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Date: Mon, 30 Mar 2026 10:07:46 +0200
From: Lorenzo Bianconi <lorenzo@kernel.org>
To: Benjamin Larsson <benjamin.larsson@genexis.eu>
Cc: Andrew Lunn <andrew+netdev@lunn.ch>,
	"David S. Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>,
	Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
	Rob Herring <robh@kernel.org>,
	Krzysztof Kozlowski <krzk+dt@kernel.org>,
	Conor Dooley <conor+dt@kernel.org>,
	Christian Marangi <ansuelsmth@gmail.com>,
	linux-arm-kernel@lists.infradead.org,
	linux-mediatek@lists.infradead.org, netdev@vger.kernel.org,
	devicetree@vger.kernel.org, Xuegang Lu <xuegang.lu@airoha.com>
Subject: Re: [PATCH net-next 00/10] net: airoha: Support multiple net_devices
 connected to the same GDM port
Message-ID: <acovUgndujK08H-4@lore-desk>
References: <20260329-airoha-eth-multi-serdes-v1-0-00f52dc360ca@kernel.org>
 <a64e0f7e-7073-4355-a3de-e8d93e2c795c@genexis.eu>
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> Hi.

Hi Ben,

>=20
> On 29/03/2026 15:07, Lorenzo Bianconi wrote:
> > EN7581 or AN7583 SoCs support connecting multiple external SerDes (e.g.
> > Ethernet or USB SerDes) to GDM3 or GDM4 ports via a hw multiplexer that
> > manages the traffic in a TDM manner.
>=20
> I think the word for this is arbiter. I think the common use of mux is as=
 a
> more fixed data path selector.


ack, I will fix it in v2.

