linux-kernel - Re: [PATCH v4 1/2] dt-bindings: arm: qcom: Document the sc7280 CRD Pro boards

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Message-ID: <Y6HHCrl0q5BhrHOY@google.com>
Date:   Tue, 20 Dec 2022 14:30:34 +0000
From:   Matthias Kaehlcke <mka@...omium.org>
To:     Rajendra Nayak <quic_rjendra@...cinc.com>
Cc:     agross@...nel.org, andersson@...nel.org, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, konrad.dybcio@...aro.org,
        linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, dianders@...omium.org
Subject: Re: [PATCH v4 1/2] dt-bindings: arm: qcom: Document the sc7280 CRD
 Pro boards

On Tue, Dec 20, 2022 at 10:30:32AM +0530, Rajendra Nayak wrote:
> 
> On 12/16/2022 7:49 PM, Matthias Kaehlcke wrote:
> > On Fri, Dec 16, 2022 at 04:59:17PM +0530, Rajendra Nayak wrote:
> > > Add compatibles for the Pro SKU of the sc7280 CRD boards
> > > which come with a Pro variant of the qcard.
> > > The Pro qcard variant has smps9 from pm8350c ganged up with
> > > smps7 and smps8.
> > > 
> > > Signed-off-by: Rajendra Nayak <quic_rjendra@...cinc.com>
> > > Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
> > > Reviewed-by: Matthias Kaehlcke <mka@...omium.org>
> > > ---
> > > v4 changes:
> > > Added the zoglin-sku1536 compatible along with hoglin-sku1536.
> > > Zoglin is same as the Hoglin variant, with the SPI Flash reduced
> > > from 64MB to 8MB
> > > 
> > >   Documentation/devicetree/bindings/arm/qcom.yaml | 6 ++++++
> > >   1 file changed, 6 insertions(+)
> > > 
> > > diff --git a/Documentation/devicetree/bindings/arm/qcom.yaml b/Documentation/devicetree/bindings/arm/qcom.yaml
> > > index 1b5ac6b02bc5..07771d4c91bd 100644
> > > --- a/Documentation/devicetree/bindings/arm/qcom.yaml
> > > +++ b/Documentation/devicetree/bindings/arm/qcom.yaml
> > > @@ -558,6 +558,12 @@ properties:
> > >             - const: google,hoglin
> > >             - const: qcom,sc7280
> > > +      - description: Qualcomm Technologies, Inc. sc7280 CRD Pro platform (newest rev)
> > > +        items:
> > > +          - const: google,zoglin-sku1536
> > > +          - const: google,hoglin-sku1536
> > 
> > Is there actually such a thing as a 'hoglin-sku1536', i.e. the Pro qcard
> > with 64MB of SPI flash, or do they all have 8MB of flash?
> 
> The SPI flash is on the CRD mother-board and not on the qcards, so if you replace
> the qcards on the CRDs with 64MB flash you would need the hoglin-sku1536 to
> boot on those.

With such a configuration how does the bootloader know it should pass the kernel
the device tree for 'hoglin-sku1536' (pro) and not the non-pro variant? IIUC the
device tree is selected based on pin strappings on the mother-board, not the
qcard.