Re: [PATCH v2 1/2] dt-bindings: arm: qcom: document qcom,msm-id and qcom,board-id

[Dmitry Baryshkov]

On 22/06/2022 10:00, Krzysztof Kozlowski wrote:
> On 21/06/2022 21:49, Dmitry Baryshkov wrote:
> > On Tue, 21 Jun 2022 at 22:32, Krzysztof Kozlowski
> > <krzysztof.kozlowski@xxxxxxxxxx> wrote:
> > > On 21/06/2022 21:26, 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.
> > > >
> > > > I might be mistaken here. I think it was expected that dtbTool would use
> > > > board compat strings to generate qcom,msm-id and qcom,board-id
> > > > properties. It's not that the bootloaders were improved.
> > >
> > > Don't ask me, I am new to this.
> > >
> > > https://lore.kernel.org/all/02ab0276-b078-fe66-8596-fcec4378722b@xxxxxxxxxxxxxx/
> >
> >
> >
> >
> > > > > 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::
> > > >
> > > > two bitfields
> > >
> > > Right, thanks.
> > >
> > > > > +             - 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).
> > > >
> > > > Could you please elaborate this?
> > >
> > > Second paragraph:
> > > https://lore.kernel.org/all/20220522195138.35943-1-konrad.dybcio@xxxxxxxxxxxxxx/
> >
> > I think this is something peculiar to Sony. Public lahaina (sm8350)
> > dts files contain both these properties:
> >
> > https://github.com/MiCode/kernel_devicetree/blob/zeus-s-oss/qcom/lahaina-hdk.dts
> > https://github.com/MiCode/kernel_devicetree/blob/zeus-s-oss/qcom/lahaina-v2.1.dtsi
> >
> > > Plus consensus with Rob:
> > > https://lore.kernel.org/all/CAL_JsqKL-mtAQ8Q9H4vLGM8izVVzDPbUAVWSdS8AmGjN6X6kcA@xxxxxxxxxxxxxx/
> >
> > I'm not sure here. But sm8350 and sm8450 dtsi files use these
> > properties. I've linked lahaina files above.
> > The waiptio dtsi (sm8450) are present at the same URL.
>
> If you did not like where the consensus is going during the discussion
> last week, I would expect to join the discussion. Not to comment after I
> implement it.

Please excuse me. I probably missed that part of the discussion. Yes, it 
was my fault.

> > > > If the AOSP team were to add e.g.
> > > > SM8350-HDK to their single RB3+RB5 images, they would still need the
> > > > qcom,board-id/qcom,msm-id properties to let the bootloader choose proper
> > > > DTB.
> > >
> > > If you have any email addresses in mind, please Cc them to invite in
> > > discussions. Otherwise I am afraid it won't be allowed. The feedback I
> > > got before was that SM8350 and newer do not require this property. Feel
> > > free to propose other way to solve comments (see "consensus with Rob"
> > > above).
> >
> > Amit is in CC list. In the past he used these properties to allow
> > single-image booting of RB3 and RB5.
> > In fact I might prefer adding more of these properties to the dts
> > files, where it makes sense, to allow adding more dt files to the
> > images we create.
> > I'd really like to be able to boot a single image on all my boards
> > (rb3, rb5, db410c, db820, ifc6560, etc).
>
> You have several options here. Use the board-compatible-encoded-scheme,
> which was merged like 6 years ago or something. Bootloader could parse
> it, dtbTool as well. Add a generic property, like Rob wanted (and
> probably fix bootloader). Or find any other way to satisfy Rob's
> comments. These properties were not accepted 6 years ago and the board
> compatible approach was merged instead. If 6 years is not enough to
> change the bootloaders, nothing will happen here ever, so we need to
> make some statement.

Let me respond to his email. Amit, you might have something to add there 
too.

Basically I think we should allow these properties to be used for all 
the Qcom boards. Marking them as 'deprecated' is fine to me, thus we 
would not endorse them. But we would still be able to use them when 
needed/wanted (like AOSP requirements for the single boot image).

--
With best wishes
Dmitry