netdev - Re: [PATCH v3 4/4] FEC mpc52xx: phy part of the driver\

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Date:	Mon, 15 Oct 2007 12:56:01 +0200
From:	Domen Puncer <domen.puncer@...argo.com>
To:	Grant Likely <grant.likely@...retlab.ca>
Cc:	galak@...nel.crashing.org, jgarzik@...ox.com,
	linuxppc-dev@...abs.org, tnt@...tnt.com, netdev@...r.kernel.org
Subject: Re: [PATCH v3 4/4] FEC mpc52xx: phy part of the driver\

On 14/10/07 16:05 -0600, Grant Likely wrote:
> On 10/14/07, Domen Puncer <domen.puncer@...argo.com> wrote:
> > PHY part of the driver for mpc5200(b) ethernet.
> 
> Assuming I understand correctly, this comment is not correct and this
> patch just adds an MDIO bus driver.  PHY drivers are in phylib and
> data transfer is setup via the core driver, correct?

Right.

> 
> It is conceivable that the PHY is connected to an alternate MDIO bus,
> or the MDIO bus is used for a PHY connected to an external Ethernet
> controller.
> 
> Speaking of which, is it possible to use this MDIO bus without the
> core FEC being initialized?

IIRC fec doesn't need any initialization for MDIO bus registers to work.

> 
> > +static struct of_device_id fec_mdio_match[] = {
> > +       {
> > +               .type = "mdio",
> > +               .compatible = "mpc5200b-fec-phy",
> 
> This is not a phy; it's an MDIO bus.  Also, shouldn't this be
> "mpc5200-..." instead of "mpc5200b-..."?

Didn't know if it's ok for mpc5200, guess it is?

> 
> > +       },
> > +       {},
> > +};
> > +
> > +struct of_platform_driver mpc52xx_fec_mdio_driver = {
> > +       .name = "mpc5200b-fec-phy",
> > +       .probe = fec_mdio_probe,
> > +       .remove = fec_mdio_remove,
> > +       .match_table = fec_mdio_match,
> 
> Inconsistent naming.  Please use the same prefix on all global/static
> symbols (ie. use "mpc52xx_mdio_" instead of the mix of
> "mpc52xx_fec_mdio_", "fec_mdio_", etc.)  I also thing that "fec_mdio_"
> is too generic because there are a number of different incompatible
> FEC devices.

OK.

> 
> > +};
> > +
> > +/* let fec driver call it, since this has to be registered before it */
> > +EXPORT_SYMBOL_GPL(mpc52xx_fec_mdio_driver);
> 
> Why not have a module_init()/module_exit() in this file?  I don't
> think the FEC driver calls this driver's functions directly anymore,
> and it's still dependent on the of_platform bus probe order anyway.

It was one way of making sure mdio driver is registered before fec.
(and of_platform bus probe order won't work for modules)
Nicer alternatives?

> 
> As an added bonus, it makes your Makefile much simpler.
> 
> > +
> > +
> > +MODULE_LICENSE("Dual BSD/GPL");
> > Index: linux.git/drivers/net/fec_mpc52xx/Makefile
> > ===================================================================
> > --- linux.git.orig/drivers/net/fec_mpc52xx/Makefile
> > +++ linux.git/drivers/net/fec_mpc52xx/Makefile
> > @@ -1,2 +1,7 @@
> >  obj-$(CONFIG_FEC_MPC52xx) += fec_mpc52xx.o
> >  fec_mpc52xx-objs := fec.o
> > +
> > +ifeq ($(CONFIG_FEC_MPC52xx_MDIO),y)
> > +       obj-$(CONFIG_FEC_MPC52xx) += fec_mpc52xx_phy.o
> > +       fec_mpc52xx_phy-objs := fec_phy.o
> > +endif
> > Index: linux.git/drivers/net/fec_mpc52xx/Kconfig
> > ===================================================================
> > --- linux.git.orig/drivers/net/fec_mpc52xx/Kconfig
> > +++ linux.git/drivers/net/fec_mpc52xx/Kconfig
> > @@ -11,5 +11,18 @@ config FEC_MPC52xx
> >         ---help---
> >           This option enables support for the MPC5200's on-chip
> >           Fast Ethernet Controller
> > +         If compiled as module, it will be called 'fec_mpc52xx.ko'.
> 
> Drop this line and make the help text the same format as the other eth
> drivers in drivers/net.

How exactly is it different now?
And most of them have the "Module will be called xxx" line.

> 
> > +
> > +config FEC_MPC52xx_MDIO
> > +       bool "FEC MII PHY driver"
> > +       depends on FEC_MPC52xx
> > +       default y
> > +       ---help---
> > +         The MPC5200's FEC can connect to the Ethernet either with
> > +         an external MII PHY chip or 10 Mbps 7-wire interface
> > +         (Motorola? industry standard).
> > +         If your board uses an external PHY, enable this.
> 
> Not strictly true.  This enables talking to a PHY using the internal
> MDIO controller.  PHY register access could just as easily be accessed
> via an alternate interface.

Not just that is also selects which mode will it use.
If you don't enable this, fec will be set up as 7-wire
( 696                 rcntrl |= FEC_RCNTRL_MII_MODE;)


> 
> > +         If not sure, enable.
> > +         If compiled as module, it will be called 'fec_mpc52xx_phy.ko'.
> 
> Drop the module name comment.
> 
> Cheers,
> g.
> 
> -- 
> Grant Likely, B.Sc., P.Eng.
> Secret Lab Technologies Ltd.
> grant.likely@...retlab.ca
> (403) 399-0195

-- 
Domen Puncer | Research & Development
.............................................................................................
Telargo d.o.o. | Zagrebška cesta 20 | 2000 Maribor | Slovenia
.............................................................................................
www.telargo.com
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