linux-kernel - Re: [RFC PATCH net-next v4 19/28] net: dsa: qca8k: make rgmii delay configurable

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Message-ID: <YJc1w9Mndqbdb71Z@lunn.ch>
Date:   Sun, 9 May 2021 03:07:15 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Ansuel Smith <ansuelsmth@...il.com>
Cc:     Florian Fainelli <f.fainelli@...il.com>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Vladimir Oltean <olteanv@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Russell King <linux@...linux.org.uk>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH net-next v4 19/28] net: dsa: qca8k: make rgmii delay
 configurable

On Sun, May 09, 2021 at 01:58:07AM +0200, Ansuel Smith wrote:
> On Sat, May 08, 2021 at 08:12:26PM +0200, Andrew Lunn wrote:
> > > +
> > > +	/* Assume only one port with rgmii-id mode */
> > 
> > Since this is only valid for the RGMII port, please look in that
> > specific node for these properties.
> > 
> > 	 Andrew
> 
> Sorry, can you clarify this? You mean that I should check in the phandle
> pointed by the phy-handle or that I should modify the logic to only
> check for one (and the unique in this case) rgmii port?

Despite there only being one register, it should be a property of the
port. If future chips have multiple RGMII ports, i expect there will
be multiple registers. To avoid confusion in the future, we should
make this a proper to the port it applies to. So assuming the RGMII
port is port 0:

                                #address-cells = <1>;
                                #size-cells = <0>;
                                port@0 {
                                        reg = <0>;
                                        label = "cpu";
                                        ethernet = <&gmac1>;
                                        phy-mode = "rgmii";
                                        fixed-link {
                                                speed = 1000;
                                                full-duplex;
                                        };
					rx-internal-delay-ps = <2000>;
					tx-internal-delay-ps = <2000>;
                                };

                                port@1 {
                                        reg = <1>;
                                        label = "lan1";
                                        phy-handle = <&phy_port1>;
                                };

                                port@2 {
                                        reg = <2>;
                                        label = "lan2";
                                        phy-handle = <&phy_port2>;
                                };

                                port@3 {
                                        reg = <3>;
                                        label = "lan3";
                                        phy-handle = <&phy_port3>;
                                };

                                port@4 {
                                        reg = <4>;
                                        label = "lan4";
                                        phy-handle = <&phy_port4>;
                                };

                                port@5 {
                                        reg = <5>;
                                        label = "wan";
                                        phy-handle = <&phy_port5>;
                                };
                        };
                };
        };

You also should validate that phy-mode is rgmii and only rgmii. You
get into odd situations if it is any of the other three rgmii modes.

    Andrew