[PATCH 2/9] ARM: dts: socfpga: add Enclustra Intel AA1

[Lothar Rubusch]

On Sun, Sep 29, 2024 at 6:55 PM Marek Vasut <marex at denx.de> wrote:
>
> On 9/28/24 12:47 AM, Lothar Rubusch wrote:
>
> [...]
>
> >>> Ideally I like to setup some Kconfig choice for base board selection
> >>> and one for boot-mode.
> >>
> >>> 1.) In the documentation control.rst I read that the u-boot.dts is
> >>> combined of several elements. Is there a way to take this base .dts,
> >>> then add a base board .dtsi by Kconfig option, and similar a
> >>> boot-mode?
> >>
> >> The -u-boot.dtsi is preprocessed by C preprocessor, just like all the
> >> other DTs, so you can have a -u-boot.dtsi file which contains C
> >> preprocessor conditional statements in it to conditionally include other
> >> .dtsi files:
> >>
> >> #if IS_ENABLED(...)
> >> #include ...
> >> #else ...
> >> ...
> >> #endif
> >
> > Going through the include list setup by the Makefile made me find my
> > mistake. Currently I may use u-boot specific stuff in arch/arm/dts and
> > include generic .dtsi fragments from dts/upstream. Note: I'm not
> > setting CONFIG_OF_UPSTREAM since I'm using the regular include list
> > which already contains dts/upstream/src/arm/intel. Is this ok? Or,
> > shall I try a different approach, which involves having
> > CONFIG_OF_UPSTREAM explicitely set in the defconfig?
>
> I'm not quite sure I understand the question. Once this platform DTs
> land in mainline and the DTs get synchronized into U-Boot, you should
> then set CONFIG_OF_UPSTREAM. Until then, you could patch the DTs into
> dts/upstream/ to test the result with OF_UPSTREAM enabled .
>

Ah, sorry. I did not explain well. Currently I patch the DTs which
should go to kernel/mainline into my local u-boot:
dts/upstream/src/arm/intel/socfpga/ as a preparation for my test
builds.

For U-boot I will need to build a devicetree file from archarm/dts. I
cannot rely just on the upstream fragments for u-boot. Imagine
settings like initial fpga bitstream loading, handoff file setup for
initialization, etc. In parts I may use .dtsi files from dts/upstream,
though, but most of the u-boot particular devicetree setup will reside
in arch/arm/dts, I guess (you may see later in the patches).

I noticed when setting the option CONFIG_OF_UPSTREAM in `make
menuconfig`, it prepends `dts/upstream/` to the included paths of the
devicetree files. The resulting path for the .dts was then
dts/upstream/arch/arm/dts/ and could not be found anymore. When I
don't activate CONFIG_OF_UPSTREAM, dts/upstream is in the Makefile's
include list anyway so that I easily can include from both locations.

In conclusion, currently I'm calling a .dts for building the u-boot DT
from arch/arm/dts. The file includes upstream stuff as .dtsi fragment
from dts/upstream and handoff from local. CONFIG_OF_UPSTREAM does not
seem to be necessary in this case.

This approach currently works for me. If you strongly disagree, I may
invest more time to find a way (or why there is currently no way) with
CONFIG_OF_UPSTREAM.

This was my question about. Anyway you may wait on v3 to understand
better in source what I'm doing, or if I'm just messing around.

> >>> 3.) What would be the best possibility to have a u-boot.dts with
> >>> handoff setup in arch/arm/dts and append .dtsi files from the general
> >>> dts/upstream - in case are there other boards are doing something
> >>> similar?
> >>
> >> See above, maybe some of it helps.
> >
> > Yes. This helped. I can set base-board and boot mode now by Kconfig
> > option with a generic .dts file. Note, it may still take some time,
> > since I'd like to test the stuff still a bit on hardware before
> > submitting something to the list.
>
> Sure

I still found some bugs. When it's working (again), I'll let you guys know..