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

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Date:   Sun, 9 May 2021 03:17:23 +0200
From:   Ansuel Smith <ansuelsmth@...il.com>
To:     Andrew Lunn <andrew@...n.ch>
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 03:07:15AM +0200, Andrew Lunn wrote:
> 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

And that is the intention of the port. I didn't want the binding to be
set on the switch node but on the rgmii node. Correct me if I'm wrong
but isn't what this patch already do?

In of_rgmii_delay I get the ports node of the current switch, iterate
every port, find the one with the phy-mode set to "rgmii-id" and check
if it's present any value. And save the value in the priv struct.
The actual delay is applied in the phylink_mac_config only if the mode
is set to rgmii-id. (the current code set by default a delay of 3000
with rgmii-id, so this is just to make this value configurable)