On 22/06/2022 11:44, Dmitry Baryshkov wrote:
> On 21/06/2022 21:56, 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.
>>
>> 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>
>> ---
>> .../devicetree/bindings/arm/qcom.yaml | 123 ++++++++++++++++++
>> include/dt-bindings/arm/qcom,ids.h | 30 +++++
>> 2 files changed, 153 insertions(+)
>> create mode 100644 include/dt-bindings/arm/qcom,ids.h
>>
>> diff --git a/Documentation/devicetree/bindings/arm/qcom.yaml b/Documentation/devicetree/bindings/arm/qcom.yaml
>> index 6c38c1387afd..05b98cde4653 100644
>> --- a/Documentation/devicetree/bindings/arm/qcom.yaml
>> +++ b/Documentation/devicetree/bindings/arm/qcom.yaml
>> @@ -403,6 +403,129 @@ properties:
>> - qcom,sm8450-qrd
>> - const: qcom,sm8450
>>
>> + # Board compatibles go above
>> +
>> + qcom,msm-id:
>> + $ref: /schemas/types.yaml#/definitions/uint32-matrix
>> + minItems: 1
>> + maxItems: 8
>> + items:
>> + items:
>> + - description: |
>> + MSM chipset ID - an exact match value consisting of three bitfields::
>> + - bits 0-15 - The unique MSM chipset ID
>> + - bits 16-31 - Reserved; should be 0
>> + - description: |
>> + Hardware revision ID - a chipset specific 32-bit ID representing
>> + the version of the chipset. It is best a match value - the
>> + bootloader will look for the closest possible match.
>> + deprecated: true
>> + description:
>> + The MSM chipset and hardware revision use by Qualcomm bootloaders. It
>> + can optionally be an array of these to indicate multiple hardware that
>> + use the same device tree. It is expected that the bootloader will use
>> + this information at boot-up to decide which device tree to use when given
>> + multiple device trees, some of which may not be compatible with the
>> + actual hardware. It is the bootloader's responsibility to pass the
>> + correct device tree to the kernel.
>> + The property is deprecated - it is not expected on newer boards
>> + (starting with SM8350).
>
> I have been thinking about this for quite a while. I think this patch is
> good.
>
> With this paragraph (and the corresponding paragraph from the next item)
> rephrased to remove references to 'newer boards':
>
> Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>
Great, thanks! And thank you for responding in previous discussions.
I'll remove entire "newer boards ..." part, fix the "two bitfields" and
change the name of the define QCOM_ID_MSM8996. I won't add more board
IDs yet, this can be in following up patches (not only my me).
Best regards,
Krzysztof
