netdev - Re: [PATCH v2 1/2] dt-bindings: net: dp83826: support TX data voltage tuning

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Date: Thu, 8 Feb 2024 09:19:43 +0000
From: POPESCU Catalin <catalin.popescu@...ca-geosystems.com>
To: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
	"davem@...emloft.net" <davem@...emloft.net>, "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>,
	"andrew@...n.ch" <andrew@...n.ch>, "hkallweit1@...il.com"
	<hkallweit1@...il.com>, "linux@...linux.org.uk" <linux@...linux.org.uk>
CC: "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>,
	"m.felsch@...gutronix.de" <m.felsch@...gutronix.de>
Subject: Re: [PATCH v2 1/2] dt-bindings: net: dp83826: support TX data voltage
 tuning

On 08.02.24 10:12, Krzysztof Kozlowski wrote:
> This email is not from Hexagon’s Office 365 instance. Please be careful while clicking links, opening attachments, or replying to this email.
>
>
> On 08/02/2024 10:08, POPESCU Catalin wrote:
>> On 08.02.24 09:50, Krzysztof Kozlowski wrote:
>>> This email is not from Hexagon’s Office 365 instance. Please be careful while clicking links, opening attachments, or replying to this email.
>>>
>>>
>>> On 08/02/2024 09:48, POPESCU Catalin wrote:
>>>> On 08.02.24 08:35, Krzysztof Kozlowski wrote:
>>>>> [You don't often get email from krzysztof.kozlowski@...aro.org. 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 07/02/2024 18:58, Catalin Popescu wrote:
>>>>>> Add properties ti,cfg-dac-minus-one-milli-percent and
>>>>>> ti,cfg-dac-plus-one-milli-percent to support voltage tuning
>>>>>> of logical levels -1/+1 of the MLT-3 encoded TX data.
>>>>>>
>>>>>> Signed-off-by: Catalin Popescu <catalin.popescu@...ca-geosystems.com>
>>>>>> ---
>>>>>> Changes in v2:
>>>>>>     - squash the 2 DT bindings patches in one single patch
>>>>>>     - drop redundant "binding" from the DT bindings patch title
>>>>>>     - rename DT properties and define them as percentage
>>>>>>     - add default value for each new DT property
>>>>>> ---
>>>>>>     .../devicetree/bindings/net/ti,dp83822.yaml    | 18 ++++++++++++++++++
>>>>>>     1 file changed, 18 insertions(+)
>>>>>>
>>>>>> diff --git a/Documentation/devicetree/bindings/net/ti,dp83822.yaml b/Documentation/devicetree/bindings/net/ti,dp83822.yaml
>>>>>> index db74474207ed..6bbd465e51d6 100644
>>>>>> --- a/Documentation/devicetree/bindings/net/ti,dp83822.yaml
>>>>>> +++ b/Documentation/devicetree/bindings/net/ti,dp83822.yaml
>>>>>> @@ -62,6 +62,24 @@ properties:
>>>>>>            for the PHY.  The internal delay for the PHY is fixed to 3.5ns relative
>>>>>>            to transmit data.
>>>>>>
>>>>>> +  ti,cfg-dac-minus-one-milli-percent:
>>>>>> +    description: |
>>>>>> +       DP83826 PHY only.
>>>>>> +       Sets the voltage ratio (with respect to the nominal value)
>>>>>> +       of the logical level -1 for the MLT-3 encoded TX data.
>>>>>> +    enum: [50000, 56250, 62500, 68750, 75000, 81250, 87500, 93750, 100000,
>>>>>> +           106250, 112500, 118750, 125000, 131250, 137500, 143750, 150000]
>>>>> I see all values being multiple of basis points, so why not using -bp
>>>>> suffix?
>>>> I can read :
>>>>
>>>>      "-bp$":
>>>>        $ref: types.yaml#/definitions/int32-array
>>>>        description: basis points (1/100 of a percent)
>>>>
>>>> In my case it's 1/1000 of a percent. As I'm not sure exactly what the
>>>> author meant by "basis points", would this apply to my patch as well?
>>> So please show me the value which does not fit in -bp.
>> "Basis points" doesn't mean anything to me, that's why I was asking for
>> confirmation :)
>> I don't have any issue to use "-bp" at all, I'm not pusing against.
> https://en.wikipedia.org/wiki/Basis_point
>
> Looks like all your values fit there, at least for these devices. Maybe
> you would need to be sure other devices do not require mpercent after all.
Got it! Indeed, "-bp" completely fits my need.
> Best regards,
> Krzysztof
>