[PATCH 00/21] Qualcomm generic board support

[ff]

> Le 5 déc. 2023 à 10:46, Sumit Garg <sumit.garg at linaro.org> a écrit :
> 
> + U-boot custodians list
> 
>> On Tue, 5 Dec 2023 at 12:58, Krzysztof Kozlowski
>> <krzysztof.kozlowski at linaro.org> wrote:
>> 
>> On 05/12/2023 08:13, Sumit Garg wrote:
>>>>> @DT bindings maintainers,
>>>>> 
>>>>> Given the ease of maintenance of DT bindings within Linux kernel
>>>>> source tree, I don't have a specific objection there. But can we ease
>>>>> DTS testing for firmware/bootloader projects by providing a versioned
>>>>> release package for DT bindings? Or if someone else has a better idea
>>>>> here please feel free to chime in.
>>>> 
>>>> This doesn't work for you?:
>>>> 
>>>> https://git.kernel.org/pub/scm/linux/kernel/git/devicetree/devicetree-rebasing.git/
>>> 
>>> Thanks, this is certainly a good step which I wasn't aware of. Further
>>> simplification can be done to decouple devicetree source files from DT
>>> bindings.
>> 
>> Why?
> 
> I suppose you are already aware that Linux DTS files are a subset of
> what could be supported by devicetree schemas. There can be
> firmware/bootloader specific properties (one example being [1]) which
> Linux kernel can simply ignore. Will you be willing to add all of
> those DT properties to Linux DTS files and maintain them?
> 
A pre-existing effort to solve the same problem as [1] is System Device Tree, discussed in the context of Linaro supported OpenAMP project. It is not just about cherry picking devices that have bindings in Linux but also information about clock and power domains or devices that are not seen by Linux.
It is obvious that the resulting bindings should be maintained upstream in the DT repo regardless of the communities adopted solution.

> However, DT bindings are something which should be common, the
> hardware description of a device should be universal. IMO, splitting
> DT bindings alone would ease the compliance process for u-boot drivers
> in quite similar manner to Linux drivers.
> 
I remember a discussion with ST on that topic related to Framebuffer. U-Boot can need a very different representation of the same device to use it while Linux need an in-depth description of all shaders and « stuff » (another reason why [1] is addressing only a portion of the problem)
So even if there is a single frame buffer binding, there should be two (at least) conformance tests.

> [1] https://github.com/devicetree-org/dt-schema/blob/main/dtschema/schemas/bootph.yaml
> 
>> 
>>> AFAIK, DT bindings should be forwards and backwards
>>> compatible.
>> 
>> The same with DTS.
>> 
>>> So if you pick up DTS or DTB from any project tree
>>> (upstream kernel or stable kernel or u-boot) then DT schema validation
>>> would ensure that corresponding DTS or DTB doesn't regress the DT
>>> bindings.
>> 
>> And why is this argument to decouple DTS from bindings?
>> 
> 
> See above.
> 
>>> 
>>> Ideally, it should be more user/CI friendly if DT bindings can be
>>> easily installed alongside devicetree schema tools [1].
>>> 
>>> [1] https://github.com/devicetree-org/dt-schema
>> 
>> Does it mean you will work on this?
> 
> I am happy to collaboratively work with DT bindings maintainers and
> the u-boot community once we can reach a consensus on the above.
> Basically the main motive here is to validate DTS files present in the
> u-boot tree and be able to reliably pass them to whichever Linux
> kernel version you are trying to boot. IOW, make Linux distros to
> reliably boot with devicetree supplied by u-boot.
> 
> -Sumit
> 
>> 
>> Best regards,
>> Krzysztof
>> 
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