[U-Boot] [PATCH] UEC PHY: Speed up initial PHY neg.

[Joakim Tjernlund]

Ben Warren <biggerbadderben at gmail.com> wrote on 2010/08/23 09:08:17:
>
>   Hi Detlev,
>
> On 8/13/2010 1:20 AM, Detlev Zundel wrote:
> > Hi Jocke,
> >
> >>>> Instead of always performing an autoneg, check if the PHY
> >>>> already has a link and if it matches one of the requested
> >>>> modes. Initially only 100MbFD is optimized this way.
> >>> Isn't it about time that we think about _not_ stopping the ethernet
> >>> device after every transaction?
> >> Hi Detlev
> >>
> >> UEC does this already, my patch was to address the initial delay
> >> you get for the first transaction. Now my PHY based boards gets the link
> >> up just as quick as Fixed PHY for the first transaction.
> > Forgive me to not look into this any deeper, but do I understand you
> > correctly that you do this by essentially no-oping the eth_halt()
> > function?  Isn't this then effectively violating what net.c expects the
> > device to do?
> >
> > I was thinking that net.c itself should not do this continous start/stop
> > thing as it has problems on many interfaces.  On one ARM machine I've
> > again seen problems with the MAC address programming because the
> > eth_halt() resets the controller and so it forgets its address again.
> > Also the USB-CDC example where the _whole interface_ on the host side is
> > being torn down after each tftp transfer prompts me to think along this
> > line.
> >
> > So in effect I guess my response was rather a ping to Ben, sorry for
> > that ;)
> >
> Sorry for the delay on this.  I'm all for changing the existing
> behavior.  It seems to me that the only time we would ever want to wind
> an interface down is if we switch the active one (even then, I'm not
> sure).  My world view is limited, but I can't imagine that even changing
> interfaces happens much in real world U-boot usage, that is the non-lab,
> non-interactive use cases.  What would you think about adding something
> like ifup and ifdown commands so that users could explicitly start/stop
> interfaces?

Sure, bringing I/F's up and down needlessly isn't a good thing. However my
patch doesn't change that behaviour. It only optimizes the need for a PHY AN
the first time one performs a eth transaction.

      Jocke

> > Cheers
> >    Detlev
> >
> regards,
> Ben
>
>