OF_UPSTREAM vs. additional dtbs

[Jan Kiszka]

On 26.08.24 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.

We are using the overlay to massage the DT presented to the OS based on
firmware configuration. So, those two belong to the firmware logically,
but - with some disclaimers, we could also try to upstream them.

Jan

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