Re: [PATCH v6 1/3] dt-bindings: arm: qcom: document qcom,msm-id and qcom,board-id

[Rob Herring]

On Tue, 05 Jul 2022 15:02:58 +0200, Krzysztof Kozlowski wrote:
> The top level qcom,msm-id and qcom,board-id properties are utilized by
> bootloaders on Qualcomm MSM platforms to determine which device tree
> should be used and passed to the kernel.
> 
> The commit b32e592d3c28 ("devicetree: bindings: Document qcom board
> compatible format") from 2015 was a consensus during discussion about
> upstreaming qcom,msm-id and qcom,board-id fields.  There are however still
> problems with that consensus:
> 1. It was reached 7 years ago but it turned out its implementation did
>    not reach all possible products.
> 
> 2. Initially additional tool (dtbTool) was needed for parsing these
>    fields to create a QCDT image consisting of multiple DTBs, later the
>    bootloaders were improved and they use these qcom,msm-id and
>    qcom,board-id properties directly.
> 
> 3. Extracting relevant information from the board compatible requires
>    this additional tool (dtbTool), which makes the build process more
>    complicated and not easily reproducible (DTBs are modified after the
>    kernel build).
> 
> 4. Some versions of Qualcomm bootloaders expect these properties even
>    when booting with a single DTB.  The community is stuck with these
>    bootloaders thus they require properties in the DTBs.
> 
> Since several upstreamed Qualcomm SoC-based boards require these
> properties to properly boot and the properties are reportedly used by
> bootloaders, document them along with the bindings header with constants
> used by: bootloader, some DTS and socinfo driver.
> 
> Link: https://lore.kernel.org/r/a3c932d1-a102-ce18-deea-18cbbd05ecab@xxxxxxxxxx/
> Co-developed-by: Kumar Gala <galak@xxxxxxxxxxxxxx>
> Signed-off-by: Kumar Gala <galak@xxxxxxxxxxxxxx>
> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx>
> Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>
> ---
>  .../devicetree/bindings/arm/qcom.yaml         | 120 ++++++++++++++
>  include/dt-bindings/arm/qcom,ids.h            | 152 ++++++++++++++++++
>  2 files changed, 272 insertions(+)
>  create mode 100644 include/dt-bindings/arm/qcom,ids.h
> 

Reviewed-by: Rob Herring <robh@xxxxxxxxxx>