linux-kernel - Re: [PATCH 1/2] dt-bindings: usb: qcom,snps-dwc3: Add support for firmware-managed resources

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Message-ID: <f96ed414-f69b-4eb6-91d5-c1db7d2a87be@oss.qualcomm.com>
Date: Mon, 1 Dec 2025 17:05:42 +0530
From: Sriram Dash <sriram.dash@....qualcomm.com>
To: Krzysztof Kozlowski <krzk@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Wesley Cheng <quic_wcheng@...cinc.com>,
        Thinh Nguyen <Thinh.Nguyen@...opsys.com>
Cc: jack.pham@....qualcomm.com, faisal.hassan@....qualcomm.com,
        krishna.kurapati@....qualcomm.com, andersson@...nel.org,
        linux-arm-msm@...r.kernel.org, linux-usb@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        Konrad Dybcio <konradybcio@...nel.org>
Subject: Re: [PATCH 1/2] dt-bindings: usb: qcom,snps-dwc3: Add support for
 firmware-managed resources

On 11/27/2025 5:43 PM, Krzysztof Kozlowski wrote:
> On 27/11/2025 11:31, Sriram Dash wrote:
>> On Qualcomm automotive SoC sa8255p, platform resources like clocks,
>> interconnect, resets, regulators and GDSC are configured remotely by
>> firmware.
>>
>> PM OPP is used to abstract these resources in firmware and SCMI perf
>> protocol is used to request resource operations by using runtime PM
>> framework APIs such as pm_runtime_get/put_sync to signal firmware
>> for managing resources accordingly for respective perf levels.
>>
>> "qcom,snps-dwc3-fw-managed" compatible helps determine if
>> the device's resources are managed by firmware.
>> Additionally, it makes the power-domains property mandatory
>> and excludes the clocks property for the controller.
>>
>> Signed-off-by: Sriram Dash <sriram.dash@....qualcomm.com>
>> ---
>>  .../devicetree/bindings/usb/qcom,snps-dwc3.yaml    | 173 +++++++++++++--------
>>  1 file changed, 111 insertions(+), 62 deletions(-)
>>
>> diff --git a/Documentation/devicetree/bindings/usb/qcom,snps-dwc3.yaml b/Documentation/devicetree/bindings/usb/qcom,snps-dwc3.yaml
>> index 8cee7c5582f2..d2d1b42fbb07 100644
>> --- a/Documentation/devicetree/bindings/usb/qcom,snps-dwc3.yaml
>> +++ b/Documentation/devicetree/bindings/usb/qcom,snps-dwc3.yaml
>> @@ -12,68 +12,65 @@ maintainers:
>>  description:
>>    Describes the Qualcomm USB block, based on Synopsys DWC3.
>>  
>> -select:
>> -  properties:
>> -    compatible:
>> -      contains:
>> -        const: qcom,snps-dwc3
>> -  required:
>> -    - compatible
> I wonder why do you think dropping some code is fine...
>
>
>> +      - items:
>> +          - enum:
>> +              - qcom,sa8255p-dwc3
>> +          - const: qcom,snps-dwc3-fw-managed
> No, you cannot keep coming with more generic compatibles.
>
> If you want generic a compatible, you already have - qcom,snps-dwc3 -
> and that "generic" part already said that everything is compatible with it.
>
> Now you claim that existing generic compatible qcom,snps-dwc3 is not
> generic enough and you need one more generic compatible.
>
> Next year you will say that two generic compatibles are not generic
> enough and you need third generic compatible.
>
> In two years we will learn that three generic compatibles are not enough...
>
> I think I was complaining on the lists a lot on this, so I am surprised
> it is still coming back.
>
> So no, you cannot claim that you need more generic compatibles because
> one generic is not generic. NAK.


Hi Krzysztof,

understood. Shall i make it platform specific then ? For example,

Say, For x1e80100, where platform resources are not managed by firmware,
use compatible = "qcom,x1e80100-dwc3", "qcom,snps-dwc3";

For Soc 8255p, where platform resources are managed by firmware, still
will use the generic compatible say,  compatible = "qcom,sa8255p-dwc3",
"qcom,snps-dwc3";


and in the driver, we will handle with the platform specific compatible.

static const struct of_device_id dwc3_qcom_of_match[] = {
        {
                .compatible     = "qcom,sa8255p-dwc3",
                .data           = (void *)true,
        },
        { .compatible = "qcom,snps-dwc3" },
        { }
};


For any other Soc where the resources are managed by firmware, we can
still reuse the compatible qcom,sa8255p-dwc3

say compatible = "qcom-foo-dwc3", "qcom,sa8255p-dwc3", "qcom,snps-dwc3";

compatible = "qcom-bar-dwc3", "qcom,sa8255p-dwc3", "qcom,snps-dwc3";

...


>
> Best regards,
> Krzysztof