Re: [net-next PATCH v2 08/15] dt-bindings: net: dsa: qca8k: Add MAC swap and clock phase properties

On Sat, Oct 09, 2021 at 11:37:10PM +0200, Andrew Lunn wrote:

quoted

Here is 2 configuration one from an Netgear r7800 qca8337:

	switch@10 {
		compatible = "qca,qca8337";
		#address-cells = <1>;
		#size-cells = <0>;
		reg = <0x10>;

		qca8k,rgmii0_1_8v;
		qca8k,rgmii56_1_8v;

		ports {
			#address-cells = <1>;
			#size-cells = <0>;

			port@0 {
				reg = <0>;
				label = "cpu";
				ethernet = <&gmac1>;
				phy-mode = "rgmii-id";

				fixed-link {
					speed = <1000>;
					full-duplex;
				};
			};

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

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

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

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

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

			port@6 {
				reg = <6>;
				label = "cpu";
				ethernet = <&gmac2>;
				phy-mode = "sgmii";

				fixed-link {
					speed = <1000>;
					full-duplex;
				};

So here, it is a second CPU port.  But some other board could connect
an SGMII PHY, and call the port lan5. Or it could be connected to an
SFP cage, and used that way. Or are you forced to use it as a CPU
port, or not use it at all?

We have a bit to set the mode. So yes it can be used to different modes.
(base-x, phy and mac)

quoted

And here is one with mac swap Tp-Link Archer c7 v4 qca8327 

	switch0@10 {
		compatible = "qca,qca8337";
		#address-cells = <1>;
		#size-cells = <0>;

		reg = <0>;
		qca,sgmii-rxclk-falling-edge;
		qca,mac6-exchange;

		ports {
			#address-cells = <1>;
			#size-cells = <0>;

			port@0 {
				reg = <0>;
				label = "cpu";
				ethernet = <&eth0>;
				phy-mode = "sgmii";

				fixed-link {
					speed = <1000>;
					full-duplex;
				};

So when looking for SGMI properties, you need to look here. Where as
in the previous example, you would look in port 6. And the reverse is
true for RGMII delays.

quoted

			};

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

			port@2 {
				reg = <2>;
				label = "lan1";
				phy-mode = "internal";
				phy-handle = <&phy_port2>;
			};

			port@3 {
				reg = <3>;
				label = "lan2";
				phy-mode = "internal";
				phy-handle = <&phy_port3>;
			};

			port@4 {
				reg = <4>;
				label = "lan3";
				phy-mode = "internal";
				phy-handle = <&phy_port4>;
			};

			port@5 {
				reg = <5>;
				label = "lan4";
				phy-mode = "internal";
				phy-handle = <&phy_port5>;
			};
		};

So here, port '6' is not used. But it could be connected to an RGMII
PHY and called lan5. Would the naming work out? What does devlink
think of it, etc. What about phy-handle? Is there an external MDIO
bus? What address would be used if there is no phy-handle?

      Andrew

In this case port6 is not used as it's not connected at all in hardware.
From the configuration list yes, it can be used as lan5 in phy mode and
it would have address 5 (internally the address are with an offset of
-1). Anyway I honestly think that we are putting too much effort in
something that can and should be handled differently. I agree that all
this mac exchange is bs and doesn't make much sense. I tried to
implement this as we currently qca8k is hardcoded to expect
the cpu port 0 for everything and doesn't actually found a valid cpu
port (aka it doesn't expect a configuration with cpu6)
I think the driver was writtent with the concept of mac exchange from
the start. That's why it's hardoced to port0.
I actually tied for fun running the switch using only the port6 cpu
port and it worked just right. So I think I will just drop the mac
exchange and fix the code to make it dynamic.

-- 
	Ansuel