Re: [PATCH v8 1/3] dt-bindings: phy: qcom,usb-snps-femto-v2: Add phy override params bindings

[Vinod Koul <vkoul@kernel.org>]

On 01-06-22, 12:26, Krishna Kurapati wrote:
> From: Sandeep Maheswaram <quic_c_sanm@quicinc.com>
> 
> Add device tree bindings for SNPS phy tuning parameters.
> 
> Signed-off-by: Sandeep Maheswaram <quic_c_sanm@quicinc.com>
> Signed-off-by: Krishna Kurapati <quic_kriskura@quicinc.com>
> Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
> ---
>  .../bindings/phy/qcom,usb-snps-femto-v2.yaml       | 96 ++++++++++++++++++++++
>  1 file changed, 96 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..daeeb04 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 +53,102 @@ properties:
>    vdda33-supply:
>      description: phandle to the regulator 3.3V supply node.
>  
> +  qcom,hs-disconnect-bp:
> +    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%).
> +      The hardware accepts only discrete values. The value closest to the
> +      provided input will be chosen as the override value for this param.
> +    minimum: -272
> +    maximum: 2156
> +
> +  qcom,squelch-detector-bp:
> +    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.
> +    minimum: -2090
> +    maximum: 1590
> +
> +  qcom,hs-amplitude-bp:
> +    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.
> +    minimum: -660
> +    maximum: 2670
> +
> +  qcom,pre-emphasis-duration-bp:
> +    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.
> +    minimum: 10000
> +    maximum: 20000
> +
> +  qcom,pre-emphasis-amplitude-bp:
> +    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.
> +    minimum: 10000
> +    maximum: 40000
> +
> +  qcom,hs-rise-fall-time-bp:
> +    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.
> +    minimum: -4100
> +    maximum: 5430
> +
> +  qcom,hs-crossover-voltage-microvolt:
> +    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.
> +    minimum: -31000
> +    maximum: 28000
> +
> +  qcom,hs-output-impedance-micro-ohms:
> +    description:
> +      In some applications, there can be significant series resistance
> +      on the D+ and D- paths between the transceiver and cable. This adjusts
> +      the driver source impedance to compensate for added series
> +      resistance on the USB. The values defined are in milli ohms.
> +      The hardware accepts only discrete values. The value closest to the
> +      provided input will be chosen as the override value for this param.
> +    minimum: -2300000
> +    maximum: 6100000
> +
> +  qcom,ls-fs-output-impedance-bp:
> +    description:
> +      This adjusts the low- and full-speed single-ended source
> +      impedance while driving high. The following adjustment values are based
> +      on nominal process, voltage, and temperature.
> +      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.
> +    minimum: -1053
> +    maximum: 1310

do we need all these values in DT, till now we have these in driver..
what is the reasoning to add these in DT instead?

-- 
~Vinod