Re: [PATCH v2 1/3] dt-bindings: phy: imx8mq-usb: improve some tuning properties

[Xu Yang <xu.yang_2@nxp.com>]

Hi Frank,

On Tue, Apr 29, 2025 at 01:55:26AM -0400, Frank Li wrote:
> On Tue, Apr 29, 2025 at 11:30:07AM +0800, Xu Yang wrote:
> > Commit b2e75563dc39 ("dt-bindings: phy: imx8mq-usb: add phy tuning
> > properties") add many tuning properties, but some parameter value doesn't
> > match the register description. It made some changes based on the original
> > value: add offset to a negative number so turn it to a non-negative number.
> > However, it's not easy to find an exact tuning value from register field
> > with such conversion.
> >
> > Because device-tree supports negative parameter number, this will improve
> > some propertie's parameter.
> >
> > Mainly include below properties:
> >  - fsl,phy-tx-vref-tune-percent
> >  - fsl,phy-tx-rise-tune-percent
> >  - fsl,phy-comp-dis-tune-percent
> 
> It should be standard unit. for example 0% to 100%. DT don't prefer you
> direct use register value.

Yes. The dtschema and driver already use standard unit.
This patch is going to correct the unintuitive expression.

Take tx-rise-tune as example, register field as below:

		00b - + 3%
 [21:20]	01b - 0 (default)
TXRISETUNE	10b - - 1%
		11b - - 3%

The valid value of tx-rise-tune is [-3%, +3%]. However, the current dtschema
add an offset which caused the valid value to [97%, 103%].

fsl,phy-tx-rise-tune-percent:
  minimum: 97
  maximum: 103

When I first added tuning property to DTS, I thought I was reading the wrong
dtschema. Other users may meet such confuse too. 

Thanks,
Xu Yang

> 
> Frank
> 
> >
> > The parameter value of above 3 properties are USB PHY specific. i.MX8MP
> > and i.MX95 USB PHY has different meanings. So this add restrictions for
> > them.
> >
> >  - fsl,phy-tx-vboost-level-microvolt
> >
> > For this property, the parameter value is wrong in register description.
> > This will correct it according to true value.
> >
> > For detailed info, please refer to i.MX8MP and i.MX95 latest reference
> > manual.
> >
> > Signed-off-by: Xu Yang <xu.yang_2@nxp.com>
> >
> > ---
> > Changes in v2:
> >  - keep widest constraints
> >  - use multipleOf for some properties
> > ---
> >  .../bindings/phy/fsl,imx8mq-usb-phy.yaml      | 60 +++++++++++++++----
> >  1 file changed, 49 insertions(+), 11 deletions(-)
> >
> > diff --git a/Documentation/devicetree/bindings/phy/fsl,imx8mq-usb-phy.yaml b/Documentation/devicetree/bindings/phy/fsl,imx8mq-usb-phy.yaml
> > index daee0c0fc915..71e5940ef4b8 100644
> > --- a/Documentation/devicetree/bindings/phy/fsl,imx8mq-usb-phy.yaml
> > +++ b/Documentation/devicetree/bindings/phy/fsl,imx8mq-usb-phy.yaml
> > @@ -42,16 +42,17 @@ properties:
> >
> >    fsl,phy-tx-vref-tune-percent:
> >      description:
> > -      Tunes the HS DC level relative to the nominal level
> > -    minimum: 94
> > -    maximum: 124
> > +      Tunes the HS DC level relative to the nominal level. It varies
> > +      between different PHY versions
> > +    minimum: -1000
> > +    maximum: 875
> >
> >    fsl,phy-tx-rise-tune-percent:
> >      description:
> >        Adjusts the rise/fall time duration of the HS waveform relative to
> > -      its nominal value
> > -    minimum: 97
> > -    maximum: 103
> > +      its nominal value. It varies between different PHY versions
> > +    minimum: -10
> > +    maximum: 20
> >
> >    fsl,phy-tx-preemp-amp-tune-microamp:
> >      description:
> > @@ -63,15 +64,14 @@ properties:
> >    fsl,phy-tx-vboost-level-microvolt:
> >      description:
> >        Adjust the boosted transmit launch pk-pk differential amplitude
> > -    minimum: 880
> > -    maximum: 1120
> > +    enum: [844, 1008, 1156]
> >
> >    fsl,phy-comp-dis-tune-percent:
> >      description:
> >        Adjust the voltage level used to detect a disconnect event at the host
> > -      relative to the nominal value
> > -    minimum: 91
> > -    maximum: 115
> > +      relative to the nominal value. It varies between different PHY versions
> > +    minimum: -60
> > +    maximum: 45
> >
> >    fsl,phy-pcs-tx-deemph-3p5db-attenuation-db:
> >      description:
> > @@ -112,6 +112,44 @@ allOf:
> >          reg:
> >            maxItems: 1
> >
> > +  - if:
> > +      properties:
> > +        compatible:
> > +          enum:
> > +            - fsl,imx8mq-usb-phy
> > +            - fsl,imx8mp-usb-phy
> > +    then:
> > +      properties:
> > +        fsl,phy-tx-vref-tune-percent:
> > +          minimum: -6
> > +          maximum: 24
> > +          multipleOf: 2
> > +        fsl,phy-tx-rise-tune-percent:
> > +          enum: [-3, -1, 0, 3]
> > +        fsl,phy-comp-dis-tune-percent:
> > +          enum: [-9, -6, -3, 0, 4, 7, 11, 15]
> > +
> > +  - if:
> > +      properties:
> > +        compatible:
> > +          contains:
> > +            enum:
> > +              - fsl,imx95-usb-phy
> > +    then:
> > +      properties:
> > +        fsl,phy-tx-vref-tune-percent:
> > +          description: 100x the original
> > +          minimum: -1000
> > +          maximum: 875
> > +          multipleOf: 125
> > +        fsl,phy-tx-rise-tune-percent:
> > +          enum: [-10, 0, 15, 20]
> > +        fsl,phy-comp-dis-tune-percent:
> > +          description: 10x the original
> > +          minimum: -60
> > +          maximum: 45
> > +          multipleOf: 15
> > +
> >    - if:
> >        required:
> >          - orientation-switch
> > --
> > 2.34.1
> >