netdev - Re: [PATCH v4 3/4] dt-bindings: net: xilinx

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Message-ID: <6fe3be1038463cf3155401650b42de89772ea5d5.camel@calian.com>
Date:   Mon, 21 Mar 2022 18:11:50 +0000
From:   Robert Hancock <robert.hancock@...ian.com>
To:     "radheys@...inx.com" <radheys@...inx.com>,
        "michals@...inx.com" <michals@...inx.com>,
        "andy.chiu@...ive.com" <andy.chiu@...ive.com>
CC:     "andrew@...n.ch" <andrew@...n.ch>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "linux@...linux.org.uk" <linux@...linux.org.uk>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "greentime.hu@...ive.com" <greentime.hu@...ive.com>,
        "harinik@...inx.com" <harinik@...inx.com>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "pabeni@...hat.com" <pabeni@...hat.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "davem@...emloft.net" <davem@...emloft.net>
Subject: Re: [PATCH v4 3/4] dt-bindings: net: xilinx_axienet: add pcs-handle
 attribute

On Mon, 2022-03-21 at 15:42 +0000, Radhey Shyam Pandey wrote:
> > -----Original Message-----
> > From: Andy Chiu <andy.chiu@...ive.com>
> > Sent: Monday, March 21, 2022 8:55 PM
> > To: Radhey Shyam Pandey <radheys@...inx.com>; robert.hancock@...ian.com;
> > Michal Simek <michals@...inx.com>
> > Cc: davem@...emloft.net; kuba@...nel.org; pabeni@...hat.com;
> > robh+dt@...nel.org; linux@...linux.org.uk; andrew@...n.ch;
> > netdev@...r.kernel.org; devicetree@...r.kernel.org; Andy Chiu
> > <andy.chiu@...ive.com>; Greentime Hu <greentime.hu@...ive.com>
> > Subject: [PATCH v4 3/4] dt-bindings: net: xilinx_axienet: add pcs-handle
> > attribute
> > 
> > Document the new pcs-handle attribute to support connecting to an external
> > PHY in SGMII or 1000Base-X modes through the internal PCS/PMA PHY.
> > 
> > Signed-off-by: Andy Chiu <andy.chiu@...ive.com>
> > Reviewed-by: Greentime Hu <greentime.hu@...ive.com>
> > ---
> >  Documentation/devicetree/bindings/net/xilinx_axienet.txt | 8 +++++++-
> >  1 file changed, 7 insertions(+), 1 deletion(-)
> > 
> > diff --git a/Documentation/devicetree/bindings/net/xilinx_axienet.txt
> > b/Documentation/devicetree/bindings/net/xilinx_axienet.txt
> > index b8e4894bc634..ba720a2ea5fc 100644
> > --- a/Documentation/devicetree/bindings/net/xilinx_axienet.txt
> > +++ b/Documentation/devicetree/bindings/net/xilinx_axienet.txt
> > @@ -26,7 +26,8 @@ Required properties:
> >  		  specified, the TX/RX DMA interrupts should be on that node
> >  		  instead, and only the Ethernet core interrupt is optionally
> >  		  specified here.
> > -- phy-handle	: Should point to the external phy device.
> > +- phy-handle	: Should point to the external phy device if exists.
> > Pointing
> > +		  this to the PCS/PMA PHY is deprecated and should be
> > avoided.
> >  		  See ethernet.txt file in the same directory.
> >  - xlnx,rxmem	: Set to allocated memory buffer for Rx/Tx in the
> > hardware
> > 
> > @@ -68,6 +69,11 @@ Optional properties:
> >  		  required through the core's MDIO interface (i.e. always,
> >  		  unless the PHY is accessed through a different bus).
> > 
> > + - pcs-handle: 	  Phandle to the internal PCS/PMA PHY in SGMII or
> > 1000Base-X
> > +		  modes, where "pcs-handle" should be preferably used to
> > point
> > +		  to the PCS/PMA PHY, and "phy-handle" should point to an
> > +		  external PHY if exists.
> 
> I would like to have Rob feedback on this pcs-handle DT property.
> 
> The use case is generic i.e. require separate handle to internal SGMII
> and external Phy so would prefer this new DT convention is 
> standardized or we discuss possible approaches on how to handle
> both phys and not add it as vendor specific property in the first 
> place.
> 

The pcs-handle property is currently used in the Freescale dpaa2 driver, so
there's some precedent for it. But I suppose if it's intended to be a standard
mechanism it should be documented more globally?

> 
> > +
> >  Example:
> >  	axi_ethernet_eth: ethernet@...00000 {
> >  		compatible = "xlnx,axi-ethernet-1.00.a";
> > --
> > 2.34.1