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

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Message-ID:
 <TY4PR01MB142828D6A83F85B08D85D3EB98299A@TY4PR01MB14282.jpnprd01.prod.outlook.com>
Date: Thu, 5 Feb 2026 07:51:33 +0000
From: Michael Dege <michael.dege@...esas.com>
To: Nikita Yushchenko <nikita.yoush@...entembedded.com>, Yoshihiro Shimoda
	<yoshihiro.shimoda.uh@...esas.com>, 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>
CC: "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-renesas-soc@...r.kernel.org" <linux-renesas-soc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH net] net: renesas: rswitch: fix forwarding offload
 statemachine

Hello Nikita,

> -----Original Message-----
> From: Nikita Yushchenko <nikita.yoush@...entembedded.com>
> Sent: Thursday, February 5, 2026 8:47 AM
> To: Michael Dege <michael.dege@...esas.com>; Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>;
> 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>
> Cc: netdev@...r.kernel.org; linux-renesas-soc@...r.kernel.org; linux-kernel@...r.kernel.org
> Subject: Re: [PATCH net] net: renesas: rswitch: fix forwarding offload statemachine
> 
> Hello Michael
> 
> > -		} else if (rdev->forwarding_offloaded) {
> > +		} else if (rdev->forwarding_offloaded &&
> > +			   !rdev->forwarding_requested) {
> >   			rswitch_change_l2_hw_offloading(rdev, false, false);
> >   		}
> 
> Although indeed the condition in the current code is not correct, I'm not sure comfortable with this
> fix.
> 
> Full condition for a port to be a valid candidate for hardware forwarding is
> 
>    rdev_for_l2_offload() && rdev->forwarding_requested
> 
> It is not obvious if at this point rdev_for_l2_offload() could get changed from the last call to
> rswitch_change_l2_hw_offloading(), so using only the partial condition at this point does not look
> good for me.
> 
> I'd suggest to either change to something like
> 
> if (rdev_for_l2_offload() && rdev->forwarding_requested && !rdev->forwarding_offloaded)
> 	rswitch_change_l2_hw_offloading(rdev, true, false); if (!(rdev_for_l2_offload() && rdev-
> >forwarding_requested) && rdev->forwarding_offloaded)
> 	rswitch_change_l2_hw_offloading(rdev, false, false);
> 
> Or maybe just
> 
> if (rdev_for_l2_offload() && rdev->forwarding_requested)
> 	rswitch_change_l2_hw_offloading(rdev, true, false); else
> 	rswitch_change_l2_hw_offloading(rdev, false, false);
> 
> since rswitch_change_l2_hw_offloading() has internal check for the current state and returns early if
> the requested change is already applied.
> 
> Nikita

Thank you for your comment.

Let me study and test your suggestion.

Best regards,

Michael