PPC4xx 2x eth phy

- Reyneke reynekejunk at hotmail.com
Wed Oct 24 17:26:25 EST 2007

Some quick feedback to the list. A few weeks ago I talked about the problem of the second ethernet connection not working when the first ethernet connection does not have a link.

Basically the problem is PHYs that don't generate a RX clock when no link is present (i.e. ET1011. It turns out that in case of the 440Epx, there is some interdependency within the EMAC which means that when EMAC1 initialises, there MUST be a RX clock on EMAC0. If that is not the case, EMAC1 will NOT send/receive even though initialisation and auto-negotiation is successful.

There is some linux code for handling missing RX clocks, but this code does not extend to the scenario where one EMAC is dependent on another EMAC's PHY having a receive clock.

   Jan Reyneke

> HI,
> We've run into a bit of an odd problem and we are not sure where to go and
> look for the cause.
> We have some 440EPx based hardware with two GIG-Ethernet ports using RGMII
> and 2x ET1011C PHY's. Problem is that eth1 will only initialise correctly
> (i.e. receive and transmit) if eth0 has a link. Eth0 always work OK,
> regardless of eth1 status. Eth1 will work OK if eth0 has a link (i.e.
> initialised) at time of setup. Once initialised, eth0 status is
> irrelevant.
> All this is during Linux boot process.
> Any ideas?
> We can access PHY registers via u-boot (mii commands). Same 1Gig link
> speed
> is used on both ports. Linux kernel is 2.6.19.

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