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

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Date:   Tue, 20 Dec 2022 19:11:57 +0200
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Rajendra Nayak <quic_rjendra@...cinc.com>,
        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 20/12/2022 18:20, Rajendra Nayak wrote:
> 
> 
> 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.

Just to clarify things, when you mention pro SKU, is it a separate SoC 
revision (like sc7280-pro vs bare sc7280), or is it a CRD revision (CRD 
Pro vs bare CRD)?

-- 
With best wishes
Dmitry