[U-Boot-Users] u-boot 1.1.1 & Intel LXT972A

VanBaren, Gerald (AGRE) Gerald.VanBaren at smiths-aerospace.com
Wed Jul 21 14:08:56 CEST 2004

> -----Original Message-----
> From: u-boot-users-admin at lists.sourceforge.net
> [mailto:u-boot-users-admin at lists.sourceforge.net]On Behalf Of
> Knowledge
> Seeker
> Sent: Tuesday, July 20, 2004 7:39 PM
> To: Wolfgang Denk; U-Boot List
> Subject: Re: [U-Boot-Users] u-boot 1.1.1 & Intel LXT972A
> Wolfgang writes "I recommend to check your clocks (both in software
> and in hardware)"
> I am a newbie, so please help me out
> - For hardware clock, need to check MDIO clock signal and it should be
> at 2.5 MHz ? (is this what I ask my hardware guy)

It should be 25MHz for 100bT.  It may be 2.5MHz if you are connecting to a 10bT switch/hub.

> - For software clock, I am looking at cpu/mpc8xx/fec.c file (around
> line # 385), line is
> fecp->fec_mii_speed = ((bd->bi_intfreq + 4999999) / 5000000) << 1;
> which evaluates to 2, is this suppose to evaluate 2.5 MHz ?
> Please explain, so that I can clear my concept and solve my problem.
> Abu Sana

No, wrong clock.  The MII speed is for the control of the PHY chip, not the data path.  We are assuming you can read and write registers on the PHY chip (you can, right?) which implies the MII clock and data lines are configured OK.

You need to make sure the clock signal generated by the PHY chip goes into your processor on the correct pin (and is the proper frequency and decent waveform, see above) and that the pin on the chip is configured properly as a clock input.  In addition, you need to verify you are configuring the FEC to use that clock for its ethernet clock (I'm assuming this is configurable like the 82xx).


> --- Wolfgang Denk <wd at denx.de> wrote:
> > Hello <???>,
> >
> > [a realname would definitely be fine.]
> >
> > In message <20040720183933.63696.qmail at web50502.mail.yahoo.com> you
> > wrote:
> >> I have LXT972A on 852T. From u-boot, I have set mac, ip and
> netmask.
> >> When I try to ping a ip address on LAN. I get "TX timeout"
> >
> > In nearly all cases of "TX timeout" I've seen so far the problem was
> > cased by bad clocks; I recommend to check your clocks (both in
> > software and in hardware).
> >
> > Best regards,
> >
> > Wolfgang Denk
> >
> > --
> > Software Engineering: Embedded and Realtime Systems, Embedded Linux
> > Phone: (+49)-8142-4596-87  Fax: (+49)-8142-4596-88  Email:
> wd at denx.de
> > In C we had to code our own bugs, in C++ we can inherit them.

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