Re: [PATCH net-next v2 12/14] net: ethernet: qualcomm: Initialize PPE L2 bridge settings

[Andrew Lunn <andrew@lunn.ch>]

> > Why is learning needed on physical ports? In general, switches forward
> > unknown destination addresses to the CPU. Which is what you want when
> > the ports are isolated from each other. Everything goes to the
> > CPU. But maybe this switch does not work like this?
> > 
> 
> L2 forwarding can be disabled in PPE in two ways:
> 
> 1.) Keep the learning enabled (which is the default HW setting) and
> configure the FDB-miss-action to redirect to CPU.
> 
> This works because even if FDB learning is enabled, we need to represent
> the bridge and the physical ports using their 'virtual switch instance'
> (VSI) in the PPE HW, and create the 'port membership' for the bridge VSI
> (the list of slave ports), before FDB based forwarding can take place. Since
> we do not yet support switchdev, these VSI are not created and packets are
> always forwarded to CPU due to FDB miss.
> 
> (or)
> 
> 2.) Explicitly disable learning either globally or on the ports.
> 
> With method 1 we can achieve packet forwarding to CPU without explicitly
> disabling learning. When switchdev is enabled later, L2 forwarding can be
> enabled as a natural extension on top of this configuration. So we have
> chosen the first approach.

How does ageing work in this setup? Will a cable unplug/plug flush all
the learned entries? Is ageing set to some reasonable default in case
a MAC address moves?

	Andrew