Direct MII connection between MPC8313 and VIRTEX FPGA

Direct MII connection between MPC8313 and VIRTEX FPGA

[Frank Prepelica]

Hi all,

we removed the ethernet PHYs (MARVELL) from our customized board (based =
on MPC8313ERDB) and=20
connected the CPU Ethernet lines directly to a FPGA which is now =
emulating the PHY. But the ifconfig=20
command cannot find that eth device anymore. Does the emulated PHY needs =
to provide MDIO=20
information that the ETH device can be found again?

Any help is very appreciated

Best regards
Frank





Frank Prepelica
Software Design Engineer

Ubidyne GmbH
Lise-Meitner-Str.-14
89081 Ulm - Germany

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frank.prepelica@ubidyne.com
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=A0
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Managing Directors:
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Re: Direct MII connection between MPC8313 and VIRTEX FPGA

[Grant Likely]

On Thu, Jun 25, 2009 at 9:11 AM, Frank
Prepelica<Frank.Prepelica@ubidyne.com> wrote:
> Hi all,
>
> we removed the ethernet PHYs (MARVELL) from our customized board (based on MPC8313ERDB) and
> connected the CPU Ethernet lines directly to a FPGA which is now emulating the PHY. But the ifconfig
> command cannot find that eth device anymore. Does the emulated PHY needs to provide MDIO
> information that the ETH device can be found again?

No, you just need to make sure that the Ethernet driver is able to
support fixed speed MII links without a PHY.  It's trivial to do, but
not all drivers support it.  Search for "current-speed" in
drivers/net/fec_mpc52xx.c for an example.

g.

-- 
Grant Likely, B.Sc., P.Eng.
Secret Lab Technologies Ltd.

Re: Direct MII connection between MPC8313 and VIRTEX FPGA

[Grant Likely]

On Mon, Jun 29, 2009 at 2:23 AM, Frank
Prepelica<Frank.Prepelica@ubidyne.com> wrote:
> Hi Grant
>
> Thanks for your response!
>
> I have searched for "current-speed" in drivers/net/fec_mpc52xx.c but I cannot find anything. However we are using the gianfar.c Ethernet driver.
> Do you know whether this driver supports fixed MII links without PHY?

What kernel version are you using?

> I've got another question regarding MII connection between and MPC and a Virtex FPGA. Whats about the PHY address which has to be set in the DTB file? Do I have to modify the DTB at all?

Yes, you need to modify the DTB.  You have a back to back MII
connection, not a phy, so you do *not* want to have a PHY node in the
device tree.

g.

-- 
Grant Likely, B.Sc., P.Eng.
Secret Lab Technologies Ltd.

AW: Direct MII connection between MPC8313 and VIRTEX FPGA

[Frank Prepelica]

> What kernel version are you using?

We are using kernel version 2.6.24. I've searched for "current speed" in =
version 2.6.28.7 and I've found that string.

> Yes, you need to modify the DTB.  You have a back to back MII
> connection, not a phy, so you do *not* want to have a PHY node in the
> device tree.

Hmm, but I do have a "PHY", don't I?. The "PHY" will be emulated in the =
FPGA. Of course, it's not a physical PHY but it should look like one.
So, do I really need the remove the complete PHY description in the DTB?


=09
		=20
=20

Frank Prepelica
Software Design Engineer

Ubidyne GmbH
Lise-Meitner-Str.-14
89081 Ulm - Germany



> -----Urspr=FCngliche Nachricht-----
> Von: Grant Likely [mailto:grant.likely@secretlab.ca]
> Gesendet: Montag, 29. Juni 2009 17:40
> An: Frank Prepelica
> Cc: linuxppc-dev@ozlabs.org
> Betreff: Re: Direct MII connection between MPC8313 and VIRTEX FPGA
>=20
> On Mon, Jun 29, 2009 at 2:23 AM, Frank
> Prepelica<Frank.Prepelica@ubidyne.com> wrote:
> > Hi Grant
> >
> > Thanks for your response!
> >
> > I have searched for "current-speed" in drivers/net/fec_mpc52xx.c but =
I
> cannot find anything. However we are using the gianfar.c Ethernet =
driver.
> > Do you know whether this driver supports fixed MII links without =
PHY?
>=20
> What kernel version are you using?
>=20
> > I've got another question regarding MII connection between and MPC =
and a
> Virtex FPGA. Whats about the PHY address which has to be set in the =
DTB
> file? Do I have to modify the DTB at all?
>=20
> Yes, you need to modify the DTB.  You have a back to back MII
> connection, not a phy, so you do *not* want to have a PHY node in the
> device tree.
>=20
> g.
>=20
> --
> Grant Likely, B.Sc., P.Eng.
> Secret Lab Technologies Ltd.

Re: Direct MII connection between MPC8313 and VIRTEX FPGA

[Grant Likely]

On Tue, Jun 30, 2009 at 2:35 AM, Frank
Prepelica<Frank.Prepelica@ubidyne.com> wrote:
>> What kernel version are you using?
>
> We are using kernel version 2.6.24. I've searched for "current speed" in =
version 2.6.28.7 and I've found that string.
>
>> Yes, you need to modify the DTB. =A0You have a back to back MII
>> connection, not a phy, so you do *not* want to have a PHY node in the
>> device tree.
>
> Hmm, but I do have a "PHY", don't I?. The "PHY" will be emulated in the F=
PGA. Of course, it's not a physical PHY but it should look like one.

No, it sounds like you don't.  If you've got a back-to-back MII
connection, then you can fix the link speed and you don't need to do
any form of PHY emulation.  ie. you don't need to wire up the MDIO
pins.

> So, do I really need the remove the complete PHY description in the DTB?

yes.

--=20
Grant Likely, B.Sc., P.Eng.
Secret Lab Technologies Ltd.