On Tue, 22 Oct 2002, Mike Silbersack wrote:
> In trying to figure out why if_xl's mii_tick is such a pig, I think I've
> stumbled upon a bug in -current's MII routines which I'd like confirmation
> on before I go ahead and fix.
> ...
> In the original version (which is still present in -stable), the MII_TICK
> case aborts out of the function due to a bunch of circumstances which
> indicate that no autonegotiation is necessary. mii_phy_tick does the
> same. HOWEVER, mii_phy_tick returns 0, which indicates to the new
> MII_TICK logic that autonegotiation _is_ necessary, thereby
> reautonegotiating _every second_.
>
> I believe that the correct fix would be:
>
> if (IFM_SUBTYPE(ife->ifm_media) != IFM_AUTO)
> - return (0);
> + return (EJUSTRETURN);
This return of 0 is apparently intentional. The comment before this
says:
/*
* If we're not doing autonegotiation, we don't need to do
* any extra work here. However, we need to check the link
* status so we can generate an announcement if the status
* changes.
*/
Here the "However" clause is not in RELENG_4. Returning 0 gets the
status updated. I think this is just too expensive to do every second.
Autonegotiation is only retried every 17 seconds (every 5 seconds in
RELENG_4).
>
> /* Read the status register twice; BMSR_LINK is latch-low. */
> reg = PHY_READ(sc, MII_BMSR) | PHY_READ(sc, MII_BMSR);
> if (reg & BMSR_LINK) {
> /*
> * See above.
> */
> - return (0);
> + return (EJUSTRETURN);
> }
I think the "However" clause applies to this return too. The status update
code does lots more than the above to determine the exact state.
> Doing this results in much quicker mii_ticks, dropping the time taken for
> the normal case from 11ms to 3ms, without any of Harti Brandt's
> optimizations. Also, I believe that this change makes it operate more
> correctly.
Bruce
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