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

[llandre]

Hi Matt,

Benjamin Herrenschmidt suggested me (see at the end of the message) to get
in touch
with you about the following problem.
I'm working with a custom 405EP-based board (PPChameleonEVB). 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
driver
changed.
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
proposed
a solution but I got no response.
What do you think?


Thanks and best regards.



At 11.57 03/03/2004, Benjamin Herrenschmidt wrote:

> > 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
> > proposed
> > a solution but I got no response.
> > What do you think?
>
>Hi ! You may well be right on this one. I don't have any 4xx HW
>at hand any more, I suggest you contact Matt Porter
><mporter at kernel.crashing.org> on this one
>(Sorry Matt, I know I'm not helping much lately...)
>
>Ben.




llandre


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