linux-kernel - Re: [PATCH v2 1/3] dt-bindings: usb: qcom,dwc3: Add multi-pd bindings for dwc3 qcom

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Date:   Mon, 25 Oct 2021 12:10:35 -0700
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Sandeep Maheswaram <quic_c_sanm@...cinc.com>
Cc:     Rob Herring <robh+dt@...nel.org>, Andy Gross <agross@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Felipe Balbi <balbi@...nel.org>,
        Stephen Boyd <swboyd@...omium.org>,
        Doug Anderson <dianders@...omium.org>,
        Matthias Kaehlcke <mka@...omium.org>,
        devicetree@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        quic_pkondeti@...cinc.com, quic_ppratap@...cinc.com
Subject: Re: [PATCH v2 1/3] dt-bindings: usb: qcom,dwc3: Add multi-pd
 bindings for dwc3 qcom

On Mon 25 Oct 02:07 PDT 2021, Sandeep Maheswaram wrote:

> Add multi pd bindings to set performance state for cx domain
> to maintain minimum corner voltage for USB clocks.
> 
> Signed-off-by: Sandeep Maheswaram <quic_c_sanm@...cinc.com>
> ---
> v2:
> Make cx domain mandatory.
> 
>  Documentation/devicetree/bindings/usb/qcom,dwc3.yaml | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/devicetree/bindings/usb/qcom,dwc3.yaml b/Documentation/devicetree/bindings/usb/qcom,dwc3.yaml
> index 2bdaba0..fd595a8 100644
> --- a/Documentation/devicetree/bindings/usb/qcom,dwc3.yaml
> +++ b/Documentation/devicetree/bindings/usb/qcom,dwc3.yaml
> @@ -42,7 +42,13 @@ properties:
>  
>    power-domains:
>      description: specifies a phandle to PM domain provider node
> -    maxItems: 1
> +    minItems: 2
> +    items:
> +      - description: cx power domain
> +      - description: USB gdsc power domain
> +
> +  required-opps:
> +    description: specifies the performance state to power domain

I'm still worried about the fact that we can't just rely on the USB GDSC
being a subdomin of CX in order to just "turn on" CX.

Afaict accepting this path forward means that for any device that sits
in a GDSC power domain we will have to replicate this series for the
related driver.

I mentioned this in v1, but I don't think we reached a conclusion.

Regards,
Bjorn

>  
>    clocks:
>      description:
> -- 
> 2.7.4
>