linux-kernel - RE: [PATCH net-next 1/3] dt-bindings: net: tja11xx: use reverse-mode to instead of rmii-refclk-in

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Message-ID:
 <PAXPR04MB8510B51569571BA58243FEB0888D2@PAXPR04MB8510.eurprd04.prod.outlook.com>
Date: Tue, 20 Aug 2024 05:13:06 +0000
From: Wei Fang <wei.fang@....com>
To: Andrew Lunn <andrew@...n.ch>
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>, "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 net-next 1/3] dt-bindings: net: tja11xx: use reverse-mode
 to instead of rmii-refclk-in

> -----Original Message-----
> From: Wei Fang
> Sent: 2024年8月16日 13:02
> To: Andrew Lunn <andrew@...n.ch>
> Cc: davem@...emloft.net; edumazet@...gle.com; kuba@...nel.org;
> pabeni@...hat.com; robh@...nel.org; krzk+dt@...nel.org;
> conor+dt@...nel.org; 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 net-next 1/3] dt-bindings: net: tja11xx: use reverse-mode
> to instead of rmii-refclk-in
> 
> > -----Original Message-----
> > From: Andrew Lunn <andrew@...n.ch>
> > Sent: 2024年8月16日 11:28
> > 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; 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 net-next 1/3] dt-bindings: net: tja11xx: use
> > reverse-mode to instead of rmii-refclk-in
> >
> > > Based on the TJA data sheet, like TJA1103/TJA1104, if the reverse
> > > mode is set. If XMII_MODE is set to MII, the device operates in
> > > revMII mode (TXCLK and RXCLK are input). If XMII_MODE is set to
> > > RMII, the device operates in revRMII mode (REF_CLK is output). So
> > > it's just that the input and output directions of xx_CLK are reversed.
> > > we don't need to tell the MAC to play the role of the PHY, in our
> > > case, we just need the PHY to provide the reference clock in RMII mode.
> >
> > If this is purely about providing a reference clock, normally 25Mhz,
> > there are a few PHY drivers which support this. Find one and copy it.
> > There is no need to invent something new.
> >
> 
> Sorry, I didn't find the correct PHY driver, could you point me to which PHY
> driver that I can refer to?
> The PHY drivers I searched for using the "clk" keyword all seem to set the
> clock via a vendor defined property. Such as,
> realtek: "realtek,clkout-disable"
> dp83867 and dp83869: "ti,clk-output-sel" and
> "ti,sgmii-ref-clock-output-enable"
> motorcomm: " motorcomm,tx-clk-1000-inverted"
> micrel: "rmii-ref"

Hi Andrew,
I still cannot find a generic method in other PHY drivers to provide
reference clock by PHY. So I think this patch is the best I could do, at
least it's more reasonable than the "nxp,rmii-refclk-in" property.