WOL question

David Christensen davidch at broadcom.com
Tue Apr 10 23:10:53 UTC 2007

> > > I think I heard once that some BIOSes turn it off during 
> the boot cycle
> > > somewhere and it is up to the OS to turn it back on. I do 
> know that some
> > > BIOSes
> > > phuck with the NIC enough to stop IPMI from working 
> during the boot.
> > >
> >
> > That would make sense; you don't want the card to generate 
> an NMI during
> > boot from a spurius WOL package before the system is ready 
> to handle it.
> Hmm, so I have two competing views about things, one is that 
> the kernel
> is actively doing something to disable WOL on shutdown, and now the
> theory that its just not rearming the system.
> I really need to know which it is, because I'm putting code 
> in the driver that
> I think should rearm it, and it doesnt work, and I've been 
> left wondering if
> my code is wrong, or if something deeper in the kernel is 
> clobbering the
> things I am trying to set up :)

Is this a NIC or a LOM?  For Broadcom NICs there is a procedure
in firmware for toggling power to the chip from MAIN to VAUX prior to 
entering D3cold so that the controller still has power and can recognize

the magic packet.  For LOM designs that's not required because the VAUX
rail is always powered by the motherboard.  The easy way to check is to
see if you still have a link LED lit on the back of the controller when
you expect to be in WoL mode.  No LED, no power.  Are you resetting the 
link speed to 100Mbps or less?  Running at 1000Mbps generally draws more
than 375mA and I've seen some systems that shutdown power to a slot when
it draws too much power in VAUX.


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