[PATCH 0/8] An effort to bring DT bindings compliance within U-boot

[Sumit Garg]

Hi Michal,

On Wed, 20 Dec 2023 at 16:14, Michal Simek <michal.simek at amd.com> wrote:
>
> Hi Sumit,
>
> On 12/14/23 14:50, Sumit Garg wrote:
> > Prerquisite
> > -----------
> >
> > This patch series requires devicetree-rebasing git repo to be added as a
> > subtree to the main U-boot repo via:
> >
> > $ git subtree add --prefix devicetree-rebasing \
> >        git://git.kernel.org/pub/scm/linux/kernel/git/devicetree/devicetree-rebasing.git \
> >        v6.6-dts --squash
> >
> > Background
> > ----------
> >
> > This effort started while I was reviewing patch series corresponding to
> > Qcom platforms [1] which was about to import modified devicetree source
> > files from Linux kernel. I suppose keeping devicetree files sync with
> > Linux kernel without any DT bindings schema validation has been a pain
> > for U-boot SoC/platform maintainers. There has been past discussions
> > about a single DT repo but that hasn't come up and Linux kernel remained
> > the place where DT source files as well as bindings are placed and
> > maintained.
> >
> > However, Linux kernel DT maintainers proposed [2] for U-boot to rather
> > use devicetree-rebasing repo [3] which is a forked copy from Linux
> > kernel for DT source files as well as bindings. It is tagged at every
> > Linux kernel major release or intermideate release candidates. So here I
> > have tried to reuse that to bring DT bingings compliance as well as a
> > standard way to maintain a regular sync of DT source files with Linux
> > kernel.
> >
> > In order to maintain devicetree files sync, U-boot will maintains a Git
> > subtree for devicetee-rebasing repo as `devicetee-rebasing/` sub-directory.
> > It will be regularly updated with every new kernel major release via
> > subtree pull as follows::
> >
> > $ git subtree pull --prefix devicetree-rebasing \
> >        git://git.kernel.org/pub/scm/linux/kernel/git/devicetree/devicetree-rebasing.git \
> >        <release-tag> --squash
> >
> > The RFC/prototype for this series has been discussed with Linux DT
> > maintainers as well as U-boot maintainers here [4]. Now we would like to
> > reach out to wider U-boot community to seek feedback.
> >
> > [1] https://lore.kernel.org/all/CAFA6WYMLUD9cnkr=R0Uur+1UeTMkKjM2zDdMJtXb3nmrLk+pDg@mail.gmail.com/
> > [2] https://lore.kernel.org/all/CAL_JsqKEjv2tSGmT+0ZiO7_qbBfhTycbGnhJhYpKDFzfO9jzDg@mail.gmail.com/
> > [3] https://git.kernel.org/pub/scm/linux/kernel/git/devicetree/devicetree-rebasing.git/
> > [4] https://github.com/u-boot/u-boot/pull/451
> >
> > Changes
> > -------
> >
> > Traditionally, U-boot placed copies of devicetree source files from Linux
> > kernel into `arch/<arch>/dts/<name>.dts`, which can be selected via:
> >
> > CONFIG_DEFAULT_DEVICE_TREE "<name>"
> >
> > SoC/board maintainers are encouraged to migrate to using mirrored copies
> > from `devicetree-rebasing/` into `dts/arch/<arch>/<vendor>` via:
> >
> > CONFIG_OF_UPSTREAM=y
> > CONFIG_DEFAULT_DEVICE_TREE "<vendor>/<name>"
> >
> > An example have been shown for Amlogic meson-gxbb SoC and corresponding
> > derived boards via patch #7 and #8.
> >
> > Devicetree bindings schema checks
> > ---------------------------------
> >
> > With devicetee-rebasing Git subtree, the devicetree bindings are also
> > regularly synced with Linux kernel as `devicetree-rebasing/Bindings/`
> > sub-directory. This allows U-boot to run devicetree bindings schema checks
> > which will bring compliance to U-boot core/drivers regarding usage of
> > devicetree.
> >
> > Dependencies
> > ------------
> >
> > The DT schema project must be installed in order to validate the DT schema
> > binding documents and validate DTS files using the DT schema. The DT schema
> > project can be installed with pip:
> >
> > $ pip3 install dtschema
> >
> > Note that 'dtschema' installation requires 'swig' and Python development
> > files installed first. On Debian/Ubuntu systems:
> >
> > $ apt install swig python3-dev
> >
> > Several executables (dt-doc-validate, dt-mk-schema, dt-validate) will be
> > installed. Ensure they are in your PATH (~/.local/bin by default).
> >
> > Recommended is also to install yamllint (used by dtschema when present).
> >
> > Running checks
> > --------------
> >
> > In order to perform validation of DTB files, use the ``dtbs_check`` target:
> >
> > $ make dtbs_check
> >
> > It is also possible to run checks with a subset of matching schema files by
> > setting the ``DT_SCHEMA_FILES`` variable to 1 or more specific schema files
> > or patterns (partial match of a fixed string). Each file or pattern should
> > be separated by ':'.
> >
> > $ make dtbs_check DT_SCHEMA_FILES=trivial-devices.yaml:rtc.yaml
> > $ make dtbs_check DT_SCHEMA_FILES=/gpio/
> > $ make dtbs_check DT_SCHEMA_FILES=trivial-devices.yaml
>
> Do you also plan to extend this to cover dt overlay + dt base generation and
> check it against DT schema.

I suppose here you are referring to DT schema checks for *.dtso ->
*.dtbo generation. I don't see corresponding checks enabled in Linux
kernel [1]. Probably Rob can share plans over there.

U-Boot tries to follow Linux kernel kbuild framework. However, if
needed we can add checks for *.dtbo generation too as a follow up
patch.

[1] https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tree/scripts/Makefile.lib#n421

-Sumit

>
> Thanks,
> Michal
>