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

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Date:   Wed, 14 Jul 2021 19:25:52 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Biju Das <biju.das.jz@...renesas.com>
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

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?

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.

	  Andrew