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Date: Fri, 22 Sep 2017 22:08:10 +0200 From: Andrew Lunn <andrew@...n.ch> To: Egil Hjelmeland <privat@...l-hjelmeland.no> Cc: vivien.didelot@...oirfairelinux.com, f.fainelli@...il.com, netdev@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH net-next 2/2] net: dsa: lan9303: Add basic offloading of unicast traffic > >I'm wondering how this is supposed to work. Please add a good comment > >here, since the hardware is forcing you to do something odd. > > > >Maybe it would be a good idea to save the STP state in chip. And then > >when chip->is_bridged is set true, change the state in the hardware to > >the saved value? > > > >What happens when port 0 is added to the bridge, there is then a > >minute pause and then port 1 is added? I would expect that as soon as > >port 0 is added, the STP state machine for port 0 will start and move > >into listening and then forwarding. Due to hardware limitations it > >looks like you cannot do this. So what state is the hardware > >effectively in? Blocking? Forwarding? > > > >Then port 1 is added. You can then can respect the states. port 1 will > >do blocking->listening->forwarding, but what about port 0? The calls > >won't get repeated? How does it transition to forwarding? > > > > Andrew > > > > I see your point with the "minute pause" argument. Although a bit > contrived use case, it is easy to fix by caching the STP state, as > you suggest. So I can do that. I don't think it is contrived. I've done bridge configuration by hand for testing purposes. I've also set the forwarding delay to very small values, so there is a clear race condition here. > How does other DSA HW chips handle port separation? Knowing that > could perhaps help me know what to look for. They have better hardware :-) Generally each port is totally independent. You can change the STP state per port without restrictions. Andrew
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