Bug in new IBM 4xx on-chip Ethernet drivers?

llandre llandre at wawnet.biz
Wed Mar 3 20:48:00 EST 2004

Hi Benjamin,

I'm working with a custom 405EP-based board. So far I used the kernel 2.4.20
and now I'm moving to the 2.4.23. I realized that the on-chip Ethernet MAC
I have a question about the function emac_phy_read in ibm_ocp_enet.c file.
In my understanding the following snippet is not correct

         /* Clear the speed bits and make a read request to the PHY */
         stacr = ((EMAC_STACR_READ | (reg & 0x1f)) & ~EMAC_STACR_CLK_100MHZ);
         stacr |= ((mii_id & 0x1F) << 5);

because it assumes the OPB clock frequency is 50MHz. If it differs,
the MII clock frequency generated by the Ethernet controller is erroneous.
For example, with OPB frequency = 66MHz, the MII clock frequency is set
to 3.3MHz (this should be 2.5MHz).
I had already reported the problem to Armin Kuster (please see the message
http://lists.linuxppc.org/linuxppc-embedded/200306/msg00134.html) and I
a solution but I got no response.
What do you think?

TIA and best regards,


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