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: <20240823-jersey-conducive-70863dd6fd27@spud>
Date: Fri, 23 Aug 2024 16:56:12 +0100
From: Conor Dooley <conor@...nel.org>
To: Wei Fang <wei.fang@....com>
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"

On Fri, Aug 23, 2024 at 01:31:02AM +0000, Wei Fang wrote:
> > -----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.

If they use a different binding, then yeah, you can add use the new
name/polarity for those devices.

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