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

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Message-ID: <e269300d-539e-9eb8-8b3c-d309f3abca1b@quicinc.com>
Date:   Tue, 20 Dec 2022 21:50:06 +0530
From:   Rajendra Nayak <quic_rjendra@...cinc.com>
To:     Matthias Kaehlcke <mka@...omium.org>
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 12/20/2022 8:00 PM, Matthias Kaehlcke wrote:
> 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.

The device tree is selected based on the pin strappings _and_ additional logic
to dynamically identify modem/non-modem(wifi) as well as pro/non-pro SKUs which
was added in the bootloaders.