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

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Message-ID: <c5b4613a-261d-429b-b59c-c264bc53e315@leica-geosystems.com>
Date: Thu, 11 Jan 2024 16:59:06 +0000
From: POPESCU Catalin <catalin.popescu@...ca-geosystems.com>
To: "Russell King (Oracle)" <linux@...linux.org.uk>
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 11.01.24 17:52, Russell King (Oracle) wrote:
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>
> On Thu, Jan 11, 2024 at 04:45:26PM +0000, POPESCU Catalin wrote:
>> On 11.01.24 17:35, Andrew Lunn wrote:
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>>>
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>>> 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 ]
>
> ?
I'm okay with that approach if there's no better one. I would need to
remove the register raw values tables from the driver and use a switch
statement to map those values to raw values.
>
> --
> RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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