[U-Boot] [PATCH] revert "tsec: Force TBI PHY to 1000Mbps fullduplex in SGMII mode"

[Li Yang]

><snip>
>
>> >My understanding is that the SGMII link is always at 1000Mbps speed -
>> >see figure 1 from the app note.  Additionally look at figure 3.  My
>> >understand from it, and the app note's text is that SGMII
>> >auto-negotiation doesn't really occur - its just passing the PHY-side
>> >auto-negotiation results to the Freescale MAC, which software then
>> >configures.  I'm not sure what the purpose of the "SGMII
>> >auto-negotiation" is - its not really auto- negotiating and the same
>> >information can be read from the PHY via its MDIO interface, which is
>what is happening on X-ES boards currently.
>>
>> I guess the point is to save MDIO signals to the external PHY and read
>> the negotiated result from the internal TBI PHY.
>
>Do the P2020DS, MPC8572DS and P1/P2 RDB boards not have an MDIO interface
>to their PHYs'?  I've never heard of a board that doesn't, and would guess
>the tsec driver in U-Boot requires a PHY to be accessible via MDIO to use
>the corresponding network interface.

I'm not sure which specific silicon omits the MDIO signal.  But quoting from
the app note you mentioned:

" Depending on the PowerQUICC part used, some eTSEC’s may or may not
provide an external
MDIO management interface. However, the TBI block for each eTSEC is
associated in a one to one
manner, even if that eTSEC does not have an external MDIO connection."

The auto-negotiation mechanism between TBI PHY and real PHY does make
it possible
to save external MDIO signals if only SGMII interface is used.

>
>I can forward you the email thread about SGMII auto-negotiation with
>Freescale's FAE off-list if you'd like as well.

Yes, please.  Thanks

- Leo