On 08/22/2017 08:39 AM, Chen-Yu Tsai wrote:

On Mon, Aug 21, 2017 at 10:23 PM, Andrew Lunn [off-list ref] wrote:

quoted

quoted

All muxes are mostly always represented the same way afaik, or do you
want to simply introduce a new compatible / property?

+         mdio-mux {
+               compatible = "allwinner,sun8i-h3-mdio-switch";
+               mdio-parent-bus = <&mdio_parent>;
+               #address-cells = <1>;
+               #size-cells = <0>;
+
+               internal_mdio: mdio@1 {
                        reg = <1>;
-                       clocks = <&ccu CLK_BUS_EPHY>;
-                       resets = <&ccu RST_BUS_EPHY>;
+                       #address-cells = <1>;
+                       #size-cells = <0>;
+                       int_mii_phy: ethernet-phy@1 {
+                               compatible = "ethernet-phy-ieee802.3-c22";
+                               reg = <1>;
+                               clocks = <&ccu CLK_BUS_EPHY>;
+                               resets = <&ccu RST_BUS_EPHY>;
+                               phy-is-integrated;
+                       };
+               };
+               mdio: mdio@0 {
+                       reg = <0>;
+                       #address-cells = <1>;
+                       #size-cells = <0>;
                };

Hi Maxim

Anybody who knows the MDIO-mux code/binding, knows that it is a run
time mux. You swap the mux per MDIO transaction. You can access all
the PHY and switches on the mux'ed MDIO bus.

However here, it is effectively a boot-time MUX. You cannot change it
on the fly. What happens when somebody has a phandle to a PHY on the
internal and a phandle to a phy on the external? Does the driver at
least return -EINVAL, or -EBUSY? Is there a representation which
eliminates this possibility?

There is only one controller. Either you use the internal PHY, which
is then directly coupled (no magnetics needed) to the RJ45 port, or
you use an external PHY over MII/RMII/RGMII. You could supposedly
have both on a board, and let the user choose one. But why bother
with the extra complexity and cost? Either you use the internal PHY
at 100M, or an external RGMII PHY for gigabit speeds.

I agree, there is no point in over-engineering any of this. I don't
think there is actually any MDIO mux per-se in that the MDIO clock and
data lines are muxed, however there has to be some kind of built-in port
multiplexer that lets you chose between connecting to the internal PHY
and any external PHY/MAC, but that is not what a "mdio-mux" node represents.

So I think what you are saying is either impossible or engineering-wise
a very stupid design, like using an external MAC with a discrete PHY
connected to the internal MAC's MDIO bus, while using the internal MAC
with the internal PHY.

Now can we please decide on something? We're a week and a half from
the 4.13 release. If mdio-mux is wrong, then we could have two mdio
nodes (internal-mdio & external-mdio).

I really don't see a need for a mdio-mux in the first place, just have
one MDIO controller (current state) sub-node which describes the
built-in STMMAC MDIO controller and declare the internal PHY as a child
node (along with 'phy-is-integrated'). If a different configuration is
used, then just put the external PHY as a child node there.

If fixed-link is required, the mdio node becomes unused anyway.

Works for everyone?
-- 
Florian
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