Re: [RFC PATCH] phylib: mdio: handle register/unregister/registersequence

[boris brezillon]

On 22/08/2013 15:15, Florian Fainelli wrote:
> 2013/8/22 boris brezillon <b.brezillon@xxxxxxxxxxx>:
> > Hello Florian,
> >
> > Thanks for your answer.
> >
> >
> > On 22/08/2013 14:43, Florian Fainelli wrote:
> > > Hello Boris,
> > >
> > > 2013/8/22 Boris BREZILLON <b.brezillon@xxxxxxxxxxx>:
> > > > Hello,
> > > >
> > > > This patch is a proposal to support the register/unregister/register
> > > > sequence on a given mdio bus.
> > > >
> > > > I use the register/unregister/register sequence to add a fallback when
> > > > the
> > > > of_mdiobus_register (this function calls mdiobus_register with phy_mask
> > > > set to ~0) does not register any phy device (because the device tree does
> > > > not define any phy).
> > > > In this case I call mdiobus_unregister and then call mdiobus_register
> > > > with
> > > > a phy_mask set to 0 to trigger a full mdio bus scan.
> > > >
> > > > I'm not sure this is the right way to do it (this is why I added RFC in
> > > > the
> > > > subject).
> > > >
> > > > Could someone help me figuring out what I should use to implement my
> > > > fallback ?
> > > >
> > > > 1) use the register/unregister/register sequence
> > > > 2) reimplement the "for (i = 0; i < PHY_MAX_ADDR; i++)" mdiobus_scan loop
> > > I think solution 2 is nicer, in that case, would it be enough in your
> > > case to export a function called mdiobus_scan()? You could call at a
> > > time you know PHY devices have a chance of having been probed?
> > mdiobus_scan is already exported:
> > struct phy_device *mdiobus_scan(struct mii_bus *bus, int addr);
> >
> > This function scans the presence of a phy device at a given address.
> >
> > What I need is a loop which scan all the possible address on the given
> > mdio bus:
> >
> > struct phy_device *mdiobus_full_scan(struct mii_bus *bus)
> > {
> >      int i;
> >      for (i = 0; i < PHY_MAX_ADDR; i++) {
> >          if ((bus->phy_mask & (1 << i)) == 0) {
> >              struct phy_device *phydev;
> >
> >              phydev = mdiobus_scan(bus, i);
> >              if (IS_ERR(phydev)) {
> >                  err = PTR_ERR(phydev);
> >                  goto error;
> >              }
> >          }
> >      }
> >      return 0;
> >
> > error:
> >      while (--i >= 0) {
> >
> >          if (bus->phy_map[i])
> >              device_unregister(&bus->phy_map[i]->dev);
> >      }
> > }
> > EXPORT_SYMBOL(mdiobus_full_scan);
> >
> > Since I am the only one who need this kind of functionnality right now, I'm
> > not sure
> > this is a good idea to export a new function.
> A possible other use case for this full-scan is when you do not detect
> a PHY connected to your MDIO bus, and that you did not register a
> fixed PHY early enough for it to have been scanned by the fixed MDIO
> bus emulation. In that case the driver may:
>
> - scan hardware MDIO bus
> - do not find any PHY, register a fixed PHY
> - trigger a fixed MDIO bus full-rescan
> - attach to the discovered fixed PHY
>
> this is something currently done by the TI CPMAC driver in
> drivers/net/ethernet/ti/cpmac.c (altough fixed_phy_add() is called
> from platform code).

Okay, then we should consider this option.

> > This behaviour may be implemented in the of_mdiobus_register function:
> > when no dt phy node are found in the mdio bus dt node, we could launch a
> > full
> > scan.
> >
> > What do you think ?
> There is an existing kind of "autoscan" feature in
> drivers/of/of_mdio.c, starting with the second foreach_child_node()
> loop, so maybe that specific part could be exported and would achieve
> what you are looking for? It relies on the Ethernet PHY nodes to be
> attached to the MDIO bus node, but I assume this is what ultimately
> happens in your case as well?

The second foreach_child_node loop only registers the dt phy nodes
which does not define any reg property (automatic address asssignement ?).

Indeed, what I need is a fallback when the device tree does not define 
any phy
device (for old device tree backward compatibility).

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