linux-kernel - Re: [v4 1/3] dt-bindings: phy: qcom,usb-snps-femto-v2: Add phy override params bindings

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Date:   Fri, 13 May 2022 12:32:51 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Krishna Kurapati PSSNV <quic_kriskura@...cinc.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Stephen Boyd <swboyd@...omium.org>,
        Doug Anderson <dianders@...omium.org>,
        Matthias Kaehlcke <mka@...omium.org>,
        Wesley Cheng <quic_wcheng@...cinc.com>,
        Vinod Koul <vkoul@...nel.org>
Cc:     devicetree@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-phy@...ts.infradead.org, quic_pkondeti@...cinc.com,
        quic_ppratap@...cinc.com, quic_vpulyala@...cinc.com,
        Sandeep Maheswaram <quic_c_sanm@...cinc.com>
Subject: Re: [v4 1/3] dt-bindings: phy: qcom,usb-snps-femto-v2: Add phy
 override params bindings

On 13/05/2022 09:33, Krishna Kurapati PSSNV wrote:
> 
> On 5/11/2022 11:49 PM, Krzysztof Kozlowski wrote:
>> On 11/05/2022 17:26, Krishna Kurapati wrote:
>>> From: Sandeep Maheswaram <quic_c_sanm@...cinc.com>
>>>
>>> Add device tree bindings for SNPS phy tuning parameters.
>>>
>>> Signed-off-by: Sandeep Maheswaram <quic_c_sanm@...cinc.com>
>>> Signed-off-by: Krishna Kurapati <quic_kriskura@...cinc.com>
>>> ---
>>>   .../bindings/phy/qcom,usb-snps-femto-v2.yaml       | 87 ++++++++++++++++++++++
>>>   1 file changed, 87 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 1ce251d..70efffe 100644
>>> --- a/Documentation/devicetree/bindings/phy/qcom,usb-snps-femto-v2.yaml
>>> +++ b/Documentation/devicetree/bindings/phy/qcom,usb-snps-femto-v2.yaml
>>> @@ -53,6 +53,93 @@ properties:
>>>     vdda33-supply:
>>>       description: phandle to the regulator 3.3V supply node.
>>>   
>>> +  qcom,hs-disconnect-bps:
>>> +    $ref: /schemas/types.yaml#/definitions/int32
>>> +    description:
>>> +      This adjusts the voltage level for the threshold used to
>>> +      detect a disconnect event at the host. Possible values are.
>>> +      The values defined are in multiples of basis points (1bp = 0.01%).
>> This means there is some minimum and maximum (100%)?
>>
>>> +      The hardware accepts only discrete values. The value closest to the
>>> +      provided input will be chosen as the override value for this param.
>>> +
>>> +  qcom,squelch-detector-bps:
>>> +    $ref: /schemas/types.yaml#/definitions/int32
>>> +    description:
>>> +      This adjusts the voltage level for the threshold used to
>>> +      detect valid high-speed data.
>>> +      The values defined are in multiples of basis points (1bp = 0.01%).
>>> +      The hardware accepts only discrete values. The value closest to the
>>> +      provided input will be chosen as the override value for this param.
>>> +
>>> +  qcom,hs-amplitude-bps:
>>> +    $ref: /schemas/types.yaml#/definitions/int32
>>> +    description:
>>> +      This adjusts the high-speed DC level voltage.
>>> +      The values defined are in multiples of basis points (1bp = 0.01%).
>>> +      The hardware accepts only discrete values. The value closest to the
>>> +      provided input will be chosen as the override value for this param.
>>> +
>>> +  qcom,pre-emphasis-duration-bps:
>>> +    $ref: /schemas/types.yaml#/definitions/int32
>>> +    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.
>>> +      The values defined are in multiples of basis points (1bp = 0.01%).
>>> +      The hardware accepts only discrete values. The value closest to the
>>> +      provided input will be chosen as the override value for this param.
>>> +
>>> +  qcom,pre-emphasis-amplitude-bps:
>>> +    $ref: /schemas/types.yaml#/definitions/int32
>>> +    description:
>>> +      This signal controls the amount of current sourced to
>>> +      DP<#> and DM<#> after a J-to-K or K-to-J transition.
>>> +      The HS Transmitter pre-emphasis current is defined in terms of unit
>>> +      amounts. One unit amount is approximately 2 mA and is defined as
>>> +      1X pre-emphasis current.
>>> +      The values defined are in multiples of basis points (1bp = 0.01%).
>>> +      The hardware accepts only discrete values. The value closest to the
>>> +      provided input will be chosen as the override value for this param.
>>> +
>>> +  qcom,hs-rise-fall-time-bps:
>>> +    $ref: /schemas/types.yaml#/definitions/int32
>>> +    description:
>>> +      This adjusts the rise/fall times of the high-speed waveform.
>>> +      The values defined are in multiples of basis points (1bp = 0.01%).
>>> +      The hardware accepts only discrete values. The value closest to the
>>> +      provided input will be chosen as the override value for this param.
>>> +
>>> +  qcom,hs-crossover-voltage-mv:
>>> +    $ref: /schemas/types.yaml#/definitions/int32
>>> +    description:
>>> +      This adjusts the voltage at which the DP<#> and DM<#>
>>> +      signals cross while transmitting in HS mode.
>>> +      The values defined are in milli volts. The hardware accepts only
>>> +      discrete values. The value closest to the provided input will be
>>> +      chosen as the override value for this param.
>>> +
>>> +  qcom,hs-output-impedance-mohm:
>>> +    $ref: /schemas/types.yaml#/definitions/int32
>> Here and in other places, please use standard units. See
>> dtschema/schemas/property-units.yaml in dtschema repo.
>>
>>
>> Best regards,
>> Krzysztof
> 
> Hi Krzystof, thanks for the input.
> 
> I see there are microvolt and microohm units present in 
> schemas/property-units.yaml
> 
> Would it be possible to add bps (basis point) to the list of standard 
> units if it makes sense to use it ?

There is already 'percent' so 'bp' could be as well, makes sense to me.
I can send a patch for it and we'll see what Rob says.


Best regards,
Krzysztof