Regards,
Lorenzo

>=20
> > As a result multiple net_devices can
> > connect to the same GDM{3,4} port and there is a theoretical "1:n"
> > relation between GDM ports and net_devices.
> >
> >             =E2=94=8C=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=
=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=
=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=
=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=
=94=80=E2=94=80=E2=94=80=E2=94=90
> >             =E2=94=82                                 =E2=94=82    =E2=
=94=8C=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=90
> >             =E2=94=82                         P1 GDM1 =E2=94=9C=E2=94=
=80=E2=94=80=E2=94=80=E2=94=80=E2=96=BAMT7530=E2=94=82
> >             =E2=94=82                                 =E2=94=82    =E2=
=94=94=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=98
> >             =E2=94=82                                 =E2=94=82      ET=
H0 (DSA conduit)
> >             =E2=94=82                                 =E2=94=82
> >             =E2=94=82              PSE/FE             =E2=94=82
> >             =E2=94=82                                 =E2=94=82
> >             =E2=94=82                                 =E2=94=82
> >             =E2=94=82                                 =E2=94=82    =E2=
=94=8C=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=90
> >             =E2=94=82                         P0 CDM1 =E2=94=9C=E2=94=
=80=E2=94=80=E2=94=80=E2=94=80=E2=96=BAQDMA0=E2=94=82
> >             =E2=94=82  P4                     P9 GDM4 =E2=94=82    =E2=
=94=94=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=98
> >             =E2=94=94=E2=94=80=E2=94=80=E2=94=AC=E2=94=80=E2=94=80=E2=
=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=
=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=
=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=AC=E2=94=80=E2=
=94=80=E2=94=80=E2=94=80=E2=94=98
> >                =E2=94=82                         =E2=94=82
> >             =E2=94=8C=E2=94=80=E2=94=80=E2=96=BC=E2=94=80=E2=94=80=E2=
=94=90                 =E2=94=8C=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=96=
=BC=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=90
> >             =E2=94=82 PPE =E2=94=82                 =E2=94=82   MUX   =
=E2=94=82
> >             =E2=94=94=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=
=94=98                 =E2=94=94=E2=94=80=E2=94=AC=E2=94=80=E2=94=80=E2=94=
=80=E2=94=80=E2=94=80=E2=94=AC=E2=94=80=E2=94=98
> >                                       =E2=94=82     =E2=94=82
> >                                    =E2=94=8C=E2=94=80=E2=94=80=E2=96=BC=
=E2=94=80=E2=94=80=E2=94=90=E2=94=8C=E2=94=80=E2=96=BC=E2=94=80=E2=94=80=E2=
=94=80=E2=94=90
> >                                    =E2=94=82 ETH =E2=94=82=E2=94=82 USB=
 =E2=94=82
> >                                    =E2=94=94=E2=94=80=E2=94=80=E2=94=80=
=E2=94=80=E2=94=80=E2=94=98=E2=94=94=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=
=94=80=E2=94=98
> >                                     ETH1   ETH2
>=20
> A more representative picture is like the following and in the GDM2 path
> there is a real mux present(not relevant for this patch series though). T=
hus
> I think it is important to have the distinction between mux and arbiter.
> (Feel free to reuse the following illustration freely).
>=20
>                 =E2=94=8C=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=
=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=
=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=
=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=
=94=80=E2=94=80=E2=94=80=E2=94=90
>                 =E2=94=82                                 =E2=94=82    =
=E2=94=8C=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=90
>    =E2=94=8C=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=
=80=E2=94=80=E2=94=80=E2=94=90  =E2=94=82                         P1 GDM1 =
=E2=94=9C=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=96=BAMT7530=E2=94=82
>    =E2=94=82   MUX   =E2=94=9C=E2=94=80=E2=94=80=E2=94=82 P2 GDM2        =
                 =E2=94=82    =E2=94=94=E2=94=80=E2=94=80=E2=94=80=E2=94=80=
=E2=94=80=E2=94=80=E2=94=98
>    =E2=94=94=E2=94=80=E2=94=AC=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=
=80=E2=94=AC=E2=94=80=E2=94=98  =E2=94=82                                 =
=E2=94=82      ETH0 (DSA conduit)
>      =E2=94=82     =E2=94=82    =E2=94=82                                =
 =E2=94=82
>   =E2=94=8C=E2=94=80=E2=94=80=E2=96=BC=E2=94=80=E2=94=80=E2=94=90=E2=94=
=8C=E2=94=80=E2=96=BC=E2=94=80=E2=94=80=E2=94=80=E2=94=90=E2=94=82         =
     PSE/FE             =E2=94=82
>   =E2=94=82 PON =E2=94=82=E2=94=82 PON =E2=94=82=E2=94=82                =
                 =E2=94=82
>   =E2=94=94=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=98=E2=94=
=94=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=98=E2=94=82         =
                        =E2=94=82
>    ETH5   XPON  =E2=94=82                                 =E2=94=82    =
=E2=94=8C=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=90
>                 =E2=94=82                         P0 CDM1 =E2=94=9C=E2=94=
=80=E2=94=80=E2=94=80=E2=94=80=E2=96=BAQDMA0=E2=94=82
>                 =E2=94=82  P4      P3 GDM3        P9 GDM4 =E2=94=82    =
=E2=94=94=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=98
>                 =E2=94=94=E2=94=80=E2=94=80=E2=94=AC=E2=94=80=E2=94=80=E2=
=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=
=AC=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=
=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=AC=E2=94=80=E2=
=94=80=E2=94=80=E2=94=80=E2=94=98
>                    =E2=94=82          =E2=94=82              =E2=94=82
>                 =E2=94=8C=E2=94=80=E2=94=80=E2=96=BC=E2=94=80=E2=94=80=E2=
=94=90  =E2=94=8C=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=96=BC=E2=94=80=E2=
=94=80=E2=94=80=E2=94=80=E2=94=90    =E2=94=8C=E2=94=80=E2=94=80=E2=94=80=
=E2=94=80=E2=96=BC=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=90
>                 =E2=94=82 PPE =E2=94=82  =E2=94=82   ARB   =E2=94=82    =
=E2=94=82   ARB   =E2=94=82
>                 =E2=94=94=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=
=94=98  =E2=94=94=E2=94=80=E2=94=AC=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=
=94=80=E2=94=AC=E2=94=80=E2=94=98    =E2=94=94=E2=94=80=E2=94=AC=E2=94=80=
=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=AC=E2=94=80=E2=94=98
>                            =E2=94=82     =E2=94=82        =E2=94=82     =
=E2=94=82
>                         =E2=94=8C=E2=94=80=E2=94=80=E2=96=BC=E2=94=80=E2=
=94=80=E2=94=90=E2=94=8C=E2=94=80=E2=96=BC=E2=94=80=E2=94=80=E2=94=80=E2=94=
=90 =E2=94=8C=E2=94=80=E2=94=80=E2=96=BC=E2=94=80=E2=94=80=E2=94=90=E2=94=
=8C=E2=94=80=E2=96=BC=E2=94=80=E2=94=80=E2=94=80=E2=94=90
>                         =E2=94=82PCIE0=E2=94=82=E2=94=82PCIE1=E2=94=82 =
=E2=94=82 ETH =E2=94=82=E2=94=82 USB =E2=94=82
>                         =E2=94=94=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=
=94=80=E2=94=98=E2=94=94=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=
=98 =E2=94=94=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=98=E2=94=
=94=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=98
>                           ETH3   ETH4    ETH1   ETH2
>=20
> MvH
> Benjamin Larsson

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