Re: [PATCH v4 4/5] net: stmmac: dwmac-sun8i: choose internal PHY via phy-is-integrated

Andrew Lunn
2017-08-31T20:59:51Z

On Thu, Aug 31, 2017 at 03:18:03PM -0500, Rob Herring wrote:
> On Sat, Aug 26, 2017 at 11:20:51PM +0200, Andrew Lunn wrote:
> > Hi Corentin
> >
> > I think we have now all agreed this is an mdio-mux, plus it is also an
> > MII mux. We should represent that in device tree. This patchset does
> > this. However, as it is now, the mux structure in DT is ignored. All
> > it does is search for the phy-is-integrated flags and goes on that.
> >
> > I made the comment that the device tree representation cannot be
> > implemented using an MDIO mux driver, because of driver loading
> > issues. However, the core of the MDIO mux code is just a library,
> > symbols exported as GPL, free for anything to use.
> >
> > What i think should happen is the mdio-mux is implemented inside the
> > MAC driver, using the mux-core as a library. The device tree structure
> > of a mix is then reflected within Linux. The mux switch callback is
> > implemented within the MAC driver. So it can reset the MAC when the
> > mux is switched. The 'phy-is-integrated' property is then no longer
> > needed.
> >
> > I would suggest a binding something like:
>
> This is looks better to me, but...
>
> > emac: ethernet@1c0b000 {
> > compatible = "allwinner,sun8i-h3-emac";
> > syscon = <&syscon>;
> > reg = <0x01c0b000 0x104>;
> > interrupts = <GIC_SPI 82 IRQ_TYPE_LEVEL_HIGH>;
> > interrupt-names = "macirq";
> > resets = <&ccu RST_BUS_EMAC>;
> > reset-names = "stmmaceth";
> > clocks = <&ccu CLK_BUS_EMAC>;
> > clock-names = "stmmaceth";
> > #address-cells = <1>;
> > #size-cells = <0>;
> >
> > phy-handle = <&int_mii_phy>;
> > phy-mode = "mii";
> > allwinner,leds-active-low;
> >
> > mdio: mdio {
> > #address-cells = <1>;
> > #size-cells = <0>;
> > }
>
> Why do you need this node still?

Hi Rob

It might not be needed, depending on how it is implemented. But:

Documentation/devicetree/bindings/net/mdio-mux.txt

It is normal for an mdio bus mux to have a phandle back to the parent
mdio bus. Also, i think the stmmac driver will only instantiate the
mdio bus if there is a node for it in the device tree.

Andrew