On Thu, Apr 30, 2009 at 6:21 PM, Kyle Moffett [off-list ref] wrote:

quoted

quoted

I'm also curious about the intent of the "mdio_instance" pointer (IE:
the "mdio-device" property).  Is that used when all the PHY devices
are attached to the MDIO bus of only one of the (multiple) emac
devices?

It's common especially on older SoCs using EMAC to have only one of
the EMAC instance with an MDIO bus for configuring the PHYs. This is one
of the reasons why I have the mutex in the low level MDIO access
routines since 2 EMACs can try to talk to the same MDIO, and this is the
problem I had with phylib back then which was doing everything in atomic
contexts.

Ok, good, the current mdiobus code seems to make handling this a good
deal easier.

Ok, I've dug through the docs on the 460EPx (the CPU I'm using), and
I'd like some confirmation of the following:

*  The EMAC hardware itself internally has its own dedicated
MDIO/MDClk lines, driven by the STACR register.

*  On many/most cpus, there is only a single set of external
MDIO/MDClk pins, driven either off the ZMII bridge or the RGMII
bridge.

*  Both bridge-types have their own internal register for switching
the external MDIO/MDClk pins between the two sets of internal
EMAC<=>bridge links.

*  Some SoCs have both an ZMII and an RGMII bridge, and the external
MDIO/MDClk pins are only connected to one of the two bridges (How do I
know which one?  Alternatively, do I just program both and hope for
the best?).

*  Some older SoCs simply export the MDIO/MDClk pins from one of their
internal EMAC chips and don't bother with running it through the
multiplexing bridge.

Are there any SoCs which actually export the MDIO/MDClk pins from
both/all of their EMACs?

Cheers,
Kyle Moffett
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