linux-kernel - Re: [PATCH v2 1/3] dt-bindings: phy: qcom,usb-snps-femto-v2: Add phy override params bindings

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Date:   Thu, 3 Mar 2022 16:59:22 +0100
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>
To:     Sandeep Maheswaram <quic_c_sanm@...cinc.com>,
        Rob Herring <robh+dt@...nel.org>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Kishon Vijay Abraham I <kishon@...com>,
        Vinod Koul <vkoul@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Wesley Cheng <wcheng@...eaurora.org>,
        Stephen Boyd <swboyd@...omium.org>,
        Doug Anderson <dianders@...omium.org>,
        Matthias Kaehlcke <mka@...omium.org>
Cc:     devicetree@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-phy@...ts.infradead.org,
        linux-usb@...r.kernel.org, quic_pkondeti@...cinc.com,
        quic_ppratap@...cinc.com
Subject: Re: [PATCH v2 1/3] dt-bindings: phy: qcom,usb-snps-femto-v2: Add phy
 override params bindings

On 03/03/2022 07:13, Sandeep Maheswaram wrote:
> Add device tree bindings for SNPS phy tuning parameters.
> 
> Signed-off-by: Sandeep Maheswaram <quic_c_sanm@...cinc.com>
> ---
>  .../bindings/phy/qcom,usb-snps-femto-v2.yaml       | 125 +++++++++++++++++++++
>  1 file changed, 125 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/phy/qcom,usb-snps-femto-v2.yaml b/Documentation/devicetree/bindings/phy/qcom,usb-snps-femto-v2.yaml
> index 0dfe691..227c097 100644
> --- a/Documentation/devicetree/bindings/phy/qcom,usb-snps-femto-v2.yaml
> +++ b/Documentation/devicetree/bindings/phy/qcom,usb-snps-femto-v2.yaml
> @@ -50,6 +50,131 @@ properties:
>    vdda33-supply:
>      description: phandle to the regulator 3.3V supply node.
>  
> +  qcom,hs-disconnect:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    description:
> +      This adjusts the voltage level for the threshold used to
> +      detect a disconnect event at the host. Possible values are.

':', instead of full stop.

> +      7 -> +21.56%
> +      6 -> +17.43%
> +      5 -> +13.32%
> +      4 -> +9.73%
> +      3 -> +6.3
> +      2 -> +3.17%
> +      1 -> 0, Design default%

Use "default:" instead. Here and in other places.

> +      0 -> -2.72%

In current form this should be an enum... but actually current form is
wrong. You should not store register values in DT. What if next version
of hardware has a different meaning of these values?

Instead, you should store here meaningful values, not register values.

This applies to all cases below.

> +
> +  qcom,squelch-detector:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    description:
> +      This adjusts the voltage level for the threshold used to
> +      detect valid high-speed data. Possible values are
> +      7-> -20.90%
> +      6-> -15.60%
> +      5-> -10.30%
> +      4-> -5.30%
> +      3-> 0, Design default%
> +      2-> +5.30%
> +      1-> +10.60%
> +      0-> +15.90%
> +
> +  qcom,hs-amplitude:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    description:
> +      This adjusts the high-speed DC level voltage.
> +      Possible values are
> +      15-> +26.70%
> +      14-> +24.30%
> +      13-> +22.20%
> +      12-> +20.00%
> +      11-> +17.80%
> +      10-> +15.60%
> +      9-> +13.30%
> +      8-> +11.10%
> +      7-> +8.90%
> +      6-> +6.50%
> +      5-> +4.40%
> +      4-> +2.30%
> +      3-> 0, Design default%
> +      2-> -2.20%
> +      1-> -4.40%
> +      0-> -6.60%
> +
> +  qcom,pre-emphasis-duration:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    description:
> +      This signal controls the duration for which the
> +      HS pre-emphasis current is sourced onto DP<#> or DM<#>.
> +      The HS Transmitter pre-emphasis duration is defined in terms of
> +      unit amounts. One unit of pre-emphasis duration is approximately
> +      650 ps and is defined as 1X pre-emphasis duration.
> +      Possible values are
> +      1-> 1x, short pre-emphasis current duration
> +      0-> 2x, long pre-emphasis current duration

I could understand encoding of percentages in way of register value, but
a boolean flag is too much.


Best regards,
Krzysztof