Subject: Re: [PATCH v3 3/4] net: stmmac: register parent MDIO node for sun8i-h3-emac

From: Corentin Labbe <[email-masked]>
Date: Tue, 22 Aug 2017 20:11:40 +0200

On Tue, Aug 22, 2017 at 09:40:24AM -0700, Florian Fainelli wrote:
> On 08/22/2017 08:39 AM, Chen-Yu Tsai wrote:
> > On Mon, Aug 21, 2017 at 10:23 PM, Andrew Lunn <[email-masked]> wrote:
> >>> 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?

If we put an external PHY with reg=1 as a child of internal MDIO, il will be merged with internal PHY node and get phy-is-integrated.

Does two MDIO node "internal-mdio" and "mdio" works for you ?
(We keep "mdio" for external MDIO for reducing the number of patchs)

Thanks
Regards

diff --git a/arch/arm/boot/dts/sunxi-h3-h5.dtsi b/arch/arm/boot/dts/sunxi-h3-h5.dtsi
index 4b599b5d26f6..d5e7cf0d9454 100644
--- a/arch/arm/boot/dts/sunxi-h3-h5.dtsi
+++ b/arch/arm/boot/dts/sunxi-h3-h5.dtsi
@@ -417,7 +417,8 @@
 			#size-cells = <0>;
 			status = "disabled";
 
-			mdio: mdio {
+			/* Only one MDIO is usable at the time */
+			internal_mdio: mdio@1 {
 				#address-cells = <1>;
 				#size-cells = <0>;
 				int_mii_phy: ethernet-phy@1 {
@@ -425,8 +426,13 @@
 					reg = <1>;
 					clocks = <&ccu CLK_BUS_EPHY>;
 					resets = <&ccu RST_BUS_EPHY>;
+					phy-is-integrated;
 				};
 			};
+			mdio: mdio@0 {
+				#address-cells = <1>;
+				#size-cells = <0>;
+			};
 		};
 
 		spi0: spi@01c68000 {