ecosystem-v3.0.0/Developer-Package

But unfortunately it does not work, which means the instructions at

https://wiki.st.com/stm32mpu/wiki/How_to_compile_the_device_tree_with_the_Developer_Package

are different from those at

https://wiki.st.com/stm32mpu/wiki/STM32MP1_Developer_Package

which bothers me.

Can I get any help on how to customize my device tree?

[Olivier GALLIEN]

Hi @MSele.1​ ,

Thanks for your post and sorry for inconvenience using the wiki.

To get what we call "source directory" I think it can be helpful to refer to

https://wiki.st.com/stm32mpu/wiki/Example_of_directory_structure_for_Packages

For reference to <Linux kernel build directory>  in

https://wiki.st.com/stm32mpu/wiki/How_to_cross-compile_with_the_Developer_Package#Modifying_a_built-in_Linux_kernel_device_driver

you have to know that this page consider you already build Linux a first time following :

https://wiki.st.com/stm32mpu/wiki/STM32MP1_Developer_Package#Building_and_deploying_the_Linux_kernel_for_the_first_time

"build directory" may depends you have decided to use in-tree or "out-tree with build folder" build mode.

For "“Size in Megabytes,�? which left in darkness!!" problem .. I will have a look

But I don't think you need to change kernel configuration just to enable CAN in device tree, right ?

Let me know if this is clearer.

Olivier

[MSele.1]

Thank you; the information at https://wiki.st.com/stm32mpu/wiki/Example_of_directory_structure_for_Packages provides information about some directories. However, if I followed installation instructions at https://wiki.st.com/stm32mpu/wiki/STM32MP15_Discovery_kits_-_Starter_Package

and at https://wiki.st.com/stm32mpu/wiki/STM32MP1_Developer_Package to the letter without deviating, what will be my <Linux kernel build directory>? Is it same as the <Linux kernel installation directory> or the <SDK installation directory>?

On another note, I just installed the starter and the developer packages only; I did not install the distribution package. Was that a mistake?

[Olivier GALLIEN]

Hi @MSele.1​ ,

Ok I think I got it .

https://wiki.st.com/stm32mpu/wiki/How_to_compile_the_device_tree_with_the_Developer_Package seems to not follow same rules than https://wiki.st.com/stm32mpu/wiki/STM32MP1_Developer_Package and https://wiki.st.com/stm32mpu/wiki/How_to_cross-compile_with_the_Developer_Package#Modifying_the_Linux_kernel_device_tree

So I recommand to ignore https://wiki.st.com/stm32mpu/wiki/How_to_compile_the_device_tree_with_the_Developer_Package and stick on the other ones.

As a summary :

For <working directory absolute path> we recommend <whatever you want>/STM32MP15-Ecosystem-v3.0.0/

So in your case <working directory absolute path> = "$HOME/STM32MPU_workspace/STM32MP15-Ecosystem-v3.0.0/"

Then all is relative from this folder.

<Linux kernel installation directory> is

<working directory absolute path>/Developer-Package/stm32mp1-openstlinux-5.10-dunfell-mp1-21-03-31/sources/arm-ostl-linux-gnueabi/linux-stm32mp-5.10.10-r0

<Linux kernel source directory>

<working directory absolute path>/Developer-Package/stm32mp1-openstlinux-5.10-dunfell-mp1-21-03-31/sources/arm-ostl-linux-gnueabi/linux-stm32mp-5.10.10-r0/linux-5.10.10

<Linux kernel build directory> in case :

* Compile and install on a build directory

-> <working directory absolute path>/Developer-Package/stm32mp1-openstlinux-5.10-dunfell-mp1-21-03-31/sources/arm-ostl-linux-gnueabi/linux-stm32mp-5.10.10-r0/build

else same as <Linux kernel source directory>

<SDK installation directory> is <working directory absolute path>/Developer-Package/SDK

Hope it help

Olivier

[MSele.1]

Thank you; this helps a lot. I have just uninstalled all prior installations to start afresh. I will bring my feedback after the whole process. Do you think I should also install the distribution package? is it necessary?

[Olivier GALLIEN]

Good to know it help, thanks !

For Distribution package, for you current need of just updating dts I would say no .. but it depends what you want to do afterward.

I recommend to read :

https://wiki.st.com/stm32mpu/wiki/Which_STM32MPU_Embedded_Software_Package_better_suits_your_needs

Olivier

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