linux-kernel - Re: [PATCH net] net: dsa: microchip: ksz9477: fix multicast filtering

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Message-ID: <CAJ+vNU3sAhtSkTjuj2ZMfa02Qk1rh1-z=1unEabrB8UOdx8nFA@mail.gmail.com>
Date: Tue, 14 Jan 2025 10:27:10 -0800
From: Tim Harvey <tharvey@...eworks.com>
To: Arun.Ramadoss@...rochip.com
Cc: Woojung.Huh@...rochip.com, UNGLinuxDriver@...rochip.com, andrew@...n.ch, 
	davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com, 
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org, olteanv@...il.com
Subject: Re: [PATCH net] net: dsa: microchip: ksz9477: fix multicast filtering

On Thu, Jan 2, 2025 at 7:29 PM <Arun.Ramadoss@...rochip.com> wrote:
>
> Hi Tim,
>
> >
> > Arun,
> >
> > Can you confirm that prior to commit 331d64f752bb ("net: dsa:
> > microchip: add the enable_stp_addr pointer in ksz_dev_ops") that packets in the bridge group were being forwarded to all ports and
> > that the intention of the patch was to limit them to only go to 'only' the cpu port?
>
> By Default, In the reserved multicast table, the forwarding port for the mac address 01:80:C2:00:00:00 (BPDU Mac address) is 10h. It means, the STP BPDU packet will be forwarded to Port 5. However, the CPU port varies depending on the board schematics. Hence to fix this, forwarding port needs to changed in reserved multicast table.
>
> Procedure for updating Override bit:
> -  0x0424 = 0x8000_0000 | dev->cpu_port. (0x10 for lan9370 and 0x20 for lan9374)
> -  0x41c   = 0x0000_0085 (write, reserved multicast table and start. Table Index is 0 which is the index for BPDU packet 01:80:c2:00:00:00)
> - 0x41c = wait till start bit is cleared.
>
> Let me know, if you need any more information.
>

Hi Arun,

Ok, that makes sense to me and falls in line with what my patch here
was trying to do. When you enable the reserved multicast table it
makes sense to update the entire table right? You are only updating
one address/group. Can you please review and comment on my patch here?

Best Regards,

Tim