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Message-ID: <3f7257ee36dc44f162a87281c8279fd5bad91dea.camel@pengutronix.de>
Subject: Re: [PATCH 1/2] dt-bindings: phy: imx8mq-usb: add phy tuning
 properties
From:   Johannes Zink <j.zink@pengutronix.de>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>,
        vkoul@kernel.org, kishon@kernel.org, shawnguo@kernel.org,
        s.hauer@pengutronix.de, kernel@pengutronix.de, festevam@gmail.com,
        linux-imx@nxp.com, robh+dt@kernel.org,
        krzysztof.kozlowski+dt@linaro.org, jun.li@nxp.com,
        haibo.chen@nxp.com, linux-phy@lists.infradead.org,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        devicetree@vger.kernel.org
Date:   Wed, 05 Apr 2023 14:14:30 +0200
In-Reply-To: <5398cbe0-c681-5dd7-0b3e-3a586cc4915f@linaro.org>
References: <20230405112118.1256151-1-j.zink@pengutronix.de>
         <20230405112118.1256151-2-j.zink@pengutronix.de>
         <5398cbe0-c681-5dd7-0b3e-3a586cc4915f@linaro.org>
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Hi Krysztof,

thanks for your review, please find my questions below.

On Wed, 2023-04-05 at 13:51 +0200, Krzysztof Kozlowski wrote:
> [snip]
> >        A phandle to the regulator for USB VBUS.
> >  
> > +  fsl,phy-tx-vref-tune:
> > +    description:
> > +      HS DC Voltage level adjustment
> 
> "Level" in what units?
> 

The datasheet just shows percent, ranging from -6 to +24%, in 2%
increments. What unit would you suggest?

> > +    $ref: /schemas/types.yaml#/definitions/uint32
> > +    enum: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15,
> > 16]
> > +
> > +  fsl,phy-tx-rise-tune:
> > +    description:
> > +      HS Transmitter Rise/Fall Time Adjustment
> > +    $ref: /schemas/types.yaml#/definitions/uint32
> > +    enum: [0, 1, 2, 3]
> > +
> > +  fsl,phy-tx-preemp-amp-tune:
> > +    description:
> > +      HS Transmitter Pre-Emphasis Current Control
> 
> If this is current then use standard unit suffixes.

According to the datasheet this is in "unit amonts" of 600uA, basically
0x600uA, 1x600uA etc. Should I just suffix it with uA then?

> 
> > +    $ref: /schemas/types.yaml#/definitions/uint32
> > +    enum: [0, 1, 2, 3]
> > +
> > +  fsl,phy-tx-vboost-level:
> > +    description:
> > +      TX Voltage Boost Level
> > +    $ref: /schemas/types.yaml#/definitions/uint32
> > +    enum: [0, 2, 3]
> > +
> > +  fsl,phy-comp-dis-tune:
> > +    description:
> > +      Disconnect Threshold Adjustment
> > +    $ref: /schemas/types.yaml#/definitions/uint32
> > +    enum: [0, 1, 2, 3, 4, 5, 6, 7]
> > +
> > +  fsl,phy-pcs-tx-deemph-3p5db:
> > +    description:
> > +      TX De-Emphasis at 3.5 dB
> > +    $ref: /schemas/types.yaml#/definitions/uint32
> > +
> > +  fsl,phy-pcs-tx-swing-full:
> > +    description:
> > +      TX Amplitude
> 
> I have feeling you just pasted here short titles from datasheet. They
> are not that helpful.

ack, I will add some more text from the register description, since I
have no other source of information on these.

Best regards
Johannes

> 
> 
> 
> Best regards,
> Krzysztof
> 
> 
> 

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