Re: [PATCH v2] net: macb: do not scan PHYs manually

Josh Cartwright
2016-04-29T00:35:15Z

On Thu, Apr 28, 2016 at 11:23:15PM +0200, Andrew Lunn wrote:
> On Thu, Apr 28, 2016 at 04:03:57PM -0500, Josh Cartwright wrote:
> > On Thu, Apr 28, 2016 at 08:59:32PM +0200, Andrew Lunn wrote:
> > > On Thu, Apr 28, 2016 at 01:55:27PM -0500, Nathan Sullivan wrote:
> > > > On Thu, Apr 28, 2016 at 08:43:03PM +0200, Andrew Lunn wrote:
> > > > > > I agree that is a valid fix for AT91, however it won't solve our problem, since
> > > > > > we have no children on the second ethernet MAC in our devices' device trees. I'm
> > > > > > starting to feel like our second MAC shouldn't even really register the MDIO bus
> > > > > > since it isn't being used - maybe adding a DT property to not have a bus is a
> > > > > > better option?
> > > > >
> > > > > status = "disabled"
> > > > >
> > > > > would be the unusual way.
> > > > >
> > > > > Andrew
> > > >
> > > > Oh, sorry, I meant we use both MACs on Zynq, however the PHYs are on the MDIO
> > > > bus of the first MAC. So, the second MAC is used for ethernet but not for MDIO,
> > > > and so it does not have any PHYs under its DT node. It would be nice if there
> > > > were a way to tell macb not to bother with MDIO for the second MAC, since that's
> > > > handled by the first MAC.
> > >
> > > Yes, exactly, add support for status = "disabled" in the mdio node.
> >
> > Unfortunately, the 'macb' doesn't have a "mdio node", or alternatively:
> > the node representing the mdio bus is the same node which represents the
> > macb instance itself. Setting 'status = "disabled"' on this node will
> > just prevent the probing of the macb instance.
>
> :-(
>
> It is very common to have an mdio node within the MAC node, for example imx6sx-sdb.dtsi

Okay, I think that makes sense. I think, then, perhaps the solution to
our problem is to:

1. Modify the macb driver to support an 'mdio' node. (And adjust the
binding document accordingly). If the node is found, it's used for
of_mdiobus_register() w/o any of the manual scan madness.
2. For backwards compatibility, in the case where an 'mdio' node does
not exist, leave the existing behavior the way it is now
(of_mdiobus_register() followed by manual scan) [perhaps warn of
deprecation as well?]
3. Update binding docs to reflect the above.

In this way, for our usecase, the 'status = "disabled"' in the newly
created 'mdio' node isn't necessary. It's sufficient for the node to
exist and be empty.

> &fec1 {
> pinctrl-names = "default";
> pinctrl-0 = <&pinctrl_enet1>;
> phy-supply = <&reg_enet_3v3>;
> phy-mode = "rgmii";
> phy-handle = <&ethphy1>;
> status = "okay";
>
> mdio {
> #address-cells = <1>;
> #size-cells = <0>;
>
> ethphy1: ethernet-phy@1 {
> reg = <1>;
> };
>
> ethphy2: ethernet-phy@2 {
> reg = <2>;
> };
> };
> };
>
> &fec2 {
> pinctrl-names = "default";
> pinctrl-0 = <&pinctrl_enet2>;
> phy-mode = "rgmii";
> phy-handle = <&ethphy2>;
> status = "okay";
> };
>
> This even has the two phys on one bus, as you described...

Yep...looks nearly exactly the same case.

Thanks,
Josh