[RFC PATCH 1/3] of: provide a binding for the 'fixed-link' property
mark.rutland at arm.com
Tue Jul 30 11:31:21 EDT 2013
On Tue, Jul 30, 2013 at 10:07:05AM +0100, Thomas Petazzoni wrote:
> Dear Grant Likely,
> On Tue, 23 Jul 2013 12:39:52 +0100, Grant Likely wrote:
> > > +Such a fixed link situation is described within an Ethernet device
> > > +Device Tree node using a 'fixed-link' property, composed of 5
> > > +elements:
> > > +
> > > + 1. A fake PHY ID, which must be unique accross all fixed-link PHYs in
> > > + the system.
> > That's just loony! :) Regardless of existing code doing this, it is
> > absolutely ridiculous to have it in the driver. The kernel should
> > handle generating a phy id transparently. I'd rather mark this field
> > as reserved in the binding and change the code to not care about it
> > anymore.
> In fact, this value is used for two things:
> * As the PHY address on the fake "fixed" MDIO bus.
> * As the PHY identifier, as reported by the MII registers PHYS_ID1
> (0x2) and PHYS_ID2 (0x3).
> I think this doesn't make sense, because the two things are completely
> unrelated. Ideally, we'd like the PHY identifier for fixed PHYs to be
> something fixed, identical for all fixed PHYs. The problem is finding
> an OUI and device number that is available for that, but maybe we can
> ask the OpenMoko people to allocate one (see
> Then, the PHY address could be generated dynamically. This would
> * Adding a fixed_phy_create() function that internally uses
> fixed_phy_add(), but before that creates an unique PHY address for
> this newly created PHY. Those unique addresses will be generated by
> incrementing a global number of fixed PHYs, up to PHY_MAX_ADDR,
> which is the maximum number of fixed PHYs that can anyway be
> registered on the fixed MDIO bus.
> fixed_phy_create() would return this PHY address (positive) on
> success, or a negative error code on failure.
> * Change of_phy_register_fixed_link() to call fixed_phy_create()
> instead of fixed_phy_add() and make it return the PHY address
> allocated by fixed_phy_create().
> * Add a of_phy_connect_fixed_link_direct() that is similar to
> of_phy_connect_fixed_link() but takes an additional PHY address as
> argument and uses that to generate the 'bus_id' used to find the
> Grant, Mark, Florian, do you have other proposals?
The above sounds good to me.
More information about the linux-arm-kernel