netdev - Re: [PATCH v3 net-next 1/2] dt-bindings: net: tja11xx: add "nxp,phy-output-refclk" property

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Message-ID: <31058f49-bac5-49a9-a422-c43b121bf049@kernel.org>
Date: Tue, 27 Aug 2024 15:26:30 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Wei Fang <wei.fang@....com>, Rob Herring <robh@...nel.org>
Cc: "davem@...emloft.net" <davem@...emloft.net>,
 "edumazet@...gle.com" <edumazet@...gle.com>,
 "kuba@...nel.org" <kuba@...nel.org>, "pabeni@...hat.com"
 <pabeni@...hat.com>, "krzk+dt@...nel.org" <krzk+dt@...nel.org>,
 "conor+dt@...nel.org" <conor+dt@...nel.org>, "andrew@...n.ch"
 <andrew@...n.ch>, "f.fainelli@...il.com" <f.fainelli@...il.com>,
 "hkallweit1@...il.com" <hkallweit1@...il.com>,
 "linux@...linux.org.uk" <linux@...linux.org.uk>,
 "Andrei Botila (OSS)" <andrei.botila@....nxp.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>,
 "imx@...ts.linux.dev" <imx@...ts.linux.dev>
Subject: Re: [PATCH v3 net-next 1/2] dt-bindings: net: tja11xx: add
 "nxp,phy-output-refclk" property

On 27/08/2024 05:25, Wei Fang wrote:
>> -----Original Message-----
>> From: Rob Herring <robh@...nel.org>
>> Sent: 2024年8月26日 23:50
>> To: Wei Fang <wei.fang@....com>
>> Cc: davem@...emloft.net; edumazet@...gle.com; kuba@...nel.org;
>> pabeni@...hat.com; krzk+dt@...nel.org; conor+dt@...nel.org;
>> andrew@...n.ch; f.fainelli@...il.com; hkallweit1@...il.com;
>> linux@...linux.org.uk; Andrei Botila (OSS) <andrei.botila@....nxp.com>;
>> netdev@...r.kernel.org; devicetree@...r.kernel.org;
>> linux-kernel@...r.kernel.org; imx@...ts.linux.dev
>> Subject: Re: [PATCH v3 net-next 1/2] dt-bindings: net: tja11xx: add
>> "nxp,phy-output-refclk" property
>>
>> On Mon, Aug 26, 2024 at 01:26:59PM +0800, Wei Fang wrote:
>>> Per the RMII specification, the REF_CLK is sourced from MAC to PHY or
>>> from an external source. But for TJA11xx PHYs, they support to output
>>> a 50MHz RMII reference clock on REF_CLK pin. Previously the
>>> "nxp,rmii-refclk-in" was added to indicate that in RMII mode, if this
>>> property present, REF_CLK is input to the PHY, otherwise it is output.
>>> This seems inappropriate now. Because according to the RMII
>>> specification, the REF_CLK is originally input, so there is no need to
>>> add an additional "nxp,rmii-refclk-in" property to declare that
>>> REF_CLK is input.
>>> Unfortunately, because the "nxp,rmii-refclk-in" property has been
>>> added for a while, and we cannot confirm which DTS use the TJA1100 and
>>> TJA1101 PHYs, changing it to switch polarity will cause an ABI break.
>>> But fortunately, this property is only valid for TJA1100 and TJA1101.
>>> For TJA1103/TJA1104/TJA1120/TJA1121 PHYs, this property is invalid
>>> because they use the nxp-c45-tja11xx driver, which is a different
>>> driver from TJA1100/TJA1101. Therefore, for PHYs using nxp-c45-tja11xx
>>> driver, add "nxp,phy-output-refclk" property to support outputting
>>> RMII reference clock on REF_CLK pin.
>>>
>>> Signed-off-by: Wei Fang <wei.fang@....com>
>>> ---
>>> V2 changes:
>>> 1. Change the property name from "nxp,reverse-mode" to
>>> "nxp,phy-output-refclk".
>>> 2. Simplify the description of the property.
>>> 3. Modify the subject and commit message.
>>> V3 changes:
>>> 1. Keep the "nxp,rmii-refclk-in" property for TJA1100 and TJA1101.
>>> 2. Rephrase the commit message and subject.
>>> ---
>>>  Documentation/devicetree/bindings/net/nxp,tja11xx.yaml | 6 ++++++
>>>  1 file changed, 6 insertions(+)
>>
>> This binding is completely broken. I challenge you to make it report any errors.
>> Those issues need to be addressed before you add more properties.
>>
> Sorry, I'm not sure I fully understand what you mean, do you mean I need

Make an intentional error in your DTS and then validate that the schema
catches it. That's the challenge.

Best regards,
Krzysztof