netdev - RE: [PATCH v2 net-next 2/3] net: phy: tja11xx: replace "nxp,rmii-refclk-in" with "nxp,phy-output-refclk"

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Message-ID:
 <PAXPR04MB85109CB5538707701F52246E88882@PAXPR04MB8510.eurprd04.prod.outlook.com>
Date: Fri, 23 Aug 2024 01:31:02 +0000
From: Wei Fang <wei.fang@....com>
To: Conor Dooley <conor@...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>, "robh@...nel.org" <robh@...nel.org>,
	"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>
Subject: RE: [PATCH v2 net-next 2/3] net: phy: tja11xx: replace
 "nxp,rmii-refclk-in" with "nxp,phy-output-refclk"

> -----Original Message-----
> From: Conor Dooley <conor@...nel.org>
> Sent: 2024年8月23日 0:14
> To: Wei Fang <wei.fang@....com>
> Cc: davem@...emloft.net; edumazet@...gle.com; kuba@...nel.org;
> pabeni@...hat.com; robh@...nel.org; 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
> Subject: Re: [PATCH v2 net-next 2/3] net: phy: tja11xx: replace
> "nxp,rmii-refclk-in" with "nxp,phy-output-refclk"
> 
> On Thu, Aug 22, 2024 at 09:37:11AM +0000, Wei Fang wrote:
> > > -----Original Message-----
> > > From: Conor Dooley <conor@...nel.org>
> > > Sent: 2024年8月22日 16:47
> > > To: Wei Fang <wei.fang@....com>
> > > Cc: davem@...emloft.net; edumazet@...gle.com; kuba@...nel.org;
> > > pabeni@...hat.com; robh@...nel.org; 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
> > > Subject: Re: [PATCH v2 net-next 2/3] net: phy: tja11xx: replace
> > > "nxp,rmii-refclk-in" with "nxp,phy-output-refclk"
> > >
> > > On Thu, Aug 22, 2024 at 09:37:20AM +0800, Wei Fang wrote:
> > > > As the new property "nxp,phy-output-refclk" is added to instead of
> > > > the "nxp,rmii-refclk-in" property, so replace the "nxp,rmii-refclk-in"
> > > > property used in the driver with the "nxp,reverse-mode" property
> > > > and make slight modifications.
> > >
> > > Can you explain what makes this backwards compatible please?
> > >
> > It does not backward compatible, the related PHY nodes in DTS also
> > need to be updated. I have not seen "nxp,rmii-refclk-in" used in the
> > upstream.
> 
> Since you have switched the polarity, devicestrees that contain
> "nxp,rmii-refclk-in" would actually not need an update to preserve
> functionality. However...
> 
> > For nodes that do not use " nxp,rmii-refclk-in", they need to be
> > updated, but unfortunately I cannot confirm which DTS use TJA11XX PHY,
> > and there may be no relevant nodes in upstream DTS.
> 
> ...as you say here, all tja11xx phy nodes that do not have the property would
> need to be updated to retain functionality. Given you can't even determine
> which devicetrees would need to be updated, I'm going to have to NAK this
> change as an unnecessary ABI break.
> 

Okay, that make sense, "nxp,rmii-refclk-in" was added only for TJA1100 and
TJA1101, although it does not seem to be a suitable property now, it cannot
be changed at present. :(
Since TJA1103/TJA1104/TJA1120/TJA1121 use different driver than TJA1100
and TJA1101, which is nxp-c4-tja11xx. I think it's fine to add " nxp,phy-output-refclk "
for these PHYs, so I will remove this patch from the patch set.