netdev - RE: [PATCH/RFC 2/2] ravb: Add GbEthernet driver support

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Message-ID: <OS0PR01MB592285AAA88B1BDA84F3C20B86139@OS0PR01MB5922.jpnprd01.prod.outlook.com>
Date:   Wed, 14 Jul 2021 17:56:46 +0000
From:   Biju Das <biju.das.jz@...renesas.com>
To:     Andrew Lunn <andrew@...n.ch>
CC:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Sergei Shtylyov <sergei.shtylyov@...il.com>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Sergey Shtylyov <s.shtylyov@...russia.ru>,
        Adam Ford <aford173@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
        Andrew Gabbasov <andrew_gabbasov@...tor.com>,
        Yuusuke Ashizuka <ashiduka@...itsu.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-renesas-soc@...r.kernel.org" 
        <linux-renesas-soc@...r.kernel.org>,
        Chris Paterson <Chris.Paterson2@...esas.com>,
        Biju Das <biju.das@...renesas.com>,
        Prabhakar Mahadev Lad <prabhakar.mahadev-lad.rj@...renesas.com>
Subject: RE: [PATCH/RFC 2/2] ravb: Add GbEthernet driver support

Hi Andrew Lunn,

Thanks for the feedback.

> Subject: Re: [PATCH/RFC 2/2] ravb: Add GbEthernet driver support
> 
> On Wed, Jul 14, 2021 at 05:01:34PM +0000, Biju Das wrote:
> > Hi Andrew Lunn,
> >
> > Thanks for the feedback.
> >
> > > Subject: Re: [PATCH/RFC 2/2] ravb: Add GbEthernet driver support
> > >
> > > > +	if (priv->phy_interface == PHY_INTERFACE_MODE_RGMII_ID) {
> > > > +		ravb_write(ndev, ravb_read(ndev, CXR31)
> > > > +			 | CXR31_SEL_LINK0, CXR31);
> > > > +	} else {
> > > > +		ravb_write(ndev, ravb_read(ndev, CXR31)
> > > > +			 & ~CXR31_SEL_LINK0, CXR31);
> > > > +	}
> > >
> > > You need to be very careful here. What value is passed to the PHY?
> >
> > PHY_INTERFACE_MODE_RGMII is the value passed to PHY.
> 
> In all four cases? So if DT contains rgmii-txid, or rgmii-rxid, the
> requested delay will not happen in either the MAC or the PHY?

OK, it is my mistake. I specified "rgmii" in DT. 

Without phy delays (rx and tx) ethernet won't work. Will fix it as "rgmii-id" in dt.

The above register(In-band Status set register) is basically used for selecting the link.

> 
> In general in Linux, MAC drivers don't add any delays, and request the PHY
> to do it. There are some MAC drivers which do it differently, they add the
> delays, but that is uncommon. So unless you have a good reason not to, i
> would suggest you leave the PHY to do the delays.

OK. 


Regards,
Biju