netdev - RE: [RFC PATCH v2 1/4] Documentation: DT: net: Add Xilinx gmiitorgmii converter device tree binding documentation

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Date:	Wed, 6 Jul 2016 14:51:28 +0000
From:	Punnaiah Choudary Kalluri <punnaiah.choudary.kalluri@...inx.com>
To:	Andrew Lunn <andrew@...n.ch>
CC:	Appana Durga Kedareswara Rao <appanad@...inx.com>,
	"robh+dt@...nel.org" <robh+dt@...nel.org>,
	"mark.rutland@....com" <mark.rutland@....com>,
	"Michal Simek" <michals@...inx.com>,
	Soren Brinkmann <sorenb@...inx.com>,
	"nicolas.ferre@...el.com" <nicolas.ferre@...el.com>,
	"f.fainelli@...il.com" <f.fainelli@...il.com>,
	Anirudha Sarangi <anirudh@...inx.com>,
	Harini Katakam <harinik@...inx.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [RFC PATCH v2 1/4] Documentation: DT: net: Add Xilinx
 gmiitorgmii converter device tree binding documentation



> -----Original Message-----
> From: Andrew Lunn [mailto:andrew@...n.ch]
> Sent: Wednesday, July 06, 2016 7:51 PM
> To: Punnaiah Choudary Kalluri <punnaia@...inx.com>
> Cc: Appana Durga Kedareswara Rao <appanad@...inx.com>;
> robh+dt@...nel.org; mark.rutland@....com; Michal Simek
> <michals@...inx.com>; Soren Brinkmann <sorenb@...inx.com>;
> nicolas.ferre@...el.com; f.fainelli@...il.com; Anirudha Sarangi
> <anirudh@...inx.com>; Harini Katakam <harinik@...inx.com>;
> netdev@...r.kernel.org; devicetree@...r.kernel.org; linux-arm-
> kernel@...ts.infradead.org; linux-kernel@...r.kernel.org
> Subject: Re: [RFC PATCH v2 1/4] Documentation: DT: net: Add Xilinx
> gmiitorgmii converter device tree binding documentation
> 
> > > Hi Kedareswara
> > >
> > > So looking at the device tree, you have the gmiitorgmii as an mdio
> > > device. It will get probed as an mdio device, and from that you know
> > > the address on the bus. However, your driver does not actually do
> > > this. xilinx_gmii2rgmii.c is just a library of two functions, and does
> > > not use any of this device tree information. You device tree binding
> > > is completely bogus.
> > >
> > > What i think is a much more logical structure, and fits the hardware,
> > > which is what DT is all about, is to make your driver an mdio driver.
> > > Also, have a phy-handle pointing to the PHY in the gmii_to_rgmii node.
> > > You then no longer need the exported gmii2rgmii_phyprobe() function.
> > >
> > > Next, you want gmiitorgmii driver to register a phy. The MAC driver
> > > can then look this up using phy-handle:
> > >
> > >        mdio {
> > >                 #address-cells = <1>;
> > >                 #size-cells = <0>;
> > >
> > >                 phy: ethernet-phy@0 {
> > >                         reg = <0>;
> > >                 };
> > >
> > >                 gmii_to_rgmii: gmii-to-rgmii@8 {
> > >                         compatible = "xlnx,gmiitorgmii";
> > >                         reg = <8>;
> > > 			phy-handle = <&phy>;
> > >                 };
> > >        };
> >
> >
> > Thanks for your inputs initially we too thought the similar implementation
> > But the GMII2RGMII converter contains only one register and it is
> >  not compatible to the standard ethernet MII interface. Also it doesn't have
> > a standard VID and PID registers So, during the mdio bus scan, this device
> will
> > not appear.
> 
> Hi Punnaiah
> 
> Use missed some subtlety in my description. I did not call the
> GMII2RGMII a PHY device, i called it an MDIO device. These are
> different things. Go look at the MDIO subsystem to figure out the
> difference.
> 
Hi Andrew

Got it. Thanks.

Punnaiah

> 	Andrew