netdev - Re: [PATCH 0/3] net: renesas: rswitch: R-Car S4 add HW offloading for layer 2 switching

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Message-ID: <79dca2df-1126-4d94-bab9-761a982090b6@cogentembedded.com>
Date: Fri, 4 Jul 2025 19:56:45 +0200
From: Nikita Yushchenko <nikita.yoush@...entembedded.com>
To: Andrew Lunn <andrew@...n.ch>
Cc: Michael Dege <michael.dege@...esas.com>,
 Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
 Niklas Söderlund <niklas.soderlund@...natech.se>,
 Paul Barker <paul@...rker.dev>, Andrew Lunn <andrew+netdev@...n.ch>,
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 netdev@...r.kernel.org, linux-renesas-soc@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/3] net: renesas: rswitch: R-Car S4 add HW offloading for
 layer 2 switching

04.07.2025 19:53, Andrew Lunn wrote:
> On Fri, Jul 04, 2025 at 11:05:14AM +0200, Nikita Yushchenko wrote:
>>> Looking at the code, it is not clear to me what would happen with:
>>>
>>> ip link add name br0 type bridge
>>> ip link set dev tsn0 master br0
>>> ip link set dev br0 up
>>> ip link set dev tsn0 up
>>> ip link add name br1 type bridge
>>> ip link set dev tsn1 master br1
>>> ip link set dev br1 up
>>> ip link set dev tsn1 up
>>
>> Per design, it shall enable hardware forwarding when two ports are in the same brdev.
> 
> So in this case, the hardware offload has been reserved by br0, but is
> in fact never used, since there is only one port in the bridge. If i
> was to then do
> 
> ip link set dev tsn2 master br1
> ip link set dev tsn2 up
> 
> br1 would not be offloaded, but done in software.

rswitch_update_offload_brdev() calculates which brdev to offload, and it only considers brdev having at 
least two rswitch ports. So in this case br1 shall get offloaded.

Nikita