linux-kernel - Re: [PATCH 1/3] dt-bindings: net: dp83826: add ti,cfg-dac-minus binding

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Message-ID: <ZaAcvwWbNmSpw/xt@shell.armlinux.org.uk>
Date: Thu, 11 Jan 2024 16:52:15 +0000
From: "Russell King (Oracle)" <linux@...linux.org.uk>
To: POPESCU Catalin <catalin.popescu@...ca-geosystems.com>
Cc: Andrew Lunn <andrew@...n.ch>,
	"davem@...emloft.net" <davem@...emloft.net>,
	"edumazet@...gle.com" <edumazet@...gle.com>,
	"kuba@...nel.org" <kuba@...nel.org>,
	"pabeni@...hat.com" <pabeni@...hat.com>,
	"robh+dt@...nel.org" <robh+dt@...nel.org>,
	"krzysztof.kozlowski+dt@...aro.org" <krzysztof.kozlowski+dt@...aro.org>,
	"conor+dt@...nel.org" <conor+dt@...nel.org>,
	"afd@...com" <afd@...com>,
	"hkallweit1@...il.com" <hkallweit1@...il.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	GEO-CHHER-bsp-development <bsp-development.geo@...ca-geosystems.com>
Subject: Re: [PATCH 1/3] dt-bindings: net: dp83826: add ti,cfg-dac-minus
 binding

On Thu, Jan 11, 2024 at 04:45:26PM +0000, POPESCU Catalin wrote:
> On 11.01.24 17:35, Andrew Lunn wrote:
> > [You don't often get email from andrew@...n.ch. Learn why this is important at https://aka.ms/LearnAboutSenderIdentification ]
> >
> > This email is not from Hexagon’s Office 365 instance. Please be careful while clicking links, opening attachments, or replying to this email.
> >
> >
> > On Thu, Jan 11, 2024 at 05:19:25PM +0100, Catalin Popescu wrote:
> >> Add property ti,cfg-dac-minus to allow for voltage tuning
> >> of logical level -1 of the MLT-3 encoded data.
> >>
> >> Signed-off-by: Catalin Popescu <catalin.popescu@...ca-geosystems.com>
> >> ---
> >>   Documentation/devicetree/bindings/net/ti,dp83822.yaml | 9 +++++++++
> >>   1 file changed, 9 insertions(+)
> >>
> >> diff --git a/Documentation/devicetree/bindings/net/ti,dp83822.yaml b/Documentation/devicetree/bindings/net/ti,dp83822.yaml
> >> index db74474207ed..2f010333be49 100644
> >> --- a/Documentation/devicetree/bindings/net/ti,dp83822.yaml
> >> +++ b/Documentation/devicetree/bindings/net/ti,dp83822.yaml
> >> @@ -62,6 +62,15 @@ properties:
> >>          for the PHY.  The internal delay for the PHY is fixed to 3.5ns relative
> >>          to transmit data.
> >>
> >> +  ti,cfg-dac-minus:
> >> +    description: |
> >> +       DP83826 PHY only.
> >> +       Sets the voltage ratio of the logical level -1 for the MLT-3 encoded data.
> >> +       0 = 50%, 1 = 56.25%, 2 = 62.50%, 3 = 68.75%, 4 = 75%, 5 = 81.25%, 6 = 87.50%,
> >> +       7 = 93.75%, 8 = 100%, 9 = 106.25%, 10 = 112.50%, 11 = 118.75%, 12 = 125%,
> >> +       13 = 131.25%, 14 = 137.50%, 15 = 143.75%, 16 = 150%.
> >> +    enum: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16]
> > We try to avoid register values in DT. We use real units. This is a
> > voltage you are configuring, so can you change the unit to millivolts?
> > Have the driver do the conversion of volts to register value.
> >
> > Is it possible to configure any of the other logical levels?
> 
> Hi Andrew,
> These are not raw register values and these are not voltage values but 
> voltage ratios. I'm mapping the voltage ratios to enum values [0-16] 
> which are converted to register raw values by the driver. I don't see a 
> better way to do this.

	enum: [ 5000, 5625, 6250, 6875, 7500, 8125, 8750, 9375, 10000,
		10625, 11250, 11875, 12500 13125, 13750, 14375, 15000 ]

?

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