linux-kernel - Re: [PATCH v2 1/2] dt-bindings: phy: Add qcom,dp-manual-pullup description

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Date:   Thu, 29 Dec 2022 19:57:29 +0100
From:   Stephan Gerhold <stephan@...hold.net>
To:     Bryan O'Donoghue <bryan.odonoghue@...aro.org>
Cc:     agross@...nel.org, andersson@...nel.org, vkoul@...nel.org,
        kishon@...nel.org, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, konrad.dybcio@...aro.org,
        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
Subject: Re: [PATCH v2 1/2] dt-bindings: phy: Add qcom,dp-manual-pullup
 description

On Thu, Dec 29, 2022 at 06:34:09PM +0000, Bryan O'Donoghue wrote:
> The original Qualcomm driver for the HighSpeed USB PHY contains a flag
> which tells the driver that the controller and PHY do not connect to VBUS.
> 
> In this case an external IC such as a Type-C port manager supplies VBUS and
> the VBUS signal is not routed to the SoC. This means we cannot detect the
> presence or absence of VBUS and cannot take action based on it.
> 
> Document the downstream boolean qcom,dp-manual-pullup to allow the HS PHY
> implement the necessary logic.
> 
> Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@...aro.org>

AFAIK it is not possible to route VBUS directly to the controller on
these SoCs so this property would likely be added to the SoC dtsi
(i.e. msm8916.dtsi and msm8939.dtsi) and used by all boards.

This means we could just bind this behavior to the existing SoC-specific
compatible (i.e. of_device_is_compatible(..., "qcom,usb-hs-phy-msm8916"))
and avoid having an extra property.

Thoughts?

Thanks,
Stephan

> ---
>  Documentation/devicetree/bindings/phy/qcom,usb-hs-phy.yaml | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/phy/qcom,usb-hs-phy.yaml b/Documentation/devicetree/bindings/phy/qcom,usb-hs-phy.yaml
> index aa97478dd0161..c55a59df71ad0 100644
> --- a/Documentation/devicetree/bindings/phy/qcom,usb-hs-phy.yaml
> +++ b/Documentation/devicetree/bindings/phy/qcom,usb-hs-phy.yaml
> @@ -80,6 +80,13 @@ properties:
>              the address is offset from the ULPI_EXT_VENDOR_SPECIFIC address
>          - description: value
>  
> +  qcom,dp-manual-pullup:
> +    type: boolean
> +    description: This flag indicates to the HS USB PHY driver that it should
> +                 enable or disable an internal pullup when powering on or
> +                 powering off the HS PHY instead of toggling the value when VBUS
> +                 is absent or present.
> +
>  required:
>    - clocks
>    - clock-names
> -- 
> 2.34.1
>