linux-kernel - Re: [RFC 1/8] dt-bindings: usb: qcom,dwc3: Add bindings to enable runtime

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Message-ID: <dbf4a48e-c808-4611-96b1-563ece1e451a@linaro.org>
Date:   Thu, 2 Nov 2023 18:40:57 +0000
From:   Caleb Connolly <caleb.connolly@...aro.org>
To:     Krishna Kurapati PSSNV <quic_kriskura@...cinc.com>,
        Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>
Cc:     quic_wcheng@...cinc.com, linux-usb@...r.kernel.org,
        Conor Dooley <conor+dt@...nel.org>,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        Andy Gross <agross@...nel.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Rob Herring <robh+dt@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        devicetree@...r.kernel.org, quic_ppratap@...cinc.com,
        quic_jackp@...cinc.com
Subject: Re: [RFC 1/8] dt-bindings: usb: qcom,dwc3: Add bindings to enable
 runtime

> Hi Caleb,
> 
>    There are two types of platforms, some use extcon and some use 
> role-switch to deliver vbus/id notifications. Extcon targets already 
> have this qscratch modifications present today in vbus and id handlers. 
> But for role-switch based targets we don't have any way to get this 
> notification to dwc3-qcom. In this implementation, I wanted to get those 
> notications from core to glue and for this we implenented vendor hooks.
> 
> The property added has been used to do two things:
> 
> 1. Register glue's vendor hooks to core driver
> 2. Do runtime_allow for glue (and by default for core as the dt is not 
> flattened)
> 
> In case of extcon, we don't want to register vendor hooks as 
> notifications are not necessary.

Could it just be enabled when role_switch is present then?
> 
> For xhci, we opted to enable runtime from userspace.

>>>         HS/FS/LS modes are supported.
>>>       type: boolean
>>> +  qcom,enable-rt:
>>> +    description:
>>> +      If present, register vendor hooks to facilitate runtime 
>>> suspend/resume
>>> +    type: boolean
>>
>> A Krzysztof pointed out, properties should define the hardware 
>> behaviour, not tot the implementation details. For this case the 
>> hardware isn't wired up to vbus, so maybe something like "qcom,no-vbus"?
>>> +
> 
> On all targets, vbus is not routed to hardware. This vbus toggle 
> indication is given to controller via qscratch only.
> 
> Regards,
> Krishna,

-- 
// Caleb (they/them)