[U-Boot-Users] MPC5121 (and MPC5200) ethernet initialization delay

Chris Morgan chmorgan at gmail.com
Tue Dec 18 18:38:39 CET 2007

On Dec 18, 2007 4:03 AM, Stefan Roese <sr at denx.de> wrote:
> On Tuesday 18 December 2007, Wolfgang Denk wrote:
> > > autonegotiation only when the ethernet interface is used. Upon TFTP
> > > download or something like this. So there should be no delay at all in
> > > U-Boot related to this ethernet initialization when you don't use
> > > ethernet.
> >
> > Right, that's how it should be in an ideal world.
> >
> > However, things are not that simple.
> >
> > First, the perception that this is how things should work has not been
> > there forever. It has riped over time, and older boards / ports do
> > things differently.
> >
> > Second, there are some CPUs / boards where "initializing" the  ether-
> > net  just  requires to whack a PY reset or simply take the PHT out of
> > reset etc. Autonegotiation then takes place  while  U-Boot  is  doing
> > other things, and by the time you want to use the Ethernet for a TFTP
> > download  or so it will be available with no or at least with greatly
> > reduced delay.
> Right. I know of such ports too and don't see any problems here since no delay
> is imposed.
> > But there are other implementations which wait for
> > autonegotiation to complete.
> I don't see a reason why a board should wait for autonegotionation to
> complete, when the interface is not used. This should be fixed.

I appreciate the responses to this email thread. Knowing more about
what is a suitable solution to the problem reduces the chance that any
proposed solution will have to be fundamentally reworked before being
accepted back into the u-boot tree.

On our end we still need to confirm with someone at Freescale that the
delay is a hardware constraint. I can work that through our support
contacts and if they aren't going to address the issue in u-boot I'm
going to see about having the work to fix this for the 512x(and likely
5200) platforms put on our internal development schedule.

Gerry, I'm copying you to get you in on the discussion. Relative to
our overall board boot time a significant amount of time is spent
waiting for the ethernet initialization so its something we want to
address and to do so in a clean fashion. Any help you guys might be
able to provide would be helpful.


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