RE: [PATCH net] net: renesas: rswitch: fix forwarding offload statemachine

Hello Nikita,

I am sorry I missed this latest message of yours.

-----Original Message-----
From: Nikita Yushchenko <nikita.yoush@cogentembedded.com>
Sent: Thursday, February 5, 2026 4:04 PM
To: Michael Dege <redacted>; Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>;
Andrew Lunn [off-list ref]; David S. Miller [off-list ref]; Eric Dumazet
[off-list ref]; Jakub Kicinski [off-list ref]; Paolo Abeni [off-list ref]
Cc: netdev@vger.kernel.org; linux-renesas-soc@vger.kernel.org; linux-kernel@vger.kernel.org
Subject: Re: [PATCH net] net: renesas: rswitch: fix forwarding offload statemachine

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The driver was originally designed to enable hardware forwarding
when not less than two ports are in forwarding state. When only one port has hw forwarding, there

is no destination to forward.

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Nikita

The current driver allows Linux to use the bridge port as local port
to the bridge. The offloading Also supports switching traffic to
Linux through the bridge port. Therefore, the offloading shouldn't Be dropped if only one external

port is up on the bridge.

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"Offloading" means - forward a frame from one hw port to other hw port
without inserting it into CPU queue. Offloaded frame is never visible to software bridge.

There is code that allows offload only if the linux bridge device used
to connect rswitch ports does not have anything else.  If it has
something else, offloading is disabled (because there is no way to know when a frame can be

processed within rswitch hw without sending it to cpu).

Ah I see the code that explicitly enabled l2 offload only when at least two ports are active is not in
mainline.

Still, l2 offload requires at least two ports participating, by definition.
When there is only one port with hw forwarding enabled, it will get empty allowed forward destination
mask.

Yes, that is right, but there are still two HW ports involved in the HW forwarding. The remaining TSN 
port and the GWCA as internal port. Therefore, it is OK from the HW viewpoint.

Best regards,

Michael