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From: Larry Chiu <larry.chiu@realtek.com>
To: Andrew Lunn <andrew@lunn.ch>
CC: Justin Lai <justinlai0215@realtek.com>,
        "kuba@kernel.org"
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        "horms@kernel.org" <horms@kernel.org>,
        Ping-Ke Shih <pkshih@realtek.com>
Subject: RE: [PATCH net-next v19 01/13] rtase: Add pci table supported in this module
Thread-Topic: [PATCH net-next v19 01/13] rtase: Add pci table supported in
 this module
Thread-Index: AQHaqC9Rjgvgl8xidUGsWwGzPtgZ5LGa66SAgAZDQWCAAA0PoP//58SAgAGQIND///9jAIAAjjtw//+ocQAAJ0pZ0A==
Date: Thu, 23 May 2024 06:29:55 +0000
Message-ID: <48072595c9c344fea9c268fd81e4d06e@realtek.com>
References: <20240517075302.7653-1-justinlai0215@realtek.com>
 <20240517075302.7653-2-justinlai0215@realtek.com>
 <d840e007-c819-42df-bc71-536328d4f5d7@lunn.ch>
 <e5d7a77511f746bdb0b38b6174ef5de4@realtek.com>
 <97e30c5f-1656-46d0-b06c-3607a90ec96f@lunn.ch>
 <f9133a36bbae41138c3080f8f6282bfd@realtek.com>
 <7aab03ba-d8ed-4c9c-8bfd-b2bbed0a922d@lunn.ch>
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> > Thank you very much for your clear reply.
> >
> > As I mentioned, it works like a NIC connected to an Ethernet Switch, no=
t a
> > Management port.
> > The packets from this GMAC are routed according to switch rules such as
> > ACL, L2, .... and it does not control packet forwarding through any spe=
cial
> > header or descriptor. In this case, we have our switch tool which is us=
ed
> > for provisioning these rules in advance. Once the switch boots up, the
> > rules will be configured into the switch after the initialization. With=
 this
> > driver and the provisioning by our switch tool, it can make switch forw=
ard
> > the frame as what you want. So it's not a DSA like device.
>=20
> How does spanning tree work? You need to send bridge PDUs out specific
> ports. Or do you not support STP and your network must never have
> loops otherwise it dies in a broadcast storm? That does not sound very
> reliable.
>=20
> There are other protocols which require sending packets out specific
> ports. Are they simply not supported?
>=20
This port is not a CPU port, nor a management port, and therefore does not=
=20
manage any protocols of the switch. These protocols are implemented by the
CPU inside the Ethernet switch core.

> > In another case, we do have other function which is used for controllin=
g
> > the switch registers instead of sending packets from the switch ports.
> > At the meanwhile, we are investigating how to implement the function to
> > Integrate into switchdev.
>=20
> In general, we don't support configuration of hardware from user
> space, which is what your switch tool sounds like. We will want to see
> a switchdev driver of some form.
>=20
> It might be you need to use VLAN overlays, using
> net/dsa/tag_8021q.c. Each port of the switch is given a dedicated
> VLAN, and the switch needs to add/strip the VLAN header. Its not
> great, but it does allow 'simple' switches to have basic functionality
> if they are missing header/dma descriptor support for selecting ports.
>=20
>         Andrew

Typically, a NIC connected to the network may go through a switch, as show
below. Our design saves the two PHYs in the middle and connects to the Host
through PCIe.

This driver just service the transmit/receive packets for one port in the R=
TL90xx
with PCIe interface. Other programs that the switch needs to execute are
managed by the CPU inside the switch core.

*               *************************
*               *                       *
*               *        PC/Host        *
*               *                       *
*               *   +-------------+     *
*               *   |      NIC    |     *
*               ***********++************
*                        | PHY |
*                          ||
*                        | PHY |                 =20
*            +-------------++----------------+   =20
*            |           | MAC |             |   =20
*            |           +-----+             |   =20
*            |                               |   =20
*            |     Ethernet Switch Core      |   =20
*            |                               |   =20
*            |   +-----+           +-----+   |   =20
*            |   | MAC |...........| MAC |   |   =20
*            +---+-----+-----------+-----+---+   =20
*                | PHY |...........| PHY |=20

                            |
                            |
                            |
                            V

*               *************************
*               *                       *
*               *        PC/Host        *
*               *                       *
*               *   +-------------+     *
*               *   |      NIC    |     *
*               ***********++************
*                          ||
*            +-------------++----------------+   =20
*            |           | MAC |             |   =20
*            |           +-----+             |   =20
*            |                               |   =20
*            |     Ethernet Switch Core      |   =20
*            |                               |   =20
*            |   +-----+           +-----+   |   =20
*            |   | MAC |...........| MAC |   |   =20
*            +---+-----+-----------+-----+---+   =20
*                | PHY |...........| PHY |=20