OF_UPSTREAM vs. additional dtbs

[Sumit Garg]

Hi Jonas,

On Mon, 26 Aug 2024 at 14:27, Jonas Karlman <jonas at kwiboo.se> wrote:
>
> Hi Sumit,
>
> On 2024-08-26 08:44, Sumit Garg wrote:
> > Hi,
> >
> > On Wed, 14 Aug 2024 at 22:14, Jan Kiszka <jan.kiszka at siemens.com> wrote:
> >>
> >> On 14.08.24 11:41, Jan Kiszka wrote:
> >>> On 13.08.24 14:52, Nishanth Menon wrote:
> >>>> On 11:16-20240813, Jan Kiszka wrote:
> >>>>> Hi all,
> >>>>>
> >>>>> I'm trying to migrate the TI AM65x IOT2050 boards to OF_UPSTREAM but I'm
> >>>>> facing issues because I need to still build the u-boot-only overlays. It
> >>>>> is also a bit weird (but works) having to specify
> >>>>>
> >>>>> CONFIG_SPL_OF_LIST="../../../../arch/arm/dts/k3-am65-iot2050-spl"
> >>>>>
> >>>
> >>> Actually, this does NOT work: I just had a long morning debugging SPL
> >>> which no longer started because it picked the non-filtered dtb. The
> >>> filtered one ended up in a folder outside of the u-boot sources because
> >>> of all those ../ and hard-wiring to dts/upstream.
> >>>
> >>>>> for our spl dtb.
> >>>>>
> >>>>> Are there means to still build certain dtb[o] files in arch/<arch>/dts?
> >>>>> I'm a bit lost in the Makefile forest.
> >>>>>
> >>>>
> >>>> Sumit: Any suggestions?
> >>>>
> >
> > Apologies for the delayed reply. I was a bit busy with other high
> > priority stuff.
> >
> >>>
> >>> I would really like to hear some better proposals than my local
> >>> workarounds to far. They don't converge although I already patched some
> >>> core Makefile (overlays are building now).
> >>>
> >>
> >> OK, I side-stepped the spl issue by using one of our variant DTBs for
> >> spl as well - happens to work.
> >
> > That's good to know.
> >
> >>
> >> For the overlays, I need to add
> >>
> >> --- a/scripts/Makefile.dts
> >> +++ b/scripts/Makefile.dts
> >> @@ -1,5 +1,7 @@
> >>  # SPDX-License-Identifier: GPL-2.0+
> >>
> >> +include $(srctree)/config.mk
> >> +
> >>  dtb-y += $(patsubst %,%.dtb,$(subst ",,$(CONFIG_DEFAULT_DEVICE_TREE) $(CONFIG_OF_LIST) $(CONFIG_SPL_OF_LIST)))
> >>
> >>  ifeq ($(CONFIG_OF_UPSTREAM_BUILD_VENDOR),y)
> >>
> >>
> >> in order to then be able to do
> >>
> >> --- a/board/siemens/iot2050/config.mk
> >> +++ b/board/siemens/iot2050/config.mk
> >> @@ -5,4 +5,12 @@
> >>  # Authors:
> >>  #   Jan Kiszka <jan.kiszka at siemens.com>
> >>
> >> +ifneq ($(CONFIG_SPL_BUILD),y)
> >> +dtbo-list = \
> >> +       k3-am6548-iot2050-advanced-m2-bkey-usb3-overlay \
> >> +       k3-am6548-iot2050-advanced-m2-bkey-ekey-pcie-overlay
> >> +
> >> +dtb-y += $(patsubst %,../../../../arch/arm/dts/%.dtbo,$(dtbo-list))
> >> +endif
> >> +
> >>  flash.bin: all
> >>
> >>
> >> Does that make sense?
> >
> > A switch to OF_UPSTREAM means that we build all the DT artifacts from
> > dts/upstream/src/ directory with the only exception that we include
> > U-Boot specific overrides via *-u-boot.dtsi from arch/<arch>/dts. In
> > case of overlays, is there any reason for IOT2050 board overlays not
> > being pushed into Linux kernel repo? AFAIU, overlays are also
> > describing puggable hardware so they shouldn't be referred to as
> > "u-boot-only" overlays.
>
> I have a related issue where I would like to build board DT from
> dts/upstream, however there is also a need for a limited U-Boot specific
> DT that only is intended for initial boot so that U-Boot at runtime can
> determine what hw revision is booting and select correct DT to use for
> U-Boot proper and OS.
>
> For now I have just set the board target to use OF_UPSTREAM=n and
> instead created minimal .dts-files in arch/<arch>/dts that include the
> full .dts-file from dts/upstream.
>
> Any suggestion on how we better can support having a U-Boot only
> .dts-file together with OF_UPSTREAM=y ?

The motivation is rather to avoid any U-Boot specific DT files.
Shouldn't you be able to create a DT overlay of v2.1 board over v1.1
and push that upstream? The runtime DT choice sounds pretty similar to
how you can choose to apply the DT overlay or not with common boot DT.
Also, bundling multiple DT within U-Boot proper FIT image can be an
alternative too.

-Sumit

>
> Please see following for more details:
> https://source.denx.de/u-boot/u-boot/-/commit/a52099b4a2ae9e8cafc79268325249bcad308012
> https://source.denx.de/u-boot/u-boot/-/blob/master/arch/arm/dts/rk3566-orangepi-3b.dts
> https://source.denx.de/u-boot/u-boot/-/blob/master/arch/arm/dts/rk3566-orangepi-3b-v1.1.dts
> https://source.denx.de/u-boot/u-boot/-/blob/master/arch/arm/dts/rk3566-orangepi-3b-v2.1.dts
>
> Regards,
> Jonas
>
> >
> > -Sumit
> >
> >>
> >> Jan
> >>
> >> --
> >> Siemens AG, Technology
> >> Linux Expert Center
> >>
>