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From:   =?UTF-8?B?w4FsdmFybyBGZXJuw6FuZGV6IFJvamFz?= <noltari@gmail.com>
Date:   Fri, 17 Mar 2023 17:40:30 +0100
Message-ID: <CAKR-sGe=+xaTmtOSkRURXCwH4kweMxNOJnPq46cSeZJJa5yXEA@mail.gmail.com>
Subject: Re: [PATCH] net: dsa: tag_brcm: legacy: fix daisy-chained switches
To:     Andrew Lunn <andrew@lunn.ch>
Cc:     f.fainelli@gmail.com, jonas.gorski@gmail.com, olteanv@gmail.com,
        davem@davemloft.net, edumazet@google.com, kuba@kernel.org,
        pabeni@redhat.com, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org
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El vie, 17 mar 2023 a las 17:32, Andrew Lunn (<andrew@lunn.ch>) escribi=C3=
=B3:
>
> On Fri, Mar 17, 2023 at 01:08:15PM +0100, =C3=81lvaro Fern=C3=A1ndez Roja=
s wrote:
> > When BCM63xx internal switches are connected to switches with a 4-byte
> > Broadcom tag, it does not identify the packet as VLAN tagged, so it add=
s one
> > based on its PVID (which is likely 0).
> > Right now, the packet is received by the BCM63xx internal switch and th=
e 6-byte
> > tag is properly processed. The next step would to decode the correspond=
ing
> > 4-byte tag. However, the internal switch adds an invalid VLAN tag after=
 the
> > 6-byte tag and the 4-byte tag handling fails.
> > In order to fix this we need to remove the invalid VLAN tag after the 6=
-byte
> > tag before passing it to the 4-byte tag decoding.
>
> Is there an errata for this invalid VLAN tag? Or is the driver simply
> missing some configuration for it to produce a valid VLAN tag?

Yes, this is a HW issue due to the fact that Broadcom Legacy switches
which use a 6-byte tag cannot identify the tag of newer Broadcom
switches using a 4-byte tag and therefore adding their own tag along
with a default VLAN tag ignoring the corresponding untag bit in those
ports.
But Florian and Jonas can probably provide more information about this
HW issue, and also this link too:
https://github.com/openwrt/openwrt/issues/10313

>
> The description does not convince me you are fixing the correct
> problem.

Well, if you think that I should fix the configuration then I'm afraid
you're wrong.

>
>         Andrew

--
=C3=81lvaro