linux-kernel - Re: [RFC 1/3] dt-bindings: usb: qcom,dwc3: Add support for multiple power-domains

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Message-ID: <986b49f5-6a4a-430d-ba6a-2f387f2a262a@quicinc.com>
Date: Tue, 5 Mar 2024 23:33:33 +0530
From: Sriram Dash <quic_sriramd@...cinc.com>
To: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        <andersson@...nel.org>, <konrad.dybcio@...aro.org>, <vkoul@...nel.org>,
        <kishon@...nel.org>, <robh@...nel.org>,
        <krzysztof.kozlowski+dt@...aro.org>, <conor+dt@...nel.org>,
        <gregkh@...uxfoundation.org>, <quic_wcheng@...cinc.com>,
        <Thinh.Nguyen@...opsys.com>, <p.zabel@...gutronix.de>,
        <linux-arm-msm@...r.kernel.org>, <linux-phy@...ts.infradead.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-usb@...r.kernel.org>, <quic_psodagud@...cinc.com>,
        <quic_nkela@...cinc.com>, <manivannan.sadhasivam@...aro.org>,
        <ulf.hansson@...aro.org>, <sudeep.holla@....com>,
        <quic_shazhuss@...cinc.com>
Subject: Re: [RFC 1/3] dt-bindings: usb: qcom,dwc3: Add support for multiple
 power-domains

On 3/5/2024 10:37 PM, Krzysztof Kozlowski wrote:
> On 05/03/2024 17:57, Sriram Dash wrote:
>> Some target systems allow multiple resources to be managed by firmware.
>> On these targets, tasks related to clocks, regulators, resets, and
>> interconnects can be delegated to the firmware, while the remaining
>> responsibilities are handled by Linux.
>>
>> To support the management of partial resources in Linux and leave the rest
>> to firmware, multiple power domains are introduced. Each power domain can
>> manage one or more resources, depending on the specific use case.
>>
>> These power domains handle SCMI calls to the firmware, enabling the
>> activation and deactivation of firmware-managed resources.
>>
>> Signed-off-by: Sriram Dash <quic_sriramd@...cinc.com>
>> ---
>>   .../phy/qcom,sc8280xp-qmp-usb3-uni-phy.yaml        | 74 ++++++++++++++++------
>>   .../bindings/phy/qcom,usb-snps-femto-v2.yaml       | 49 ++++++++++++--
>>   .../devicetree/bindings/usb/qcom,dwc3.yaml         | 37 ++++++++++-
>>   3 files changed, 130 insertions(+), 30 deletions(-)
>>
>> diff --git a/Documentation/devicetree/bindings/phy/qcom,sc8280xp-qmp-usb3-uni-phy.yaml b/Documentation/devicetree/bindings/phy/qcom,sc8280xp-qmp-usb3-uni-phy.yaml
>> index 1e2d4dd..53b9ba9 100644
>> --- a/Documentation/devicetree/bindings/phy/qcom,sc8280xp-qmp-usb3-uni-phy.yaml
>> +++ b/Documentation/devicetree/bindings/phy/qcom,sc8280xp-qmp-usb3-uni-phy.yaml
>> @@ -44,7 +44,32 @@ properties:
>>       maxItems: 5
>>   
>>     power-domains:
>> -    maxItems: 1
>> +    description: specifies a phandle to PM domain provider node
> 
> Please drop all redundant descriptions. Adding them is not even related
> to this patch.
> 

Thanks Krzysztof for the super quick response !
Sure. will drop the description for power-domain
and power-doamin-names.

>> +    minItems: 1
>> +    maxItems: 2
>> +
>> +  power-domain-names:
>> +    description:
>> +      A list of power domain name strings sorted in the same order as the
>> +      power-domains property.
>> +
>> +      For platforms where some resource are firmware managed, the name
>> +      corresponding to the index of an SCMI domain provider can be
>> +      "usb_core" or "usb_transfer".
>> +    items:
>> +      - const: usb_core
>> +      - const: usb_transfer
> 
> How is this related to fw-managed? I fail to see it. Don't mix
> independent problems in one patch.
> 

Some of the the resources like clocks, regulators, etc will be 
controlled by the firmware instead of OS. However, some resources
still will be controlled by OS (interrupts for example).

So, to support the management of partial resources in Linux, and
offload the other resource management to firmware, multiple power 
domains are introduced. They will be corresponding to different
hw blocks.

Do you suggest splitting the addition of power-domain-names and
addition of fw-managed property in separate patches for bindings!

>> +
>> +  qmp,fw-managed:
> 
> Please do not upstream vendor code directly, but perform basic
> adjustment to upstream Linux kernel. There is no such company as gmp.
> 
> Run this first through your internal review process.
> 

This property is newly introduced for the qmp superspeed phy and
similar dt properties are introduced for hsphy and dwc3 qcom
controller glue layer driver. It will govern the suspend/ resume
of the resources (by firmware or OS) as required.

>> +    description:
>> +      Some targets allow multiple resources to be managed by firmware.
> 
> You miss clear mapping between compatibles and this property - allOf
> restricting it to specific SoCs.
> 
> Is this different property than qcom,controlled-remotely?
> 

No. unlike "qcom,controlled-remotely", which lets the OS know only to
consume the resources, "qmp,fw-managed" property will decide the
resource management and trigger the suspend/ resume from OS, which
will be handled by the firmware.

Can we reuse the property "qcom,controlled-remotely" here? If so,
we can replace the aformentioned property with qmp phy, hsphy, and
controller glue layer property. Please suggest.

> Best regards,
> Krzysztof
>