CONFIG_FEC is not good for mpc8xx ethernet?

[Shawn Jin]

>> On MPC8xx you want drivers/net/fs_enet/mii-fec.c.  This is just the
>> MDIO driver; it doesn't handle any particular PHY.  I don't know if
>> there is a driver specifically for AM79C874, though the generic PHY
>> support may be good enough.
>
> Maybe.
>
> I can found one related patch for supporting PHY AM79C874 on 2.6.15,
> ------
> http://lists.ozlabs.org/pipermail/linuxppc-embedded/2005-November/021043.html
>
> But I don't see that on the latest kernel, and also I don't know the history
> completely for that. Maybe its already merged into one generic PHY driver but
> I'm not sure.

Thank Scott & Tiejun for valuable information.

The problem for me is that the PHY failed to be probed. The related
error messages are shown below. I even tried the patch Tiejun pointed
out. But that doesn't help. The phy ID read from the bus was all Fs.

FEC MII Bus: probed
mdio_bus fa200e00: error probing PHY at address 0

I don't know if AM79C874 requires any special handling. But from the
comment in mdiobb_cmd() there seems to be something special.
        /*
         * Send a 32 bit preamble ('1's) with an extra '1' bit for good
         * measure.  The IEEE spec says this is a PHY optional
         * requirement.  The AMD 79C874 requires one after power up and
         * one after a MII communications error.  This means that we are
         * doing more preambles than we need, but it is safer and will be
         * much more robust.
         */

If there is any network action in u-boot, e.g., tftp or ping, the PHY
can be successfully probed after that. Any hints what went wrong with
the PHY?

Thanks,
-Shawn.