[vortex] 3c905C: Packet losses (a more precise description)

[Andrew Morton]

Donald Becker wrote:
> 
> On Thu, 6 Jul 2000, Andrew Morton wrote:
> 
> > Andrew Morton wrote:
> > > Untested patch:
> > >         /* Set the full-duplex bit. */
> > >         outb(((vp->info1 & 0x8000) || vp->full_duplex ? 0x20 : 0) |
> >
> >           ^^^^ Make this an outw
> >
> > > -                (dev->mtu > 1500 ? 0x40 : 0), ioaddr + Wn3_MAC_Ctrl);
> > > +                (dev->mtu > 1500 ? 0x40 : 0) | 0x100, ioaddr + Wn3_MAC_Ctrl);
> 
> Errrmm, no, that's not right either.
> You should never force-on flow control unless you are in full duplex mode.

Yup.  This was just a "suck it and see" experiment...

> And you really shouldn't enable flow control when you haven't negotiated
> it.  Otherwise you might stop transmitting when someone sends network-wide
> flow control packets.

Not sure I understand that.  If someone sends a network-wide PAUSE, they
presumably want you to pause??

When I put flow control support into the 2.4 driver I decided to ignore
the partner's capabilities and rely upon the user knowing what he is
doing.  So if you give the 'flow_ctrl=1' module option, it's simply
enabled (if full duplex).  I guess I should have examined partner
capabilities as well.

But one thing I definitely didn't want to do was to enable flow control
by default, based on partner capabilites.  As it can do strange things,
it should be opt-in.

> I recall reading a section that stated the flow control bit would be set
> automatically based on the autonegotiation results.  Writing the upper byte
> of Wn3_MAC_Ctrl would override the automatic setting.  Thus the driver only
> writes the lower byte.  However, I can't find the note stating this.
> Perhaps I just dreamed it.

Dreaming, I think.  I guess it's easy to get confused once you've
written drivers for every adapter known to mankind...